Since about October 2019, Betelgeuse (the bright reddish star at Orion’s shoulder in the brightest constellation in the sky that is about 600 – 700 ly distant from us) has begun a sharp dimming that has now gone beyond what has been seen in modern observations. As of the end of January, it was down about
2.5 1.4 in apparent magnitude (corrected from the added graph).
Here is its “portrait” — it is one of the few stars we have seen as a disk:
ADDED: a plot of apparent magnitude:
Discussion at WUWT suggests that by about Feb 21 we should see an uptick if this is something that is near-normal. Odds are, we don’t have a long enough instrumented observation base to make a definitive decision, we are watching and learning. (I am influenced here, by experience with a mountain that moved beyond the usual and helped to re-write volcanology. I’d love to see a proper expertise weighted elicitation yielding a projection, but that’s not likely.)
As it is a red giant, it is thought to be end of life, and is due for supernova within the next 100,000 years.
As, normally we only see a supernova after it has happened, we do not know what precursors look like.
Some concerns have been expressed, that we may suffer x-ray bursts should that happen, but those tend to be aligned with the polar axis and such is thought to be unlikely. If it does go supernova, it will blaze up to high brightness, reaching that of the full moon approximately, then will fade away leaving behind a neutron star (or possibly a black hole, it seems to be borderline).
Here is a recent video:
This is a reminder that we are observing, we do not know to certainty. END
PS: Further digging gives a nigh on 40 year trend from cloudy nights. That suggests an earlier dip to mag 3. (Lower mag is brighter.)
U/D, Feb 17: HT LM, here is a video courtesy ESO:
In the video, we see a discussion of shape shifting and surface dimming; Betelgeuse is anything but a compact nearly spherical ball: