Thanks to NASA’s Hubble Space Telescope observations, we may know why.
A new study published in The Astrophysical Journal on Thursday (and available in arXiv) examines the ultraviolet light emitted by Betelgeuse during the Great Eclipse event usingFortunately, the eclipse occurred just as Hubble scientists wanted to observe Betelgeuse with a telescope, providing an opportunity to understand why the star began to darken.
Betelgeuse is a massive star, about 700 times larger than our sun. If you release it into our solar system, it will swallow Mercury, Venus, Earth, Mars,Jupiter would be a snack, too. And it is coming to an end in its life cycle, somewhere in the next 100,000 years. When the supergiant began to eclipse last year, there were some believers who thought the explosion process might have begun.
Hubble’s observations suggest otherwise. By looking at Betelgeuse at UV wavelengths, the researchers were able to get a better look at the surface and atmosphere of the star. They found a mass of bright, hot material moving out of the star’s southern hemisphere at about 200,000 miles per hour and eventually being thrown into space.
“This material was two to four times brighter than the normal brightness of the star,” said Andrea Dupre, associate director at the Harvard-Smithsonian Center for Astrophysics and lead author of the study, in a statement from NASA. About a month after the eruption, the southern part of Betelgeuse darkened noticeably, she said.
Dupree and her team believe that this material may have begun to cool as it moved through space, forming a dense cloud of dust that partially obscured Betelgeuse. It just so happens that the Earth was in the perfect position to “see” the dust cloud in front, as if Betelgeuse shot the dust cloud directly at us. If it happens on the other side of Betelgeuse, we’ll probably never know.
Explosive bursts of the star are expected at the end of their lives, and when they die or “go supernova,” they emit a shock wave that pushes elements into space. The activity is critical to fill space with heavy elements such as carbon, which can then become new stars elsewhere in the universe, so these stars are critical to the cosmic circle of life.
Betelgeuse is still acting a little weird. Observations of NASA’s stereo spacecraft observed a supergiant between late June and early August and noticed that Betelgeuse unexpectedly eclipsed again. NASA notes that additional observations will be made in late August, when the star returns to the night sky and can again be seen by telescopes.