Delta Sagittarii
 Location of δ Sagittarii (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 |
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|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 20m 59.64354s[1] |
| Declination | -29° 49′ 41.1659″[1] |
| Apparent magnitude (V) | +2.70[2] |
| Characteristics | |
| Spectral type | K3 III[3] |
| U−B color index | +1.55[2] |
| B−V color index | +1.38[2] |
| Astrometry | |
| Radial velocity (Rv) | –19.9[4] km/s |
| Proper motion (μ) | RA: +32.54[1] mas/yr Dec.: –25.57[1] mas/yr |
| Parallax (π) | 9.38 ± 0.18[1] mas |
| Distance | 348 ± 7 ly (107 ± 2 pc) |
| Details | |
| Mass | 3.35 ± 0.34[5] M☉ |
| Radius | 129[5] R☉ |
| Luminosity | 2,500[5] L☉ |
| Surface gravity (log g) | 0.74 ± 0.10[5] |
| Temperature | 3,600 ± 300[5] K |
| Other designations | |
Delta Sagittarii (δ Sgr, δ Sagittarii) is a double star[6] in the southern zodiac constellation of Sagittarius. It has the traditional names Kaus Media, Kaus Meridionalis, and Media, which come from the Arabic قوس qaws 'bow' and Latin media 'middle'. The apparent visual magnitude of this star is +2.70,[2] making it easily visible to the naked eye. Parallax measurements place the distance at roughly 348 light-years (107 parsecs) from Earth.[1]
This is a giant star with a stellar classification K3 III. It has a mass of about 3.4 times that of the Sun, while the outer envelope has expanded to 129 times the Sun's radius. With an effective temperature of roughly 3,600 K, it is radiating 2,500 times the luminosity of the Sun.[5]
It has three dim companions:[citation needed]
- a 14th magnitude star at a separation of 26 arcseconds,
- a 15th magnitude star at a separation of 40 arcseconds, and
- a 13th magnitude star at a separation of 58 arcseconds from the primary.
It is not certain that these stars form a physical system or whether they are merely aligned by chance.
In the Hindu system of astrology, this star is also called "Purvashada Nakshatra". In ancient Chinese astronomy, it is the 4th star of 6 stars in the Dipper or 'South Dipper' mansion of the Black Tortoise of the North.[citation needed]
[edit] See also
[edit] References
- ^ a b c d e f 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 d Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99), Bibcode 1966CoLPL...4...99J
- ^ Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode 1982mcts.book.....H
- ^ 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 Schröder, K.-P.; Cuntz, M. (April 2007), "A critical test of empirical mass loss formulas applied to individual giants and supergiants", Astronomy and Astrophysics 465 (2): 593–601, arXiv:astro-ph/0702172, Bibcode 2007A&A...465..593S, doi:10.1051/0004-6361:20066633
- ^ a b "del Sgr -- Star in double system", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Delta+Sagittarii, retrieved 2012-01-11
[edit] External links
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