document_title: Globular cluster

question_text: where are most of the milky ways globular clusters found

question_tokens: where are most of the milky ways globular clusters found

text: Globular cluster

text: Observation history[edit]

text:
Early globular cluster discoveries

Cluster name
Discovered by
Year

M22
Abraham Ihle
1665

ω Cen
Edmond Halley
1677

M5
Gottfried Kirch
1702

M13
Edmond Halley
1714

M71
Philippe Loys de Chéseaux
1745

M4
Philippe Loys de Chéseaux
1746

M15
Jean-Dominique Maraldi
1746

M2
Jean-Dominique Maraldi
1746

text: The first known globular cluster, now called M22, was discovered in 1665 by Abraham Ihle, a German amateur astronomer.[11] However, given the small aperture of early telescopes, individual stars within a globular cluster were not resolved until Charles Messier observed M4 in 1764.[12] The first eight globular clusters discovered are shown in the table. Subsequently, Abbé Lacaille would list NGC 104, NGC 4833, M55, M69, and NGC 6397 in his 1751–52 catalogue. The M before a number refers to Charles Messier's catalogue, while NGC is from the New General Catalogue by John Dreyer.

text: When William Herschel began his comprehensive survey of the sky using large telescopes in 1782 there were 34 known globular clusters. Herschel discovered another 36 himself and was the first to resolve virtually all of them into stars. He coined the term "globular cluster" in his Catalogue of a Second Thousand New Nebulae and Clusters of Stars published in 1789.[13]

text: The number of globular clusters discovered continued to increase, reaching 83 in 1915, 93 in 1930 and 97 by 1947. A total of 152 globular clusters have now been discovered in the Milky Way galaxy, out of an estimated total of 180 ± 20.[4] These additional, undiscovered globular clusters are believed to be hidden behind the gas and dust of the Milky Way.

text: Beginning in 1914, Harlow Shapley began a series of studies of globular clusters, published in about 40 scientific papers. He examined the RR Lyrae variables in the clusters (which he assumed were Cepheid variables) and used their period–luminosity relationship for distance estimates. Later, it was found that RR Lyrae variables are fainter than Cepheid variables, which caused Shapley to overestimate the distances of the clusters.[14]

text: Of the globular clusters within the Milky Way, the majority are found in a halo around the galactic core, and the large majority are located in the celestial sky centered on the core. In 1918, this strongly asymmetrical distribution was used by Shapley to make a determination of the overall dimensions of the galaxy. By assuming a roughly spherical distribution of globular clusters around the galaxy's center, he used the positions of the clusters to estimate the position of the Sun relative to the galactic center.[15] While his distance estimate was in significant error (although within the same order of magnitude as the currently accepted value), it did demonstrate that the dimensions of the galaxy were much greater than had been previously thought. His error was due to interstellar dust in the Milky Way, which absorbs and diminishes the amount of light from distant objects, such as globular clusters, that reaches the Earth, thus making them appear to be more distant than they are.

text: Shapley's measurements also indicated that the Sun is relatively far from the center of the galaxy, also contrary to what had previously been inferred from the apparently nearly even distribution of ordinary stars. In reality, most ordinary stars lie within the galaxy's disk and those stars that lie in the direction of the galactic centre and beyond are thus obscured by gas and dust, whereas globular clusters lie outside the disk and can be seen at much further distances.

text: Classification of globulars[edit]

text: Shapley was subsequently assisted in his studies of clusters by Henrietta Swope and Helen Battles Sawyer (later Hogg). In 1927–29, Shapley and Sawyer categorized clusters according to the degree of concentration each system has toward its core. The most concentrated clusters were identified as Class I, with successively diminishing concentrations ranging to Class XII. This became known as the Shapley–Sawyer Concentration Class (it is sometimes given with numbers [Class 1–12] rather than Roman numerals.)[16] In 2015, a new type of globular cluster was proposed on the basis of observational data, the dark globular clusters.[17]

text: Formation[edit]

text: The formation of globular clusters remains a poorly understood phenomenon and it remains uncertain whether the stars in a globular cluster form in a single generation or are spawned across multiple generations over a period of several hundred million years. In many globular clusters, most of the stars are at approximately the same stage in stellar evolution, suggesting that they formed at about the same time.[19] However, the star formation history varies from cluster to cluster, with some clusters showing distinct populations of stars. An example of this is the globular clusters in the Large Magellanic Cloud (LMC) that exhibit a bimodal population. During their youth, these LMC clusters may have encountered giant molecular clouds that triggered a second round of star formation.[20] This star-forming period is relatively brief, compared to the age of many globular clusters.[21] It has also been proposed that the reason for this multiplicity in stellar populations could have a dynamical origin. In the Antennae galaxy, for example, the Hubble Space Telescope has observed clusters of clusters, regions in the galaxy that span hundreds of parsecs, where many of the clusters will eventually collide and merge. Many of them present a significant range in ages, hence possibly metallicities, and their merger could plausibly lead to clusters with a bimodal or even multiple distribution of populations.[22]

text: Observations of globular clusters show that these stellar formations arise primarily in regions of efficient star formation, and where the interstellar medium is at a higher density than in normal star-forming regions. Globular cluster formation is prevalent in starburst regions and in interacting galaxies.[24] Research indicates a correlation between the mass of a central supermassive black holes (SMBH) and the extent of the globular cluster systems of elliptical and lenticular galaxies. The mass of the SMBH in such a galaxy is often close to the combined mass of the galaxy's globular clusters.[25]

text: No known globular clusters display active star formation, which is consistent with the view that globular clusters are typically the oldest objects in the Galaxy, and were among the first collections of stars to form. Very large regions of star formation known as super star clusters, such as Westerlund 1 in the Milky Way, may be the precursors of globular clusters.[26]

text: Composition[edit]

text: Globular clusters are generally composed of hundreds of thousands of low-metal, old stars. The type of stars found in a globular cluster are similar to those in the bulge of a spiral galaxy but confined to a volume of only a few million cubic parsecs. They are free of gas and dust and it is presumed that all of the gas and dust was long ago turned into stars.

text: Globular clusters can contain a high density of stars; on average about 0.4 stars per cubic parsec, increasing to 100 or 1000 stars per cubic parsec in the core of the cluster.[28] The typical distance between stars in a globular cluster is about 1 light year,[29] but at its core, the separation is comparable to the size of the Solar System (100 to 1000 times closer than stars near the Solar System).[30]

text: However, they are not thought to be favorable locations for the survival of planetary systems. Planetary orbits are dynamically unstable within the cores of dense clusters because of the perturbations of passing stars. A planet orbiting at 1 astronomical unit around a star that is within the core of a dense cluster such as 47 Tucanae would only survive on the order of 108 years.[31] There is a planetary system orbiting a pulsar (PSR B1620−26) that belongs to the globular cluster M4, but these planets likely formed after the event that created the pulsar.[32]

text: Some globular clusters, like Omega Centauri in the Milky Way and G1 in M31, are extraordinarily massive, with several million solar masses (M☉) and multiple stellar populations. Both can be regarded as evidence that supermassive globular clusters are in fact the cores of dwarf galaxies that are consumed by the larger galaxies.[33] About a quarter of the globular cluster population in the Milky Way may have been accreted along with their host dwarf galaxy.[34]

text: Several globular clusters (like M15) have extremely massive cores which may harbor black holes,[35] although simulations suggest that a less massive black hole or central concentration of neutron stars or massive white dwarfs explain observations equally well.

text: Metallic content[edit]

text: Globular clusters normally consist of Population II stars, which have a low proportion of elements other than hydrogen and helium when compared to Population I stars such as the Sun. Astronomers refer to these heavier elements as metals and to the proportions of these elements as the metallicity. These elements are produced by stellar nucleosynthesis and then are recycled into the interstellar medium, where they enter the next generation of stars. Hence the proportion of metals can be an indication of the age of a star, with older stars typically having a lower metallicity.[37]

text: The Dutch astronomer Pieter Oosterhoff noticed that there appear to be two populations of globular clusters, which became known as Oosterhoff groups. The second group has a slightly longer period of RR Lyrae variable stars.[38] Both groups have weak lines of metallic elements. But the lines in the stars of Oosterhoff type I (OoI) cluster are not quite as weak as those in type II (OoII).[38] Hence type I are referred to as "metal-rich" (for example, Terzan 7[39]) while type II are "metal-poor" (for example, ESO 280-SC06[40]).

text: These two populations have been observed in many galaxies, especially massive elliptical galaxies. Both groups are nearly as old as the universe itself and are of similar ages, but differ in their metal abundances. Many scenarios have been suggested to explain these subpopulations, including violent gas-rich galaxy mergers, the accretion of dwarf galaxies, and multiple phases of star formation in a single galaxy. In the Milky Way, the metal-poor clusters are associated with the halo and the metal-rich clusters with the bulge.[41]

text: In the Milky Way it has been discovered that the large majority of the low metallicity clusters are aligned along a plane in the outer part of the galaxy's halo. This result argues in favor of the view that type II clusters in the galaxy were captured from a satellite galaxy, rather than being the oldest members of the Milky Way's globular cluster system as had been previously thought. The difference between the two cluster types would then be explained by a time delay between when the two galaxies formed their cluster systems.[42]

text: Exotic components[edit]

text: Globular clusters have a very high star density, and therefore close interactions and near-collisions of stars occur relatively often. Due to these chance encounters, some exotic classes of stars, such as blue stragglers, millisecond pulsars and low-mass X-ray binaries, are much more common in globular clusters. A blue straggler is formed from the merger of two stars, possibly as a result of an encounter with a binary system.[43] The resulting star has a higher temperature than comparable stars in the cluster with the same luminosity, and thus differs from the main sequence stars formed at the beginning of the cluster.[44]

text: Astronomers have searched for black holes within globular clusters since the 1970s. The resolution requirements for this task, however, are exacting, and it is only with the Hubble space telescope that the first confirmed discoveries have been made. In independent programs, a 4,000 M☉ intermediate-mass black hole has been suggested to exist based on HST observations in the globular cluster M15 and a 20,000 M☉ black hole in the Mayall II cluster in the Andromeda Galaxy.[45] Both x-ray and radio emissions from Mayall II appear to be consistent with an intermediate-mass black hole.[46]

text: These are of particular interest because they are the first black holes discovered that were intermediate in mass between the conventional stellar-mass black hole and the supermassive black holes discovered at the cores of galaxies. The mass of these intermediate mass black holes is proportional to the mass of the clusters, following a pattern previously discovered between supermassive black holes and their surrounding galaxies.

