Denebola
 Denebola is located at the left apex on this map of the constellation. |
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| Constellation | Leo |
| Right ascension | 11h 49m 03.57834s[1] |
| Declination | +14° 34′ 19.4090″[1] |
| Apparent magnitude (V) | 2.113[2] |
| Characteristics | |
| Spectral type | A3 V[3] |
| U−B color index | +0.153[2] |
| B−V color index | +0.107[2] |
| Variable type | δ Sct[4] |
| Astrometry | |
| Radial velocity (Rv) | –0.2[5] km/s |
| Proper motion (μ) | RA: –497.68[1] mas/yr Dec.: –114.67[1] mas/yr |
| Parallax (π) | 90.91 ± 0.52[1] mas |
| Distance | 35.9 ± 0.2 ly (11.00 ± 0.06 pc) |
| Details | |
| Mass | 1.75[6] M☉ |
| Radius | 1.728[6] R☉ |
| Luminosity | 15[6] L☉ |
| Surface gravity (log g) | 4.0[7] |
| Temperature | 8,500[7] K |
| Metallicity [Fe/H] | +0.00[6] dex |
| Rotational velocity (v sin i) | 128[8] km/s |
| Age | (1–3.8) × 108[6] years |
| Other designations | |
Denebola (β Leo, β Leonis, Beta Leonis) is the second brightest star in the zodiac constellation of Leo. It is an A-type main sequence star with 75% more mass than the Sun and twelve times the Sun's luminosity. Based upon parallax measurements, this star is at a distance of about 36 light-years (11 parsecs) from Earth. Its apparent visual magnitude is 2.14, making it readily visible to the naked eye. Denebola is a Delta Scuti type variable star, meaning its luminosity varies very slightly over a period of a few hours.[4]
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[edit] Etymology
Its name is shortened from Deneb Alased, from the Arabic phrase ذنب الاسد ðanab al-asad "tail of the lion", as it represents the lion's tail—the star's position in the Leo constellation. (Deneb in Cygnus has a similar name origin.) On R. A. Proctor's 1871 star chart of the northern hemisphere it was designated Deneb Aleet. To ancient Chinese astronomers, it formed part of the five-star Woo Ti Tsi 五帝座一: the Seat of the Twelve Emperors. In astrology, Denebola was believed to portend misfortune and disgrace.[11]
In Johann Bayer's Uranometria, published in 1603, the star was designated β Leonis; for the second-brightest star in the constellation of Leo. In 1725, John Flamsteed designated this star 94 Leo. (The Flamsteed designation was assigned on the basis of increasing right ascension within the constellation, rather than luminosity.) Additional designations followed as this star was recorded in subsequent star catalogues.
[edit] Properties
Denebola is a relatively young star with an age estimated at less than 400 million years. Interferometric observations give a radius that is about 173% that of the Sun. However, the high rate of rotation results in an oblate shape with an equatorial bulge. It has 75% more mass than the Sun, which results in a much higher overall luminosity and a shorter life span on the main sequence.[6]
Based upon the star's spectrum, it has a stellar classification of A3 V,[3] with the luminosity class 'V' indicating this is a normal main sequence star that is generating energy through the nuclear fusion of hydrogen at its core. The effective temperature of Denebola's outer envelope is about 8,500 K, which results in the white hue typical of A-type stars. Denebola has a high projected rotational velocity of 128 km/s, which is of the same order of magnitude as for the very rapidly rotating star Achernar. Compare this to the Sun's more leisurely equatorial rotation velocity of 2 km/s.[7] This star is believed to be a Delta Scuti variable star that exhibits fluctuations in luminosity of 0.025 magnitudes roughly ten times per day.[4]
Denebola shows a strong infrared excess, which most likely means there is a circumstellar debris disk of cool dust in orbit around it.[12] As our solar system is believed to have formed out of such a disk, Denebola and similar stars such as Vega and Beta Pictoris may be good candidate locations for extrasolar planets. The dust surrounding Denebola has a temperature of about 120 K (−153 °C). Observations with the Herschel Space Observatory have provided resolved images, which show the disk to be located at 39 Astronomical Units from the star, or 39 times the distance from the Earth to the Sun.[13]
Kinematic studies have shown that Denebola is part of a stellar association dubbed the IC 2391 supercluster. All the stars of this group share a roughly common motion through space, although they are not gravitationally bound. This suggests that they were born in the same location, and perhaps initially formed an open cluster. Other stars in this association include Alpha Pictoris, Beta Canis Minoris and the open cluster IC 2391. In total more than sixty probable members of the group have been identified.[14]
[edit] In Military
Denebola is used for the name of three United States navy ships: USS Denebola (AD-12), USS Denebola (AF-56) and USNS Denebola (T-AKR-289).
[edit] See also
[edit] References
- ^ a b c d e van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
- ^ a b c Gutierrez-Moreno, Adelina et al. (1966), A System of photometric standards, 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode 1966PDAUC...1....1G
- ^ a b Cowley, A. et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal 74: 375–406, Bibcode 1969AJ.....74..375C, doi:10.1086/110819
- ^ a b c Mkrtichian, D. E.; Yurkov, A. (5th-7th November 1997). "β Leo - Back to Delta Scuti Stars?". Proceedings of the 20th Stellar Conference of the Czech and Slovak Astronomical Institutes. Brno, Czech Republic: Dordrecht, D. Reidel Publishing Co.. pp. 172. Bibcode 1998vsr..conf..143M. ISBN 80-85882-08-6.
- ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick, ed., The Revision of the General Catalogue of Radial Velocities, University of Toronto: International Astronomical Union, http://adsabs.harvard.edu/abs/1967IAUS...30...57E, retrieved 2009-09-10
- ^ a b c d e f Di Folco, E. et al (2004). "VLTI near-IR interferometric observations of Vega-like stars". Astronomy and Astrophysics 426 (2): 601–617. Bibcode 2004A&A...426..601D. doi:10.1051/0004-6361:20047189.
- ^ a b c Acke, B.; Waelkens, C. (2004). "Chemical analysis of 24 dusty (pre-)main sequence stars". Astronomy and Astrophysics 427 (3): 1009–1017. arXiv:astro-ph/0408221. Bibcode 2004A&A...427.1009A. doi:10.1051/0004-6361:20041460.
- ^ Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode 2007A&A...463..671R, doi:10.1051/0004-6361:20065224
- ^ "SIMBAD query result: V* bet Leo -- Variable Star of delta Sct type". Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Denebola. Retrieved 2007-06-18.
- ^ "Denebola". Alcyone. http://www.alcyone.de/SIT/mainstars/SIT000544.htm. Retrieved 2006-08-10.
- ^ Allen, Richard Hinckley (1899). Star Names and their Meanings. New York, Leipzig: G. E. Stechert.
- ^ Cote, J. (1987). "B and A type stars with unexpectedly large colour excesses at IRAS wavelengths". Astronomy and Astrophysics 181 (1): 77–84. Bibcode 1987A&A...181...77C.
- ^ Matthews, B. C. et al (2010). "Resolving debris discs in the far-infrared: Early highlights from the DEBRIS survey". Astronomy and Astrophysics 518: L135. Bibcode 2010A&A...518L.135M. doi:10.1051/0004-6361/201014667.
- ^ Eggen, O. J. (1991). "The IC 2391 supercluster". Astronomical Journal 102: 2028–2040. Bibcode 1991AJ....102.2028E. doi:10.1086/116025.
[edit] External links
- Kaler, Jim. "Denebola". Stars. University of Illinois. http://stars.astro.illinois.edu/sow/denebola.html. Retrieved 2012-01-14.
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