Castor (star)
From Wikipedia, the free encyclopedia
 The position of Castor within the Gemini Constellation. |
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| Observation data Epoch J2000 |
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|---|---|
| Constellation (pronunciation) |
Gemini |
| Right ascension | 07h 34m 36s |
| Declination | +31° 53' 18" |
| Apparent magnitude (V) | 1.96 / 2.91 |
| Characteristics | |
| Spectral type | A1 V / A2 Vm |
| U-B color index | 0.02 |
| B-V color index | 0.04 |
| Astrometry | |
| Radial velocity (Rv) | 5.2 / −1.2 km/s |
| Proper motion (μ) | RA: −206.33 mas/yr Dec.: −148.18 mas/yr |
| Parallax (π) | 65.50 ± 1.10 mas |
| Distance | 49.8 ± 0.8 ly (15.3 ± 0.3 pc) |
| Absolute magnitude (MV) | 1.33 /2.28 |
| Details | |
| Mass | 2.15 / 1.7 M☉ |
| Radius | 2.3 / 1.6 R☉ |
| Luminosity | 30 / 14 L☉ |
| Temperature | 10,300 / 8,840 K |
| Metallicity | 950% / 280% Sun |
| Age | 200 million years |
| Other designations | |
| Database references | |
| SIMBAD | Castor Aa data |
| Database references | |
| SIMBAD | Castor Ba data |
Castor (α Gem / α Geminorum / Alpha Geminorum) is the second brightest star in the constellation Gemini and one of the brightest stars in the nighttime sky. Although it has the Bayer designation "alpha", it is actually fainter than Beta Geminorum (Pollux).
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[edit] Physical characteristics
Castor was discovered to be a visual binary in 1678, with the magnitude of its components being 2.8 and 2.0. The separation of the components is about 6" and the period of revolution is around 350 years. Each of the components of Castor is itself a spectroscopic binary, making Castor a quadruple star system. Castor has a faint companion separated from it by about 72" but having the same parallax and proper motion; this companion is also a spectroscopic binary with a period slightly less than 1 day. Castor can thus be considered to be a sextuple star system, with six individual stars gravitationally bound together. Component C has the variable star designation YY Geminorum.
[edit] The Castor system
| Parameter | Star Component | |||||
|---|---|---|---|---|---|---|
| Aa | Ab | Ba | Bb | Ca | Cb | |
| Spectral type | A1 V | Unknown (probably M5 V) | A2 Vm | M2 V | M0.5 Ve | M0.5 Ve |
| Mass (M☉) | 2.15 | 0.4–0.6 | 1.7 | 0.4–0.6 | 0.62 | 0.57 |
| Radius (R☉) | 2.3 | ? | 1.6 | ? | 0.76 | 0.68 |
[edit] Etymology and Culture
Castor and Pollux are the two "heavenly twin" stars that give the constellation Gemini (meaning "twins" in Latin) its name. The name Castor is traditionally thought by some people to carry the meaning "Beaver", after the generic name of the beaver. Actually the name Castor refers specifically to Castor, one of the twin sons of Zeus and Leda. The star also has the Arabic name Al-Ras al-Taum al-Muqadim, which literally means "The Head of the Foremost Twin". The Chinese recognized Castor as Yin, which is, according to the Chinese, one of the two fundamental principles upon which all things depend.
[edit] External links
- Castor 6. SolStation. Retrieved on December 5, 2005.
