Arizona State University
Arizona State University is a public metropolitan research university on five campuses across the Phoenix metropolitan area, four regional learning centers throughout Arizona. ASU is one of the largest public universities by enrollment in the U. S; as of fall 2018, the university had about 80,000 students attending classes across its metro campuses, including 66,000-plus undergraduates and more than 12,000 postgraduates. The university is organized into 17 colleges, featuring more than 170 cross-discipline centers and institutes. ASU offers 350 degree options for undergraduates students, as well as more than 400 graduate degree and certificate programs. ASU has nearly 600 ASU scholar-athletes across 26 varsity-level sports; the Arizona State Sun Devils compete in the Pac-12 Conference and have won 59 Pac-10/Pac-12 championships dating to 1979, have captured 24 NCAA championships dating to its first title in 1965. In addition to its athletic program, the university is home to over 1,100 registered student organizations.
ASU's charter, approved by the board of regents in 2014, is based on the "New American University" model created by ASU President Michael M. Crow upon his appointment as the institution's 16th president in 2002, it defines ASU as "a comprehensive public research university, measured not by whom it excludes, but rather by whom it includes and how they succeed. Since 2005, ASU has been ranked among the top research universities in the U. S. public and private, based on research output, development, research expenditures, number of awarded patents and awarded research grant proposals. The 2019 university ratings by U. S. News & World Report rank ASU No. 1 among the Most Innovative Schools in America for the fourth year in a row. U. S. News & World Report shows 84% of the student applications get accepted. A diverse faculty of more than 4,400 scholars includes 4 Nobel laureates, 6 Pulitzer Prize winners, 4 MacArthur Fellows Program "Genius Grant" members and 19 National Academy of Sciences members.
Additionally, among the faculty are 180 Fulbright Program American Scholars, 72 National Endowment for the Humanities fellows, 38 American Council of Learned Societies fellows, 36 members of the Guggenheim Fellowship, 21 members of the American Academy of Arts and Sciences, 9 National Academy of Engineering members and 3 National Academy of Medicine members. The National Academies has bestowed "highly prestigious" recognition on 227 ASU faculty members. Arizona State University was established as the Territorial Normal School at Tempe on March 12, 1885, when the 13th Arizona Territorial Legislature passed an act to create a normal school to train teachers for the Arizona Territory; the campus consisted of a single, four-room schoolhouse on a 20-acre plot donated by Tempe residents George and Martha Wilson. Classes began with 33 students on February 8, 1886; the curriculum evolved over the years and the name was changed several times. In 1923, the school stopped offering high school courses and added a high school diploma to the admissions requirements.
In 1925, the school became the Tempe State Teachers College and offered four-year Bachelor of Education degrees as well as two-year teaching certificates. In 1929, the 9th Arizona State Legislature authorized Bachelor of Arts in Education degrees as well, the school was renamed the Arizona State Teachers College. Under the 30-year tenure of president Arthur John Matthews, the school was given all-college student status; the first dormitories built in the state were constructed under his supervision in 1902. Of the 18 buildings constructed while Matthews was president, six are still in use. Matthews envisioned an "evergreen campus," with many shrubs brought to the campus, implemented the planting of 110 Mexican Fan Palms on what is now known as Palm Walk, a century-old landmark of the Tempe campus. During the Great Depression, Ralph Waldo Swetman was hired to succeed President Matthews, coming to Arizona State Teachers College in 1930 from Humboldt State Teachers College where he had served as president.
He served a three-year term. During his tenure, enrollment at the college doubled. Matthews conceived of a self-supported summer session at the school at Arizona State Teachers College, a first for the school. In 1933, Grady Gammage president of Arizona State Teachers College at Flagstaff, became president of Arizona State Teachers College at Tempe, beginning a tenure that would last for nearly 28 years, second only to Swetman's 30 years at the college's helm. Like President Arthur John Matthews before him, Gammage oversaw the construction of several buildings on the Tempe campus, he guided the development of the university's graduate programs. During his presidency, the school's name was changed to Arizona State College in 1945, to Arizona State University in 1958. At the time, two other names were considered: Tempe University and State University at Tempe. Among Gammage's greatest achievements in Tempe was the Frank Lloyd Wright-desig
X-rays make up X-radiation, a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 100 eV to 100 keV. X-ray wavelengths are shorter than those of UV rays and longer than those of gamma rays. In many languages, X-radiation is referred to with terms meaning Röntgen radiation, after the German scientist Wilhelm Röntgen who discovered these on November 8, 1895, credited as its discoverer, who named it X-radiation to signify an unknown type of radiation. Spelling of X-ray in the English language includes the variants x-ray, X ray. Before their discovery in 1895 X-rays were just a type of unidentified radiation emanating from experimental discharge tubes, they were noticed by scientists investigating cathode rays produced by such tubes, which are energetic electron beams that were first observed in 1869. Many of the early Crookes tubes undoubtedly radiated X-rays, because early researchers noticed effects that were attributable to them, as detailed below.
