Timeline of knowledge about galaxies, clusters of galaxies, and large-scale structure
Encyclopedia
Timeline
of galaxies
, clusters of galaxies
, and large-scale structure of the cosmos
Timeline
A timeline is a way of displaying a list of events in chronological order, sometimes described as a project artifact . It is typically a graphic design showing a long bar labeled with dates alongside itself and events labeled on points where they would have happened.-Uses of timelines:Timelines...
of galaxies
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
, clusters of galaxies
Galaxy cluster
A galaxy cluster is a compact cluster of galaxies. Basic difference between a galaxy group and a galaxy cluster is that there are many more galaxies in a cluster than in a group. Also, galaxies in a cluster are more compact and have higher velocity dispersion. One of the key features of cluster is...
, and large-scale structure of the cosmos
Pre-20th Century
- 400s BC5th century BCThe 5th century BC started the first day of 500 BC and ended the last day of 401 BC.-Overview:This century saw the beginning of a period of philosophical brilliance among Western civilizations, particularly the Greeks which would continue all the way through the 4th century until the time of...
— DemocritusDemocritusDemocritus was an Ancient Greek philosopher born in Abdera, Thrace, Greece. He was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated an atomic theory for the cosmos....
proposes that the bright band in the night sky known as the Milky WayMilky WayThe Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
might consist of starStarA star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s, - 300s BC4th century BCThe 4th century BC started the first day of 400 BC and ended the last day of 301 BC. It is considered part of the Classical era, epoch, or historical period.-Overview:This century marked the height of Classical Greek civilization in all of its aspects...
— AristotleAristotleAristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
believes the Milky Way to be caused by "the ignition of the fiery exhalation of some stars which were large, numerous and close together" and that the "ignition takes place in the upper part of the atmosphereAtmosphereAn atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
, in the region of the world which is continuous with the heavenly motionsSublunary sphereThe sublunary sphere is a concept derived from Greek astronomy. It is the region of the cosmos from the Earth to the Moon, consisting of the four classical elements: earth, water, air, and fire. Beginning with the Moon, up to the limits of the universe, everything is made of aether...
", - 964 AD964Year 964 was a leap year starting on Friday of the Julian calendar.- Religion :* May 22 – Pope Benedict V begins his pontificate as the 132nd pope, chosen by the people of Rome over Pope Leo VIII....
— Abd al-Rahman al-Sufi (Azophi), a Persian astronomerIslamic astronomyIslamic astronomy or Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and...
, makes the first recorded observations of the Andromeda GalaxyAndromeda GalaxyThe Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
and the Large Magellanic CloudLarge Magellanic CloudThe Large Magellanic Cloud is a nearby irregular galaxy, and is a satellite of the Milky Way. At a distance of slightly less than 50 kiloparsecs , the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and Canis Major Dwarf Galaxy lying closer to the center...
in his Book of Fixed StarsBook of Fixed StarsThe Book of Fixed Stars is an astronomical text written by Abd al-Rahman al-Sufi around 964. The book was written in Arabic, although the author himself was Persian...
, and which are the first galaxies other than the Milky Way to be observed from Earth, - 11th century — Abū Rayhān al-Bīrūnī, another Persian astronomer, describes the Milky WayMilky WayThe Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
galaxy as a collection of numerous nebulousNebulaA nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...
stars, - 11th century — Ibn al-Haytham (Alhazen), an Arabian astronomerIslamic astronomyIslamic astronomy or Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and...
, refutes Aristotle's theory on the Milky Way by making the first attempt at observing and measuring the Milky Way's parallaxParallaxParallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...
, and he thus "determined that because the Milky Way had no parallax, it was very remote from the earthEarthEarth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and did not belong to the atmosphere", - 12th century — Ibn BajjahIbn BajjahAbū-Bakr Muhammad ibn Yahya ibn al-Sāyigh , known as Ibn Bājjah , was an Andalusian polymath: an astronomer, logician, musician, philosopher, physician, physicist, psychologist, botanist, poet and scientist. He was known in the West by his Latinized name, Avempace...
