The star Betelgeuse visibly dimmed in 2019. We have just found a reason why: Betelgeuse blew out and is still recovering. The red supergiant star, which is about 530 light-years from Earth, is among the brightest in the night sky. The star forms the “shoulder” of the constellation Orion. It's also geriatric, nearing the end of its stellar life, and will eventually explode in a supernova visible from Earth, though it might take another 100,000 years, according to 2021 research.
In late 2019, Betelgeuse's light started to dim. By February 2020, it had lost two-thirds of its normal luminosity visible from Earth. Scientists studying the bizarre dimming concluded that the star itself was not imminently going supernova but that a giant dust cloud had covered some of the star's light. Now, scientists using the Hubble Space Telescope have revealed that this dust cloud was the result of an enormous ejection from the star's surface: A plume more than 1 million miles (1.6 million kilometers) across may have risen from inside the star, producing the equivalent of a starquake, a shock that blew out a chunk of the star's surface 400 million times larger than those usually seen in the sun’s coronal mass ejections.
"Betelgeuse continues doing some very unusual things right now; the interior is sort of bouncing," study author Andrea Dupree, associate director of the Harvard & Smithsonian Center for Astrophysics, said in a statement. This is uncharted territory in star science, Dupree said. "We've never before seen a huge mass ejection of the surface of a star," she said. "We are left with something going on that we don't completely understand. It's a totally new phenomenon that we can observe directly and resolve surface details with Hubble. We're watching stellar evolution in real-time."
The new research also incorporated information from a variety of other stellar observatories, such as the STELLA Robotic Observatory in Spain's Canary Islands, and NASA's Earth-orbiting STEREO-A spacecraft. By piecing together different types of data, Dupree and her team were able to put together a narrative of the blowout and its aftermath. The eruption blew off a chunk of the star's photosphere leaving behind a cool spot that was further occluded by the dust cloud from the blowout. The chunk of the photosphere was several times the mass of Earth's moon, according to NASA's statement. This cool spot and dust cloud explain why Betelgeuse's light dimmed. The star is still feeling the reverberations. Before the eruption, Betelgeuse had a pulsating pattern, dimming and brightening on a 400-day cycle, which is now gone, at least temporarily. It's possible that the convection cells inside the star are still sloshing around, disrupting this pattern.
The star's outer atmosphere seems to be back to normal, but its surface may still be unsteady. The eruption isn't evidence for Betelgeuse going supernova anytime soon, the researchers said, but it does show how old stars lose mass. If Betelgeuse does finally die in a stellar explosion, the light will be visible in the daytime from Earth, but the star is too far away to have any impact on our planet.
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By: Zubin Sidhu
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References:
Pappas, Stephanie. “One of the Brightest Stars in the Sky Dimmed in 2019. Now We Know Why.” Livescience.Com, 12 Aug. 2022, www.livescience.com/betelgeuse-blowout.
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