B90 (star)

B90 (often referred to as [W60] B90) is a large, highly luminous red supergiant star similar to Betelgeuse in the Large Magellanic Cloud.

Discovery
B90 was discovered in 1956 by Karl Gordon Henize in a catalogue of H-alpha emission stars and nebulae in the Large Magellanic Cloud. He designated it LHA 120-N 132E, indicating emission line nebula 132E on plate 120. The LHA is originally LHα, standing for H-alpha emission objects identified at the Lamont-Hussey Observatory.

Properties
B90 is believed to be one of the largest, most luminous red supergiants in the Large Magellanic Cloud. Its luminosity was first measured to be of more than 280,000 solar luminosities and a radius of around 1,390 solar radii, although a more detailed study put it at and.

Mass-loss
The star has episodic mass-loss with a high rate of yr−1 and a nebula of ~1 pc (~3 ly) surrounding the star. This nebula could indicate that the star has a bow shock, which supplies evidence that the star does undergo episodic mass-loss, which makes it more likely that this is the case for almost all red supergiants.

The variability of the star and possible "great dimming" events are also consistent with episodic mass-loss, similar to those of Betelgeuse and RW Cephei. The rebrightening of B90, just like RW Cephei, took twice as long as that of Betelgeuse which could indicate a relation between the time taken and the radius of red supergiants, where B90 is.

Velocity
B90 has a very high velocity of (19 – 27) ± 11 km s−1 towards its nebular bar, therefore proving that it is a "walkaway" star. This potentially makes the possibility that it has a bow shock more likely.