text: Claims of intermediate mass black holes have been met with some skepticism. The heaviest objects in globular clusters are expected to migrate to the cluster center due to mass segregation. As pointed out in two papers by Holger Baumgardt and collaborators, the mass-to-light ratio should rise sharply towards the center of the cluster, even without a black hole, in both M15[47] and Mayall II.[48]

text: Color-magnitude diagram[edit]

text: The Hertzsprung-Russell diagram (HR-diagram) is a graph of a large sample of stars that plots their visual absolute magnitude against their color index. The color index, B−V, is the difference between the magnitude of the star in blue light, or B, and the magnitude in visual light (green-yellow), or V. Large positive values indicate a red star with a cool surface temperature, while negative values imply a blue star with a hotter surface.

text: When the stars near the Sun are plotted on an HR diagram, it displays a distribution of stars of various masses, ages, and compositions. Many of the stars lie relatively close to a sloping curve with increasing absolute magnitude as the stars are hotter, known as main-sequence stars. However the diagram also typically includes stars that are in later stages of their evolution and have wandered away from this main-sequence curve.

text: As all the stars of a globular cluster are at approximately the same distance from us, their absolute magnitudes differ from their visual magnitude by about the same amount. The main-sequence stars in the globular cluster will fall along a line that is believed to be comparable to similar stars in the solar neighborhood. The accuracy of this assumption is confirmed by comparable results obtained by comparing the magnitudes of nearby short-period variables, such as RR Lyrae stars and cepheid variables, with those in the cluster.[50]

text: By matching up these curves on the HR diagram the absolute magnitude of main-sequence stars in the cluster can also be determined. This in turn provides a distance estimate to the cluster, based on the visual magnitude of the stars. The difference between the relative and absolute magnitude, the distance modulus, yields this estimate of the distance.[51]

text: When the stars of a particular globular cluster are plotted on an HR diagram, in many cases nearly all of the stars fall upon a relatively well defined curve. This differs from the HR diagram of stars near the Sun, which lumps together stars of differing ages and origins. The shape of the curve for a globular cluster is characteristic of a grouping of stars that were formed at approximately the same time and from the same materials, differing only in their initial mass. As the position of each star in the HR diagram varies with age, the shape of the curve for a globular cluster can be used to measure the overall age of the star population.[52]

text: However, the above-mentioned historic process of determining the age and distance to globular clusters is not as robust as first thought, since the morphology and luminosity of globular cluster stars in color-magnitude diagrams are influenced by numerous parameters, many of which are still being actively researched. Certain clusters even display populations that are absent from other globular clusters (e.g., blue hook stars), or feature multiple populations. The historical paradigm that all globular clusters consist of stars born at exactly the same time, or sharing exactly the same chemical abundance, has likewise been overturned (e.g., NGC 2808).[53] Further, the morphology of the cluster stars in a color-magnitude diagram, and that includes the brightnesses of distance indicators such as RR Lyrae variable members, can be influenced by observational biases. One such effect is called blending, and it arises because the cores of globular clusters are so dense that in low-resolution observations multiple (unresolved) stars may appear as a single target. Thus the brightness measured for that seemingly single star (e.g., an RR Lyrae variable) is erroneously too bright, given those unresolved stars contributed to the brightness determined.[54][55] Consequently, the computed distance is wrong, and more importantly, certain researchers have argued that the blending effect can introduce a systematic uncertainty into the cosmic distance ladder, and may bias the estimated age of the Universe and the Hubble constant.

text: The most massive main-sequence stars will also have the highest absolute magnitude, and these will be the first to evolve into the giant star stage. As the cluster ages, stars of successively lower masses will also enter the giant star stage. Thus the age of a single population cluster can be measured by looking for the stars that are just beginning to enter the giant star stage. This forms a "knee" in the HR diagram, bending to the upper right from the main-sequence line. The absolute magnitude at this bend is directly a function of the age of globular cluster, so an age scale can be plotted on an axis parallel to the magnitude.

text: In addition, globular clusters can be dated by looking at the temperatures of the coolest white dwarfs. Typical results for globular clusters are that they may be as old as 12.7 billion years.[56] This is in contrast to open clusters which are only tens of millions of years old.

text: The ages of globular clusters place a bound on the age limit of the entire universe. This lower limit has been a significant constraint in cosmology. Historically, astronomers were faced with age estimates of globular clusters that appeared older than cosmological models would allow. However, better measurements of cosmological parameters through deep sky surveys and satellites such as the Hubble Space Telescope appear to have resolved this issue.[57]

text: Evolutionary studies of globular clusters can also be used to determine changes due to the starting composition of the gas and dust that formed the cluster. That is, the evolutionary tracks change with changes in the abundance of heavy elements. The data obtained from studies of globular clusters are then used to study the evolution of the Milky Way as a whole.[58]

text: In globular clusters a few stars known as blue stragglers are observed, apparently continuing the main sequence in the direction of brighter, bluer stars. The origins of these stars is still unclear, but most models suggest that these stars are the result of mass transfer in multiple star systems.[43]

text: Morphology[edit]

text: In contrast to open clusters, most globular clusters remain gravitationally bound for time periods comparable to the life spans of the majority of their stars. However, a possible exception is when strong tidal interactions with other large masses result in the dispersal of the stars.

text: After they are formed, the stars in the globular cluster begin to interact gravitationally with each other. As a result, the velocity vectors of the stars are steadily modified, and the stars lose any history of their original velocity. The characteristic interval for this to occur is the relaxation time. This is related to the characteristic length of time a star needs to cross the cluster as well as the number of stellar masses in the system.[60] The value of the relaxation time varies by cluster, but the mean value is on the order of 109 years.

text:
Ellipticity of globular clusters

Galaxy
Ellipticity[61]

Milky Way
0.07±0.04

LMC
0.16±0.05

SMC
0.19±0.06

M31
0.09±0.04

text: Although globular clusters generally appear spherical in form, ellipticities can occur due to tidal interactions. Clusters within the Milky Way and the Andromeda Galaxy are typically oblate spheroids in shape, while those in the Large Magellanic Cloud are more elliptical.[62]

text: Radii[edit]

text: Astronomers characterize the morphology of a globular cluster by means of standard radii. These are the core radius (rc), the half-light radius (rh), and the tidal (or Jacobi) radius (rt). The overall luminosity of the cluster steadily decreases with distance from the core, and the core radius is the distance at which the apparent surface luminosity has dropped by half.[63] A comparable quantity is the half-light radius, or the distance from the core within which half the total luminosity from the cluster is received. This is typically larger than the core radius.

text: Note that the half-light radius includes stars in the outer part of the cluster that happen to lie along the line of sight, so theorists will also use the half-mass radius (rm)—the radius from the core that contains half the total mass of the cluster. When the half-mass radius of a cluster is small relative to the overall size, it has a dense core. An example of this is Messier 3 (M3), which has an overall visible dimension of about 18 arc minutes, but a half-mass radius of only 1.12 arc minutes.[64]

text: Almost all globular clusters have a half-light radius of less than 10 pc, although there are well-established globular clusters with very large radii (i.e. NGC 2419 (Rh = 18 pc) and Palomar 14 (Rh = 25 pc)).[65]

text: Finally the tidal radius, or Hill sphere, is the distance from the center of the globular cluster at which the external gravitation of the galaxy has more influence over the stars in the cluster than does the cluster itself. This is the distance at which the individual stars belonging to a cluster can be separated away by the galaxy. The tidal radius of M3 is about 40 arc minutes,[66] or about 113 pc[67] at the distance of 10.4 kpc.

text: Mass segregation, luminosity and core collapse[edit]

text: In measuring the luminosity curve of a given globular cluster as a function of distance from the core, most clusters in the Milky Way increase steadily in luminosity as this distance decreases, up to a certain distance from the core, then the luminosity levels off. Typically this distance is about 1–2 parsecs from the core. However about 20% of the globular clusters have undergone a process termed "core collapse". In this type of cluster, the luminosity continues to increase steadily all the way to the core region.[68] An example of a core-collapsed globular is M15.

text: Core-collapse is thought to occur when the more massive stars in a globular cluster encounter their less massive companions. Over time, dynamic processes cause individual stars to migrate from the center of the cluster to the outside. This results in a net loss of kinetic energy from the core region, leading the remaining stars grouped in the core region to occupy a more compact volume. When this gravothermal instability occurs, the central region of the cluster becomes densely crowded with stars and the surface brightness of the cluster forms a power-law cusp.[69] (Note that a core collapse is not the only mechanism that can cause such a luminosity distribution; a massive black hole at the core can also result in a luminosity cusp.)[70] Over a lengthy period of time this leads to a concentration of massive stars near the core, a phenomenon called mass segregation.

text: The dynamical heating effect of binary star systems works to prevent an initial core collapse of the cluster. When a star passes near a binary system, the orbit of the latter pair tends to contract, releasing energy. Only after the primordial supply of binaries is exhausted due to interactions can a deeper core collapse proceed.[71][72] In contrast, the effect of tidal shocks as a globular cluster repeatedly passes through the plane of a spiral galaxy tends to significantly accelerate core collapse.[73]

text: The different stages of core-collapse may be divided into three phases. During a globular cluster's adolescence, the process of core-collapse begins with stars near the core. However, the interactions between binary star systems prevents further collapse as the cluster approaches middle age. Finally, the central binaries are either disrupted or ejected, resulting in a tighter concentration at the core.

text: The interaction of stars in the collapsed core region causes tight binary systems to form. As other stars interact with these tight binaries, they increase the energy at the core, which causes the cluster to re-expand. As the mean time for a core collapse is typically less than the age of the galaxy, many of a galaxy's globular clusters may have passed through a core collapse stage, then re-expanded.[74]

text: The Hubble Space Telescope has been used to provide convincing observational evidence of this stellar mass-sorting process in globular clusters. Heavier stars slow down and crowd at the cluster's core, while lighter stars pick up speed and tend to spend more time at the cluster's periphery. The globular star cluster 47 Tucanae, which is made up of about 1 million stars, is one of the densest globular clusters in the Southern Hemisphere. This cluster was subjected to an intensive photographic survey, which allowed astronomers to track the motion of its stars. Precise velocities were obtained for nearly 15,000 stars in this cluster.[76]

text: A 2008 study by John Fregeau of 13 globular clusters in the Milky Way shows that three of them have an unusually large number of X-ray sources, or X-ray binaries, suggesting the clusters are middle-aged. Previously, these globular clusters had been classified as being in old age because they had very tight concentrations of stars in their centers, another test of age used by astronomers. The implication is that most globular clusters, including the other ten studied by Fregeau, are not in middle age as previously thought, but are actually in 'adolescence'.[77]

text: The overall luminosities of the globular clusters within the Milky Way and the Andromeda Galaxy can be modeled by means of a gaussian curve. This gaussian can be represented by means of an average magnitude Mv and a variance σ2. This distribution of globular cluster luminosities is called the Globular Cluster Luminosity Function (GCLF). (For the Milky Way, Mv = −7.20 ± 0.13, σ = 1.1 ± 0.1 magnitudes.)[78] The GCLF has also been used as a "standard candle" for measuring the distance to other galaxies, under the assumption that the globular clusters in remote galaxies follow the same principles as they do in the Milky Way.