(Avempace) of Islamic SpainAl-AndalusAl-Andalus was the Arabic name given to a nation and territorial region also commonly referred to as Moorish Iberia. The name describes parts of the Iberian Peninsula and Septimania governed by Muslims , at various times in the period between 711 and 1492, although the territorial boundaries...
proposes the Milky Way to be made up of many stars but that it appears to be a continuous image due to the effect of refractionRefractionRefraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...
in the Earth's atmosphereEarth's atmosphereThe atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
, - 14th century — Ibn Qayyim Al-Jawziyya of SyriaSyriaSyria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....
proposes the Milky Way galaxy to be "a myriad of tiny stars packed together in the sphere of the fixed stars" and that these stars are larger than planetPlanetA planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s, - 1521 — Ferdinand MagellanFerdinand MagellanFerdinand Magellan was a Portuguese explorer. He was born in Sabrosa, in northern Portugal, and served King Charles I of Spain in search of a westward route to the "Spice Islands" ....
observes the Magellanic CloudsMagellanic CloudsThe two Magellanic Clouds are irregular dwarf galaxies visible in the southern hemisphere, which are members of our Local Group and are orbiting our Milky Way galaxy...
during his circumnavigating expedition, - 1610 — Galileo GalileiGalileo GalileiGalileo Galilei , was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations and support for Copernicanism...
uses a telescopeTelescopeA telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
to determine that the bright band on the skySkyThe sky is the part of the atmosphere or outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons. During daylight, the sky of Earth has the appearance of a pale blue surface because the air scatters the sunlight. The sky is sometimes...
, the "Milky WayMilky WayThe Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
", is composed of many faint starStarA star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s - 1750 — Thomas WrightThomas Wright (astronomer)Thomas Wright was an English astronomer, mathematician, instrument maker, architect and garden designer. He was the first to describe the shape of the Milky Way and speculate that faint nebulae were distant galaxies....
discusses galaxiesGalaxyA galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
and the shape of the Milky Way, - 1755 — Drawing on Wright's work, Immanuel KantImmanuel KantImmanuel Kant was a German philosopher from Königsberg , researching, lecturing and writing on philosophy and anthropology at the end of the 18th Century Enlightenment....
conjectures that the galaxy is a rotating disk of stars held together by gravity, and that the nebulaNebulaA nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...
e are separate such galaxies; he calls them Island Universes - 1785 — William HerschelWilliam HerschelSir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...
carried the first attempt to describe the shape of the Milky Way and the position of the Sun in it by carefully counting the number of stars in different regions of the sky. He produced a diagram of the shape of the galaxy with the solar system close to the center. - 1845 — Lord RosseWilliam Parsons, 3rd Earl of RosseWilliam Parsons, 3rd Earl of Rosse, Knight of the Order of St Patrick was an Irish astronomer who had several telescopes built. His 72-inch telescope "Leviathan", built 1845, was the world's largest telescope until the early 20th century.-Life:He was born in Yorkshire, England, in the city of...
discovers a nebula with a distinct spiral shape
Early 20th Century
- 1918 — Harlow ShapleyHarlow ShapleyHarlow Shapley was an American astronomer.-Career:He was born on a farm in Nashville, Missouri, and dropped out of school with only the equivalent of a fifth-grade education...
demonstrates that globular clusterGlobular clusterA globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...
s are arranged in a spheroid or halo whose center is not the EarthEarthEarth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, and decides, correctly, that it is center is the center of the galaxy, - 1920 — Harlow Shapley and Heber Curtis debate whether or not the spiral nebulae lie within the Milky Way,
- 1923 — Edwin HubbleEdwin HubbleEdwin Powell Hubble was an American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way - our own galaxy...
resolves the Shapley-Curtis debate by finding CepheidsCepheid variableA Cepheid is a member of a class of very luminous variable stars. The strong direct relationship between a Cepheid variable's luminosity and pulsation period, secures for Cepheids their status as important standard candles for establishing the Galactic and extragalactic distance scales.Cepheid...
