Timeline of neutron stars, pulsars, supernovae, and white dwarfs
Cygnus X-1 (abbreviated Cyg X-1) is a galactic X-ray source in the constellation Cygnus and was the first such source widely accepted to be a black hole. It was discovered in 1971 during a rocket flight and is one of the strongest X-ray sources detectable from Earth, producing a peak X-ray flux density of 2.3×10−23 W/(m2⋅Hz) (2.3×103 jansky). It remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 21.2 times the mass of the Sun and has been shown to be too small to be any known kind of normal star or other likely object besides a black hole. If so, the radius of its event horizon has 300 km "as upper bound to the linear dimension of the source region" of occasional X-ray bursts lasting only for about 1 ms.
The Small Magellanic Cloud (SMC), or Nubecula Minor, is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a D25 isophotal diameter of about 5.78 kiloparsecs (18,900 light-years), and contains several hundred million stars. It has a total mass of approximately 7 billion solar masses. At a distance of about 200,000 light-years, the SMC is among the nearest intergalactic neighbors of the Milky Way and is one of the most distant objects visible to the naked eye.
Centaurus X-3 is an X-ray pulsar with a period of 4.84 seconds. It was the first X-ray pulsar to be discovered, and the third X-ray source to be discovered in the constellation Centaurus. The system consists of a neutron star orbiting a massive, O-type supergiant star dubbed Krzeminski's star after its discoverer, Wojciech Krzemiński. Matter is being accreted from the star onto the neutron star, resulting in X-ray emission.
Scorpius X-1 is an X-ray source located roughly 9000 light years away in the constellation Scorpius. Scorpius X-1 was the first extrasolar X-ray source discovered, and, aside from the Sun, it is the strongest apparent non-transient source of X-rays in the sky. The X-ray flux varies day-to-day, and is associated with an optically visible star, V818 Scorpii, that has an apparent magnitude which fluctuates between 12-13.
The Coma Cluster is a large cluster of galaxies that contains over 1,000 identified galaxies. Along with the Leo Cluster, it is one of the two major clusters comprising the Coma Supercluster. It is located in and takes its name from the constellation Coma Berenices.
The Perseus cluster is a cluster of galaxies in the constellation Perseus. It has a recession speed of 5,366 km/s and a diameter of 863′. It is one of the most massive objects in the known universe, containing thousands of galaxies immersed in a vast cloud of multimillion-degree gas.
The Cygnus Loop is a large supernova remnant (SNR) in the constellation Cygnus, an emission nebula measuring nearly 3° across. Some arcs of the loop, known collectively as the Veil Nebula or Cirrus Nebula, emit in the visible electromagnetic range. Radio, infrared, and X-ray images reveal the complete loop.
The Vela Pulsar is a radio, optical, X-ray- and gamma-emitting pulsar associated with the Vela Supernova Remnant in the constellation of Vela. Its parent Type II supernova exploded approximately 11,000–12,300 years ago.
NGC 4151 is an intermediate spiral Seyfert galaxy with weak inner ring structure located 15.8 megaparsecs from Earth in the constellation Canes Venatici. The galaxy was first mentioned by William Herschel on March 17, 1787; it was one of the six Seyfert galaxies described in the paper which defined the term. It is one of the nearest galaxies to Earth to contain an actively growing supermassive black hole. The black hole would have a mass on the order of 2.5 million to 30 million solar masses. It was speculated that the nucleus may host a binary black hole, with about 40 million and about 10 million solar masses respectively, orbiting with a 15.8-year period. This is, however, still a matter of active debate.
Remo Ruffini. He is the Director of ICRANet, International Centre for Relativistic Astrophysics Network and the President of the International Centre for Relativistic Astrophysics (ICRA). Ruffini initiated the International Relativistic Astrophysics PhD, a common graduate school program of several universities and research institutes for the education of theoretical astrophysicists. He is the Director of the Erasmus Mundus IRAP PhD program. He has been Professor of Theoretical Physics at the University of Rome "Sapienza" from 1978 to 2012.
4U 1700-37 is one of the stronger binary X-ray sources in the sky, and is classified as a high-mass X-ray binary. It was discovered by the Uhuru satellite. The "4U" designation refers to the fourth Uhuru catalog.
Circinus X-1 is an X-ray binary star system that includes a neutron star. Observation of Circinus X-1 in July 2007 revealed the presence of X-ray jets normally found in black hole systems; it is the first of the sort to be discovered that displays this similarity to black holes. Circinus X-1 may be among the youngest X-ray binaries observed.
Astrophysical X-ray sources are astronomical objects with physical properties which result in the emission of X-rays.
The history of X-ray astronomy begins in the 1920s, with interest in short wave communications for the U.S. Navy. This was soon followed by extensive study of the earth's ionosphere. By 1927, interest in the detection of X-ray and ultraviolet (UV) radiation at high altitudes inspired researchers to launch Goddard's rockets into the upper atmosphere to support theoretical studies and data gathering. The first successful rocket flight equipped with instrumentation able to detect solar ultraviolet radiation occurred in 1946. X-ray solar studies began in 1949. By 1973 a solar instrument package orbited on Skylab providing significant solar data.
The Chamaeleon complex is a large star forming region (SFR) at the surface of the Local Bubble that includes the Chamaeleon I, Chamaeleon II, and Chamaeleon III dark clouds. It occupies nearly all of the constellation Chamaeleon and overlaps into Apus, Musca, Carina and Octans. The mean density of X-ray sources is about one source per square degree.
The Lockman Hole is an area of the sky in which minimal amounts of neutral hydrogen gas are observed from the perspective of Earth. The Lockman Hole is a relatively clear window on distant objects, which makes it an attractive area of the sky for observational astronomy surveys. It is located near the pointer stars of the Big Dipper in the constellation Ursa Major and is ~15 square degrees in size.
GR Muscae, also known as 2S 1254-690 is a binary star system in the constellation Musca composed of a neutron star of between 1.2 and 1.8 times the mass of the Sun and a low-mass star likely to be around the mass of the Sun in close orbit. A magnitude 19 blue star was pinpointed as the optical counterpart of the X-ray source in 1978. Its apparent magnitude varies from 18 to 19.1 over a period of 0.16 days.
4U 1543-475 is a recurrent X-ray transient located in the southern constellation Lupus, the wolf. IL Lupi is its variable star designation. It has an apparent magnitude that fluctuates between 14.6 and 16.7, making it readily visible in large telescopes but not to the naked eye. The object is located relatively far at a distance of approximately 17,000 light years based on Gaia DR3 parallax measurements.
GT Muscae, also known as 12 Muscae, is a variable star about 400 light years from the Earth, in the constellation Musca. It is a 5th magnitude star, so it should be faintly visible to the naked eye of an observer far from city lights. It is a quadruple star system, consisting of a spectroscopic binary containing an RS Canum Venaticorum variable star, orbiting an eclipsing binary. It varies in brightness from magnitude 4.96 to 5.23. GT Muscae is a very active X-ray source.