text: N-body simulations[edit]

text: Computing the interactions between the stars within a globular cluster requires solving what is termed the N-body problem. That is, each of the stars within the cluster continually interacts with the other N−1 stars, where N is the total number of stars in the cluster. The naive CPU computational "cost" for a dynamic simulation increases in proportion to N 2 (each of N objects must interact pairwise with each of the other N objects), so the potential computing requirements to accurately simulate such a cluster can be enormous.[79] An efficient method of mathematically simulating the N-body dynamics of a globular cluster is done by subdividing into small volumes and velocity ranges, and using probabilities to describe the locations of the stars. The motions are then described by means of a formula called the Fokker–Planck equation. This can be solved by a simplified form of the equation, or by running Monte Carlo simulations and using random values. However the simulation becomes more difficult when the effects of binaries and the interaction with external gravitation forces (such as from the Milky Way galaxy) must also be included.[80]

text: The results of N-body simulations have shown that the stars can follow unusual paths through the cluster, often forming loops and often falling more directly toward the core than would a single star orbiting a central mass. In addition, due to interactions with other stars that result in an increase in velocity, some of the stars gain sufficient energy to escape the cluster. Over long periods of time this will result in a dissipation of the cluster, a process termed evaporation.[81] The typical time scale for the evaporation of a globular cluster is 1010 years.[60] In 2010 it became possible to directly compute, star by star, N-body simulations of a globular cluster over the course of its lifetime.[82]

text: Binary stars form a significant portion of the total population of stellar systems, with up to half of all stars occurring in binary systems. Numerical simulations of globular clusters have demonstrated that binaries can hinder and even reverse the process of core collapse in globular clusters. When a star in a cluster has a gravitational encounter with a binary system, a possible result is that the binary becomes more tightly bound and kinetic energy is added to the solitary star. When the massive stars in the cluster are sped up by this process, it reduces the contraction at the core and limits core collapse.[44]

text: The ultimate fate of a globular cluster must be either to accrete stars at its core, causing its steady contraction,[83] or gradual shedding of stars from its outer layers.[84]

text: Intermediate forms[edit]

text: The distinction between cluster types is not always clear-cut, and objects have been found that blur the lines between the categories. For example, BH 176 in the southern part of the Milky Way has properties of both an open and a globular cluster.[86]

text: In 2005, astronomers discovered a completely new type of star cluster in the Andromeda Galaxy, which is, in several ways, very similar to globular clusters. The new-found clusters contain hundreds of thousands of stars, a similar number to that found in globular clusters. The clusters share other characteristics with globular clusters such as stellar populations and metallicity. What distinguishes them from the globular clusters is that they are much larger – several hundred light-years across – and hundreds of times less dense. The distances between the stars are, therefore, much greater within the newly discovered extended clusters. Parametrically, these clusters lie somewhere between a globular cluster and a dwarf spheroidal galaxy.[87]

text: How these clusters are formed is not yet known, but their formation might well be related to that of globular clusters. Why M31 has such clusters, while the Milky Way does not, is not yet known. It is also unknown if any other galaxy contains these types of clusters, but it would be very unlikely that M31 is the sole galaxy with extended clusters.[87]

text: Tidal encounters[edit]

text: When a globular cluster has a close encounter with a large mass, such as the core region of a galaxy, it undergoes a tidal interaction. The difference in the pull of gravity between the part of the cluster nearest the mass and the pull on the furthest part of the cluster results in a tidal force. A "tidal shock" occurs whenever the orbit of a cluster takes it through the plane of a galaxy.

text: As a result of a tidal shock, streams of stars can be pulled away from the cluster halo, leaving only the core part of the cluster. These tidal interaction effects create tails of stars that can extend up to several degrees of arc away from the cluster.[88] These tails typically both precede and follow the cluster along its orbit. The tails can accumulate significant portions of the original mass of the cluster, and can form clumplike features.[89]

text: The globular cluster Palomar 5, for example, is near the apogalactic point of its orbit after passing through the Milky Way. Streams of stars extend outward toward the front and rear of the orbital path of this cluster, stretching out to distances of 13,000 light-years.[90] Tidal interactions have stripped away much of the mass from Palomar 5, and further interactions as it passes through the galactic core are expected to transform it into a long stream of stars orbiting the Milky Way halo.

text: Tidal interactions add kinetic energy into a globular cluster, dramatically increasing the evaporation rate and shrinking the size of the cluster.[60] Not only does tidal shock strip off the outer stars from a globular cluster, but the increased evaporation accelerates the process of core collapse. The same physical mechanism may be at work in dwarf spheroidal galaxies such as the Sagittarius Dwarf, which appears to be undergoing tidal disruption due to its proximity to the Milky Way.

text: Orbits[edit]

text: There are many globular clusters with a retrograde orbit round the Milky Way Galaxy.[91] A hypervelocity globular cluster was discovered around Messier 87 in 2014, having a velocity in excess of the escape velocity of M87.[92]

text: Planets[edit]

text: Astronomers are searching for exoplanets of stars in globular star clusters.[93]

text: In 2000, the results of a search for giant planets in the globular cluster 47 Tucanae were announced. The lack of any successful discoveries suggests that the abundance of elements (other than hydrogen or helium) necessary to build these planets may need to be at least 40% of the abundance in the Sun. Terrestrial planets are built from heavier elements such as silicon, iron and magnesium. The very low abundance of these elements in globular clusters means that the member stars have a far lower likelihood of hosting Earth-mass planets, when compared to stars in the neighborhood of the Sun. Hence the halo region of the Milky Way galaxy, including globular cluster members, are unlikely to host habitable terrestrial planets.[94]

text: In spite of the lower likelihood of giant planet formation, just such an object has been found in the globular cluster Messier 4. This planet was detected orbiting a pulsar in the binary star system PSR B1620-26. The eccentric and highly inclined orbit of the planet suggests it may have been formed around another star in the cluster, then was later "exchanged" into its current arrangement.[95] The likelihood of close encounters between stars in a globular cluster can disrupt planetary systems, some of which break loose to become free floating planets. Even close orbiting planets can become disrupted, potentially leading to orbital decay and an increase in orbital eccentricity and tidal effects.[96]


document_title: Rudd (surname)

question_text: where does the last name rudd come from

question_tokens: where does the last name rudd come from

root

text: Rudd (surname)

text: Rudd is a surname of English, Scottish, Welsh and Jewish origin.

tag: p

text: People with the surname[edit]

text:
Alyson Rudd, British journalist
Amber Rudd, British Conservative Party MP
Archibald Rudd, English footballer
Bevil Rudd (1894–1948), South African athlete, Olympic gold medalist
Billy Rudd (born 1941), English footballer
Charles Rudd (1844–1916), business associate of Cecil John Rhodes
Christopher Rudd (born 1963), English cricketer
Daniel Rudd (1854–1933), founder of the National Black Catholic Congress
Delaney Rudd (born 1962), American professional basketball player 1989-1993
Dwayne Rudd (born 1976), American professional football linebacker
Eldon Rudd (1920–2002), American politician, U.S. Representative from Arizona 1977-1987
George Thomas Rudd (c.1795-1847), English entomologist
Hughes Rudd (1921–1992), American television journalist
Jim Rudd (born 1943), American lobbyist and politician
Jim Rudd (rugby league) rugby league footballer who played in the 1920s
John Rudd (disambiguation), several people
Jonathan Rudd (disambiguation), several people
Kevin Rudd (born 1957), Australian politician, Prime Minister of Australia 2007-2010 and 2013
Mark William Rudd (born 1947), American educator and anti-war activist
Mike Rudd (born 1945), New Zealander musician
Nigel Rudd (born 1946), British fellow of the Institute of Chartered Accountants
Paul Rudd (born 1969), American film and stage actor
Paul Rudd (DJ) (born 1979), English music producer and DJ
Paul Ryan Rudd (1940–2010), American actor
Phil Rudd (born 1954), drummer of the Australian band AC/DC
Ricky Rudd (born 1956), American NASCAR driver
Roland Rudd (born 1961), English businessman and public relations executive, brother of Amber Rudd
Roswell Rudd (1935–2017), American jazz trombonist
Roy H. Rudd (1906–1997), New York politician
Steele Rudd, pseudonym of Arthur Hoey Davis (1868-1935), Australian author
Stephen A. Rudd (1874–1936), American politician, U.S. Representative from New York 1931-1936
Tony Rudd (1924-2017), English stockbroker and father of Amber Rudd and Roland Rudd
Van Thanh Rudd (born 1973), Australian artist and activist, nephew of Kevin Rudd
Xavier Rudd (born 1978), Australian folk musician

tag: ul

text: This page lists people with the surname Rudd. If an internal link intending to refer to a specific person led you to this page, you may wish to change that link by adding the person's given name(s) to the link.