in the Andromeda galaxyAndromeda GalaxyThe Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the... - 1930 — Robert Trumpler uses open clusterOpen clusterAn open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...
observations to quantify the absorptionAbsorption (electromagnetic radiation)In physics, absorption of electromagnetic radiation is the way by which the energy of a photon is taken up by matter, typically the electrons of an atom. Thus, the electromagnetic energy is transformed to other forms of energy for example, to heat. The absorption of light during wave propagation is...
of lightLightLight or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
by interstellar dust in the galactic planeGalactic planeThe galactic plane is the plane in which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles...
; this absorption had plagued earlier models of the Milky Way, - 1932 — Karl Guthe JanskyKarl Guthe JanskyKarl Guthe Jansky was an American physicist and radio engineer who in August 1931 first discovered radio waves emanating from the Milky Way. He is considered one of the founding figures of radio astronomy.- Early life :...
discovers radio noise from the center of the Milky Way, - 1933 — Fritz ZwickyFritz ZwickyFritz Zwicky was a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and observational astronomy.- Biography :Fritz Zwicky was born in Varna, Bulgaria to a Swiss father....
applies the virial theorem to the Coma Cluster and obtains evidence for unseen massMassMass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
, - 1936 — Edwin Hubble introduces the spiral, barred spiral, elliptical, and irregular galaxy classifications,
- 1939 — Grote ReberGrote ReberGrote Reber was an amateur astronomer and pioneer of radio astronomy. He was instrumental in investigating and extending Karl Jansky's pioneering work, and conducted the first sky survey in the radio frequencies...
discovers the radio source Cygnus ACygnus ACygnus A is one of the most famous radio galaxies, and among the strongest radio sources in the sky.It was discovered by Grote Reber in 1939. In 1951, Cygnus A, along with Cassiopeia A, and Puppis A were the first "radio stars" identified with an optical source, of these, Cygnus A became the first...
, - 1943 — Carl Keenan SeyfertCarl Keenan SeyfertCarl Keenan Seyfert was an American astronomer.He is best known for his 1943 research paper on high-excitation line emission from the centers of some spiral galaxies, which are named Seyfert galaxies after him...
identifies six spiral galaxies with unusually broad emission lines, named Seyfert galaxiesSeyfert galaxySeyfert galaxies are a class of galaxies with nuclei that produce spectral line emission from highly ionized gas, named after Carl Keenan Seyfert, the astronomer who first identified the class in 1943...
, - 1949 — J.G. Bolton, G.J. Stanley, and O.B. Slee identify NGC 4486 (M87) and NGC 5128 as extragalactic radio sources,
Mid-20th Century
- 1953 — Gerard de VaucouleursGérard de Vaucouleurs-External links:* * http://nedwww.ipac.caltech.edu/level5/normal_galaxies.html-Other resources:...
discovers that the galaxies within approximately 200 million light years of the Virgo clusterVirgo ClusterThe Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member...
are confined to a giant superclusterSuperclusterSuperclusters are large groups of smaller galaxy groups and clusters and are among the largest known structures of the cosmos. They are so large that they are not gravitationally bound and, consequently, partake in the Hubble expansion.-Existence:...
disk, - 1954 — Walter BaadeWalter BaadeWilhelm Heinrich Walter Baade was a German astronomer who worked in the USA from 1931 to 1959.-Biography:He took advantage of wartime blackout conditions during World War II, which reduced light pollution at Mount Wilson Observatory, to resolve stars in the center of the Andromeda galaxy for the...
and Rudolph MinkowskiRudolph MinkowskiRudolph Minkowski was a German-American astronomer. His father was the physiologist Oskar Minkowski and his uncle was Hermann Minkowski....
identify the extragalactic optical counterpart of the radio source Cygnus A, - 1959 — Hundreds of radio sources are detected by the Cambridge InterferometerCambridge InterferometerThe Cambridge Interferometer was a radio telescope interferometer built by Martin Ryle and Antony Hewish in the early 1950s to the west of Cambridge . The interferometer consisted of an array of 4 fixed elements to survey the sky...
which produces the 3C catalogueThird Cambridge Catalogue of Radio SourcesThe Third Cambridge Catalogue of Radio Sources is an astronomical catalogue of celestial radio sources detected originally at 159 MHz, and subsequently at 178 MHz. It was published in 1959 by members of the Radio Astronomy Group of the University of Cambridge...
