# Beta Centauri

Observation data Epoch J2000 | |
---|---|

Constellation | Centaurus |

Right ascension | 14^{h} 03^{m} 49.4^{s} |

Declination | −60° 22′ 23″ |

Apparent magnitude (V) | 0.60 |

Characteristics | |

Spectral type | B1III |

U-B color index | −0.98 |

B-V color index | −0.22 |

Variable type | β Cep |

Astrometry | |

Radial velocity (R_{v}) | 5.9 km/s |

Proper motion (μ) | RA: −33.96 mas/yr Dec.: −2.506 mas/yr |

Parallax (π) | 6.21 0.56 mas |

Distance | 0 ± 0 ly (0 ± 0 pc) |

Absolute magnitude (M_{V}) | −5.42 |

Details ^{}
| |

Mass | 12 M_{☉} |

Luminosity | 11200 | L_{☉} |

Other designations | |

Database references | |

SIMBAD | data |

**Beta Centauri**(β Cen / β Centauri), also known as

**Hadar**or

**Agena**, is the second brightest star in the constellation Centaurus and the tenth brightest star in the nighttime sky. Beta Centauri is a blue-white giant star that is approximately 525 light-years from the solar system. The name

*Hadar*comes from the Arabic word for "ground", while the name

*Agena*comes from Latin words for "the knee".

In 1935, J.G. Voute identified Beta Centauri as a double star, giving it the identifier VOU 31. The companion is separated from the primary by 1.3", and has remained so since the discovery, although the position angle has changed slightly. This would indicate that the orbital period is very long, if the pair are actually gravitationally associated. The primary is also a spectroscopic binary, having at least one companion with an orbital period of 352 days, and possibly other companions.

Beta Centauri is well-known in the Southern Hemisphere as the inner of the two "Pointers" to the Southern Cross. A line made from the other pointer, Alpha Centauri, through Beta Centauri leads to within a few degrees of Gacrux, the star at the top of the cross. Using Gacrux, a navigator can draw a line with Acrux to effectively determine south.

The star is not actually shown on the Australian flag, although the Commonwealth Star is placed in a manner suggesting that it is.

**This article or section may be confusing or unclear for some readers.**

Please [improve the article] or discuss this issue on the talk page. This article has been tagged since

**August 2007**.

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**constellation**of Orion is the area outlined in the dashed yellow line. Orion contains a striking and well-known star pattern that has the form of a hunter.]] A

**constellation**is any one of the 88 areas into which the sky — or the celestial sphere — is divided.

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**Centaurus**

Click for larger image

List of stars in Centaurus

**Abbreviation:**Cen

**Genitive:**Centauri

**Symbology:**the Centaur

**Right ascension:**13 h

**Declination:**−50

**Area:**1060 sq. deg.

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**Right ascension**(abbrev.

**RA**; symbol

**α**) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.

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In astronomy,

**declination**(abbrev.**dec**or**δ**) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle.**.....**Click the link for more information. The

**apparent magnitude**(**) of a celestial body is a measure of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the atmosphere.***m***.....**Click the link for more information. In astronomy,

**stellar classification**is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics.**.....**Click the link for more information.**color index**is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. To measure the index, one observes the magnitude of an object successively through two different filters, such as U and B, or B and V, where U is

**.....**Click the link for more information.

**color index**is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. To measure the index, one observes the magnitude of an object successively through two different filters, such as U and B, or B and V, where U is

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*Variable Star*Author Robert A. Heinlein & Spider Robinson

Cover artist Stephan Martiniere

Country United States

Language English

Genre(s) Science fiction

Publisher Tor Books

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**Beta Cephei variables**are variable stars which exhibit variations in their brightness due to pulsations of the stars' surfaces. The point of maximum brightness roughly corresponds to the maximum contraction of the star. Typically, Beta Cephei variables change in brightness by 0.

