The Centaurus constellation is located in the southern hemisphere. It lies in the third quadrant of the southern hemisphere and can be seen at latitudes between +25° and -90°. It is the ninth largest constellation in the sky, occupying an area of 1060 square degrees, and contains the largest number of the brightest stars among the constellations. Alpha Centauri and Beta Centauri are two of the top ten brightest stars in the sky. It is also home to Centaurus A, one of the brightest galaxies in the night sky, and to the globular cluster Omega Centauri. The famous Blue Planetary nebula, also known as the Southerner, is also located in Centaurus. There are three meteor showers associated with the constellation: the Alpha Centaurids, the Omicron Centaurids, and the Theta Centaurids.
The constellation represents the centaur, the half-man half-horse creature from Greek mythology. Sources differ on which centaur the constellation represents, but usually it is taken to be Heracles’ mentor Chiron. It was one of the constellations catalogued by the Greek astronomer Ptolemy in the 2nd century, but it had been mentioned in earlier Greek texts by the astronomer Eudoxus and the poet Aratus.
Alpha Centauri is the fourth brightest star in the sky. It is a multiple star system, only 4.365 light years distant and has an apparent visual magnitude of -0.27. Alpha Centauri A, the brightest component in the system, has a visual magnitude of -0.01. It is similar to the Sun: a yellow-white main sequence star belonging to the spectral type G2V, about 10% more massive than the Sun.
Beta Centauri is the tenth brightest star in night sky, is also called Hadar or Agena. It is 350 light-years from Earth. It is a system of three B-type stars. The two brightest stars orbit each other every 357 days and form a spectroscopic binary—a star that is seen as a binary only through analysis of the velocities seen in its spectrum. The third star is a fourth-magnitude star, and it orbits the other two every 225 years.
Centaurus A is the fifth brightest galaxy in the sky and one of the closest radio galaxies to the solar system. It is either a lenticular or giant elliptical galaxy, between 10 and 16 million light years distant. The galaxy has an apparent visual magnitude of 6.84. It is believed to contain a supermassive black hole at its centre. It is thought to be undergoing collision with a spiral galaxy, which it is in the process of devouring. As a result, there is an intense burst of star formation in Centaurus A. More than 100 star forming regions have been observed in the galaxy’s disk. In 1986, a type Ia supernova, SN 1986G, with a white dwarf star exploding, was spotted in the galaxy.
Omega Centauri is a globular cluster in Centaurus, also known as NGC 5139. It is located about 4 degrees south of Centaurus A. The cluster has an apparent magnitude of 3.7 and is approximately 15,800 light years distant. It orbits the Milky Way Galaxy and is one of the largest, brightest globular clusters known that are associated with the Milky Way. The cluster is visible to the naked eye. Originally listed as a star by Ptolemy, Omega Centauri was later rediscovered by Edmond Halley who listed it as a nebula in 1677, and eventually by the English astronomer John Frederick William Herschel, who recognized is as a cluster in the 1830s. The cluster contains several million Population II stars. The stars located in the centre of the cluster lie extremely close to each other, only 0.1 light years away.
NGC 4945 is one of the brightest galaxies in the Centaurus A/M83 group and the second brightest galaxy in the Centaurus A subgroup. It was discovered by James Dunlop in 1826.T he galaxy is approximately 11.7 million light years distant and has an apparent visual magnitude of 9.3. It is a spiral galaxy that contains an unusual, energetic Seyfert II nucleus, one that might contain a large black hole.
NGC3918 or the Blue Planetary nebula, sometimes also referred to as the Southerner, is a bright planetary nebula in Centaurus. It is the brightest planetary nebula in the far southern region of the sky. The nebula has an apparent visual magnitude of 8.5 and can be observed in a small telescope. It was discovered by John Herschel in 1834 and is approximately 4,900 light years distant.
Credits: Constellation Guide, NASA, Sky & Telescope, Wikipedia.