. Many of these are later found to be distant quasars and radio galaxies - 1960 — Thomas Matthews determines the radio position of the 3CThird Cambridge Catalogue of Radio SourcesThe Third Cambridge Catalogue of Radio Sources is an astronomical catalogue of celestial radio sources detected originally at 159 MHz, and subsequently at 178 MHz. It was published in 1959 by members of the Radio Astronomy Group of the University of Cambridge...
source 3C 48 to within 5", - 1960 — Allan SandageAllan SandageAllan Rex Sandage was an American astronomer. He was Staff Member Emeritus with the Carnegie Observatories in Pasadena, California. He is best known for determining the first reasonably accurate value for the Hubble constant and the age of the universe.-Career:Sandage was one of the most...
optically studies 3C 48 and observes an unusual blue quasistellar object, - 1962 — Cyril Hazard, M.B. Mackey, and A.J. Shimmins use lunar occultations to determine a precise position for the quasarQuasarA quasi-stellar radio source is a very energetic and distant active galactic nucleus. Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that were point-like, similar to stars, rather than...
3C 273 and deduce that it is a double source, - 1962 — Olin Eggen, Donald Lynden-BellDonald Lynden-BellDonald Lynden-Bell CBE FRS is an English astrophysicist, best known for his theories that galaxies contain massive black holes at their centre, and that such black holes are the principal source of energy in quasars. He was a co-recipient, with Maarten Schmidt, of the inaugural Kavli Prize for...
, and Allan SandageAllan SandageAllan Rex Sandage was an American astronomer. He was Staff Member Emeritus with the Carnegie Observatories in Pasadena, California. He is best known for determining the first reasonably accurate value for the Hubble constant and the age of the universe.-Career:Sandage was one of the most...
theorize galaxy formation by a single (relatively) rapid monolithic collapse, with the halo forming first, followed by the disk. - 1963 — Maarten SchmidtMaarten SchmidtMaarten Schmidt is a Dutch astronomer who measured the distances of quasars.Born in Groningen, The Netherlands, Schmidt studied with Jan Hendrik Oort. He earned his Ph.D. degree from Leiden Observatory in 1956....
identifies the redshifted Balmer lines from the quasar 3C 273 - 1973 — Jeremiah Ostriker and James Peebles discover that the amount of visible matter in the disks of typical spiral galaxies is not enough for Newtonian gravitation to keep the disks from flying apart or drastically changing shape,
- 1973 — Donald Gudehus finds that the diameters of the brightest cluster galaxies have increased due to merging,
- 1974 — B.L. Fanaroff and J.M. RileyJulia RileyJulia M. Riley a Fellow of Girton College, works at the Cavendish Astrophysics Group, University of Cambridge in the area of radio astronomy. In 1974, along with Fanaroff, she wrote a famous paper classifying radio galaxies into two types based on their morphology . These became known as...
distinguish between edge-darkened (FR I) and edge-brightened (FR II) radio sources, - 1976 — Sandra Faber and Robert JacksonRobert Jackson (scientist)Robert Earl Jackson is a scientist, who, with Sandra M. Faber, in 1976 discovered the Faber-Jackson relation between the luminosity of an elliptical galaxy and the velocity dispersion in its center....