Crookes tubes created free electrons by ionization of the residual air in the tube by a high DC voltage of anywhere between a few kilovolts and 100 kV. This voltage accelerated the electrons coming from the cathode to a high enough velocity that they created X-rays when they struck the anode or the glass wall of the tube; the earliest experimenter thought to have produced. In 1785 he presented a paper to the Royal Society of London describing the effects of passing electrical currents through a evacuated glass tube, producing a glow created by X-rays; this work was further explored by his assistant Michael Faraday. When Stanford University physics professor Fernando Sanford created his "electric photography" he unknowingly generated and detected X-rays. From 1886 to 1888 he had studied in the Hermann Helmholtz laboratory in Berlin, where he became familiar with the cathode rays generated in vacuum tubes when a voltage was applied across separate electrodes, as studied by Heinrich Hertz and Philipp Lenard.
His letter of January 6, 1893 to The Physical Review was duly published and an article entitled Without Lens or Light, Photographs Taken With Plate and Object in Darkness appeared in the San Francisco Examiner. Starting in 1888, Philipp Lenard, a student of Heinrich Hertz, conducted experiments to see whether cathode rays could pass out of the Crookes tube into the air, he built a Crookes tube with a "window" in the end made of thin aluminum, facing the cathode so the cathode rays would strike it. He found that something came through, that would cause fluorescence, he measured the penetrating power of these rays through various materials. It has been suggested that at least some of these "Lenard rays" were X-rays. In 1889 Ukrainian-born Ivan Pulyui, a lecturer in experimental physics at the Prague Polytechnic who since 1877 had been constructing various designs of gas-filled tubes to investigate their properties, published a paper on how sealed photographic plates became dark when exposed to the emanations from the tubes.
Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his announcement, it was formed on the basis of the electromagnetic theory of light. However, he did not work with actual X-rays. In 1894 Nikola Tesla noticed damaged film in his lab that seemed to be associated with Crookes tube experiments and began investigating this radiant energy of "invisible" kinds. After Röntgen identified the X-ray, Tesla began making X-ray images of his own using high voltages and tubes of his own design, as well as Crookes tubes. On November 8, 1895, German physics professor Wilhelm Röntgen stumbled on X-rays while experimenting with Lenard tubes and Crookes tubes and began studying them, he wrote an initial report "On a new kind of ray: A preliminary communication" and on December 28, 1895 submitted it to Würzburg's Physical-Medical Society journal. This was the first paper written on X-rays. Röntgen referred to the radiation as "X"; the name stuck.
They are still referred to as such in many languages, including German, Danish, Swedish, Estonian, Japanese, Georgian and Norwegian. Röntgen received the first Nobel Prize in Physics for his discovery. There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a reconstruction by his biographers: Röntgen was investigating cathode rays from a Crookes tube which he had wrapped in black cardboard so that the visible light from the tube would not interfere, using a fluorescent screen painted with barium platinocyanide, he noticed a faint green glow from the screen, about 1 meter away. Röntgen realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow, he found they could pass through books and papers on his desk. Röntgen threw himself into investigating these unknown rays systematically. Two months after his initial discovery, he published his paper. Röntgen discovered their medical use when he made a picture of his wife's hand on a photographic plate formed due to X-rays.
The photograph of his wife's hand was the first photograph of a human body part using X-rays. When she saw the picture, she said "I have seen my death."The discovery of X-rays stimul
Speed of light
The speed of light in vacuum denoted c, is a universal physical constant important in many areas of physics. Its exact value is 299,792,458 metres per second, it is exact because by international agreement a metre is defined as the length of the path travelled by light in vacuum during a time interval of 1/299792458 second. According to special relativity, c is the maximum speed at which all conventional matter and hence all known forms of information in the universe can travel. Though this speed is most associated with light, it is in fact the speed at which all massless particles and changes of the associated fields travel in vacuum; such particles and waves travel at c regardless of the motion of the source or the inertial reference frame of the observer. In the special and general theories of relativity, c interrelates space and time, appears in the famous equation of mass–energy equivalence E = mc2; the speed at which light propagates through transparent materials, such as glass or air, is less than c.
