Virgo In The Sky

Virgo in the Sky: Virgo (IPA: /ˈvəː(r)gəʊ/, Latin: virgin, symbol , Unicode ♍) is a constellation of the zodiac. Lying between Leo to the west and the Libra to the east, it is one of the largest constellations in the sky. It can be easily found through its bright α star, Spica. The most prominent star in Virgo is Spica (α Vir), which was sometimes considered to represent an ear of wheat in Virgo's hand. Spica makes it easy to locate Virgo, as it can be found by following the curve of the Big Dipper to Arcturus in Boötes and continuing from there in the same curve ("follow the arc to Arcturus and speed on to Spica"). Other bright stars in Virgo include β Vir (Zavijava), γ Vir (Porrima), δ Vir (Auva) and ε Vir (Vindemiatrix). Other fainter stars that were also given names are ζ Vir (Heze), η Vir (Zaniah), ι Vir (Syrma) and μ Vir (Rijl al Awwa). The star 70 Virginis is an extrasolar planetary system with one confirmed planet 6.6 times the mass of Jupiter. Because of the presence of a galaxy cluster (consequently called the Virgo cluster) within its borders 5° to 10° west of ε Vir (Vindemiatrix), this constellation is especially rich in galaxies. Some examples are M49 (elliptical), M58 (spiral), M59 (elliptical), M60 (elliptical), M61 (spiral), M84 (elliptical), M86 (elliptical), M87 (elliptical and a famous radiosource), M89 (elliptical) and M90 (spiral). A noted galaxy that is not part of the cluster is M104, a spiral galaxy also called the Sombrero Galaxy. It is located about 10° due west of Spica. Who exactly Virgo was considered to represent is uncertain; in history, it has been associated with nearly every prominent goddess, including Ishtar, Isis, Cybele, Mary, Mother of Jesus, and Athena. Virgo may also feature, along with Ursa Major, and Ursa Minor, as part of the source of the myth of Callisto, either as Callisto herself, or as Hera. Persephone (who in some mythologies, notably the Eleusinian Mysteries, was considered to be a form of Demeter) is often mentioned as well, Virgo being visible mainly in the spring months when she was believed to have risen from the underworld. According to one interpretation, the constellation depicts Astraea, the virgin daughter of the god Zeus and the goddess Themis. Astraea was known as the goddess of justice, and was identified as this constellation due to the presence of the scales of justice Libra nearby, and supposedly ruled the world at one point with her wise ways until mankind became so callous she returned to skies disgusted.

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 Vir. 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 neighboring constellation of Leo around the year 2440. Cataloged by the numbers M87 and NGC4486, Virgo A is a giant elliptical galaxy in the constellation Virgo. An active interstellar object about 60 million light years away from earth whose nucleus provides the strongest observational evidence for the existence of a black hole. Virgo A is the most powerful known source of radio energy among the thousands of galactic systems comprising the so-called Virgo Cluster, this is turn is part of a “local” Super cluster of about 1,000 galaxies. Messier 87 (also known as M87, Virgo A or NGC 4486) is a giant elliptical galaxy. The galaxy is the largest and brightest galaxy within the Virgo Cluster.[citation needed] The galaxy also contains a notable active galactic nucleus that is a strong source of multiwavelength radiation, particularly radio waves. Since this is the largest giant elliptical galaxy near Earth and since it is one of the brightest radio sources in the sky, it is a popular target for both amateur astronomy observations and professional astronomy study. M87 is estimated to have a mass, within 32 kpc of its center, of 2.6 ± 0.3 ×1012 M☉. M87 has an unusually huge population (perhaps the greatest known around any one galaxy) of globular clusters as compared to the Milky Way's 150-200. A 2006 survey out to 25′ of its core estimates that there are 12,000 ± 800 globulars around M87. In 1918 Lick Observatory astronomer Heber Curtis discovered a jet of matter coming from M87 which he described as "a curious straight ray". This jet extends at least 5000 light-years from the nucleus of M87 and is made up of matter ejected from the galaxy, most likely by a black hole (a fact made more likely by the discovery of a disk of rapidly rotating gas around the nucleus of M87). Astronomers believe that the black hole in this galaxy has a mass of approximately 3 billion (3×109) solar masses. M87 has also been found to be a strong source of X-rays. Its proximity means that it is one of the best studied radio galaxies. In pictures taken by the Hubble Space Telescope in 1999, the motion of M87's jet was measured at four to six times the speed of light. This motion is believed to be a visual result of the relativistic velocity of the jet, and not true superluminal motion. However, detection of such motion supports the theory that quasars, BL Lac objects and radio galaxies may all be the same phenomenon, known as active galaxies, viewed from different perspectives. Observations made by Chandra X-ray Observatory indicate the presence of loops and rings in the hot X-ray emitting gas that permeate the cluster and surround M87. These loops and rings are generated by pressure waves. The pressure waves are caused by variations in the rate at which material is ejected from the supermassive black hole in jets. The distribution of loops suggests that minor eruptions occur every six million years. One of the rings, caused by a major eruption, is a shock wave 85,000 light-years in diameter around the black hole. Other remarkable features observed include narrow X-ray emitting filaments up to 100,000 light-years long, and a large cavity in the hot gas caused by a major eruption 70 million years ago. The regular eruptions prevent a huge reservoir of

gas from cooling and forming stars implying that M87’s evolution may have been seriously affected preventing it from becoming a large Spiral galaxy. The observations also imply the presence of sound waves: 56 octaves below middle C for the minor eruptions and 58 to 59 below middle C for the major eruptions. M87 is also a very good source of Gamma Rays. Gamma rays are the most energetic rays of the electromagnetic specturm; more than a million times as powerful as visible light. Gamma rays coming from M87 have been seen since the late 1990's, but recently, using the HESS Cherenkov telescopes; scientists have measured the variations of the gamma ray flux coming from M87, and found that the variations change over a matter of days. It is generally accepted that a supermassive black hole is located in the center of M87, with a mass of several thousand million solar masses. However, the fact that the variations can change over several days make the immediate vicinity of the supermassive black hole in M87 (about the size of our solar system), the most promising location of the gamma rays. In general is the surface area is smaller, the faster the variations, and vice versa. Source: Local High School Notes on astronomy and http://wikipedia.com under the search codes: Virgo, Messier 87 Date: Thursday, November 30, 2006