discover the Faber-Jackson relation between the luminosityLuminosityLuminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
of an elliptical galaxy and the velocityVelocityIn physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
dispersion in its center. In 1991 the relation is revised by Donald Gudehus, - 1977 — R. Brent TullyR. Brent TullyR. Brent Tully is an astronomer at the Institute for Astronomy in Honolulu, Hawaii.Tully's specialty is astrophysics of galaxies. He, along with J. Richard Fisher, proposed the now-famous Tully-Fisher relation in a paper, A New Method of Determining Distances to Galaxies, published in Astronomy...
and Richard FisherJ. Richard FisherJ. Richard Fisher is an astronomer at the National Radio Astronomy Observatory at Charlottesville, VA. He received his Ph.D. in Astronomy from the University of Maryland, College Park and his B.S. in Physics from the Pennsylvania State University.Fisher, along with R...
publish the Tully-Fisher relationTully-Fisher relationIn astronomy, the Tully–Fisher relation, published by astronomers R. Brent Tully and J. Richard Fisher in 1977, is an empirical relationship between the intrinsic luminosity of a spiral galaxy and its velocity width...
between the luminosity of an isolated spiral galaxy and the velocity of the flat part of its rotation curve, - 1978 — Steve Gregory and Laird ThompsonLaird A. ThompsonLaird A. Thompson , is a professor of astronomy at the University of Illinois at Urbana-Champaign. Thompson graduated with a B.A. in both physics and astronomy from the University of California, Los Angeles in 1969. He received his Ph.D...
describe the Coma supercluster, - 1978 — Donald Gudehus finds evidence that clusters of galaxies are moving at several hundred kilometers per second relative to the cosmic microwave background radiation,
- 1978 — Vera RubinVera RubinVera Rubin is an American astronomer who pioneered work on galaxy rotation rates. She is famous for uncovering the discrepancy between the predicted angular motion of galaxies and the observed motion, by studying galactic rotation curves...
, Kent FordKent FordW. Kent Ford, Jr. was an astronomer involved with the theory of dark matter. He worked with scientist Vera Rubin, who used his advanced spectrometer in her studies of space and matter. This spectrometer allowed the pair to drastically change the way dark matter was viewed, by analyzing the...
, N. Thonnard, and Albert Bosma measure the rotation curves of several spiral galaxies and find significant deviations from what is predicted by the Newtonian gravitation of visible stars, - 1978 — Leonard SearleLeonard SearleLeonard Searle was an English-born American astronomer who worked on theories of the Big Bang. He was born in Mitcham, a suburb of London, and studied at St Andrews in Scotland and Princeton in New Jersey. After receiving his doctorate he started working at the University of Toronto in 1953,...
and Robert Zinn theorize that galaxy formation occurs through the merger of smaller groups.
Late 20th Century
- 1981 — Robert KirshnerRobert KirshnerRobert Kirshner is the Clowes Professor of Science in the Harvard-Smithsonian Center for Astrophysics at Harvard University. Kirshner has worked in several areas of astronomy including the physics of supernovae, supernova remnants, the Large-scale structure of the cosmos, and the use of Supernovae...
, August Oemler, Paul SchechterPaul L. SchechterPaul L. Schechter is an astrophysicist and observational cosmologist. He is the William A. M. Burden Professor of Astrophysics at MIT.Schechter received his bachelor's degree from Cornell in 1968, and his Ph.D. degree from Caltech in 1975...
, and Stephen Shectman find evidence for a giant voidBoötes voidThe Boötes void or the Great Void is a huge and approximately spherically shaped region of space, containing very few galaxies. It is located in the vicinity of the constellation Boötes, hence its name...
in BoötesBoötesBoötes is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from the Greek Βοώτης, Boōtēs, meaning herdsman or plowman...
with a diameter of approximately 100 million light years, - 1985 — Robert Antonucci and J. Miller discover that the Seyfert II galaxy NGC 1068 has broad lines which can only be seen in polarized reflected light,
- 1986 — Amos Yahil, David WalkerDavid Walker-Musicians:* Dave Walker , British musician, member of the band Fleetwood Mac* David Walker , American opera singer* David Walker , American singer of Southern Gospel music...