The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material. For example, for visible light the refractive index of glass is around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200,000 km/s. For many practical purposes and other electromagnetic waves will appear to propagate instantaneously, but for long distances and sensitive measurements, their finite speed has noticeable effects. In communicating with distant space probes, it can take minutes to hours for a message to get from Earth to the spacecraft, or vice versa; the light seen from stars left them many years ago, allowing the study of the history of the universe by looking at distant objects. The finite speed of light limits the theoretical maximum speed of computers, since information must be sent within the computer from chip to chip; the speed of light can be used with time of flight measurements to measure large distances to high precision. Ole Rømer first demonstrated in 1676 that light travels at a finite speed by studying the apparent motion of Jupiter's moon Io.
In 1865, James Clerk Maxwell proposed that light was an electromagnetic wave, therefore travelled at the speed c appearing in his theory of electromagnetism. In 1905, Albert Einstein postulated that the speed of light c with respect to any inertial frame is a constant and is independent of the motion of the light source, he explored the consequences of that postulate by deriving the theory of relativity and in doing so showed that the parameter c had relevance outside of the context of light and electromagnetism. After centuries of precise measurements, in 1975 the speed of light was known to be 299792458 m/s with a measurement uncertainty of 4 parts per billion. In 1983, the metre was redefined in the International System of Units as the distance travelled by light in vacuum in 1/299792458 of a second; the speed of light in vacuum is denoted by a lowercase c, for "constant" or the Latin celeritas. In 1856, Wilhelm Eduard Weber and Rudolf Kohlrausch had used c for a different constant shown to equal √2 times the speed of light in vacuum.
The symbol V was used as an alternative symbol for the speed of light, introduced by James Clerk Maxwell in 1865. In 1894, Paul Drude redefined c with its modern meaning. Einstein used V in his original German-language papers on special relativity in 1905, but in 1907 he switched to c, which by had become the standard symbol for the speed of light. Sometimes c is used for the speed of waves in any material medium, c0 for the speed of light in vacuum; this subscripted notation, endorsed in official SI literature, has the same form as other related constants: namely, μ0 for the vacuum permeability or magnetic constant, ε0 for the vacuum permittivity or electric constant, Z0 for the impedance of free space. This article uses c for the speed of light in vacuum. Since 1983, the metre has been defined in the International System of Units as the distance light travels in vacuum in 1⁄299792458 of a second; this definition fixes the speed of light in vacuum at 299,792,458 m/s. As a dimensional physical constant, the numerical value of c is different for different unit systems.
In branches of physics in which c appears such as in relativity, it is common to use systems of natural units of measurement or the geometrized unit system where c = 1. Using these units, c does not appear explicitly because multiplication or division by 1 does not affect the result; the speed at which light waves propagate in vacuum is independent both of the motion of the wave source and of the inertial frame of reference of the observer. This invariance of the speed of light was postulated by Einstein in 1905, after being motivated by Maxwell's theory of electromagnetism and the lack of evidence for the luminiferous aether, it is only possible to verify experimentally that the two-way speed of light is frame-independent, because it is impossible to measure the one-way speed of light without some convention as to how clocks at the source and at the detector should be synchronized. However
Cosmic Origins Spectrograph
The Cosmic Origins Spectrograph is a science instrument, installed on the Hubble Space Telescope during Servicing Mission 4 in May 2009. It is designed for ultraviolet spectroscopy of faint point sources with a resolving power of ≈1,550–24,000. Science goals include the study of the origins of large scale structure in the universe, the formation and evolution of galaxies, the origin of stellar and planetary systems and the cold interstellar medium. COS was developed and built by the Center for Astrophysics and Space Astronomy at the University of Colorado at Boulder and the Ball Aerospace and Technologies Corporation in Boulder, Colorado. COS is installed into the axial instrument bay occupied by the Corrective Optics Space Telescope Axial Replacement instrument, is intended to complement the Space Telescope Imaging Spectrograph, repaired during the same mission. While STIS operates across a wider wavelength range, COS is many times more sensitive in the UV; the Cosmic Origins Spectrograph is an ultraviolet spectrograph, optimized for high sensitivity and moderate spectral resolution of compact objects.
