HD 168607

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HD 168607
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 21m 14.889s
Declination −16° 22′ 31.76″
Apparent magnitude (V) 8.25v
Spectral type B9Ia+[1]
U−B color index 0.63
B−V color index 1.35
J−K color index 1.085
Variable type Alpha Cygni
Radial velocity (Rv) -30 km/s
Proper motion (μ) RA: -0.27 mas/yr
Dec.: -1.01 mas/yr
Parallax (π) 1.85 ± 1.29 mas
Distance approx. 2,000 ly
(approx. 500 pc)
Absolute magnitude (MV) −8.4[1]
Luminosity 240,000[1] L
Surface gravity (log g) 1.0[1] cgs
Temperature 9,300[1] K
Database references
Other designations

HD 168607 is a blue hypergiant and luminous blue variable (LBV) star located in the constellation of Sagittarius, easy to see with amateur telescopes. It forms a pair with HD 168625, also a blue hypergiant and possible luminous blue variable, that can be seen at the south-east of M17, the Omega Nebula.

Physical Properties[edit]

HD 168607 is usually assumed to be at the same distance of the Omega Nebula (2.2 kiloparsecs, 7,200 light years, from the Sun) and may be physically associated with HD 168625.[2] Assuming this distance is correct, this star [3] is 240,000 times brighter than our Sun with a surface temperature of 9300 °K.[3] Its apparent magnitude has a variation of 0.25-0.30 m. with a period of 64 days; however, unlike other LBVs, no eruptions have been detected so far.[4]

Unlike its neighbour HD 168625, no nebula has been found around this star.[5]


  1. ^ a b c d e Bibcode1992A&A...264...88V
  2. ^ Chentsov, E.L.; Gorda, E.S. (2004). "Spatial Closeness of the White Hypergiants HD 168607 and HD 168625". Astronomy Letters 30: 145–180. Bibcode:2004AstL...30..461C. doi:10.1134/1.1774398. 
  3. ^ a b van Genderen, A.M. (2001). "S Doradus variables in the Galaxy and the Magellanic Clouds". Astronomy & Astrophysics 366: 508–531. Bibcode:2001A&A...366..508V. doi:10.1051/0004-6361:20000022. 
  4. ^ Sterken, C.; Arentoft, T.; Duerbeck, E.; Brogt (1999). "Light variations of the blue hypergiants HD 168607 and HD 168625 (1973-1999)". Astronomy & Astrophysics 349: 532–536. Bibcode:1999A&A...349..532S. 
  5. ^ Hutsemekers, D.; vanDrom, E.; Gosset, E.; Melnick, J. (1994). "A dusty nebula around the luminous blue variable candidate HD 168625". Astronomy and Astrophysics 2904: 906–914. Bibcode:1994A&A...290..906H.