, and Michael Rowan-RobinsonMichael Rowan-RobinsonMichael Rowan-Robinson is an astronomer and astrophysicist. He was educated at Pembroke College, Cambridge and is Professor of Astrophysics and until May 2007 was Head of the Astrophysics Group at Imperial College London. From 1981 to 1982, he gave public lectures as professor of astronomy at...
find that the direction of the IRASIRASThe Infrared Astronomical Satellite was the first-ever space-based observatory to perform a survey of the entire sky at infrared wavelengths....
galaxy density dipoleDipoleIn physics, there are several kinds of dipoles:*An electric dipole is a separation of positive and negative charges. The simplest example of this is a pair of electric charges of equal magnitude but opposite sign, separated by some distance. A permanent electric dipole is called an electret.*A...
agrees with the direction of the cosmic microwave background temperature dipole, - 1987 — David Burstein, Roger DaviesRoger Davies (astrophysicist)Roger Llewelyn Davies is a British astronomer and cosmologist, one of the so-called Seven Samurai collaboration who discovered an apparent concentration of mass in the Universe called the Great Attractor. He is the Philip Wetton Professor of Astrophysics at Oxford University...
, Alan DresslerAlan DresslerAlan Michael Dressler is an American astronomer at the Carnegie Institution for Science of Washington, D.C.. Among his works is the popularization Voyage To The Great Attractor: Exploring Intergalactic Space....
, Sandra FaberSandra M. FaberSandra Moore Faber is a University Professor of Astronomy and Astrophysics at the University of California, Santa Cruz, and works at the Lick Observatory.In 1966, she obtained a B.A., with high honors, in physics from Swarthmore College....
, Donald Lynden-BellDonald Lynden-BellDonald Lynden-Bell CBE FRS is an English astrophysicist, best known for his theories that galaxies contain massive black holes at their centre, and that such black holes are the principal source of energy in quasars. He was a co-recipient, with Maarten Schmidt, of the inaugural Kavli Prize for...
, R.J. Terlevich, and Gary WegnerGary A. WegnerGary Alan Wegner is an American astronomer, the endowed Leede '49 Professor of Physics and Astronomy at Dartmouth College, and recipient of the Alexander Von Humboldt Prize. Wegner was also a member of a famous group of seven astronomers called the Seven Samurai who, in the 1980s, discovered the...
claim that a large group of galaxies within about 200 million light years of the Milky Way are moving together towards the "Great AttractorGreat AttractorThe Great Attractor is a gravity anomaly in intergalactic space within the range of the Centaurus Supercluster that reveals the existence of a localised concentration of mass equivalent to tens of thousands of Milky Ways, observable by its effect on the motion of galaxies and their associated...
" in the direction of HydraHydra (constellation)Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees. It has a long history, having been included among the 48 constellations listed by the 2nd century astronomer Ptolemy. It is commonly represented as a water snake...
and CentaurusCentaurusCentaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.-Stars:...
, - 1987 — R. Brent TullyR. Brent TullyR. Brent Tully is an astronomer at the Institute for Astronomy in Honolulu, Hawaii.Tully's specialty is astrophysics of galaxies. He, along with J. Richard Fisher, proposed the now-famous Tully-Fisher relation in a paper, A New Method of Determining Distances to Galaxies, published in Astronomy...
discovers the Pisces-Cetus Supercluster ComplexPisces-Cetus Supercluster ComplexThe Pisces-Cetus Supercluster Complex is a complex of galaxy superclusters or galaxy filament that includes the Virgo Supercluster .-Discovery:...
, a structure one billion light years long and 150 million light years wide, - 1989 — Margaret GellerMargaret GellerMargaret Joan Geller is an American astronomer and professor. She is a Senior Astronomer at the Smithsonian Astrophysical Observatory, and has written numerous articles and produced several award-winning scientific short films....
and John HuchraJohn HuchraJohn Peter Huchra [pronounced HUCK-rah] was an American astronomer and professor. He was the Vice Provost for Research Policy at Harvard University and a Professor of Astronomy at the Harvard-Smithsonian Center for Astrophysics. He was also a former chair of the United States National Committee...
discover the "Great WallGreat Wall (astronomy)The Great Wall , sometimes specifically referred to as the CfA2 Great Wall, is one of the largest known super-structures in the Universe...