COS has two principal channels, one for Far Ultraviolet spectroscopy covering 90–205 nm and one for Near Ultraviolet spectroscopy spanning 170–320 nm. The FUV channel can work with one of three diffraction gratings, the NUV with one of four, providing both low and medium resolution spectra. In addition, COS has a narrow field of view NUV imaging mode intended for target acquisition. One key technique for achieving high sensitivity in the FUV is minimizing the number of optics; this is done because FUV reflection and transmission efficiencies are quite low compared to what is common at visible wavelengths. In accomplishing this, the COS FUV channel uses a single optic to diffract the light from HST, correct for the Hubble spherical aberration, focus the diffracted light onto the FUV detector and correct for astigmatism typical of this sort of instrument. Since aberration correction is performed after the light passes into the instrument, the entrance to the spectrograph must be an extended aperture, rather than the traditional narrow entrance slit, in order to allow the entire aberrated HST image from a point source to enter the instrument.
The 2.5 arc second diameter entrance aperture allows ≈ 95% of the light from compact sources to enter COS, yielding high sensitivity at the design resolution for compact sources. Post launch performance matched expectations. Instrument sensitivity is close to pre-launch calibration values, detector background is exceptionally low. FUV resolution is lower than pre-launch predictions due to mid-frequency polishing errors on the HST primary mirror, while NUV resolution exceeds pre-launch values in all modes. Thanks to the minimal number of reflections, the G140L mode, G130M central wavelength settings added after 2010, can observe light at wavelengths down to ~90nm, shorter, despite the low reflectivity of the MgF2 coated optics at these wavelengths; the Cosmic Origins Spectrograph is designed to enable the observation of faint, point-like UV targets at moderate spectral resolution, allowing COS to observe hot stars in the Milky Way and to observe the absorption features in the spectra of active galactic nuclei.
Observations are planned of extended objects. Spectroscopy provides a wealth of information about distant astronomical objects, unobtainable through imaging: Spectroscopy lies at the heart of astrophysical inference. Our understanding of the origin and evolution of the cosmos critically depends on our ability to make quantitative measurements of physical parameters such as the total mass, motions and composition of matter in the Universe. Detailed information on all of these properties can be gleaned from high-quality spectroscopic data. For distant objects, some of these properties can only be measured through spectroscopy. Ultraviolet spectroscopy provides some of the most fundamental diagnostic data necessary for discerning the physical characteristics of planets, stars and interstellar and intergalactic matter; the UV offers access to spectral features that provide key diagnostic information that cannot be obtained at other wavelengths. Obtaining absorption spectra of interstellar and intergalactic gas forms the basis of many of the COS science programs.
These spectra will address questions such as how was the Cosmic Web formed, how much mass can be found in interstellar and intergalactic gas, what is the composition and temperature of this gas. In general, COS will address questions such as: What is the large-scale structure of matter in the Universe? How did galaxies form out of the intergalactic medium? What types of galactic halos and outflowing winds do star-forming galaxies produce? How were the chemical elements for life created in massive stars and supernovae? How do stars and planetary systems form from dust grains in molecular clouds? What is the composition of planetary atmospheres and comets in our Solar System? Some specific programs include the following: Large-Scale Structure of Baryonic Matter: With its high FUV spectroscopic sensitivity, COS uniquely suited for exploring the Lyman-alpha forest; this is the ‘forest’ of absorption spectra seen in the spectra of distant galaxies and quasars caused by intergalactic gas clouds, which may contain the majority of baryonic matter in the universe.
A supernova is an event that occurs upon the death of certain types of stars. Supernovae are more energetic than novae. In Latin, nova means "new", referring astronomically to what appears to be a temporary new bright star. Adding the prefix "super-" distinguishes supernovae from ordinary novae, which are far less luminous; the word supernova was coined by Walter Baade and Fritz Zwicky in 1931. Only three Milky Way, naked-eye supernova events have been observed during the last thousand years, though many have been seen in other galaxies; the most recent directly observed supernova in the Milky Way was Kepler's Supernova in 1604, but two more recent supernova remnants have been found. Statistical observations of supernovae in other galaxies suggest they occur on average about three times every century in the Milky Way, that any galactic supernova would certainly be observable with modern astronomical telescopes. Supernovae may expel much, if not all, of the material away from a star at velocities up to 30,000 km/s or 10% of the speed of light.
