Betelgeuse is the tenth brightest star in the night sky, the second brightest in the constellation Orion. For almost a year now, she's been acting strange.
In December 2019, it faded greatly and continued to lose brightness until February 2020, eventually losing two-thirds of its brightness. Astronomers suspected that it was about to explode into a supernova, but then the star recovered and by April returned to its usual brightness.
An international team of scientists studied what happened and the results of this study were recently published. The authors suggested that Betelgeuse “sneezed” with a cloud of dense and hot gas.
Betelgeuse is a variable star, so changing brightness is common for her. Fading and brightening periods are typically 420 days.
But at the end of last year, it faded too much. Various suggestions have been voiced: that the star is about to explode in a supernova, a cloud of dust is the culprit, or the reason is in huge star spots.
A team led by Andrea K. Dupree, associate director of the Harvard-Smithsonian Center for Astrophysics, put forward a new hypothesis: the darkening was caused by the ejection of hot, dense clouds of plasma, which temporarily blocked the star from us. That is, the star "sneezed".
This conclusion was based on Hubble's observations. As noted in the press release , earlier with the help of Hubble, astronomers had already noticed convective zones on Betelgeuse, and in the fall of 2019, scientists noticed that a huge spot of hot and dense gas was moving through the outer atmosphere of the star.
The authors of the study believe that, having flown off millions of kilometers, this gas cooled and turned into a cloud of dust, which blocked the star from us.
However, the whole hypothesis rests only on observations from Hubble.
(NASA / ESA / and E. Wheatley (STScI)) - An illustration of the tarnishing of Betelgeuse. The penultimate picture is a side view, and the last one is a view from Earth.
It is important to note that not only the volume of this plasma ejection (twice the usual amount), but also the ejection point were unusual. Plasma shot out from the equator in the southern hemisphere. Usually, such ejections occur from the poles.
What is happening now? In late June and early August 2020, Betelgeuse was observed by the STELLA observatory in Spain. The star has begun to fade again!
As we remember, changes in star brightness usually occur only every 420 days, which means that the next dimming began a year earlier.
Scientists, of course, will continue to observe, because this is a great chance to learn more about the behavior of stars, especially in old age, when their supernova explosion is close.
A scientific article on Betelgeuse's “sneeze” was published in The Astrophysical Journal. DOI: 10.3847 / 1538-4357 / aba516 .