Centaurus
A large southern constellation with the nearest star system to Earth.
Centaurus is a bright, large constellation in the southern sky. It was one of the 48 constellations cataloged by the 2nd-century astronomer Ptolemy and is still among the 88 modern constellations. In Greek myth, it depicts a centaur—half human, half horse. (The zodiac also has a centaur constellation: Sagittarius.) Its notable stars include Alpha Centauri, the nearest star system to our own; Beta Centauri, a neighbor in the sky; and HR 5171, one of the largest stars ever found. The constellation also holds Omega Centauri, the brightest globular cluster seen from Earth and the largest known in the Milky Way, possibly the leftover core of a dwarf galaxy.
**Features** Centaurus is a large constellation packed with bright stars, including two brighter than magnitude 1, and many famous deep-sky objects—though the Milky Way does not run through it.
**Stars** Centaurus has several very bright stars. Its alpha and beta stars serve as "southern pointer stars" to locate the constellation Crux. It contains 281 stars above magnitude 6.5 (visible without a telescope), more than any other constellation. Alpha Centauri, the closest star system to the Sun, has a high proper motion; in about 4,000 years it will be only half a degree from Beta Centauri. Alpha Centauri is a triple system: a binary pair orbited by Proxima Centauri, currently the nearest star to the Sun. Traditionally called Rigil Kentaurus ("foot of the centaur") or Toliman ("two male ostriches"), the system has an overall magnitude of −0.28 and lies 4.4 light-years away. The two main stars are both yellow-hued: one at magnitude −0.01, the other at 1.35. Proxima, a red dwarf of magnitude 11.0, appears nearly 2 degrees from the close pair and orbits them in about a million years. It is also a flare star, brightening by over a magnitude during minutes-long outbursts. The binary pair orbits each other every 80 years and will appear closest through telescopes in 2037 and 2038; together they form the third-brightest "star" in the night sky. Beta Centauri (also called Hadar or Agena) lies beyond Proxima toward the narrow axis of Crux, forming with Alpha a far-southern limb of the constellation. It is a double star: the primary is a blue-hued giant of magnitude 0.6, 525 light-years away; the secondary is magnitude 4.0, separated enough to need strong magnification.
Quick Facts
- Abbreviation
- Cen
- Genitive
- Centauri
- Symbolism
- the Centaur
- Ra
- 11 · 05 · 20.9415–15 · 03 · 11.1071
- Dec
- -29.9948788–-64.6957885
- Family
- Hercules
- Areatotal
- 1060
- Arearank
- 9th
- Numbermainstars
- 11
- Numberbfstars
- 69
- Numberstarsplanets
- 15
- Numberbrightstars
- 10
Facts from the source article.
Lore & Background
Centaurus is a large constellation with many bright stars, including two stars brighter than magnitude 1, and a number of well-known deep-sky objects, though the Milky Way does not lie within its borders. Its alpha and beta stars are used as 'southern pointer stars' to help observers find the constellation Crux. Centaurus has 281 stars above magnitude 6.5 visible to the unaided eye, the most of any constellation. Alpha Centauri, the closest star system to the Sun, has a high proper motion and will be a mere half-degree from Beta Centauri in approximately 4000 years. Alpha Centauri is a triple star system composed of a binary system orbited by Proxima Centauri, currently the nearest star to the Sun. Traditionally called Rigil Kentaurus or Toliman, the system has an overall magnitude of −0.28 and is 4.4 light-years from Earth. Proxima is a red dwarf and a flare star with minutes-long outbursts where it brightens by over a magnitude. Beta Centauri, also called Hadar and Agena, is a double star with a blue-hued giant primary of magnitude 0.6, 525 light-years from Earth. The northerly star Theta Centauri, officially named Menkent, is an orange giant star of magnitude 2.06 and is the only bright star of Centaurus easily visible from mid-northern latitudes.
Reader's Guide
Centaurus is notable for containing Alpha Centauri, the nearest star system to the Solar System, and its neighbor Beta Centauri, both used as pointer stars to Crux. The constellation also hosts HR 5171, one of the largest stars yet discovered, and Omega Centauri, the brightest globular cluster as visible from Earth and the largest identified in the Milky Way, possibly a remnant of a dwarf galaxy. Omega Centauri is classified as a Shapley class VIII cluster, meaning its center is loosely concentrated, and it is one of only two globular clusters given a Bayer letter. The constellation is rich in deep-sky objects, including open clusters NGC 3766 and NGC 5460, the planetary nebula NGC 3918 (the Blue Planetary), and several galaxies such as NGC 4622, NGC 5253, NGC 4945, NGC 5102, and the active galaxy Centaurus A (NGC 5128). Centaurus A, at 11 million light-years away, has a supermassive black hole at its core and is one of the closest active galaxies to Earth. The constellation also contains the white dwarf star BPM 37093, nicknamed 'Lucy' for its crystalline carbon structure, and PDS 70, a T Tauri star around which the first conclusive image of a protoplanetary disk containing a nascent exoplanet was captured in July 2018.
Did You Know?
- Alpha Centauri is the nearest star system to the Solar System, at 4.4 light-years away.
- Omega Centauri is the largest and brightest globular cluster in the Milky Way, with a diameter of 150 light-years.
- The white dwarf star BPM 37093 has carbon atoms thought to have formed a crystalline structure, earning it the nickname 'Lucy'.
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