Theta Muscae
A triple star system with a Wolf-Rayet primary.
Theta Muscae is a multiple star system in the southern constellation Musca. It contains a Wolf-Rayet star and two massive companions, and with an apparent magnitude of 5.5 it is the second-brightest Wolf–Rayet star in the sky. Much of its visual brightness comes from the massive companions, and it is not one of the closest of its type.
Quick Facts
- Bayer designation
- θ Muscae
- Apparent magnitude
- 5.5
- Constellation
- Musca
- Estimated distance
- about 7,400 light-years (460 million astronomical units)
- Spectral type (primary)
- WC5 or 6
- Spectral type (close companion)
- O6 or O7
- Spectral type (supergiant companion)
- O9.5/B0Iab
Facts from the source article.
Description
The primary component of Theta Muscae is a carbon-sequence Wolf–Rayet star, a highly luminous hot blue star that has shed its hydrogen envelope and emits carbon amid a strong stellar wind. It is the second-brightest such star after Gamma Velorum. θ Mus lies beyond useful visual parallax measurements, with an estimated distance of about 7,400 light-years. French explorer Nicolas-Louis de Lacaille gave the star its Bayer designation in 1756.
Triple system
Theta Muscae A consists of a spectroscopic binary—a Wolf–Rayet star (WC5 or 6) and an O-type main-sequence star (O6 or O7) orbiting every 19 days—and a blue supergiant (O9.5/B0Iab) about 46 milliarcseconds away. At the estimated distance, the binary stars are roughly 0.5 AU apart and the supergiant about 100 AU from them. The Wolf–Rayet star dominates the spectrum but is visually only about a quarter as bright as the supergiant. Combined, the three stars are likely over a million times as luminous as the Sun. Their stellar winds produce a shock front that generates X-rays.
More in Bright Stars by Bayer Designation: Binary and Multiple Stars
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