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A quasar is an extremely luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Gas in the disc falling towards the black hole heats up and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosities thousands of times greater than that of a galaxy such as the Milky Way. Quasars are usually categorized as a subclass of the more general category of AGN. The redshifts of quasars are of cosmological origin.
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that the luminosity is not produced by stars. Such excess, non-stellar emissions have been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an active galaxy. The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy.
A microquasar, the smaller version of a quasar, is a compact region surrounding a stellar black hole with a mass several times that of its companion star. The matter being pulled from the companion star forms an accretion disk around the black hole. This accretion disk may become so hot, due to friction, that it begins to emit X-rays. The disk also projects narrow streams or "jets" of subatomic particles at near-light speed, generating a strong radio wave emission.
The beetroot is the taproot portion of a beet plant, usually known in North America as beets while the vegetable is referred to as beetroot in British English, and also known as the table beet, garden beet, red beet, dinner beet or golden beet.
Christopher Fulton McKee is an astrophysicist.
Eleanor Margaret Burbidge, FRS (née Peachey; 12 August 1919 – 5 April 2020) was a British-American observational astronomer and astrophysicist. In the 1950s, she was one of the founders of stellar nucleosynthesis and was first author of the influential B2FH paper. During the 1960s and 1970s she worked on galaxy rotation curves and quasars, discovering the most distant astronomical object then known. In the 1980s and 1990s she helped develop and utilise the Faint Object Spectrograph on the Hubble Space Telescope. Burbidge was also well known for her work opposing discrimination against women in astronomy.
Joseph Frank Sambrook was a British molecular biologist known for his studies of DNA oncoviruses and the molecular biology of normal and cancerous cells.
The American Antiquarian Society (AAS), located in Worcester, Massachusetts, is both a learned society and a national research library of pre-twentieth-century American history and culture. Founded in 1812, it is the oldest historical society in the United States with a national focus. Its main building, known as Antiquarian Hall, is a U.S. National Historic Landmark in recognition of this legacy. The mission of the AAS is to collect, preserve and make available for study all printed records of what is now known as the United States of America. This includes materials from the first European settlement through the year 1876.
The 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 extremely distant galaxies in early stages of their evolution. While the WFPC2 took very deep optical images, nearby fields were simultaneously imaged by the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).
Kenneth Irwin Kellermann is an American astronomer at the National Radio Astronomy Observatory. He is best known for his work on quasars. He won the Helen B. Warner Prize for Astronomy of the American Astronomical Society in 1971, and the Bruce Medal of the Astronomical Society of the Pacific in 2014.
William Nielsen Brandt is the Verne M. Willaman Professor of Astronomy & Astrophysics and a professor of physics at the Pennsylvania State University. He is best known for his work on active galaxies, cosmological X-ray surveys, starburst galaxies, normal galaxies, and X-ray binaries.
Simon David Manton White, FRS, is a British astrophysicist. He was one of directors at the Max Planck Institute for Astrophysics before his retirement in late 2019.
ULAS J1120+0641 was the most distant known quasar when discovered in 2011, surpassed in 2017 by ULAS J1342+0928. ULAS J1120+0641 was the first quasar discovered beyond a redshift of z = 7. Its discovery was reported in June 2011.
Jonathan Christopher McDowell is an astronomer and astrophysicist at the Harvard–Smithsonian Center for Astrophysics. He is a staff member at the Chandra X-ray Center. McDowell is the author and editor of Jonathan's Space Report, an e-mail-distributed newsletter documenting satellite launches.
SDSS J1254+0846 is a face-on binary quasar pair which is in the process of merging. This binary quasar is the first resolved luminous pair to be observed in the act of merging. The pair is composed of two luminous radio-quiet quasars located at redshift z=0.44, being SDSS J125455.09+084653.9 and SDSS J125454.87+084652.1, or SDSS J1254+0846 collectively. These designations also refer to their host galaxies. This pair provide evidence for the theory that quasars are switched on by galactic collisions. The pair are optically separated by 3.6 arcseconds, giving the real separation as 21 kpc. Tidal tails some 75 kpc have been detected around the galaxies. Thus the two galaxies involved are disc galaxies. The pair was first detected by the Sloan Digital Sky Survey, hence the "SDSS" designations. The tidal tails were first observed by the Magellan Telescopes. A computer simulation by Thomas Cox of the Carnegie Institute corroborated the hypothesis that these were two merging galaxies. This binary quasar, was at the time of discovery in 2010, the lowest redshift binary quasar then observed.
Neta Bahcall is an Israeli astrophysicist and cosmologist specializing in dark matter, the structure of the universe, quasars, and the formation of galaxies. Bahcall is the Eugene Higgins Professor of Astronomy at Princeton University.
Nadia Zakamska is a Russian-American astronomer who is a professor at Johns Hopkins University.
TON 618 is a hyperluminous, broad-absorption-line, radio-loud quasar and Lyman-alpha blob located near the border of the constellations Canes Venatici and Coma Berenices, with the projected comoving distance of approximately 18.2 billion light-years from Earth. It possesses one of the most massive black holes ever found, at 40.7 billion M☉.
Dara J. Norman is an astronomer and the deputy director of the Community Science and Data Center at the National Science Foundation's National Optical-Infrared Astronomy Research Laboratory (NOIRLab) in Tucson, Arizona. She is also the Association of Universities for Research in Astronomy Diversity Advocate at NOAO. Her research centers on the influence of Active Galactic Nuclei (AGN) on the evolution of galaxies. In 2020, she was inducted into the inaugural cohort of American Astronomical Society Fellows in recognition of her leadership and achievements.
References
- ↑ "AAS 234 Press Conference: Cold Quasars & Hot Cosmology". AAS Press Office via YouTube. 12 June 2019. Retrieved 13 June 2019.
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