tag: table

text: SurnamesSurnames of English origin

text: All set index articles


document_title: Houston

question_text: how many miles from houston to louisiana border

question_tokens: how many miles from houston to louisiana border

text: Houston

text: History[edit]

text:
Historical affiliations

Spanish Empire 1769–1821
Mexican Empire 1821–1823
United Mexican States 1823–1836
Republic of Texas 1836–1846
United States of America 1846–1860
Confederate States of America 1860–1865
United States of America 1865–present

tag: div

text: On August 30, 1836, two real estate entrepreneurs from New York, Augustus Chapman Allen and John Kirby Allen, purchased 6,642 acres (26.88 km2) of land along Buffalo Bayou with the intent of founding a city.[19][20] The Allen brothers decided to name the city after Sam Houston, the popular general at the Battle of San Jacinto,[20] who was elected President of Texas in September 1836. The great majority of slaves in Texas came with their owners from the older slave states. Sizable numbers, however, came through the domestic slave trade. New Orleans was the center of this trade in the Deep South, but slave dealers were in Houston. Thousands of enslaved African Americans lived near the city before the Civil War. Many of them near the city worked on sugar and cotton plantations, while most of those in the city limits had domestic and artisan jobs. Houston was granted incorporation on June 5, 1837, with James S. Holman becoming its first mayor.[12] In the same year, Houston became the county seat of Harrisburg County (now Harris County) and the temporary capital of the Republic of Texas.[21] In 1840, the community established a chamber of commerce in part to promote shipping and waterborne business at the newly created port on Buffalo Bayou.[22]

text: By 1860, Houston had emerged as a commercial and railroad hub for the export of cotton.[21] Railroad spurs from the Texas inland converged in Houston, where they met rail lines to the ports of Galveston and Beaumont. During the American Civil War, Houston served as a headquarters for General John Bankhead Magruder, who used the city as an organization point for the Battle of Galveston.[23] After the Civil War, Houston businessmen initiated efforts to widen the city's extensive system of bayous so the city could accept more commerce between downtown and the nearby port of Galveston. By 1890, Houston was the railroad center of Texas.

text: In 1900, after Galveston was struck by a devastating hurricane, efforts to make Houston into a viable deep-water port were accelerated.[24] The following year, the discovery of oil at the Spindletop oil field near Beaumont prompted the development of the Texas petroleum industry.[25] In 1902, President Theodore Roosevelt approved a $1-million improvement project for the Houston Ship Channel. By 1910, the city's population had reached 78,800, almost doubling from a decade before. African Americans formed a large part of the city's population, numbering 23,929 people, which was nearly one-third of the residents.[26]

text: President Woodrow Wilson opened the deep-water Port of Houston in 1914, seven years after digging began. By 1930, Houston had become Texas' most populous city and Harris County the most populous county.[27] In 1940, the Census Bureau reported Houston's population as 77.5% white and 22.4% black.[28]

text: When World War II started, tonnage levels at the port decreased and shipping activities were suspended; however, the war did provide economic benefits for the city. Petrochemical refineries and manufacturing plants were constructed along the ship channel because of the demand for petroleum and synthetic rubber products by the defense industry during the war.[29] Ellington Field, initially built during World War I, was revitalized as an advanced training center for bombardiers and navigators.[30] The Brown Shipbuilding Company was founded in 1942 to build ships for the U.S. Navy during World War II. Due to the boom in defense jobs, thousands of new workers migrated to the city, both blacks and whites competing for the higher-paying jobs. President Roosevelt had established a policy of nondiscrimination for defense contractors, and blacks gained some opportunities, especially in shipbuilding, although not without resistance from whites and increasing social tensions that erupted into occasional violence. Economic gains of blacks who entered defense industries continued in the postwar years.[31]

text: In 1945, the M.D. Anderson Foundation formed the Texas Medical Center. After the war, Houston's economy reverted to being primarily port-driven. In 1948, the city annexed several unincorporated areas, more than doubling its size. Houston proper began to spread across the region.[12][32]

text: In 1950, the availability of air conditioning provided impetus for many companies to relocate to Houston, where wages were lower than those in the North; this resulted in an economic boom and produced a key shift in the city's economy toward the energy sector.[33][34]

text: The increased production of the expanded shipbuilding industry during World War II spurred Houston's growth,[35] as did the establishment in 1961 of NASA's "Manned Spacecraft Center" (renamed the Lyndon B. Johnson Space Center in 1973). This was the stimulus for the development of the city's aerospace industry. The Astrodome, nicknamed the "Eighth Wonder of the World",[36] opened in 1965 as the world's first indoor domed sports stadium.

text: During the late 1970s, Houston had a population boom as people from the Rust Belt states moved to Texas in large numbers.[37] The new residents came for numerous employment opportunities in the petroleum industry, created as a result of the Arab oil embargo. With the increase in professional jobs, Houston has become a destination for many college-educated persons, including African Americans in a reverse Great Migration from northern areas.

text: In 1997, Houstonians elected Lee P. Brown as the city's first African American mayor.[38]

text: In June 2001, Tropical Storm Allison dumped up to 40 inches (1,000 mm) of rain on parts of Houston, causing what was then the worst flooding in the city's history. The storm cost billions of dollars in damage and killed 20 people in Texas.[39] By December of that same year, Houston-based energy company Enron collapsed into the third-largest ever U.S. bankruptcy during an investigation surrounding fabricated partnerships that were allegedly used to hide debt and inflate profits.

text: In August 2005, Houston became a shelter to more than 150,000 people from New Orleans, who evacuated from Hurricane Katrina.[40] One month later, about 2.5 million Houston-area residents evacuated when Hurricane Rita approached the Gulf Coast, leaving little damage to the Houston area. This was the largest urban evacuation in the history of the United States.[41][42] In September 2008, Houston was hit by Hurricane Ike. As many as 40% of residents refused to leave Galveston Island because they feared the type of traffic problems that had happened after Hurricane Rita.

text: During the floods in 2015 and 2016, parts of the city were covered in several inches of water.[43]

text: In 2017, Houston hosted Super Bowl LI.[44] This is the third Super Bowl for the city, with the previous games being held in 1974 and 2004.[45]

text: In late August 2017, Hurricane Harvey caused severe flooding in the Houston area, with some areas receiving over 50 inches (1,300 mm) of rain.[46] Winds reached up to 145 miles per hour, and rainfall exceeded 50 inches in several areas locally, breaking the national record for rainfall. The total estimated damage from the flash floods were initially estimated to exceed $50 billion U.S. dollars, and it is considered to be one of the worst natural disasters in the history of the United States.[47]

text: Geography[edit]

text: Houston is located 165 miles (266 km) east of Austin,[48] 112 miles (180 km) west of the Louisiana border, and 250 miles (400 km) south of Dallas.[49] According to the United States Census Bureau, the city has a total area of 656.3 square miles (1,700 km2); this comprises 634.0 square miles (1,642 km2) of land and 22.3 square miles (58 km2) covered by water.[50] The Piney Woods are north of Houston. Most of Houston is located on the gulf coastal plain, and its vegetation is classified as temperate grassland and forest. Much of the city was built on forested land, marshes, swamp, or prairie which resembles the Deep South, and are all still visible in surrounding areas. The flatness of the local terrain, when combined with urban sprawl, has made flooding a recurring problem for the city.[51] Downtown stands about 50 feet (15 m) above sea level,[52] and the highest point in far northwest Houston is about 125 feet (38 m) in elevation.[53][54] The city once relied on groundwater for its needs, but land subsidence forced the city to turn to ground-level water sources such as Lake Houston, Lake Conroe, and Lake Livingston.[12][55] The city owns surface water rights for 1.20 billion gallons of water a day in addition to 150 million gallons a day of groundwater.[56]

text: Houston has four major bayous passing through the city that accept water from the extensive drainage system. Buffalo Bayou runs through downtown and the Houston Ship Channel, and has three tributaries: White Oak Bayou, which runs through the Houston Heights community northwest of Downtown and then towards Downtown; Brays Bayou, which runs along the Texas Medical Center;[57] and Sims Bayou, which runs through the south of Houston and downtown Houston. The ship channel continues past Galveston and then into the Gulf of Mexico.[29]

text: Geology[edit]

text: Houston is flat marshy area where an extensive drainage system has been built. The adjoining prairie land drains into the city which is prone to flooding.[58] Underpinning Houston's land surface are unconsolidated clays, clay shales, and poorly cemented sands up to several miles deep. The region's geology developed from river deposits formed from the erosion of the Rocky Mountains. These sediments consist of a series of sands and clays deposited on decaying organic marine matter, that over time, transformed into oil and natural gas. Beneath the layers of sediment is a water-deposited layer of halite, a rock salt. The porous layers were compressed over time and forced upward. As it pushed upward, the salt dragged surrounding sediments into salt dome formations, often trapping oil and gas that seeped from the surrounding porous sands. The thick, rich, sometimes black, surface soil is suitable for rice farming in suburban outskirts where the city continues to grow.[59][60]

text: The Houston area has over 150 active faults (estimated to be 300 active faults) with an aggregate length of up to 310 miles (500 km),[61][62][63] including the Long Point–Eureka Heights fault system which runs through the center of the city. No significant historically recorded earthquakes have occurred in Houston, but researchers do not discount the possibility of such quakes having occurred in the deeper past, nor occurring in the future. Land in some areas southeast of Houston is sinking because water has been pumped out of the ground for many years. It may be associated with slip along the faults; however, the slippage is slow and not considered an earthquake, where stationary faults must slip suddenly enough to create seismic waves.[64] These faults also tend to move at a smooth rate in what is termed "fault creep",[55] which further reduces the risk of an earthquake.

text: Climate[edit]

text: Houston's climate is classified as humid subtropical (Cfa in the Köppen climate classification system), typical of the South. While not located in "Tornado Alley", like much of the rest of Texas, spring supercell thunderstorms sometimes bring tornadoes to the area. Prevailing winds are from the south and southeast during most of the year, which bring heat and moisture from the nearby Gulf of Mexico.[65]

text: During the summer, temperatures commonly reach over 90 °F (32 °C), with an average of 106.5 days per year, including a majority from June to September, with a high of 90 °F (32 °C) or above and 4.6 days at or over 100 °F (38 °C).[66] However, humidity usually yields a higher heat index. Summer mornings average over 90% relative humidity.[67] Although sea breezes are present, they don't offer substantial relief, except in the southeastern areas of the city closer to the Gulf.[68] To cope with the strong humidity and heat, people use air conditioning in nearly every vehicle and building. In 1980, Houston was described as the "most air-conditioned place on earth".[69] Officially, the hottest temperature ever recorded in Houston is 109 °F (43 °C), which was reached both on September 4, 2000, and August 28, 2011.[66]

text: Houston has mild winters. In January, the normal mean temperature at Intercontinental Airport is 53.1 °F (11.7 °C), while that station has an average of 13 days with a low at or below freezing. Snowfall is rare. Recent snow events in Houston include a storm on December 24, 2004 when 1.0 in (2.5 cm) of snow accumulated in parts of the metro area.[70] Falls of at least 1.0 in (25 mm) on both December 10, 2008, and December 4, 2009, marked the first time measurable snowfall had occurred in two consecutive years in the city's recorded history. The coldest temperature officially recorded in Houston was 5 °F (−15 °C) on January 18, 1930.[66] Houston has historically received an ample amount of rainfall, averaging about 49.8 in (1,260 mm) annually per 1981–2010 normals. Localized flooding often occurs, owing to the extremely flat topography and widespread typical clay-silt prairie soils, which do not drain quickly.

