Beta Librae
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Libra |
| Right ascension | 15h 17m 00.47s |
| Declination | −09° 22′ 58.3″ |
| Apparent magnitude (V) | 2.61 |
| Characteristics | |
| Spectral type | B8 V |
| U−B color index | −0.36 |
| B−V color index | −0.11 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | −35.2 km/s |
| Proper motion (μ) | RA: −0.096 mas/yr Dec.: −0.019 mas/yr |
| Parallax (π) | 20.38 ± 0.87 mas |
| Distance | 160 ± 7 ly (49 ± 2 pc) |
| Absolute magnitude (MV) | -0.84 |
| Details | |
| Mass | 3.5+0.3 −0.2[1] M☉ |
| Radius | 1.2 R☉ |
| Luminosity | 130 L☉ |
| Temperature | 12,000 K |
| Rotational velocity (v sin i) | 230 km/s |
| Age | 80+50 −40[1] Myr |
| Other designations | |
Beta Librae (β Lib, β Librae) is the brightest star in the constellation Libra. It has the traditional name Zubeneschamali (
/ˌzuːbənˌɛʃəˈmeɪli/) and the Latin name Lanx Borealis[3] ("the northern scale [of the Balance]"). The name Zubeneschamali is derived from the Arabic الزبن الشمالية (al-zuban al-šamāliyya) meaning "The Northern Claw".[4]
Its galactic coordinates are l° 352.0, b° +39.2.
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[edit] Description
Beta Librae is a blue dwarf star of spectral type B8 (main sequence star), a little less evolved than Sirius. It has apparent magnitude 2.7.
At a distance of 160 light years from Earth, it is about 130 times more luminous than the Sun and has a surface temperature of 12,000 K, double that of the Sun. This high temperature produces light with a simple spectrum, making it ideal for examining the interstellar gas and dust between us and the star. Like many stars of its kind, it is spinning rapidly, over 100 times faster than the Sun. This type of hydrogen-fusing star often appears blue-white, but Beta Librae is often described as greenish, the only greenish star visible to the naked eye.[5]
The small periodic variations in the magnitude of the Beta Librae imply the presence of a companion star which is not directly observable from earth.[6]
[edit] History
According to Eratosthenes Beta Librae was observed to be brighter than Antares. Ptolemy, three hundred and fifty years later, said it was as bright as Antares. The discrepancy may be due to Antares becoming brighter, but this is not known for certain. It could simply be caused by Beta Librae being a variable star with a variability of 0.03 of a magnitude.[4]
[edit] See also
[edit] References
- ^ a b
- ^ "HD 135742 -- Variable Star", SIMBAD Astronomical Object Database, http://simbad.u-strasbg.fr/sim-id.pl?protocol=html&Ident=beta+librae, retrieved 2007-01-22
- ^ Philippe La Hire, "Tabulae Astronomicae" (1727), see star table, page 13.
- ^ a b AAS (2006). "LIBRA – A Balanced View (page 7 of PDF)". Auckland Astronomical Society. http://www.astronomy.org.nz/Documents/Journal/journal_200606.pdf. Retrieved 2009-01-25.
- ^ Kaler, James B. (2006), "Zubeneschamali", Stars (University of Illinois), http://www.astro.uiuc.edu/~kaler/sow/zubenes.html, retrieved 2006-07-03
- ^ Mark Fisher (1999-2006), "Zuben Elschemali", The Electronic Sky, http://www.glyphweb.com/esky/stars/zubenelschemali.html, retrieved 2009-01-25
[edit] External links
Find more Arabic Star Names and their meanings at the following site:
- Moh'd Odeh (1998-2006). "Arabic Star Names". Islamic Crescents' Observation Project. http://www.icoproject.org/star.html. Retrieved 2006-07-03.
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