WR 124
Like Eta Carinae, WR 124 (or QR Sagittae) is a massive star with a mass of more than 30 M☉ and a luminosity of 562,000 L☉.1 Both of these belong to a class of stars known as Wolf-Rayet stars, which are highly-evolved, meaning they have run out of hydrogen to fuse in their cores and they are fusing heavier elements like helium, nitrogen, carbon, etc. Many Wolf-Rayet stars are typically shrouded in a nebula created by the expelled outer layers of the star - WR stars are highly luminous objects with intense radiation pressure resulting in heavy solar winds (as high as 1500 miles per hour) which have expelled their outer layers and are constantly losing mass during their Wolf-Rayet phase - in some cases, losing up to two-thirds of their original mass.2
The nebula around WR 124, dubbed M1-67, is also peculiar in the sense that it shows an infrared bow shock, where the edge of the magnetosphere of the star collides with the interstellar medium. This bow shock travelling at around 180 km/s3 shows that WR 124 is a runaway star, and it is travelling in a different direction than its surrounding stars or clusters. Runaway stars with odd peculiar velocities (read: speeds which are faster than usual or in a different direction than its embedded cluster or surroundings) are theorised to be caused by ejection from a binary pair due to a close encounter with another binary pair or by catching the wrong end of a supernova explosion. So it is presumable that WR 124 had an incident like that in its recent past.
Further Reading
- Certain massive runaway stars produce spectacular bow shocks. The Milky Way Project from the Citizen Science Alliance aims to create a catalog of stellar wind-bubbles in our galaxy, and it’s a great place to marvel at some of these striking astronomical phenomena.
- EarthSky: What is a runaway star? has more details on runaway stars and what causes them.
- Phil Plait from SYFY Wire has a more elaborate write-up on WR 124.