text: Houston has excessive ozone levels and is routinely ranked among the most ozone-polluted cities in the United States.[71] Ground-level ozone, or smog, is Houston's predominant air pollution problem, with the American Lung Association rating the metropolitan area's ozone level twelfth on the "Most Polluted Cities by Ozone" in 2017, after major cities such as Los Angeles, Phoenix, New York City and Denver.[72] The industries located along the ship channel are a major cause of the city's air pollution.[73]

text: As of August 27, 2017, Houston and its surrounding areas received intense flash flooding due to Hurricane Harvey.[74]

text:
[show]Climate data for Houston (Intercontinental Airport), 1981–2010 normals,[a] extremes 1888–present[b]

Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Year

Record high °F (°C)
84
(29)
91
(33)
96
(36)
95
(35)
99
(37)
107
(42)
105
(41)
109
(43)
109
(43)
99
(37)
89
(32)
85
(29)
109
(43)

Mean maximum °F (°C)
78.4
(25.8)
80.8
(27.1)
84.8
(29.3)
88.9
(31.6)
93.6
(34.2)
97.0
(36.1)
98.4
(36.9)
100.4
(38)
96.9
(36.1)
91.8
(33.2)
85.0
(29.4)
80.0
(26.7)
101.0
(38.3)

Average high °F (°C)
62.9
(17.2)
66.3
(19.1)
73.0
(22.8)
79.6
(26.4)
86.3
(30.2)
91.4
(33)
93.7
(34.3)
94.5
(34.7)
89.7
(32.1)
82.0
(27.8)
72.5
(22.5)
64.3
(17.9)
79.7
(26.5)

Daily mean °F (°C)
53.1
(11.7)
56.4
(13.6)
62.7
(17.1)
69.5
(20.8)
76.9
(24.9)
82.4
(28)
84.4
(29.1)
84.6
(29.2)
79.8
(26.6)
71.5
(21.9)
62.3
(16.8)
54.4
(12.4)
69.9
(21.1)

Average low °F (°C)
43.2
(6.2)
46.5
(8.1)
52.5
(11.4)
59.4
(15.2)
67.6
(19.8)
73.5
(23.1)
75.1
(23.9)
74.8
(23.8)
69.8
(21)
60.9
(16.1)
52.1
(11.2)
44.6
(7)
60.0
(15.6)

Mean minimum °F (°C)
26.7
(−2.9)
29.5
(−1.4)
34.0
(1.1)
42.0
(5.6)
53.3
(11.8)
65.2
(18.4)
69.4
(20.8)
68.6
(20.3)
55.7
(13.2)
43.4
(6.3)
34.5
(1.4)
27.5
(−2.5)
23.5
(−4.7)

Record low °F (°C)
5
(−15)
6
(−14)
21
(−6)
31
(−1)
42
(6)
52
(11)
62
(17)
54
(12)
45
(7)
29
(−2)
19
(−7)
7
(−14)
5
(−15)

Average precipitation inches (mm)
3.38
(85.9)
3.20
(81.3)
3.41
(86.6)
3.31
(84.1)
5.09
(129.3)
5.93
(150.6)
3.79
(96.3)
3.76
(95.5)
4.12
(104.6)
5.70
(144.8)
4.34
(110.2)
3.74
(95)
49.77
(1,264.2)

Average precipitation days (≥ 0.01 in)
9.6
9.2
8.8
6.8
8.0
10.6
9.1
8.3
8.0
7.9
8.2
9.5
104.0

Average relative humidity (%)
74.7
73.4
72.7
73.1
75.0
74.6
74.4
75.1
76.8
75.4
76.0
75.5
74.7

Mean monthly sunshine hours
143.4
155.0
192.5
209.8
249.2
281.3
293.9
270.5
236.5
228.8
168.3
148.7
2,577.9

Percent possible sunshine
44
50
52
54
59
67
68
66
64
64
53
47
58

Source: NOAA (relative humidity 1969–1990, sun 1961–1990)[66][76][77]

text:
[show]Climate data for Houston (William P. Hobby Airport), 1981–2010 normals, extremes 1941–present

Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Year

Record high °F (°C)
85
(29)
87
(31)
96
(36)
94
(34)
100
(38)
105
(41)
104
(40)
106
(41)
108
(42)
96
(36)
90
(32)
84
(29)
108
(42)

Average high °F (°C)
63.0
(17.2)
66.0
(18.9)
72.4
(22.4)
78.8
(26)
85.4
(29.7)
90.1
(32.3)
92.1
(33.4)
92.6
(33.7)
88.4
(31.3)
81.2
(27.3)
72.4
(22.4)
64.5
(18.1)
78.9
(26.1)

Daily mean °F (°C)
54.1
(12.3)
57.3
(14.1)
63.3
(17.4)
69.8
(21)
77.0
(25)
82.0
(27.8)
83.8
(28.8)
84.2
(29)
80.1
(26.7)
72.1
(22.3)
63.2
(17.3)
55.6
(13.1)
70.3
(21.3)

Average low °F (°C)
45.1
(7.3)
48.5
(9.2)
54.3
(12.4)
60.9
(16.1)
68.7
(20.4)
73.9
(23.3)
75.5
(24.2)
75.7
(24.3)
71.7
(22.1)
63.1
(17.3)
53.9
(12.2)
46.7
(8.2)
61.5
(16.4)

Record low °F (°C)
10
(−12)
14
(−10)
22
(−6)
36
(2)
44
(7)
56
(13)
64
(18)
64
(18)
50
(10)
33
(1)
25
(−4)
9
(−13)
9
(−13)

Average precipitation inches (mm)
3.87
(98.3)
3.21
(81.5)
3.20
(81.3)
3.25
(82.6)
4.75
(120.7)
7.10
(180.3)
4.66
(118.4)
5.06
(128.5)
5.21
(132.3)
5.99
(152.1)
4.32
(109.7)
4.03
(102.4)
54.65
(1,388.1)

Average precipitation days (≥ 0.01 in)
9.2
9.0
8.0
7.1
7.3
9.9
9.1
9.8
9.1
7.6
8.5
9.1
103.7

Source: NOAA (sun 1961–1990)[66]

text: Cityscape[edit]

text: Houston was incorporated in 1837 under the ward system of representation. The ward designation is the progenitor of the 11 current-day geographically oriented Houston City Council districts. Locations in Houston are generally classified as either being inside or outside the Interstate 610 Loop. The inside encompasses the central business district and many residential neighborhoods that antedate World War II. More recently, high-density residential areas have been developed within the loop. The city's outlying areas, suburbs, and enclaves are located outside the loop. Beltway 8 encircles the city another 5 miles (8.0 km) farther out.

text: Though Houston is the largest city in the United States without formal zoning regulations, it has developed similarly to other Sun Belt cities because the city's land use regulations and legal covenants have played a similar role.[78][79] Regulations include mandatory lot size for single-family houses and requirements that parking be available to tenants and customers. Such restrictions have had mixed results. Though some[79] have blamed the city's low density, urban sprawl, and lack of pedestrian-friendliness on these policies, the city's land use has also been credited with having significant affordable housing, sparing Houston the worst effects of the 2008 real estate crisis.[80] The city issued 42,697 building permits in 2008 and was ranked first in the list of healthiest housing markets for 2009.[81]

text: Voters rejected efforts to have separate residential and commercial land-use districts in 1948, 1962, and 1993. Consequently, rather than a single central business district as the center of the city's employment, multiple districts have grown throughout the city in addition to downtown which include Uptown, Texas Medical Center, Midtown, Greenway Plaza, Memorial City, Energy Corridor, Westchase, and Greenspoint.

text: Architecture[edit]

text: Houston has the fourth-tallest skyline in North America (after New York City, Chicago, and Toronto) and 12th-tallest in the world, as of 2014[update].[82][83][84] A seven-mile (11 km) system of tunnels and skywalks links downtown buildings containing shops and restaurants, enabling pedestrians to avoid summer heat and rain while walking between buildings.

text: In the 1960s, Downtown Houston consisted of a collection of midrise office structures. Downtown was on the threshold of an energy industry–led boom in 1970. A succession of skyscrapers was built throughout the 1970s—many by real estate developer Gerald D. Hines—culminating with Houston's tallest skyscraper, the 75-floor, 1,002-foot (305 m)-tall JPMorgan Chase Tower (formerly the Texas Commerce Tower), completed in 1982. It is the tallest structure in Texas, 15th tallest building in the United States, and the 85th-tallest skyscraper in the world, based on highest architectural feature. In 1983, the 71-floor, 992-foot (302 m)-tall Wells Fargo Plaza (formerly Allied Bank Plaza) was completed, becoming the second-tallest building in Houston and Texas. Based on highest architectural feature, it is the 17th-tallest in the United States and the 95th-tallest in the world. In 2007, downtown Houston had over 43 million square feet (4,000,000 m²) of office space.[85]

text: Centered on Post Oak Boulevard and Westheimer Road, the Uptown District boomed during the 1970s and early 1980s when a collection of midrise office buildings, hotels, and retail developments appeared along Interstate 610 West. Uptown became one of the most prominent instances of an edge city. The tallest building in Uptown is the 64-floor, 901-foot (275 m)-tall, Philip Johnson and John Burgee designed landmark Williams Tower (known as the Transco Tower until 1999). At the time of construction, it was believed to be the world's tallest skyscraper outside a central business district. The new 20-story Skanska building[86] and BBVA Compass Plaza[87] are the newest office buildings built in Uptown after 30 years. The Uptown District is also home to buildings designed by noted architects I. M. Pei, César Pelli, and Philip Johnson. In the late 1990s and early 2000s, a mini-boom of midrise and highrise residential tower construction occurred, with several over 30 stories tall.[88][89][90] Since 2000 more than 30 high-rise buildings have gone up in Houston; all told, 72 high-rises tower over the city, which adds up to about 8,300 units.[91] In 2002, Uptown had more than 23 million square feet (2,100,000 m²) of office space with 16 million square feet (1,500,000 m²) of class A office space.[92]

text:
The Niels Esperson Building stood as the tallest building in Houston from 1927 to 1929.

