Companion for Betelgeuse confirmed! Beloved red star has a blue-white buddy (earthsky.org)

[eppur_se_muova]

It's confirmed! The beloved red supergiant star Betelgeuse has a companion! Astronomers announced it yesterday, saying that the companion appears to be an A- or B-type pre-main-sequence star. It's a hot, young, blue-white star that hasn't yet begun burning hydrogen in its core.

The companion orbits close to Betelgeuse itself, within the supergiant star’s extended outer atmosphere.

And Betelgeuse is much more massive than its companion. It has already spent the hydrogen fuel in its core and evolved to the red giant stage. Betelgeuse, famously, will explode someday soon as a supernova. That'll happen anytime between tonight and 100,000 years from now, making Betelgeuse blaze in our sky, visible even in the daytime.

But the companion might never get a chance to evolve. Its lifetime will likely be cut short by Betelgeuse. Hear directly from astrophysicist Steven Howell, who led the discovery team, about the discovery of Betelgeuse's companion. Prefer to read? Read more here.

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more, incl. video and lots o' links: https://earthsky.org/space/companion-for-betelgeuse-confirmed-famous-binaries/?mc_cid=3bda6b4ca8

Ummm, I think they mean it hasn't yet burned up much of the hydrogen in its core yet. No fusion, no star.

[Igel]

1. Perhaps a bit of the lithium.

But if it's pre-main sequence it's not quite at hydrostatic equilibrium. Still losing mass from bipolar jets, its temperature coming from all the gravitational energy from the infalling matter becoming kinetic--thermal.

Tidal forces may be slowing the companion's reaching the main sequence.