This drives an expanding and fast-moving shock wave into the surrounding interstellar medium, in turn, sweeping up an expanding shell of gas and dust, observed as a supernova remnant. Supernovae create and eject the bulk of the chemical elements produced by nucleosynthesis. Supernovae play a significant role in enriching the interstellar medium with the heavier atomic mass chemical elements. Furthermore, the expanding shock waves from supernovae can trigger the formation of new stars. Supernova remnants are expected to accelerate a large fraction of galactic primary cosmic rays, but direct evidence for cosmic ray production was found only in a few of them so far, they are potentially strong galactic sources of gravitational waves. Theoretical studies indicate that most supernovae are triggered by one of two basic mechanisms: the sudden re-ignition of nuclear fusion in a degenerate star or the sudden gravitational collapse of a massive star's core. In the first instance, a degenerate white dwarf may accumulate sufficient material from a binary companion, either through accretion or via a merger, to raise its core temperature enough to trigger runaway nuclear fusion disrupting the star.
In the second case, the core of a massive star may undergo sudden gravitational collapse, releasing gravitational potential energy as a supernova. While some observed supernovae are more complex than these two simplified theories, the astrophysical collapse mechanics have been established and accepted by most astronomers for some time. Owing to the wide range of astrophysical consequences of these events, astronomers now deem supernova research, across the fields of stellar and galactic evolution, as an important area for investigation; the earliest recorded supernova HB9 was viewed by Indians 5,000-years ago and recorded in the oldest Star chart. The SN 185, was viewed by Chinese astronomers in 185 AD; the brightest recorded supernova was SN 1006, which occurred in 1006 AD and was described by observers across China, Iraq and Europe. The observed supernova SN 1054 produced the Crab Nebula. Supernovae SN 1572 and SN 1604, the latest to be observed with the naked eye in the Milky Way galaxy, had notable effects on the development of astronomy in Europe because they were used to argue against the Aristotelian idea that the universe beyond the Moon and planets was static and unchanging.
Johannes Kepler began observing SN 1604 at its peak on October 17, 1604, continued to make estimates of its brightness until it faded from naked eye view a year later. It was the second supernova to be observed in a generation. There is some evidence that the youngest galactic supernova, G1.9+0.3, occurred in the late 19th century more than Cassiopeia A from around 1680. Neither supernova was noted at the time. In the case of G1.9+0.3, high extinction along the plane of the galaxy could have dimmed the event sufficiently to go unnoticed. The situation for Cassiopeia A is less clear. Infrared light echos have been detected showing that it was a type IIb supernova and was not in a region of high extinction. Before the development of the telescope, only five supernovae were seen in the last millennium. Compared to a star's entire history, the visual appearance of a galactic supernova is brief spanning several months, so that the chances of observing one is once in a lifetime. Only a tiny fraction of the 100 billion stars in a typical galaxy have the capacity to become a supernova, restricted to either those having large mass or extraordinarily rare kinds of binary stars containing white dwarfs.
However and discovery of extragalactic supernovae are now far more common. The first such observation was of SN 1885A in the Andromeda galaxy. Today and professional astronomers are finding several hundred every year, some when near maximum brightness, others on old astronomical photographs or plates. American astronomers Rudolph Minkowski and Fritz Zwicky developed the modern supernova classification scheme beginning in 1941. During the 1960s, astronomers found that the maximum intensities of supernovae could be used as standard candles, hence indicators of astronomical distances; some of the most distant supernovae observed in 2003, appeared dimmer than expected. This supports the view. Techniques were developed for reconstructing supernovae events that have no written records of being observed; the date of the Cassiopeia A supernova event was determined from light echoes off nebulae, while the age of supernova remnant RX J0852.0-4622 was estimated from temperature
Advanced Camera for Surveys
The Advanced Camera for Surveys is a third-generation axial instrument aboard the Hubble Space Telescope. The initial design and scientific capabilities of ACS were defined by a team based at Johns Hopkins University. ACS was assembled and tested extensively at Ball Aerospace & Technologies Corp. and the Goddard Space Flight Center and underwent a final flight-ready verification at the Kennedy Space Center before integration in the cargo bay of the Columbia orbiter. It was launched on March 1, 2002 as part of Servicing Mission 3B and installed in HST on March 7, replacing the Faint Object Camera, the last original instrument. ACS cost US$86 million at that time. ACS is a versatile instrument that became the primary imaging instrument aboard HST, it offered several important advantages over other HST instruments: three independent, high-resolution channels covering the ultraviolet to the near-infrared regions of the spectrum, a large detector area and quantum efficiency, resulting in an increase in HST's discovery efficiency by a factor of ten, a rich complement of filters, coronagraphic and grism capabilities.