The JPMorgan Chase Tower is the tallest building in Texas and the tallest 5-sided building in the world.

The Williams Tower is the tallest building in the US outside a central business district.

The Bank of America Center by Philip Johnson is an example of postmodern architecture.

JPMorgan Chase Tower in Houston, Texas is the tallest composite building in the world.

text: Demographics[edit]

text:
Historical population

Census
Pop.

%±

1850
2,396

—

1860
4,845

102.2%

1870
9,332

92.6%

1880
16,513

77.0%

1890
27,557

66.9%

1900
44,633

62.0%

1910
78,800

76.6%

1920
138,276

75.5%

1930
292,352

111.4%

1940
384,514

31.5%

1950
596,163

55.0%

1960
938,219

57.4%

1970
1,232,802

31.4%

1980
1,595,138

29.4%

1990
1,630,553

2.2%

2000
1,953,631

19.8%

2010
2,100,263

7.5%

Est. 2016
2,303,482
[93]
9.7%

U.S. Decennial Census
2011 estimate

text: Greater Houston is the most ethnically diverse metropolitan area in the country. In the Houston region, non-Hispanic whites make up 38 percent of the population, Hispanics 36 percent, African-Americans 17 percent and Asians 9 percent.[19]

text: Houston is multicultural, in part because of its many academic institutions and strong industries, as well as being a major port city. Over 90 languages are spoken in the city.[94] It has among the youngest populations in the nation,[95][96][97] partly due to an influx of immigrants into Texas.[98] An estimated 400,000 illegal immigrants reside in the Houston area.[99]

text: According to the 2010 U.S. Census, whites made up 51% of Houston's population; 26% of the total population was non-Hispanic Whites. Blacks or African Americans made up 25% of Houston's population. American Indians made up 0.7% of the population. Asians made up 6% (1.7% Vietnamese, 1.3% Chinese, 1.3% Indian, 0.9% Pakistani, 0.4% Filipino, 0.3% Korean, 0.1% Japanese), while Pacific Islanders made up 0.1%. Individuals from some other race made up 15.2% of the city's population, of which 0.2% were non-Hispanic. Individuals from two or more races made up 3.3% of the city. At the 2000 Census, 1,953,631 people inhabited the city, and the population density was 3,371.7 people per square mile (1,301.8/km²). The racial makeup of the city was 49.3% White, 25.3% African American, 6.3% Asian, 0.7% American Indian, 0.1% Pacific Islander, 16.5% from some other race, and 3.1% from two or more races. In addition, Hispanics made up 37.4% of Houston's population, while non-Hispanic Whites made up 30.8%,[100] down from 62.4% in 1970.[28]

text: The median income for a household in the city was $37,000, and for a family was $40,000. Males had a median income of $32,000 versus $27,000 for females. The per capita income was $20,000. About 19% of the population and 16% of families were below the poverty line. Of the total population, 26% of those under the age of 18 and 14% of those 65 and older were living below the poverty line.

text: According to a 2014 study by the Pew Research Center, 73% of the population of the city identified themselves as Christians, with 50% professing attendance at a variety of churches that could be considered Protestant, and 19% professing Roman Catholic beliefs.[101][102] while 20% claim no religious affiliation. The same study says that other religions (including Judaism, Buddhism, Islam, and Hinduism) collectively make up about 7% of the population

text:
[hide]Racial composition
2010[103]
1990[28]
1970[28]

White
50.5%
52.7%
73.4%

—Non-Hispanic whites
25.6%
40.6%
62.4%[104]

Black or African American
23.7%
28.1%
25.7%,[100]

Hispanic or Latino (of any race)
43.7%
27.6%
11.3%[104]

Asian
6.0%
4.1%
0.4%

text: Economy[edit]

text:
Top publicly traded companies
in Houston for 2013
with Texas and U.S. ranks

Texas

Corporation

US

2

Phillips 66

4

5

ConocoPhillips

45

7

Enterprise Products Partners

64

8

Sysco

65

9

Plains All American Pipeline

77

11

Halliburton

106

14

Baker Hughes

135

18

National Oilwell Varco

144

21

Apache Corporation

167

22

Marathon Oil

174

23

Waste Management

200

29

EOG Resources

233

30

Kinder Morgan

265

34

Cameron International

310

35

KBR

334

37

Group 1 Automotive

343

38

CenterPoint Energy

344

39

Enbridge Energy Partners

38

42

Quanta Services

413

44

FMC Technologies

417

46

Targa Resources

435

48

MRC Global

451

49

Calpine

459

51

Spectra Energy

451

Notes

Rankings for fiscal year ended January 31, 2013

Energy and oil (21 companies)

Source: Fortune[105]

text: Houston is recognized worldwide for its energy industry—particularly for oil and natural gas—as well as for biomedical research and aeronautics. Renewable energy sources—wind and solar—are also growing economic bases in the city.[106][107] The Houston Ship Channel is also a large part of Houston's economic base. Because of these strengths, Houston is designated as a global city by the Globalization and World Cities Study Group and Network and global management consulting firm A.T. Kearney.[15] The Houston area is the top U.S. market for exports, surpassing New York City in 2013, according to data released by the U.S. Department of Commerce's International Trade Administration. In 2012, the Houston–The Woodlands–Sugar Land area recorded $110.3 billion in merchandise exports.[108] Petroleum products, chemicals, and oil and gas extraction equipment accounted for roughly two-thirds of the metropolitan area's exports last year. The top three destinations for exports were Mexico, Canada, and Brazil.[109]

text: The Houston area is a leading center for building oilfield equipment.[110] Much of its success as a petrochemical complex is due to its busy ship channel, the Port of Houston.[111] In the United States, the port ranks first in international commerce and 10th among the largest ports in the world.[16][112] Unlike most places, high oil and gasoline prices are beneficial for Houston's economy, as many of its residents are employed in the energy industry.[113] Houston is the beginning or end point of numerous oil, gas, and products pipelines:[114]

text: The Houston–The Woodlands–Sugar Land MSA's gross domestic product (GDP) in 2012 was $489 billion, making it the fourth-largest of any metropolitan area in the United States and larger than Austria's, Venezuela's, or South Africa's GDP.[115] Only 26 countries other than the United States have a gross domestic product exceeding Houston's regional gross area product (GAP).[116] In 2010, mining (which consists almost entirely of exploration and production of oil and gas in Houston) accounted for 26.3% of Houston's GAP up sharply in response to high energy prices and a decreased worldwide surplus of oil production capacity, followed by engineering services, health services, and manufacturing.[117]

text: The University of Houston System's annual impact on the Houston area's economy equates to that of a major corporation: $1.1 billion in new funds attracted annually to the Houston area, $3.13 billion in total economic benefit, and 24,000 local jobs generated.[119][120] This is in addition to the 12,500 new graduates the U.H. System produces every year who enter the workforce in Houston and throughout the state of Texas. These degree-holders tend to stay in Houston. After five years, 80.5% of graduates are still living and working in the region.[120]

text: In 2006, the Houston metropolitan area ranked first in Texas and third in the U.S. within the category of "Best Places for Business and Careers" by Forbes magazine.[121] Foreign governments have established 92 consular offices in Houston's metropolitan area, the third-highest in the nation.[122] Forty foreign governments maintain trade and commercial offices here with 23 active foreign chambers of commerce and trade associations.[123] Twenty-five foreign banks representing 13 nations operate in Houston, providing financial assistance to the international community.[124]

text: In 2008, Houston received top ranking on Kiplinger's Personal Finance Best Cities of 2008 list, which ranks cities on their local economy, employment opportunities, reasonable living costs, and quality of life.[125] The city ranked fourth for highest increase in the local technological innovation over the preceding 15 years, according to Forbes magazine.[126] In the same year, the city ranked second on the annual Fortune 500 list of company headquarters,[127] first for Forbes magazine's Best Cities for College Graduates,[128] and first on their list of Best Cities to Buy a Home.[129] In 2010, the city was rated the best city for shopping, according to Forbes.[130]

text: In 2012, the city was ranked number one for paycheck worth by Forbes and in late May 2013, Houston was identified as America's top city for employment creation.[131][132]

text: In 2013, Houston was identified as the number one U.S. city for job creation by the U.S. Bureau of Statistics after it was not only the first major city to regain all the jobs lost in the preceding economic downturn, but also after the crash, more than two jobs were added for every one lost. Economist and vice president of research at the Greater Houston Partnership Patrick Jankowski attributed Houston's success to the ability of the region's real estate and energy industries to learn from historical mistakes. Furthermore, Jankowski stated that "more than 100 foreign-owned companies relocated, expanded or started new businesses in Houston" between 2008 and 2010, and this openness to external business boosted job creation during a period when domestic demand was problematically low.[132] Also in 2013, Houston again appeared on Forbes' list of Best Places for Business and Careers.[133]

text: Culture[edit]

text: Located in the American South, Houston is a diverse city with a large and growing international community.[134] The metropolitan area is home to an estimated 1.1 million (21.4 percent) residents who were born outside the United States, with nearly two-thirds of the area's foreign-born population from south of the United States–Mexico border.[135] Additionally, more than one in five foreign-born residents are from Asia.[135] The city is home to the nation's third-largest concentration of consular offices, representing 86 countries.[136]

text: Many annual events celebrate the diverse cultures of Houston. The largest and longest-running is the annual Houston Livestock Show and Rodeo, held over 20 days from early to late March, and is the largest annual livestock show and rodeo in the world.[137] Another large celebration is the annual night-time Houston Pride Parade, held at the end of June.[138] Other annual events include the Houston Greek Festival,[139] Art Car Parade, the Houston Auto Show, the Houston International Festival,[140] and the Bayou City Art Festival, which is considered to be one of the top five art festivals in the United States.[141][142]

text: Houston received the official nickname of "Space City" in 1967 because it is the location of NASA's Lyndon B. Johnson Space Center. Other nicknames often used by locals include "Bayou City", "Clutch City", "Magnolia City", and "H-Town".

text: Arts and theater[edit]

text: The Houston Theater District, located downtown, is home to nine major performing arts organizations and six performance halls. It is the second-largest concentration of theater seats in a downtown area in the United States.[143][144][145] Houston is one of few United States cities with permanent, professional, resident companies in all major performing arts disciplines: opera (Houston Grand Opera), ballet (Houston Ballet), music (Houston Symphony Orchestra), and theater (The Alley Theatre, Theatre Under the Stars).[18][146] Houston is also home to folk artists, art groups and various small progressive arts organizations.[147] Houston attracts many touring Broadway acts, concerts, shows, and exhibitions for a variety of interests.[148] Facilities in the Theater District include the Jones Hall—home of the Houston Symphony Orchestra and Society for the Performing Arts—and the Hobby Center for the Performing Arts.

