There's a lot of discussion about the dimming of Betelgeuse on astrotwitter at the moment.
This simulation by Bernd Freytag et al. spanning just 16 years shows just how crazily variable red supergiant stars can be due to convection & magnetic fields.
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astro.uu.se/~bf/publicatio…
This simulation by Bernd Freytag et al. spanning just 16 years shows just how crazily variable red supergiant stars can be due to convection & magnetic fields.
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astro.uu.se/~bf/publicatio…
That 3D magnetohydrodynamical simulation using the CO5BOLD code is of a 5 solar mass star with a radius of 600 solar radii (IIRC – need to check) & shows roughly what you'd see with the naked eye. It's very red because red supergiants are cooler than the Sun, around 3500K. 2/
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Betelgeuse is larger, ~11–20 solar masses & 900 solar radii (630 million km, 80% of the distance between the Sun & Jupiter), but the same physics applies: huge convection cells from the core to the surface, with magnetic fields threading through, as seen here by Freytag et al. 3/
To put none too fine a point on it, red supergiants like Betelgeuse don't look much like a scaled up version of our Sun, i.e. a fairly crisp, uniform ball at visible wavelengths with a few sunspots. RSG's are highly structured & variable both in size & brightness. 4/
And remarkably, despite Betelgeuse being at ~220 parsecs, 45 million times further away than the Sun, adaptive optics & interferometry are beginning to reveal its surface structure, as nicely summarised by @Astro_MiguelM in this thread. 5/
Re: the dimming of Betelgeuse, the latest results show that it's down at V~1.3 mag now, probably "just" due to the superposition of the minima of two general periodicities around 425 days & 5.9 years. It's probably not going supernova soon. 6/6
Coda: have just seen this very extensive & informative thread about Betelgeuse by @emsque which also features an MHD simulation by the Freytag group 👍