The observations undertaken with ACS provided astronomers with a view of the Universe with uniquely high sensitivity, as exemplified by the Hubble Ultra-Deep Field, encompass a wide range of astronomical phenomena, from comets and planets in the Solar System to the most distant quasars known. On 25 June 2006 ACS went out of action due to electronic failure, it was powered up after switching to its redundant set of electronics. The instrument sub-systems, including the CCD detectors, all seemed to be working well and after some engineering tests, ACS resumed science operations on July 4, 2006. On 23 September 2006, the ACS again failed, though by 9 October the problem had been diagnosed and resolved. On January 27, 2007 the ACS failed due to a short circuit in its backup power supply; the instrument's Solar Blind Channel was returned to operation on 19 February 2007 using the side-1 electronics. The Wide Field Channel was returned to service by STS-125 in May 2009; the High Resolution Channel, remains offline.
ACS includes three independent channels, each optimized for specific scientific tasks: The WFC is the most utilized channel of ACS. Its detector consists of two butted 2048x4096, 15 µm/pixel charge-coupled devices for a total of 16 megapixels manufactured by Scientific Imaging Technologies; the WFC plate scale is 0.05″ per pixel and it has an effective field-of-view of 202″×202″. The spectral range of the WFC detector is 350–1100 nm. An example of a use of this channel was SWEEPS, which found 16 candidate exoplanets in the Galactic core; the HRC, permanently disabled since 2007 due to an electrical fault, provided ultra-sharp views over a smaller field-of-view. The channel used two light suppression options for imaging faint objects around bright stars, improving the contrast of targets close to bright sources by tenfold; the first was a commandable coronagraphic mask that included two occulting spots, one of diameter 1.8" at the center of the field and the other of diameter 3.0" nearer to a corner.
The first spot was the most popular of the two, for example, for imaging circumstellar disks around nearby bright stars or the host galaxies of luminous quasars. The second was the so-called Fastie Finger, 0.8" in width and 5" in length, located at the entrance of the HRC dewar window. The HRC detector was a 1024×1024 SITe CCD which had a smaller field-of-view than the WFC but twice the spatial sampling; this detector was significantly more sensitive than the WFC at near-ultraviolet wavelengths. The Multi Anode Microchannel Array of the SBC is a low-background photon-counting device optimized for the ultraviolet in the wavelength range of 115–170 nm, it consists of a photocathode, a microchannel plate, an anode array. Its spatial sampling is 0.030" per pixel and its field-of-view is 25"×25". The ACS SBC is in fact. ACS possesses a set of 38 dispersers distributed among three wheels. Two of these wheels are shared by the HRC and WFC light paths while the third is dedicated to the SBC; the HRC and WFC elements consist of eleven broad-band filters, one medium-band filter, five narrow-band filters, three visible and three ultraviolet polarizers, one prism for the HRC, one grism.
Four of the filters so can be used with the HRC only. The primary broad-band filters are equivalent to the u, g, r, i, z filters of the ground-based Sloan Digital Sky Survey. Five linear ramp filters divided into three individual segments each provide continuous imaging capability from 380 nm to 1070 nm and so ensure adequate sampling of emission lines over a large range in redshift. Only the middle segment is accessible to the HRC; the SBC wheel is populated with one medium-band filter, five long-pass filters, two objective prisms. March 7, 2002, ACS installed in the Hubble Space Telescope June 19, 2006. January 27, 2007 the ACS failed due to a short circuit in its backup power supply. 2009, ACS/WFC repaired Faint Object Camera Near Infrared Camera and Multi-Object Spectrometer Space Telescope Imaging Spectrograph Wide Field and Planetary Camera Wide Field and Planetary Camera 2 the ACS Web site at Johns Hopkins University, which includes a complete description of the ins
Chandra X-ray Observatory
The Chandra X-ray Observatory known as the Advanced X-ray Astrophysics Facility, is a Flagship-class space telescope launched on STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, enabled by the high angular resolution of its mirrors. Since the Earth's atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes. Chandra is an Earth satellite in a 64-hour orbit, its mission is ongoing as of 2019. Chandra is one of the Great Observatories, along with the Hubble Space Telescope, Compton Gamma Ray Observatory, the Spitzer Space Telescope; the telescope is named after the Nobel Prize-winning Indian-American astrophysicist Subrahmanyan Chandrasekhar. Its mission is similar to that of ESA's XMM-Newton spacecraft launched in 1999. In 1976 the Chandra X-ray Observatory was proposed to NASA by Riccardo Giacconi and Harvey Tananbaum. Preliminary work began the following year at Marshall Space Flight Center and the Smithsonian Astrophysical Observatory.