", a sheet of galaxies more than 500 million light years long and 200 million wide, but only 15 million light years thick, - 1990 — Michael Rowan-RobinsonMichael Rowan-RobinsonMichael Rowan-Robinson is an astronomer and astrophysicist. He was educated at Pembroke College, Cambridge and is Professor of Astrophysics and until May 2007 was Head of the Astrophysics Group at Imperial College London. From 1981 to 1982, he gave public lectures as professor of astronomy at...
and Tom Broadhurst discover that the IRAS galaxy IRAS F10214+4724 is the brightest known object in the UniverseUniverseThe Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...
, - 1991 — Donald Gudehus discovers a serious systematic bias in certain cluster galaxy data (surface brightness vs. radius parameter, and the
method) which affect galaxy distances and evolutionary history; he devises a new distance indicator, the reduced galaxian radius parameter, 
, which is free of biases, - 1992 — First detection of large-scale structure in the cosmic microwave backgroundCosmic microwave background radiationIn cosmology, cosmic microwave background radiation is thermal radiation filling the observable universe almost uniformly....
indicating the seeds of the first clusters of galaxies in the early Universe - 1995 — First detection of small-scale structure in the cosmic microwave background
- 1995 — Hubble Deep FieldHubble Deep FieldThe Hubble Deep Field is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area 2.5 arcminutes across, two parts in a million of the whole sky, which is equivalent in angular size to a 65 mm tennis...
survey of galaxies in field 144 arc seconds across. - 1998 — The 2dF Galaxy Redshift Survey2dF Galaxy Redshift SurveyIn astronomy, the 2dF Galaxy Redshift Survey , 2dF or 2dFGRS is a redshift survey conducted by the Anglo-Australian Observatory with the 3.9m Anglo-Australian Telescope between 1997 and 11 April 2002. The data from this survey were made public on 30 June 2003...
maps the large-scale structure in a section of the Universe close to the Milky Way - 1998 — Hubble Deep Field SouthHubble Deep Field SouthThe Hubble Deep Field South is a composite of several hundred individual images taken using the Hubble Space Telescope's Wide Field and Planetary Camera 2 over 10 days in September and October 1998. It followed the great success of the original Hubble Deep Field in facilitating the study of...
- 1998 — Discovery of accelerating universeAccelerating universeThe accelerating universe is the observation that the universe appears to be expanding at an increasing rate, which in formal terms means that the cosmic scale factor a has a positive second derivative, implying that the velocity at which a given galaxy is receding from us should be continually...
- 2000 — Data from several cosmic microwave backgroundCosmic microwave background radiationIn cosmology, cosmic microwave background radiation is thermal radiation filling the observable universe almost uniformly....
experiments give strong evidence that the Universe is "flat" (space is not curved, although space-time is), with important implications for the formation of large-scale structure
Early 21st Century
- 2001 — First data release from the on-going Sloan Digital Sky SurveySloan Digital Sky SurveyThe Sloan Digital Sky Survey or SDSS is a major multi-filter imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project was named after the Alfred P...
- 2004 — The European Southern ObservatoryEuropean Southern ObservatoryThe European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...
discovers Abell 1835 IR1916, the most distant galaxy yet seen from Earth. - 2004 — The Arcminute Microkelvin ImagerArcminute Microkelvin ImagerThe Arcminute Microkelvin Imager consists of a pair of interferometric radio telescopes - the Small and Large Arrays - located at the Mullard Radio Astronomy Observatory near Cambridge. AMI was designed, built and is operated by the Cavendish Astrophysics Group...
begins to map the distribution of distant clusters of galaxies