HD 168625 [SEP] constellation
HD 168625
HD 168625 (V4030 Sagittarii) is a blue hypergiant and candidate luminous blue variable located in the constellation of Sagittarius easy to see with amateur telescopes. It forms a visual pair with the also blue hypergiant (and luminous blue variable) HD 168607 and is located to the south-east of M17, the Omega Nebula.
Distance.
The distance of HD 168625 and its association with the Omega Nebula and HD 168607 is dubious; while some authors think both stars are physically associated and belong to the stellar
association Serpens OB1, at a distance to the Sun of 2.2 kiloparsecs (7.200 light years), others think HD 168625 is farther, at a distance estimated to be 2.8 kiloparsecs (kpc) (9,100 light years) and unrelated to the former objects. The parallax published in Gaia Data Release 2 indicates a distance close to 1,600 pc, consistent with HD 168607.
Physical characteristics.
Assuming a distance of 2.2 kiloparsecs, HD 168625 is 220,000 times brighter than the Sun, having a surface temperature of 12,000 K. It