HD 168607

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HD 168607
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 21m 14.889s[1]
Declination −16° 22′ 31.76″[1]
Apparent magnitude (V) 8.28[2] (var)
Spectral type B9Ia+[3]
U−B color index 0.41[2]
B−V color index 1.54[2]
J−K color index 1.06[2]
Variable type LBV[4]
Radial velocity (Rv) -30[5] km/s
Proper motion (μ) RA: -0.27[1] mas/yr
Dec.: -1.01[1] mas/yr
Parallax (π) 1.85 ± 1.29[1] mas
Distance approx. 2,000 ly
(approx. 500 pc)
Absolute magnitude (MV) −8.4[6]
Luminosity 240,000[6] L
Surface gravity (log g) 1.0[6] cgs
Temperature 9,300[6] K
Other designations
V4029 Sgr, HD  168607, BD -16°4829, SAO 161374, HIP 89956, AAVSO 1815-16
Database references
HD 168607 is the right star of the pair below the Omega Nebula. The other is the hypergiant HD 168625.

HD 168607 (V4029 Sgr) 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.[7] Assuming this distance is correct, this star [8] is 240,000 times brighter than the Sun with a surface temperature of 9300 K.[8] Its apparent magnitude has a variation of 0.25-0.30 m. with a period of 64 days, but no outburst has been observed.[9] Unlike its neighbour HD 168625, no nebula has been found around this star.[10]


  1. ^ a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752free to read. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D. 
  3. ^ Chentsov, E. L.; Ermakov, S. V.; Klochkova, V. G.; Panchuk, V. E.; Bjorkman, K. S.; Miroshnichenko, A. S. (2003). "An atlas of spectra of B6-A2 hypergiants and supergiants from 4800 to 6700Å". Astronomy and Astrophysics. 397 (3): 1035–1042. Bibcode:2003A&A...397.1035C. doi:10.1051/0004-6361:20021430. 
  4. ^ Nazé, Y.; Rauw, G.; Hutsemékers, D. (2012). "The first X-ray survey of Galactic luminous blue variables". Astronomy & Astrophysics. 538: A47. arXiv:1111.6375free to read. Bibcode:2012A&A...538A..47N. doi:10.1051/0004-6361/201118040. 
  5. ^ Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878free to read. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. 
  6. ^ a b c d Van Genderen, A. M.; Van Den Bosch, F. C.; Dessing, F.; Fehmers, G. C.; Van Grunsven, J.; Van Der Heiden, R.; Janssens, A. M.; Kalter, R.; Van Der Meer, R. L. J.; Van Ojik, R.; Smit, J. M.; Zijderveld, M. J. (1992). "Light variations of massive stars (Alpha Cygni variables). XIII - the B-type hypergiants R81 (LBV), HD 80077 (LBV?), HD 168607 = V 4029 Sagittarii (LBV) and HD 168625 = V 4030 Sagittarii". Astronomy and Astrophysics. 264: 88. Bibcode:1992A&A...264...88V. 
  7. ^ Chentsov, E.L.; Gorda, E.S. (2004). "Spatial Closeness of the White Hypergiants HD 168607 and HD 168625". Astronomy Letters. 30 (7): 145–180. Bibcode:2004AstL...30..461C. doi:10.1134/1.1774398. 
  8. ^ a b van Genderen, A.M. (2001). "S Doradus variables in the Galaxy and the Magellanic Clouds". Astronomy & Astrophysics. 366 (2): 508–531. Bibcode:2001A&A...366..508V. doi:10.1051/0004-6361:20000022. 
  9. ^ Sterken, C.; Arentoft, T.; Duerbeck, H.W.; Brogt, E. (1999). "Light variations of the blue hypergiants HD 168607 and HD 168625 (1973-1999)". Astronomy & Astrophysics. 349: 532–536. Bibcode:1999A&A...349..532S. 
  10. ^ 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.