I cannot remain silent about #Betelgeuse. After all, it was the main subject of my PhD. I offer you below a recap of my favorite results on this star. (Image: apod.nasa.gov/apod/ap101117.…) 
First, according to L. Z. Fang (1981) in the 1st century BC, Chinese astronomers identified Betelgeuse as yellow (while Antares was identified as red). Mistake ? Indicative of a young red supergiant ?
More recently, of course, I cannot not cite Michelson & Pease 1921 who first determined the angular diameter of a star other than the Sun. Which star ? Betelgeuse of course ! It was @MtWilsonObs and you can still see their instrument and the domes of the CHARA array there.
In 1998, Uitenbroek et al. observed the chromosphere of the star with @HUBBLE_space and suggested the rotation axis. iopscience.iop.org/article/10.108…
In 2009, Haubois et al. obtained the first high dynamic range image of Betelgeuse in the infrared (where we truely see the photosphre of the star) using the IOTA interferometer. (false colors) aanda.org/component/arti…
Still in 2009, @PierreKervella observed it with VLT/NACO @ESO. The adaptive optics in the infrared showed the gas surrounding the star (represented by the red circle, false colors). aanda.org/component/arti…
In 2010, the magnetic field of the star is measured by Aurière et al. at the Pic du Midi observatory using TBL/Narval. aanda.org/articles/aa/ab…
In 2011, @PierreKervella strikes again with VLT/VISIR @ESO revealing the dust around the star in the mid-infrared. The previous NACO image is at the center (false colors). aanda.org/articles/aa/ab…
In 2011, Ohnaka et al. showed that the diameter variation in the visible do not translate in the infrared and that there were cabon monoxide motions in the atmosphere of the star using VLTI/AMBER (false colors) @ESO aanda.org/articles/aa/ab…
In 2012, Decin et al. published outstanding results obtained with @ESAHerschel showing the interface between the wind of the star and the interstellar medium (false colors). aanda.org/articles/aa/ab…
In 2013, Dupree et al. released an ultraviolet monitoring of the star with @NASAHubble (false colors) eas-journal.org/articles/eas/a…
In 2016, I followed a bright spot on the surface using VLTI/PIONIER in the infrared (false colors) @ESO. aanda.org/articles/aa/ab…
Also in 2016, Aurière et al. followed the same feature with spectropolarimetry with TBL/Narval at the Pic du Midi in France. aanda.org/articles/aa/ab…
Again in 2016, a result awaited by several generations of astronomers was obtained by @PierreKervella using VLT/SPHERE @ESO : the first visible image of the surface of a star other than the Sun ! (top intensity, bottom polarization : no it is not round !) aanda.org/articles/aa/ab…
In 2017, O'Gorman et al. published an @almaobs image in the radio domain (continuum) showing the radio photosphere (false colors). aanda.org/articles/aa/ab…
In 2018, @PierreKervella confirmed the rotation axis of 1998 and extended the period to 30yrs ! These were @almaobs line emission observations. aanda.org/articles/aa/ab…
Also in 2018, Mathias et al. published eight years of monitoring of the magnetic field with TBL/Narval at the Pic du Midi. aanda.org/articles/aa/ab…
Still with TBL/Narval, López Ariste et al. (2018) published the "movie" of the surface of the star using spectropolarimetry at TBL/Narval, still in France. aanda.org/articles/aa/ab…
And finally in 2019, Haubois et al. presented VLT/NACO and VLT/SPHERE (@ESO) observations of a dust shell around the star. aanda.org/articles/aa/ab…
I hope I didn't forget any obvious result in this #Betelgeuse thread. In any case, the papers I cited contain refs to other studies. What now ? Betelgeuse is at its lowest luminosity after decades of photometric monitoring. Previous studies show they can be several explanations
Convection activity or dust obscuration are the most probable. In the coming days/weeks we expect the star to get brighter. Will it go supernova ? Most probably not: models suggest it is a "young" red supergiant. But who knows ? Our understanding remains partial.
In any case, it is good to see that my favorite star triggers so much interest and we will continue to observe it (as long as our time and funding proposals are granted !). Thanks to all who are studying it !
I conclude this thread on #Betelgeuse with the AAVSO light curve of Betelgeuse (in green) and Mira (in black) with the same vertical scale. If you want to see weird stuffs, the sky is full of them !
