Astronomy:HD 189245
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 20h 00m 20.249s[1] |
| Declination | −33° 42′ 12.42″[1] |
| Apparent magnitude (V) | 5.66[2] |
| Characteristics | |
| Spectral type | F8.5 V Fe−0.6 CH−0.5[3] |
| U−B color index | −0.04[2] |
| B−V color index | +0.498[4] |
| Astrometry | |
| Radial velocity (Rv) | −13.2[5] km/s |
| Proper motion (μ) | RA: +128.794[1] mas/yr Dec.: −289.360[1] mas/yr |
| Parallax (π) | 45.1537 ± 0.0551[1] mas |
| Distance | 72.23 ± 0.09 ly (22.15 ± 0.03 pc) |
| Absolute magnitude (MV) | 4.06[6] |
| Details | |
| Surface gravity (log g) | 4.31[3] cgs |
| Temperature | 6,333[3] K |
| Metallicity [Fe/H] | −0.09[3] dex |
| Rotational velocity (v sin i) | 72.6[7] km/s |
| Age | 100 or 500[4] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 189245 is the Henry Draper catalogue designation for a solitary[9] star in the southern constellation of Sagittarius. It has an apparent visual magnitude of 5.66,[2] which means it is faintly visible to the naked eye. Parallax measurements from the Hipparcos satellite indicate a distance of 72 light years from the Sun.[1] It is drifting closer with a heliocentric radial velocity of −13 km/s.[5]
The stellar classification of this star is F8.5 V Fe−0.6 CH−0.5,[3] indicating that it is an F-type main sequence star with a spectrum that shows deficiencies in iron (Fe) and methylidyne (CH) in its outer atmosphere. It is a variable star with an active chromosphere and is a source of X-ray emission.[3][10] HD 189245 is spinning rapidly with a projected rotational velocity of 72.6[7] km/s. Gyrochronology indicates this is a young star with an estimated age of 500 million years. However, the amount of X-ray emission suggests an even younger star that is roughly 100 million years old.[4]
The velocity components of HD 189245 indicate that it is a likely member of the AB Doradus moving group of stars, which share a common motion through space. This group has an age of around 50 million years and is centered at a point 98 ly (30 pc) from the Sun.[11]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G. Gaia EDR3 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 Corben, P. M. et al. (1972), "U, B, V photometry of 500 southern stars", Monthly Notes of the Astronomical Society of South Africa 31: 7–22, Bibcode: 1972MNSSA..31....8C.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Gray, R. O. et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal 132 (1): 161–170, doi:10.1086/504637, Bibcode: 2006AJ....132..161G.
- ↑ 4.0 4.1 4.2 Vican, Laura (June 2012), "Age Determination for 346 Nearby Stars in the Herschel DEBRIS Survey", The Astronomical Journal 143 (6): 135, doi:10.1088/0004-6256/143/6/135, Bibcode: 2012AJ....143..135V.
- ↑ 5.0 5.1 Nordström, B. et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14,000 F and G dwarfs", Astronomy and Astrophysics 418: 989–1019, doi:10.1051/0004-6361:20035959, Bibcode: 2004A&A...418..989N.
- ↑ Reiners, Ansgar (January 2006), "Rotation- and temperature-dependence of stellar latitudinal differential rotation", Astronomy and Astrophysics 446 (1): 267–277, doi:10.1051/0004-6361:20053911, Bibcode: 2006A&A...446..267R
- ↑ 7.0 7.1 Schröder, C. et al. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo", Astronomy and Astrophysics 493 (3): 1099–1107, doi:10.1051/0004-6361:200810377, Bibcode: 2009A&A...493.1099S, http://goedoc.uni-goettingen.de/goescholar/bitstream/handle/1/9690/aa10377-08.pdf?sequence=2[yes|permanent dead link|dead link}}]
- ↑ "HD 189245". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+189245.
- ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E.
- ↑ Jeffries, R. D.; Jewell, S. J. (September 1993), "The Kinematics of Active Late Type Stars Observed by the ROSAT Wide-Field Camera", Monthly Notices of the Royal Astronomical Society 264 (1): 106, doi:10.1093/mnras/264.1.106, Bibcode: 1993MNRAS.264..106J.
- ↑ Nakajima, Tadashi; Morino, Jun-Ichi (January 2012), "Potential Members of Stellar Kinematic Groups within 30 pc of the Sun", The Astronomical Journal 143 (1): 2, doi:10.1088/0004-6256/143/1/2, Bibcode: 2012AJ....143....2N.
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