Crater (constellation) in the context of "Binary star"

A quasar (/ˈkweɪzɑːr/ KWAY-zar) 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 accretion onto 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.

PKS 1127−145 is a radio-loud quasar located in the constellation of Crater. This is a Gigahertz Peaked Spectrum object with a redshift of (z) 1.187, first discovered by astronomers in 1966. Its radio spectrum appears to be flat making it a flat-spectrum radio quasar, or an FSRQ in short.

Delta Crateris (δ Crt, δ Crateris) is a solitary star in the southern constellation of Crater. With an apparent visual magnitude of 3.56, it is the brightest star in this rather dim constellation. It has an annual parallax shift of 17.017 mas as measured from Earth, indicating Delta Crateris lies at a distance of 192 ly from the Sun.

Alpha Crateris (α Crateris, abbreviated Alpha Crt, α Crt), officially named Alkes /ˈælkɛs/, is a star in the constellation of Crater. It is a cool giant star about 49.1 parsecs (160 ly) away.

Beta Crateris, Latinized from β Crateris, is a binary star system in the southern constellation of Crater. It is visible to the naked eye with an apparent visual magnitude of 4.46. Based upon an annual parallax shift of 9.59 mas as seen from Earth, it is around 340 light years from the Sun.

This is an astrometric binary star system with an orbital period of 6.0 years and a projected separation of 8.3 AU. The orbit has an estimated semimajor axis of 9.3 AU. The primary component A is listed as an A-type giant star with a stellar classification of A2 III. However, Houk and Smith-Moore (1988) give a main sequence classification of A1 V, while Abt and Morrell (1995) list it as a subgiant star with a class of A2 IV. The spectrum shows enhanced barium, possibly as a result of a previous mass transfer event.

NGC 3981 is an unbarred spiral galaxy located 65 million light-years away in the constellation of Crater. It was discovered on February 7, 1785, by William Herschel.

NGC 3981 is a member of the NGC 4038 Group which is part of the Virgo Supercluster.