In the meantime, in 1978, NASA launched the first imaging X-ray telescope, into orbit. Work continued on the AXAF project throughout the 1990s. In 1992, to reduce costs, the spacecraft was redesigned. Four of the twelve planned mirrors were eliminated. AXAF's planned orbit was changed to an elliptical one, reaching one third of the way to the Moon's at its farthest point; this eliminated the possibility of improvement or repair by the space shuttle but put the observatory above the Earth's radiation belts for most of its orbit. AXAF was tested by TRW in Redondo Beach, California. AXAF was renamed Chandra as part of a contest held by NASA in 1998, which drew more than 6,000 submissions worldwide; the contest winners, Jatila van der Veen and Tyrel Johnson, suggested the name in honor of Nobel Prize–winning Indian-American astrophysicist Subrahmanyan Chandrasekhar. He is known for his work in determining the maximum mass of white dwarf stars, leading to greater understanding of high energy astronomical phenomena such as neutron stars and black holes.
Fittingly, the name Chandra means "moon" in Sanskrit. Scheduled to be launched in December 1998, the spacecraft was delayed several months being launched in July 23, 1999, at 04:31 UTC by Space Shuttle Columbia during STS-93. Chandra was deployed from Columbia at 11:47 UTC; the Inertial Upper Stage's first stage motor ignited at 12:48 UTC, after burning for 125 seconds and separating, the second stage ignited at 12:51 UTC and burned for 117 seconds. At 22,753 kilograms, it was the heaviest payload launched by the shuttle, a consequence of the two-stage Inertial Upper Stage booster rocket system needed to transport the spacecraft to its high orbit. Chandra has been returning data since the month, it is operated by the SAO at the Chandra X-ray Center in Cambridge, with assistance from MIT and Northrop Grumman Space Technology. The ACIS CCDs suffered particle damage during early radiation belt passages. To prevent further damage, the instrument is now removed from the telescope's focal plane during passages.
Although Chandra was given an expected lifetime of 5 years, on September 4, 2001, NASA extended its lifetime to 10 years "based on the observatory's outstanding results." Physically Chandra could last much longer. A 2004 study performed at the Chandra X-ray Center indicated that the observatory could last at least 15 years. In July 2008, the International X-ray Observatory, a joint project between ESA, NASA and JAXA, was proposed as the next major X-ray observatory but was cancelled. ESA resurrected the project as the Advanced Telescope for High Energy Astrophysics with a proposed launch in 2028. On October 10, 2018, Chandra entered safe mode operations, due to a gyroscope glitch. NASA reported. Within days, the 3-second error in data from one gyro was understood, plans were made to return Chandra to full service; the gyroscope that experienced the glitch is otherwise healthy. The data gathered by Chandra has advanced the field of X-ray astronomy. Here are some examples of discoveries supported by observations from Chandra: The first light image, of supernova remnant Cassiopeia A, gave astronomers their first glimpse of the compact object at the center of the remnant a neutron star or black hole.
In the Crab Nebula, another supernova remnant, Chandra showed a never-before-seen ring around the central pulsar and jets that had only been seen by earlier telescopes. The first X-ray emission was seen from the supermassive black hole, Sagittarius A*, at the center of the Milky Way. Chandra found much more cool gas than expected spiraling into the center of the Andromeda Galaxy. Pressure fronts were observed in detail for the first time in Abell 2142, where clusters of galaxies are merging; the earliest images in X-rays of the shock wave of a supernova were taken of SN 1987A. Chandra showed for the first time the shadow of a small galaxy as it is being cannibalized by a larger one, in an image of Perseus A. A new type of black hole was discovered in galaxy M82, mid-mass objects purported to be the missing link between stellar-sized black holes and super massive black holes. X-ray emission lines were associated for the first time with a gamma-ray burst