text: The Museum District's cultural institutions and exhibits attract more than 7 million visitors a year.[149][150] Notable facilities include The Museum of Fine Arts, Houston Museum of Natural Science, the Contemporary Arts Museum Houston, the Station Museum of Contemporary Art, Holocaust Museum Houston, and the Houston Zoo.[151][152][153] Located near the Museum District are The Menil Collection, Rothko Chapel, and the Byzantine Fresco Chapel Museum.

text: Bayou Bend is a 14-acre (5.7 ha) facility of the Museum of Fine Arts that houses one of America's most prominent collections of decorative art, paintings, and furniture. Bayou Bend is the former home of Houston philanthropist Ima Hogg.[154]

text: The National Museum of Funeral History is located in Houston near the George Bush Intercontinental Airport. The museum houses the original Popemobile used by Pope John Paul II in the 1980s along with numerous hearses, embalming displays, and information on famous funerals.

text: Venues across Houston regularly host local and touring rock, blues, country, dubstep, and Tejano musical acts. While Houston has never been widely known for its music scene,[155] Houston hip-hop has become a significant, independent music scene that is influential nationwide.[156]

text: Tourism and recreation[edit]

text: The Theater District is a 17-block area in the center of downtown Houston that is home to the Bayou Place entertainment complex, restaurants, movies, plazas, and parks. Bayou Place is a large multilevel building containing full-service restaurants, bars, live music, billiards, and Sundance Cinema. The Bayou Music Center stages live concerts, stage plays, and stand-up comedy. Space Center Houston is the official visitors' center of NASA's Lyndon B. Johnson Space Center. The Space Center has many interactive exhibits including moon rocks, a shuttle simulator, and presentations about the history of NASA's manned space flight program. Other tourist attractions include the Galleria (Texas's largest shopping mall, located in the Uptown District), Old Market Square, the Downtown Aquarium, and Sam Houston Race Park.

text: Of worthy mention are Houston's current Chinatown and the Mahatma Gandhi District. Both areas offer a picturesque view of Houston's multicultural makeup. Restaurants, bakeries, traditional-clothing boutiques, and specialty shops can be found in both areas.

text: Houston is home to 337 parks, including Hermann Park, Terry Hershey Park, Lake Houston Park, Memorial Park, Tranquility Park, Sesquicentennial Park, Discovery Green, and Sam Houston Park. Within Hermann Park are the Houston Zoo and the Houston Museum of Natural Science. Sam Houston Park contains restored and reconstructed homes which were originally built between 1823 and 1905.[157] A proposal has been made to open the city's first botanic garden at Herman Brown Park.[158]

text: Of the 10 most populous U.S. cities, Houston has the most total area of parks and green space, 56,405 acres (228 km2).[159] The city also has over 200 additional green spaces—totaling over 19,600 acres (79 km2) that are managed by the city—including the Houston Arboretum and Nature Center. The Lee and Joe Jamail Skatepark is a public skatepark owned and operated by the city of Houston, and is one of the largest skateparks in Texas consisting of a 30,000-ft2 (2,800 m2)in-ground facility. The Gerald D. Hines Waterwall Park—located in the Uptown District of the city—serves as a popular tourist attraction and for weddings and various celebrations. A 2011 study by Walk Score ranked Houston the 23rd most walkable of the 50 largest cities in the United States.[160] Wet'n'Wild SplashTown is a water park located north of Houston.

text: The Bayport Cruise Terminal on the Houston Ship Channel is port of call for both Princess Cruises and Norwegian Cruise Line.[161]

text: Sports[edit]

text: Houston has sports teams for every major professional league except the National Hockey League. The Houston Astros are a Major League Baseball expansion team formed in 1962 (known as the "Colt .45s" until 1965) that made one World Series appearance in 2005.[162] The Houston Rockets are a National Basketball Association franchise based in the city since 1971. They have won two NBA Championships: in 1994 and 1995 under star players Hakeem Olajuwon, Otis Thorpe, Clyde Drexler, Vernon Maxwell, and Kenny Smith.[163] The Houston Texans are a National Football League expansion team formed in 2002. The Houston Dynamo is a Major League Soccer franchise that has been based in Houston since 2006, winning two MLS Cup titles in 2006 and 2007. The Houston Dash team plays in the National Women's Soccer League.[164] The Scrap Yard Dawgs, a women's professional softball team, are expected to play in the National Pro Fastpitch from 2016.[165][166]

text: Minute Maid Park (home of the Astros) and Toyota Center (home of the Rockets), are located in downtown Houston. Houston has the NFL's first retractable-roof stadium with natural grass, NRG Stadium (home of the Texans).[167] Minute Maid Park is also a retractable-roof stadium. Toyota Center also has the largest screen for an indoor arena in the United States built to coincide with the arena's hosting of the 2013 NBA All-Star Game.[168] BBVA Compass Stadium is a soccer-specific stadium for the Houston Dynamo, the Texas Southern Tigers football team, and Houston Dash, located in East Downtown. In addition, NRG Astrodome was the first indoor stadium in the world, built in 1965.[169] Other sports facilities include Hofheinz Pavilion (Houston Cougars basketball), Rice Stadium (Rice Owls football), and Reliant Arena. TDECU Stadium is where the University of Houston Houston Cougars football team plays.[170] Houston has hosted several major sports events: the 1968, 1986 and 2004 Major League Baseball All-Star Games; the 1989, 2006 and 2013 NBA All-Star Games; Super Bowl VIII and Super Bowl XXXVIII, as well as hosting the 2005 World Series and 1981, 1986, 1994 and 1995 NBA Finals, winning the latter two. NRG Stadium hosted Super Bowl LI on February 5, 2017.[171]

text: The city has hosted several major professional and college sporting events, including the annual Houston Open golf tournament. Houston hosts the annual Houston College Classic baseball tournament every February and the Texas Bowl in December.[172]

text: The Grand Prix of Houston, an annual auto race on the IndyCar Series circuit is held on a 1.7-mile temporary street circuit in Reliant Park. The October 2013 event was held using a tweaked version of the 2006–2007 course.[173] The event has a 5-year race contract through 2017 with IndyCar.[174] In motorcycling, the Astrodome hosted an AMA Supercross Championship round from 1974 to 2003 and the NRG Stadium since 2003.

text: Government and politics[edit]

text: The city of Houston has a strong mayoral form of municipal government.[175] Houston is a home rule city and all municipal elections in the state of Texas are nonpartisan.[175][176] The city's elected officials are the mayor, city controller and 16 members of the Houston City Council.[177] The current mayor of Houston is Sylvester Turner, a Democrat elected on a nonpartisan ballot. Houston's mayor serves as the city's chief administrator, executive officer, and official representative, and is responsible for the general management of the city and for seeing that all laws and ordinances are enforced.[178]

text: The original city council line-up of 14 members (nine district-based and five at-large positions) was based on a U.S. Justice Department mandate which took effect in 1979.[179] At-large council members represent the entire city.[177] Under the city charter, once the population in the city limits exceeded 2.1 million residents, two additional districts were to be added.[180] The city of Houston's official 2010 census count was 600 shy of the required number; however, as the city was expected to grow beyond 2.1 million shortly thereafter, the two additional districts were added for, and the positions filled during, the August 2011 elections.

text: The city controller is elected independently of the mayor and council. The controller's duties are to certify available funds prior to committing such funds and processing disbursements. The city's fiscal year begins on July 1 and ends on June 30. Chris Brown is the city controller, serving his first term as of January 2016.

text: As the result of a 2015 referendum in Houston, a mayor is elected for a four-year term, and can be elected to as many as two consecutive terms.[181] The term limits were spearheaded in 1991 by conservative political activist Clymer Wright.[182] During 1991–2015, the city controller and city council members were subjected to a two-year, three-term limitation – the 2015 referendum amended term limits to two four-year terms. As of 2017 some councilmembers who served two terms and won a final term will have served eight years in office, whereas a freshman councilmember who won a position in 2013 can serve up to two additional terms under the previous term limit law – a select few will have at least 10 years of incumbency once their term expires.

text: Houston is considered to be a politically divided city whose balance of power often sways between Republicans and Democrats. Much of the city's wealthier areas vote Republican while the city's working class and minority areas vote Democratic. According to the 2005 Houston Area Survey, 68 percent of non-Hispanic whites in Harris County are declared or favor Republicans while 89 percent of non-Hispanic blacks in the area are declared or favor Democrats. About 62 percent of Hispanics (of any race) in the area are declared or favor Democrats.[183] The city has often been known to be the most politically diverse city in Texas, a state known for being generally conservative.[183] As a result, the city is often a contested area in statewide elections.[183] In 2009, Houston became the first US city with a population over 1 million citizens to elect a gay mayor, by electing Annise Parker.

text: Crime[edit]

text: Houston had 302 homicides in 2016, and is one of three cities (along with Chicago and Baltimore) driving an increase in the nation's overall murder rate. Officials predicted there would be 323 homicides in 2016, which proved to be false.[184]

text: Houston's murder rate ranked 46th of U.S. cities with a population over 250,000 in 2005 (per capita rate of 16.3 murders per 100,000 population).[185] In 2010, the city's murder rate (per capita rate of 11.8 murders per 100,000 population) was ranked sixth among U.S. cities with a population of over 750,000 (behind New York City, Chicago, Detroit, Dallas, and Philadelphia)[186] according to the FBI.

text: Murders fell by 37 percent from January to June 2011, compared with the same period in 2010. Houston's total crime rate including violent and nonviolent crimes decreased by 11 percent.[187]

text: Houston is a significant hub for trafficking of cocaine, cannabis, heroin, MDMA, and methamphetamine due to its size and proximity to major illegal drug exporting nations.[188] Houston is one of the country's largest hubs for human trafficking.[189]

text: In the early 1970s, Houston, Pasadena and several coastal towns were the site of the Houston mass murders, which at the time were the deadliest case of serial killing in American history.[190][191]

text: Education[edit]

text: Seventeen school districts exist within the city of Houston. The Houston independent School District (HISD) is the seventh-largest school district in the United States and the largest in Texas.[192] HISD has 112 campuses that serve as magnet or vanguard schools—specializing in such disciplines as health professions, visual and performing arts, and the sciences. There are also many charter schools that are run separately from school districts. In addition, some public school districts also have their own charter schools.

