Delta2 Lyrae
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 18h 54m 30.2838s |
| Declination | +36° 53′ 55.007″ |
| Apparent magnitude (V) | 4.30v |
| Characteristics | |
| Spectral type | M4 II |
| U−B color index | +1.65 |
| B−V color index | +1.68 |
| Astrometry | |
| Radial velocity (Rv) | -25.55 km/s |
| Proper motion (μ) | RA: −7.36 mas/yr Dec.: 4.06 mas/yr |
| Parallax (π) | 4.43 ± 0.18 mas |
| Distance | 740 ± 30 ly (226 ± 9 pc) |
| Details | |
| Mass | 7.3[1] M☉ |
| Radius | 286[1] - 381[2] R☉ |
| Luminosity | 12,900[1] - 23,100[2] L☉ |
| Surface gravity (log g) | 0[3] cgs |
| Temperature | 3,550[3] - 3,650[2] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Delta2 Lyrae (δ2 Lyr) is a 4th magnitude star in the constellation Lyra, approximately 900 light years away from Earth. It is one of the M4II spectral standard stars,[4] meaning it is a bright giant star with a surface temperature around 3,600 kelvins. It puts out more energy than 10,000 suns, although more than 90% of it at longer than visual wavelengths. Direct angular measurements, combined with the Hipparcos parallax, give a radius of 1.1[5] - 1.3[6] astronomical units, comparable to the size calculated from other observed data.
It began life as a hot blue main sequence star, but now is a large cool asymptotic giant branch star with a degenerate helium core. It is a semi-regular variable star that has its brightness change by 0.2 magnitudes over an ill-defined period. Delta2 Lyrae was once thought to form a visual binary with the star Delta1 Lyrae, but it does not, only appearing to do so to the naked eye.
The spectral type of the nearby star system CCDM J18545+3654BC suggests that they are at the same distance as Delta2 Lyrae, which could mean that the three stars form a triple star system. In this case, CCDM J18545+3654BC would be 24,000 AU away from Delta2 Lyrae, and it would take 24,000 years for it to make an orbit. The two stars in the CCDM J18545+3654BC system take at least 10,500 years to make an orbit and are separated by 600AU.
Delta2 Lyrae is the brightest member of the scattered open cluster Stephenson 1.[7][8]
References
- ↑ 1.0 1.1 1.2 Tsuji, T. (2007). "Isotopic abundances of Carbon and Oxygen in Oxygen-rich giant stars". Proceedings of the International Astronomical Union 2: 307. arXiv:astro-ph/0610180. doi:10.1017/S1743921307000622.
- ↑ 2.0 2.1 2.2 Blum, R. D.; Ramirez, S. V.; Sellgren, K.; Olsen, K. (2003). "Really Cool Stars and the Star Formation History at the Galactic Center". The Astrophysical Journal 597: 323. arXiv:astro-ph/0307291. Bibcode:2003ApJ...597..323B. doi:10.1086/378380.
- ↑ 3.0 3.1 Levesque, E. M.; Massey, P.; Olsen, K. A. G.; Plez, B.; Josselin, E.; Maeder, A.; Meynet, G. (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not as Cool as We Thought". The Astrophysical Journal 628 (2): 973. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901.
- ↑ Bibcode: 1989BICDS..36...27G
- ↑ Dyck, H. M.; Benson, J. A.; Van Belle, G. T.; Ridgway, S. T. (1996). "Radii and Effective Temperatures for K and M Giants and Supergiants". The Astronomical Journal 111: 1705. Bibcode:1996AJ....111.1705D. doi:10.1086/117910.
- ↑ Richichi, A.; Percheron, I.; Khristoforova, M. (2005). "CHARM2: An updated Catalog of High Angular Resolution Measurements". Astronomy and Astrophysics 431 (2): 773. Bibcode:2005A&A...431..773R. doi:10.1051/0004-6361:20042039.
- ↑ Stephenson, C. B. (1959). "A Possible New Galactic Cluster Involving δ Lyrae". Publications of the Astronomical Society of the Pacific 71: 145. Bibcode:1959PASP...71..145S. doi:10.1086/127349.
- ↑ "Simbad page for Stephenson 1".
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