Artist's Impression of Star Spots on Betelgeuse.
Betelgeuse, the closest red supergiant star to us, is growing a super-sized star spot as it cools down at the end of its life, according to a new study.
A massive star spot a hundred times larger than the Sun could explain its recent odd behavior.
Betelgeuse—pronounced “betelgerz” or “beetlejuice” and also known as Alpha Orionis—rapidly faded in brightness from late 2019 through May 2020, prompting many to suggest that it could be a sign that the star was about to go supernova.
By February 2020 it was only half as bright as normal, but it stabilized thereafter.
Betelgeuse, which is around 650 light years distant, will explode as a Type IIP supernova sometimes within the next 100,000 years, leaving behind a neutron star.
A few theories since have speculated that the cause of Betelgeuse’s “deep minimum” of 2019-2020 could be:
The new study, published today in The Astrophysical Journal Letters, essentially backs-up the second theory by suggesting that the surface of Betelgeuse itself underwent a significant change in the form of a gigantic star spot.
The constellation of Orion, with Betelgeuse.
Using the 15-meter James Clerk Maxwell Telescope (JCMT) in Hawai`i, an international team of astronomers from the UK, Germany, Taiwan, the US and Chile detected the light coming from dust grains around Betelgeuse.
“We were able to collect a type of light called submillimetre light that is not visible to the human eye,” said Dr. Steve Mairs, Senior Scientist at the JCMT. “This provided the crucial information that allowed us to conclude that there was no dust in the way; Betelgeuse was feeling shy with a face full of spots.”
The findings suggest that star spots around 10% cooler than the rest of the star’s surface formed over 50% to 70% of Betelgeuse. The star spot is a hundred times larger than the Sun.
“What surprised us was that Betelgeuse turned 20% darker during its dimming event even in submillimetre light,” said Dr. Thavisha Dharmawardena, postdoctoral researcher at the Max Planck Institute for Astronomy, Germany . “This behaviour is not at all compatible with the presence of dust. It was very exciting to realise that the star itself had undergone this massive change”.
According to the scientists, the simultaneous darkening in visible and submillimetre light suggests that Betelgeuse’s surface temperature decreased by 200°C/360 °F.
Star spots are common in giant stars, but not on this scale. However, it’s unlikely that Betelgeuse is about to undergo the biggest possible of changes. “The sudden fading of Betelgeuse does not mean it is going supernova,” said Professor Albert Zijlstra from The University of Manchester, one of the authors. “It is a supergiant star growing a super-sized star spot.”
Betelgeuse is 900 times larger than the Sun. If it was in our Solar System in place of the Sun, Jupiter would be in close orbit. Mercury, Venus, the Earth, Mars and the asteroid belt would all be inside Betelgeuse.
Wishing you clear skies and wide eyes.
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