Delta2 Lyrae

From Wikipedia, the free encyclopedia
Jump to: navigation, search
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
Spectral type M4 II
U−B color index +1.65
B−V color index +1.68
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)
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
Delta2 Lyrae, 12 Lyrae, HR 7139, BD+36°3319, HD 175588, SAO 67559, HIP 92791, GC 25959
Database references

Delta2 Lyrae2 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]


  1. ^ a b c 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.  edit
  2. ^ a b c 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.  edit
  3. ^ a b 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.  edit
  4. ^ Bibcode1989BICDS..36...27G
  5. ^ 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.  edit
  6. ^ 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.  edit
  7. ^ 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.  edit
  8. ^ "Simbad page for Stephenson 1".