Thread by @chmn_victor

Here are some news about #Betelgeuse! Robin Leadbeater, an amateur spectroscopist, has just posted the evolution of Betelgeuse's spectrum in the near-infrared. On this graph, we can see the spectra from the 4th of February and from the 28th of December, as well as the ratio

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between the two (in pink). As we can see, for the past 2 months, the near-IR brightness of Betelgeuse remained mainly unchanged (ratio between 1 and 1.02) EXCEPT for the H-alpha absorption band.
Its luminosity was multiplied by 1.2 for the last two months! That is
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significantly higher than the rest of the far-IR spectrum.
But was is the H-alpha absorption band? It's the spectral line of a wavelength of 656 nm, indicating that a hydrogen electron jumped from an energy level to a higher energy level (2 -> 3).
Why does it jump? Because

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the electron absorbed energy comming from a photon. But this photon needs to have a very precise amount of energy, or the electron won't be able to "jump".
And, as you might have guessed it, photons with a wavelength of 656 nm have the right amount of energy.
So, what does

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it mean for Betelgeuse?
We know that the near-IR luminosity didn't change much, so the fact that the H-alpha band got brighter might mean that there is less Hydrogen in the outer layer of Betelgeuse.
But I am no professional, and this is just a guess. But it seems like

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something interesting is happening on Betelgeuse!
@starstrickenSF would you have any idea what this could mean?

(source of the graph: aavso.org/betelgeuse)

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.@Astro_MiguelM do you think this could have a link with a cooling of the surface or dust ejecta?

@Badrizio says it could suggest a mass loss.