text: The Houston area encompasses more than 300 private schools,[193][194][195] many of which are accredited by Texas Private School Accreditation Commission recognized agencies. The Houston Area independent schools offer education from a variety of different religious as well as secular viewpoints.[196] The Houston area Catholic schools are operated by the Archdiocese of Galveston-Houston.

text: Colleges and universities[edit]

text: Four distinct state universities are located in Houston. The University of Houston is a nationally recognized Tier One research university, and is the flagship institution of the University of Houston System.[197][198][199] The third-largest university in Texas, the University of Houston has nearly 44,000 students on its 667-acre campus in southeast Houston.[200] The University of Houston–Clear Lake and the University of Houston–Downtown are stand-alone universities; they are not branch campuses of the University of Houston. Located in the historic community of Third Ward is Texas Southern University, one of the largest and most comprehensive historically black universities in the United States. Texas Southern University is also the only public independent university in Houston.

text: Several private institutions of higher learning—ranging from liberal arts colleges, such as the University of St. Thomas, Houston's only Catholic university, to Rice University, the nationally recognized research university—are located within the city. Rice, with a total enrollment of slightly more than 6,000 students, has a number of distinguished graduate programs and research institutes, such as the James A. Baker Institute for Public Policy.[201] Houston Baptist University, affiliated with the Baptist General Convention of Texas, offers bachelor's and graduate degrees. It was founded in 1960 and is located in the Sharpstown area in Southwest Houston.

text: Three community college districts exist with campuses in and around Houston. The Houston Community College System serves most of Houston. The northwestern through northeastern parts of the city are served by various campuses of the Lone Star College System, while the southeastern portion of Houston is served by San Jacinto College, and a northeastern portion is served by Lee College.[202] The Houston Community College and Lone Star College systems are within the 10 largest institutions of higher learning in the United States.

text: Media[edit]

text: The primary network-affiliated television stations are KPRC-TV (NBC), KHOU-TV (CBS), KTRK-TV (ABC), KRIV (Fox), KIAH (The CW), and KTXH (MyNetworkTV). KTRK-TV, KRIV and KTXH operate as owned-and-operated stations of their networks.

text: The Houston–The Woodlands–Sugar Land metropolitan area is served by one public television station and one public radio station. KUHT (HoustonPBS) is a PBS member station and is the first public television station in the United States. Houston Public Radio is listener-funded and comprises one NPR member station, KUHF (KUHF News). The University of Houston System owns and holds broadcasting licenses to KUHT and KUHF. The stations broadcast from the Melcher Center for Public Broadcasting, located on the campus of the University of Houston.

text: Houston is served by the Houston Chronicle, its only major daily newspaper with wide distribution. The Hearst Corporation, which owns and operates the Houston Chronicle, bought the assets of the Houston Post—its long-time rival and main competition—when Houston Post ceased operations in 1995. The Houston Post was owned by the family of former Lieutenant Governor Bill Hobby of Houston. The only other major publication to serve the city is the Houston Press—a free alternative weekly with a weekly readership of more than 300,000.[203]

text: Infrastructure[edit]

text: Healthcare[edit]

text: Houston is the seat of the internationally renowned Texas Medical Center, which contains the world's largest concentration of research and healthcare institutions.[204] All 49 member institutions of the Texas Medical Center are non-profit organizations. They provide patient and preventive care, research, education, and local, national, and international community well-being. Employing more than 73,600 people, institutions at the medical center include 13 hospitals and two specialty institutions, two medical schools, four nursing schools, and schools of dentistry, public health, pharmacy, and virtually all health-related careers. It is where one of the first—and still the largest—air emergency service, Life Flight, was created, and a very successful inter-institutional transplant program was developed. More heart surgeries are performed at the Texas Medical Center than anywhere else in the world.[205]

text: Some of the academic and research health institutions at the center include MD Anderson Cancer Center, Baylor College of Medicine, UT Health Science Center, Memorial Hermann Hospital, Houston Methodist Hospital, Texas Children's Hospital, and University of Houston College of Pharmacy.

text: The Baylor College of Medicine has annually been considered within the top ten medical schools in the nation; likewise, the MD Anderson Cancer Center has consistently ranked as one of the top two U.S. hospitals specializing in cancer care by U.S. News & World Report since 1990.[206][207] The Menninger Clinic, a renowned psychiatric treatment center, is affiliated with Baylor College of Medicine and the Houston Methodist Hospital System.[208] With hospital locations nationwide and headquarters in Houston, the Triumph Healthcare hospital system is the third largest long term acute care provider nationally.[209]

text: Transportation[edit]

text: Highways[edit]

text: This section needs to be updated. Please update this article to reflect recent events or newly available information. (March 2016)

text: 71.7% of residents drive alone to work.[210] Houston's freeway system comprises 739.3 miles (1,189.8 km) of freeways and expressways in a ten-county metropolitan area.[211] However, the Texas Transportation Institute's annual Urban Mobility Report found that Houston had the fourth-worst congestion in the country with commuters spending an average of 58 hours in traffic in 2009.[212]

text: Houston's highway system has a hub-and-spoke freeway structure serviced by multiple loops. The innermost loop is Interstate 610, which encircles downtown, the medical center, and many core neighborhoods with around a 8-mile (13 km) diameter. Beltway 8 and its freeway core, the Sam Houston Tollway, form the middle loop at a diameter of roughly 23 miles (37 km). A proposed highway project, State Highway 99 (Grand Parkway), will form a third loop outside Houston, totaling 180 miles in length and making an almost-complete circumference, with the exception of crossing the ship channel. As of June 2014, two of eleven segments of State Highway 99 have been completed to the west of Houston, and three northern segments totaling 38 miles. In addition to the Sam Houston Tollway loop mentioned above, the Harris County Toll Road Authority currently operates four spoke tollways: The Katy Managed Lanes of Interstate 10, the Hardy Toll Road, the Westpark Tollway, and the Fort Bend Parkway Extension. Other spoke roads either planned or under construction include Crosby Freeway, and the future Alvin Freeway.

text: Houston's freeway system is monitored by Houston TranStar—a partnership of four government agencies that are responsible for providing transportation and emergency management services to the region.[213]

text: Transit systems[edit]

text: The Metropolitan Transit Authority of Harris County (METRO) provides public transportation in the form of buses, light rail, and lift vans.

text: METRO began light rail service on January 1, 2004, with the inaugural track ("Red Line") running about 8 miles (13 km) from the University of Houston–Downtown (UHD), which traverses through the Texas Medical Center and terminates at NRG Park. METRO is currently in the design phase of a 10-year expansion plan that will add five more lines.[214] and expand the current Red Line. Amtrak, the national passenger rail system, provides service three times a week to Houston via the Sunset Limited (Los Angeles–New Orleans), which stops at the Houston Amtrak Station on the north side of the downtown area. The station saw 14,891 boardings and alightings in fiscal year 2008.[215] In 2012, there was a 25 percent increase in ridership to 20,327 passengers embarking from the Houston Amtrak Station.[216]

text: Cycling[edit]

text: Houston has the largest number of bike commuters in Texas with over 160 miles of dedicated bikeways.[217] The city is currently in the process of expanding its on and off street bikeway network.[218] A bicycle sharing system known as Houston B-Cycle currently operates 29 different stations in downtown and neighboring areas.[219]

text: Airports[edit]

text: Houston is served by three airports, two of which are commercial that served 52 million passengers in 2007 and managed by the Houston Airport System.[220] The Federal Aviation Administration and the state of Texas selected the "Houston Airport System as Airport of the Year" for 2005,[221] largely because of its multi-year, $3.1 billion airport improvement program for both major airports in Houston.

text: The primary city airport is George Bush Intercontinental Airport (IAH), the tenth-busiest in the United States for total passengers, and twenty eighth-busiest worldwide. Bush Intercontinental currently ranks fourth in the United States for non-stop domestic and international service with 182 destinations.[222] In 2006, the United States Department of Transportation named IAH the fastest-growing of the top ten airports in the United States.[223] The Houston Air Route Traffic Control Center stands on the George Bush Intercontinental Airport grounds.

text: Houston was the headquarters of Continental Airlines until its 2010 merger with United Airlines with headquarters in Chicago; regulatory approval for the merger was granted in October of that year. Bush Intercontinental became United Airlines' largest airline hub.[224] The airline retained a significant operational presence in Houston while offering more than 700 daily departures from the city.[225][226] In early 2007, Bush Intercontinental Airport was named a model "port of entry" for international travelers by U.S. Customs and Border Protection.[227]

text: The second-largest commercial airport is William P. Hobby Airport (named Houston International Airport until 1967) which operates primarily short- to medium-haul domestic flights. However, in 2015 Southwest Airlines launched service from a new international terminal at Hobby airport to several destinations in Mexico, Central America, and the Caribbean. These were the first international flights flown from Hobby since 1969.[228] Houston's aviation history is showcased in the 1940 Air Terminal Museum located in the old terminal building on the west side of the airport. Hobby Airport has been recognized with two awards for being one of the top five performing airports in the world and for customer service by Airports Council International.[229]

text: Houston's third municipal airport is Ellington Airport (a former U.S. Air Force base) used by military, government, NASA, and general aviation sectors.[230]

text: Sister cities[edit]

text: The Houston Office of Protocol and International Affairs is the city's liaison to Houston's sister cities and to the national governing organization, Sister Cities International. Through their official city-to-city relationships, these volunteer associations promote people-to-people diplomacy and encourage citizens to develop mutual trust and understanding through commercial, cultural, educational, and humanitarian exchanges.[231][232]

text:
Abu Dhabi (United Arab Emirates) – 2001
Baku (Azerbaijan) – 1976
Basrah (Iraq) – 2015[233]
Chiba (Japan) – 1973
Grampian Region, Aberdeen (United Kingdom) – 1979[234]
Guayaquil (Ecuador) – 1987
Huelva (Spain) – 1969
Istanbul (Turkey) – 1986
Karachi (Pakistan) – 2009
Leipzig (Germany) – 1993
Luanda (Angola) – 2003
Nice (France) – 1973
Perth (Australia) – 1983
Shenzhen (China) – 1986
Stavanger (Norway) – 1980
Taipei (Taiwan) – 1963
Tampico (Mexico) – 2003
Tyumen (Russia) – 1995
Wuhan (China) – 2016