We stargazers have spent our entire lives seeing the star Betelgeuse as a bright star in the very noticeable constellation Orion the Hunter. But, in late 2019, Betelgeuse began an unprecedented dimming. Now Betelgeuse is at about 36% of its normal brightness, a change noticeable even to the unaided eye. That is interesting and exciting, in part because it’s known that Betelgeuse is the sort of star that will explode someday. The notion that the dimming of Betelgeuse might be tied to an impending explosion has set the astronomy world buzzing. On February 14, 2020, the European Southern Observatory (ESO) released new before and after images of Betelgeuse – before the dimming and after the dimming began – showing not only that the star has decreased in brightness but also that its shape has changed.
Check out this impressive image of the surface of Betelgeuse, taken with the SPHERE instrument at VLT. Thanks to its extreme adaptive optics, SPHERE can correct the atmospheric turbulence, yielding super sharp images. Great job, @Astro_MiguelMhttps://t.co/fTFtuKiFlx
— Juan Carlos Munoz (@astro_jcm) February 14, 2020
Astronomer Miguel Montargès at Katholieke Universiteit Leuven in Belgium led these observations, using ESO’s Very Large Telescope (VLT) in Chile. ESO said in a statement that his team has been watching the star:
… since December, aiming to understand why it’s becoming fainter. Among the first observations to come out of their campaign is a stunning new image of Betelgeuse’s surface, taken late last year with the SPHERE instrument.
Taken in visible light, the images highlight the changes occurring to the star both in brightness and in apparent shape.
… astronomers don’t think this is happening now. They have other hypotheses to explain what exactly is causing the shift in shape and brightness seen in the SPHERE images.
The two scenarios we are working on are a cooling of the surface due to exceptional stellar activity or dust ejection towards us. Of course, our knowledge of red supergiants remains incomplete, and this is still a work in progress, so a surprise can still happen.
ESO said that Montargès and his team needed the VLT to study Betelgeuse, which is over 700 light-years away.
Another new image, obtained with the VISIR instrument on the VLT, shows the infrared light being emitted by the dust surrounding Betelgeuse in December 2019. These observations were made by a team led by Pierre Kervella from the Observatory of Paris in France, who explained that the wavelength of the image is similar to that detected by heat cameras. The clouds of dust, which resemble flames in the VISIR image, are formed when the star sheds its material back into space.
Emily Cannon is a Ph.D. student at KU Leuven, working with SPHERE images of red supergiants. She commented:
The phrase ‘we are all made of stardust’ is one we hear a lot in popular astronomy, but where exactly does this dust come from? Over their lifetimes, red supergiants like Betelgeuse create and eject vast amounts of material even before they explode as supernovae. Modern technology has enabled us to study these objects, hundreds of light-years away, in unprecedented detail giving us the opportunity to unravel the mystery of what triggers their mass loss.
Bottom line: The European Southern Observatory’s Very Large Telescope obtained high resolution images of Betelgeuse in December 2019. The star looks remarkably different from images taken in January 2019. Astronomers are still trying to figure out what is happening to the star.