Delta² Lyrae

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Delta2 Lyrae[1]
Observation data
Epoch J2000.0
Constellation
(pronunciation)		 Lyra
Right ascension 18h 54m 30.2838s
Declination +36° 53' 55.007"
Apparent magnitude (V) 4.30
Characteristics
Spectral type M4II
U-B color index +1.65
B-V color index +1.67
Astrometry
Radial velocity (Rv) -26.4 km/s
Proper motion (μ) RA: -6.73 mas/yr
Dec.: 3.26 mas/yr
Parallax (π) 3.63 ± 0.56 mas
Distance approx. 900 ly
(approx. 280 pc)
Other designations
Delta2 Lyrae, 12 Lyrae, HR 7139, BD+36°3319, HD 175588, SAO 67559, HIP 92791, GC 25959

Delta2 Lyrae (δ2 Lyr) is a 4th magnitude star in the constellation Lyra, approximately 900 light years away from Earth. It is a class M4II star, meaning it is a bright giant star with a surface temperature under 3,500 kelvins. It shines with the light of 6,500 Suns, and has a radius of 200 solar radii, or 0.95 times the radius of Earth's orbit, though other measurements give an even larger radius of 1.3 astronomical units.[2]

It began life 75 million years ago as a bluish white B3 spectral type star of six solar masses, with a surface temperature between 11,000 and 25,000 kelvins. It now possesses a dead helium core, and is becoming an even larger giant. 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 an optical double with the star Delta1 Lyrae, but it does not, only appearing to do so the naked eye.[2]

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 trinary 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.[2]

[edit] References

  1. ^ Simbad Query Result. Simbad. Retrieved on October 15, 2007.
  2. ^ a b c Simbad Query Result. Simbad. Retrieved on October 15, 2007.