Beta Canum Venaticorum
Epoch J2000 Equinox J2000
|Right ascension||12h 33m 44.54482s|
|Declination||+41° 21′ 26.9248″|
|Apparent magnitude (V)||4.26|
|Spectral type||G0 V|
|U−B color index||0.04|
|B−V color index||0.58|
|Radial velocity (Rv)||+6.9 km/s|
|Proper motion (μ)||RA: –704.75 mas/yr
Dec.: +292.74 mas/yr
|Parallax (π)||118.49 ± 0.20 mas|
|Distance||27.53 ± 0.05 ly
(8.44 ± 0.01 pc)
|Absolute magnitude (MV)||4.64|
|Mass||1.025 ± 0.050 M☉|
|Radius||1.123 ± 0.028 R☉|
|Luminosity||1.151 ± 0.018 L☉|
|Surface gravity (log g)||4.60 cgs|
|Temperature||5,653 ± 72 K|
|Metallicity [Fe/H]||–0.21 dex|
|Rotational velocity (v sin i)||2.9 ± 0.4 km/s|
|Age||5.3 to 7.1 Gyr|
Beta Canum Venaticorum (β CVn, β Canum Venaticorum) is a G-type main-sequence star in the northern constellation Canes Venatici. At an apparent visual magnitude of 4.26, it is the second-brightest star in this relatively faint constellation. Based upon an annual parallax shift of 118.49 mas, this star is 27.53 light-years (8.44 parsecs) distant from the Earth.
Along with the brighter star Cor Caroli, the pair form the "southern dog" in this constellation that represents hunting dogs. The name Chara was originally applied to the "southern dog", but it later became used specifically to refer to Beta Canum Venaticorum. Chara (χαρά) means Joy in Greek.
In Chinese, 常陳 (Cháng Chén), meaning Imperial Guards, refers to an asterism consisting of β Canum Venaticorum, α Canum Venaticorum, 10 Canum Venaticorum, 6 Canum Venaticorum, 2 Canum Venaticorum, and 67 Ursae Majoris. Consequently, β Canum Venaticorum itself is known as 常陳四 (Cháng Chén sì, English: the Fourth Star of Imperial Guards.)
At apparent magnitude 4.26, Beta Canum Venaticorum is the second brightest star in the constellation. It has a stellar classification of G0 V, and so is a G-type main sequence star. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. The spectrum of this star shows a very weak emission line of singly ionized calcium (Ca II) from the chromosphere, making it a useful reference star for a reference spectrum to compare with other stars in a similar spectral category. (The Ca-II emission lines are readily accessible and can be used to measure the level of activity in a star's chromosphere.)
β CVn is considered to be slightly metal-poor, which means it has a somewhat lower portion of elements heavier than helium when compared to the Sun. In terms of mass, age and evolutionary status, however, this star is very similar to the Sun. As a result it has been called a solar analog. It is about 3% more massive than the Sun, with a radius 12% larger than the Sun's and 15% greater luminosity.
The components of this star's space velocity are (U, V, W) = (–25, 0, +2) km/s. In the past it was suggested that it may be a spectroscopic binary. However, further analysis of the data does not seem to bear that out. In addition, a search for a brown dwarf in orbit around this star failed to discover any such companion, at least down to the sensitivity limit of the instrument used.
Possibility of life
In 2006, astronomer Margaret Turnbull labeled Beta CVn as the top stellar system candidate to search for extraterrestrial life forms. Because of its solar-type properties, astrobiologists have listed it among the most astrobiologically interesting stars within 10 parsecs of the Sun. However, as of 2009, this star is not known to host planets.
Chara and Asterion in Military
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