A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion disk, while the two are similar. While they are similar, an accretion disk is hotter, and spins much faster. It is also found on black holes, not stars. This process should not be confused with the accretion process thought to build up the planets themselves. Externally illuminated photo-evaporating protoplanetary disks are called proplyds.
Rashid Alievich Sunyaev is a German, Soviet, and Russian astrophysicist of Tatar descent. He got his MS degree from the Moscow Institute of Physics and Technology (MIPT) in 1966. He became a professor at MIPT in 1974. Sunyaev was the head of the High Energy Astrophysics Department of the Russian Academy of Sciences, and has been chief scientist of the Academy's Space Research Institute since 1992. He has also been a director of the Max Planck Institute for Astrophysics in Garching, Germany since 1996, and Maureen and John Hendricks Distinguished Visiting Professor in the School of Natural Sciences at the Institute for Advanced Study in Princeton since 2010. In February 2022, he signed an open letter from Russian scientists and science journalists condemning Russia's invasion of Ukraine.
In astrophysics, accretion is the accumulation of particles into a massive object by gravitationally attracting more matter, typically gaseous matter, into an accretion disk. Most astronomical objects, such as galaxies, stars, and planets, are formed by accretion processes.
Beta Lyrae officially named Sheliak, the traditional name of the system, is a multiple star system in the constellation of Lyra. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 960 light-years distant from the Sun.
Viktor Sergeevich Safronov was a Soviet astronomer who put forward the low-mass-nebula model of planet formation, a consistent picture of how the planets formed from a disk of gas and dust around the Sun.
A protoplanetary nebula or preplanetary nebula is an astronomical object which is at the short-lived episode during a star's rapid evolution between the late asymptotic giant branch (LAGB)[a] phase and the subsequent planetary nebula (PN) phase. A PPN emits strongly in infrared radiation, and is a kind of reflection nebula. It is the second-from-the-last high-luminosity evolution phase in the life cycle of intermediate-mass stars.
A bipolar outflow comprises two continuous flows of gas from the poles of a star. Bipolar outflows may be associated with protostars, or with evolved post-AGB stars.
Z Andromedae is a binary star system consisting of a red giant and a white dwarf. It is the prototype of a type of cataclysmic variable star known as symbiotic variable stars or simply Z Andromedae variables. The brightness of those stars vary over time, showing a quiescent, more stable phase and then an active one with a more pronounced variability and stronger brightening and/or dimming.
Astronomy Letters is a Russian peer-reviewed scientific journal. The journal covers research on all aspects of astronomy and astrophysics, including high energy astrophysics, cosmology, space astronomy, theoretical astrophysics, radio astronomy, extra galactic astronomy, stellar astronomy, and investigation of the Solar system.
Roger David Blandford, FRS, FRAS is a British theoretical astrophysicist, best known for his work on black holes.
Astronomy Reports, is a Russian, monthly, peer reviewed, scientific journal. This journal tends to focus its publishing efforts on original research regarding astronomical topics. Other types of reporting are also included such as chronicles, proceedings of international conferences, and book reviews. Founded in 1924, it is described as the most prominent astronomy journal during the age of the Soviet Union. Originally a print version, it is also available online. The editor-in-chief was Alexander A. Boyarchuk, Institute of Astronomy of the Russian Academy of Sciences, Moscow, Russia.
Alexey Maksimovich Fridman was a Soviet and Russian physicist specializing in astrophysics, physics of gravitating systems and plasma physics. He discovered new types of instabilities in gravitating media, created the theory of planetary rings and predicted the existence of small Uranus satellites that were later discovered. He also developed the hydrodynamic theory of spiral structure in galaxies. Fridman worked at the Institute of Astronomy of the Russian Academy of Sciences, INASAN, and was professor at the Moscow Institute of Physics and Technology and at Moscow State University.
Cosmic Research is a bimonthly peer-reviewed scientific journal that was established in 1963. It is published by MAIK Nauka/Interperiodica and published online by Springer Science+Business Media. The editor-in-chief is Anatoli A. Petrukovich. The journal is a continuation of the Soviet-Russian publication Artificial Earth Satellites, in existence between 1960 and 1964.
Priyamvada (Priya) Natarajan is a theoretical astrophysicist and professor in the departments of astronomy and physics at Yale University. She is noted for her work in mapping dark matter and dark energy, particularly in gravitational lensing and in models describing the assembly and accretion histories of supermassive black holes. She authored the book Mapping the Heavens: The Radical Scientific Ideas That Reveal the Cosmos.
An exocomet, or extrasolar comet, is a comet outside the Solar System, which includes rogue comets and comets that orbit stars other than the Sun. The first exocomets were detected in 1987 around Beta Pictoris, a very young A-type main-sequence star. There are now a total of 27 stars around which exocomets have been observed or suspected.
Steven Andrew Balbus is an American-born astrophysicist who is the Savilian Professor of Astronomy at the University of Oxford and a professorial fellow at New College, Oxford. In 2013, he shared the Shaw Prize for Astronomy with John F. Hawley.
Oleg Vladimirovich Besov is a Russian mathematician. He heads the Department of Function Theory at the Steklov Institute of Mathematics, where he defended his PhD in 1960 and habilitation in 1966. He was an Invited Speaker at the ICM in 1970 in Nice. He is professor at the Moscow Institute of Physics and Technology and a member of the Russian Academy of Sciences and European Academy of Sciences. A festschrift was published in honor of Besov's 70th birthday.
SU Ursae Majoris, or SU UMa, is a close binary star in the northern circumpolar constellation of Ursa Major. It is a periodic cataclysmic variable that varies in magnitude from a peak of 10.8 down to a base of 14.96. The distance to this system, as determined from its annual parallax shift of 4.53 mas, is 719 light-years. It is moving further from the Earth with a heliocentric radial velocity of +27 km/s.
AK Scorpii is a Herbig Ae/Be star and spectroscopic binary star about 459 light-years distant in the constellation Scorpius. The star belongs to the nearby Upper Centaurus–Lupus star-forming region and the star is actively accreting material. The binary is surrounded by a circumbinary disk that was imaged with VLT/SPHERE in scattered light and with ALMA.
TX Ursae Majoris is an eclipsing binary star system in the northern circumpolar constellation of Ursa Major. With a combined apparent visual magnitude of 6.97, the system is too faint to be readily viewed with the naked eye. The pair orbit each other with a period of 3.063 days in a circular orbit, with their orbital plane aligned close to the line of sight from the Earth. During the primary eclipse, the net brightness decreases by 1.74 magnitudes, while the secondary eclipse results in a drop of just 0.07 magnitude. TX UMa is located at a distance of approximately 780 light years from the Sun based on parallax measurements, but is drifting closer with a mean radial velocity of −13 km/s.
