Beta Draconis
 Location of β Draconis (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Draco |
| Right ascension | 17h 30m 25.96170s[1] |
| Declination | +52° 18′ 04.9993″[1] |
| Apparent magnitude (V) | 2.79[2] |
| Characteristics | |
| Spectral type | G2 II[3] |
| U−B color index | +0.64[4] |
| B−V color index | +0.98[4] |
| R−I color index | +0.48[4] |
| Astrometry | |
| Radial velocity (Rv) | −20.0 ± 0.9[5] km/s |
| Proper motion (μ) | RA: −15.89[1] mas/yr Dec.: +12.28[1] mas/yr |
| Parallax (π) | 8.58 ± 0.10[1] mas |
| Distance | 380 ± 4 ly (117 ± 1 pc) |
| Absolute magnitude (MV) | –2.28[6] |
| Details | |
| Mass | 6.0 ± 0.2[2] M☉ |
| Radius | 40[7] R☉ |
| Luminosity | 1,000[8] L☉ |
| Surface gravity (log g) | 1.86 ± 0.04[2] cgs |
| Temperature | 5,160 ± 150[2] K |
| Rotational velocity (v sin i) | 13[4] km/s |
| Age | 65[2] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Beta Draconis (β Draconis, β Dra) is the third brightest star in the northern circumpolar constellation of Draco. It has the traditional name Rastaban, which has also been used for Gamma Draconis.[7][10] With an apparent visual magnitude of 2.79,[2] it is bright enough to be easily seen with the naked eye. Based upon parallax measurements from the Hipparcos astrometry satellite,[11][12] it lies at a distance of about 380 light-years (120 parsecs) from Earth.[1]
Compared to the Sun, this is an enormous star with six times the mass and roughly 40 times the radius. At this size, Beta Draconis is emitting about 950 times the luminosity of the Sun from its outer envelope at an effective temperature of 5,160 K,[2] giving it the yellow hue of a G-type star.[13] The spectrum matches a stellar classification of G2 Ib–IIa,[2] with the luminosity class notation Ib–IIa indicating it lies part way between the bright giant and giant stages of its stellar evolution. It is about 67 million years old.[2]
This is a binary star system, with a binary star designation of ADS 10611, in which the supergiant is orbited by a dwarf companion once every four millennia or so.[5][7]
Name
The traditional name, from the Arabic phrase ra's ath-thu'ban ("head of the serpent") is less commonly written Rastaben. It is also known as Asuia and Alwaid, the latter meaning "who is to be destroyed," though some trace it to Arabic al'awwad ("the lute player"). It is part of the asterism of the Mother Camels (Arabic al'awa'id), along with γ Dra (Eltanin), μ Dra (Erakis), ν Dra (Kuma) and ξ Dra (Grumium), which was later known as the Quinque Dromedarii.[14]
In Chinese, 天棓 (Tiān Bàng), meaning Celestial Flail, refers to an asterism consisting of β Draconis, ξ Draconis, ν Draconis, γ Draconis and ι Herculis.[15] Consequently, β Draconis itself is known as 天棓三 (Tiān Bàng sān, English: the Third Star of Celestial Flail.)[10][16][17]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 4.0 4.1 4.2 4.3 4.4 HR 6536, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line September 17, 2008.
- ↑ 5.0 5.1 5.2 * bet Dra -- Star in double system, database entry, SIMBAD. Accessed on line September 17, 2008.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 7.0 7.1 7.2 Rastaban, Stars, Jim Kaler. Accessed on line September 17, 2008.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Entry 17304+5218, The Washington Double Star Catalog, United States Naval Observatory. Accessed on line September 17, 2008.
- ↑ 10.0 10.1 pp. 207–208, Star-names and Their Meanings, Richard Hinckley Allen, New York, London: G. E. Stechert, 1899.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ↑ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ↑ Alwaid, Constellations of Words, Anne Wright. Accessed on line September 17, 2008.
External links
- Dibon-Smith, Richard (1992). StarList 2000: A Quick Reference Star Catalog for Astronomers. New York: John Wiley & Sons. ISBN 0-471-55895-8