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**Astrometry**is the branch of astronomy that relates to precise measurements and explanations of the positions and movements of stars and other celestial bodies. Although once thought of as an esoteric field with little useful application for the future, the information obtained by

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**Radial velocity**is the velocity of an object in the direction of the line of sight (i.e. its speed straight towards you, or away from you). The light of an object with a substantial radial velocity will be subject to Doppler effect, so the wavelength of the light decreases for

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**Metre per second**(U.S. spelling:

**meter per second**) is an SI derived unit of both speed (scalar) and velocity (vector quantity which specifies both magnitude and a specific direction), defined by distance in metres divided by time in seconds.

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The

**proper motion**of a star is the measurement of its change in position in the sky over time after improper motions are accounted for. This contrasts with radial velocity which is the measurement of the change in distance toward or away from the viewer over time.**.....**Click the link for more information. A

**minute of arc**,**arcminute**, or**MOA**is a unit of angular measurement, equal to one sixtieth (1/60) of one degree.^{[1]}Since one degree is defined as one three hundred sixtieth (1/360) of a circle, 1 MOA is 1/21600 of the amount of arc in a closed circle, or**.....**Click the link for more information. A

**year**(from Old English*gēr*) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. By extension, this can be applied to any planet: for example, a "Martian year" is the time in which Mars completes its own orbit.**.....**Click the link for more information. A

**minute of arc**,**arcminute**, or**MOA**is a unit of angular measurement, equal to one sixtieth (1/60) of one degree.^{[1]}Since one degree is defined as one three hundred sixtieth (1/360) of a circle, 1 MOA is 1/21600 of the amount of arc in a closed circle, or**.....**Click the link for more information. A

**year**(from Old English*gēr*) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. By extension, this can be applied to any planet: for example, a "Martian year" is the time in which Mars completes its own orbit.**.....**Click the link for more information.**Parallax**, or more accurately

**motion parallax**(Greek:

*παραλλαγή (parallagé)*= alteration) is the change of angular position of two stationary points relative to each other as seen by an observer, caused by the motion of an

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A

**minute of arc**,**arcminute**, or**MOA**is a unit of angular measurement, equal to one sixtieth (1/60) of one degree.^{[1]}Since one degree is defined as one three hundred sixtieth (1/360) of a circle, 1 MOA is 1/21600 of the amount of arc in a closed circle, or**.....**Click the link for more information.**Distance**is a numerical description of how far apart objects are at any given moment in time. In physics or everyday discussion, distance may refer to a physical length, a period of time, or an estimation based on other criteria (e.g. "two counties over").

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**1 light-year**=

SI units

010

^{15}m 010

^{12}km

Astronomical units

010

^{3}AU 0 pc

US customary / Imperial units

010

^{15}ft 010

^{12}mi

**light-year**or

**lightyear**(symbol:

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**parsec**(symbol pc) is a unit of length used in astronomy. The length of the parsec is based on the method of trigonometric parallax, one of the oldest methods for measuring the distances to stars.

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In astronomy,

**absolute magnitude**is the apparent magnitude,*m*, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. It allows the overall brightnesses of objects to be compared without regard to distance.**.....**Click the link for more information.**Mass**is a fundamental concept in physics, roughly corresponding to the intuitive idea of "how much matter there is in an object". Mass is a central concept of classical mechanics and related subjects, and there are several definitions of mass within the framework of relativistic

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The

**solar mass**is a standard way to express mass in astronomy, used to describe the masses of other stars and galaxies. It is equal to the mass of the Sun, about two nonillion kilograms or about 332,950 times the mass of the Earth.**.....**Click the link for more information.**Luminosity**has different meanings in several different fields of science.

## In photometry and color imaging

*luminosity*

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The

It is equal to the luminosity of the Sun, which is 3.827 × 10

**solar luminosity**, , is a unit of luminosity (power emitted in the form of photons) conventionally used by astronomers to give the luminosities of stars.It is equal to the luminosity of the Sun, which is 3.827 × 10

^{26}W, or 3.**.....**Click the link for more information. A

**star catalogue**, or**star catalog**, is an astronomical catalog that lists stars. In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the years, and this**.....**Click the link for more information.This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.