The mystery of the Betelgeuse obfuscation has finally been solved

In December 2019, Astronomers have noticed a strange and dramatic dimming of light from Betelgeuse, a bright red star in the constellation Orion. They puzzled over this phenomenon and wondered if it was a sign that the star was about to transform into a supernova. Several months later, they narrowed the most likely explanations to two: a short-lived cold spot on the star’s southern surface (similar to a sun spot), or a mass of dust that makes the star appear faint to observers on Earth. We now have our answer, according to new paper Published in the magazine nature. Dust is Primary culprit, but it is associated with the short onset of the cold spot.

Like Ars’ John Timmer I mentioned last yearBetelgeuse is one of the closest massive stars to Earth, about 700 light-years away. It is an ancient star that has reached the stage where it glows dull red and is expanding, with only its hot core having a weak gravitational grip on its outer layers. The star has what feels like a heartbeat, albeit very slow and erratic. Over time, the star rotates through periods in which its surface expands and then contracts.

One of these courses is fairly regular, taking just over five years to complete. It is a shorter, more irregular cycle that takes from less than a year to 1.5 years to complete. While they are easy to track with ground-based telescopes, these shifts do not cause the kind of drastic changes in the star’s light that would explain the changes seen during the dimming event.

In late 2019, Betelgeuse fainted so much that the difference was visible to the naked eye. The dimming continued, with brightness dropping 35 percent in mid-February, before shining again in April 2020.

Telescopes directed at the giant were able to determine that – instead of a coordinated and uniform decrease in illumination – Betelgeuse unevenly distributed, giving the star a strange, compressed shape when viewed from Earth. This raised a lot of questions about what was going on with the giant, with some experts speculating that due to Betelgeuse’s size and advanced age, the strange behavior was a sign of a supernova in the making.

By the middle of 2020, astronomers had changed their tune. He just happened to have an international team of observers Hubble Space Telescope He pointed to Betelgeuse before, during and after the blackout event. Combined with some timely ground observations, this ultraviolet data indicated that the large burps that formed a cloud of dust near the star may have caused the star to darken.

“Using Hubble, we can see the material leaving the surface of the star and exiting through the atmosphere, before the dust formed that made the star look faint.” Andrea Dupree said:, an astronomer at the Harvard-Smithsonian Center for Astrophysics who made these observations. She is also a co-author on the new paper.

Photo: M. Montargues et al. / ESO

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