The Virgo Constellation

Virgo is one of the constellations of the zodiac. Its name is Latin for virgin. Lying between Leo to the west and Libra to the east, it is the second-largest constellation in the sky (after Hydra) and the largest constellation in the zodiac. It can be easily found through its brightest star, Spica. The bright star Spica makes it easy to locate Virgo, as it can be found by following the curve of the Big Dipper/Plough to Arcturus in Boötes and continuing from there in the same curve (“follow the arc to Arcturus and speed on to Spica”). Due to the effects of precession, the First Point of Libra, (also known as the autumn equinox point) lies within the boundaries of Virgo very close to β Virginis. This is one of the two points in the sky where the celestial equator crosses the ecliptic (the other being the First Point of Aries, now in the constellation of Pisces.) This point will pass into the neighbouring constellation of Leo around the year 2440.

Besides Spica, other bright stars in Virgo include β Virginis (Zavijava), γ Virginis (Porrima), δ Virginis (Auva) and ε Virginis(Vindemiatrix). Other fainter stars that were also given names are ζ Virginis (Heze), η Virginis (Zaniah), ι Virginis (Syrma), κ Virginis (Kang), λ Virginis (Khambalia) and φ Virginis (Elgafar). The star 70 Virginis has one of the first known extrasolar planetary systems with one confirmed planet 7.5 times the mass of Jupiter. The star Chi Virginis has one of the most massive planets ever detected, at a mass of 11.1 times that of Jupiter. The sun-like star 61 Virginis has three planets: one is a super-Earth and two are Neptune-mass planets. SS Virginis is a variable star with a noticeable red colour. It varies in magnitude from a minimum of 9.6 to a maximum of 6.0 over a period of approximately one year.

Because of the presence of a galaxy cluster (consequently called the Virgo Cluster) within its borders 5° to 12° west of ε Vir (Vindemiatrix), this constellation is especially rich in galaxies. Some examples are Messier 49 (elliptical), Messier 58 (spiral), Messier 59 (elliptical), Messier 60 (elliptical), Messier 61 (spiral), Messier 84  (lenticular), Messier 86 (lenticular), Messier 87 (elliptical and a famous radio source), Messier 89 (elliptical) and Messier 90 (spiral). A noted galaxy that is not part of the cluster is the Sombrero Galaxy (M104), an unusual spiral galaxy. It is located about 10° due west of Spica. NGC 4639 is a face-on barred spiral galaxy located 78 Mly from Earth (redshift 0.0034). Its outer arms have a high number of Cepheid variables, which are used as standard candles to determine astronomical distances. Because of this, astronomers used several Cepheid variables in NGC 4639 to calibrate type 1a supernovae as standard candles for more distant galaxies. Because of this, astronomers used several Cepheid variables, which are used as standard candles to determine astronomical distances. Because of this, astronomers used several Cepheid variables in NGC 4639 to calibrate type 1a supernovae as standard candles for more distant galaxies. NGC 4981 was discovered on 17 April 1784 by William Herschel.

Virgo possesses several galaxy clusters, one of which is HCG 62. A Hickson Compact Group, HCG 62 is at a distance of 200 Mly from Earth (redshift 0.0137) and possesses a large central elliptical galaxy. It has a heterogeneous halo of extremely hot gas, posited to be due to the active galactic nucleus at the core of the central elliptical galaxy. M87 is the largest galaxy in the Virgo cluster and is at a distance of 60 Mly from Earth (redshift 0.0035). It is a major radio source, partially due to its jet of electrons being flung out of the galaxy by its central supermassive black hole. Because this jet is visible in several different wavelengths, it is of interest to astronomers who wish to observe black holes in a unique galaxy. M84 is another elliptical radio galaxy in the constellation of Virgo; it is at a distance of 60 Mly (redshift 0.0035) as well. Astronomers have surmised that the speed of the gas clouds orbiting the core (approximately 400 km/s) indicates the presence of an object with a mass 300 million times that of the sun, which is most likely a black hole. The Sombrero Galaxy, M104, is an edge-on spiral galaxy located 28 million light-years from Earth (redshift 0.0034). It has a bulge at its centre made up of older stars that is larger than normal. It is surrounded by large, bright globular clusters and has a very prominent dust lane made up of polycyclic aromatic hydrocarbons. NGC 4438 is a peculiar galaxy with an active galactic nucleus, at a distance of 50 Mly from Earth (redshift 0.0035). Its supermassive black hole is ejecting jets of matter, creating bubbles with a diameter of up to 78 ly. NGC 4261 also has a black hole 20 ly from its centre with a mass of 1.2 billion solar masses. It is located at a distance of 45 Mly from Earth (redshift 0.0075) and has an unusually dusty disk with a diameter of 300 ly. Along with M84 and M87, NGC 4261 has strong emissions in the radio spectrum. NGC 4567 and NGC 4568 form a pair of spiral galaxies in the Virgo Cluster, located approximately 59.4 million light years from the solar system. The galaxies are in the process of colliding with each other. Their apparent magnitude is 10.9. The Siamese Twins were discovered by William Herschel in 1784. A supernova was observed in the galaxies in 2004. NGC 4526 is a lenticular galaxy. It belongs to the Virgo cluster. The galaxy has a visual magnitude of 10.7 and is about 55 million light years distant. Two supernovae were discovered in the galaxy: SN 1969E in 1969 and SN 1994D in 1994. IC 1101 is a supergiant elliptical galaxy in the Abell 2029 galaxy cluster located about 1.07 Gly from Earth. At the diameter of 5.5 million light-years or more than 50 times the size of the Milky Way, it was the largest known galaxy in the universe.

Virgo is also home to the quasar 3C 273 which was the first quasar ever to be identified. With a magnitude of ~12.9, it is also the optically brightest quasar in the sky. Credits: Constellation Guide, Wikipedia.