66 Ophiuchi
Star in the constellation Ophiuchus / From Wikipedia, the free encyclopedia
66 Ophiuchi is a binary[6] variable star[13] in the equatorial constellation of Ophiuchus. It has the variable star designation V2048 Ophiuchi, while 66 Ophiuchi is the Flamsteed designation. This object is visible to the naked eye as a faint, blue-white hued point of light with a baseline apparent visual magnitude of 4.60.[2] It is located approximately 650 light years away from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −13 km/s.[5] The star has a peculiar velocity of 13.1±3.2 km/s[14] relative to its neighbors.
The primary star, known as 66 Ophiuchi A, is a main sequence Be star with a stellar classification of B2Ve.[3] Be stars are rapidly rotating stars that eject gas from their equators due to their rotation, forming disks that produce emission lines. 66 Ophiuchi A's disk extends out to 115 R☉.[15] Like many other Be stars, it is a γ Cas variable; a shell star with a circumstellar disc of gas and is exhibiting irregular changes in brightness, ranging from 4.85 up to 4.55 magnitude.[4] The star is 14 million years old with 9.6[6] times the Sun's mass and is spinning rapidly with a projected rotational velocity of 250 km/s.[10] It is radiating 1,525[7] times the Sun's luminosity from its photosphere at an effective temperature of 22,000 K.[9] Because of its rotation, it has a polar equatorial radius 4.50 that of the Sun, but an equatorial radius 5.11 that of the Sun.[15]
A magnitude 6.5 visual companion at an angular separation of 0.1″ has been reported, and is known as 66 Ophiuchi B.[16] It is 2.61 magnitudes fainter than the primary. This corresponds to a mass of about 3.8 times that of the Sun, and a spectral class of about B8.[6]