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![](https://pbs.twimg.com/media/EQuRWbYU8AAWP07.png)
Its luminosity was multiplied by 1.2 for the last two months! That is
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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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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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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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@starstrickenSF would you have any idea what this could mean?
(source of the graph: aavso.org/betelgeuse)
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@Badrizio says it could suggest a mass loss.