The Comeback Kids –
“We’re watching stellar evolution in real time.”
Jennifer Ouellette –
Astronomers are baffled by this phenomenon and wonder if it is Signs the star is about to go supernova. After a few months, they narrowed down the most likely explanations to two: a brief cold spot on the star’s southern surface (similar to a sunspot) or a cloud of dust making it appear dimmer to observers on Earth. Last year, astronomers determined that dust was the culprit, linked to the brief appearance of cold spots.
The ESO team concluded that a bubble was ejected and pushed Farther out through the star’s outward pulsation — sort of like a star’s “hiccup”. When convection-driven cold spots appear on the surface, the local temperature drop is enough to condense heavier elements, such as silicon, into solid dust, forming a veil that obscures the star’s southern hemisphere brightness.
This illustration depicts the change in brightness of the red supergiant star Betelgeuse after a large mass ejection from its visible surface.
NASA/ESA/Elizabeth Wheatley (STScI)
According to the authors of this latest paper, the event was more than a star hiccup. A large convective plume more than a million miles across emerges from deep within the red giant star. The resulting shocks and pulsations are enough to create an SME that blasts a chunk of the star’s photosphere into space. This creates cold spots covered in dust clouds, which explain the dimming.
The red giant just recovered from that catastrophic event recovered in. “Betelgeuse now continues to do some very unusual things; it’s kind of bouncing on the inside,” said co-author Andrea Dupri of the Harvard-Smithsonian Center for Astrophysics, who likened the activity to a plate jelly. Its signature pulsation also ceased—hopefully temporarily—perhaps because the internal convective cells “shocked around like an unbalanced washing machine tub” as the photosphere began a slow process of rebuilding itself. “We have never seen the surface of a star before Huge mass ejection,” Dupri said. “We’re left with something we don’t fully understand. It’s an entirely new phenomenon that we can observe directly and resolve with Hubble for surface details. We’re watching stellar evolution in real time.” Webb Space Telescope may be able to detect in infrared light to the ejected material as it continues to move away from the star, which may tell astronomers more about what’s going on — and its effects on other similar stars.
DOI: arXiv, 2022. 10.48550/arXiv.2208.01676 (About DOI ).
List image of ESO/P. Corvera/M. Montargès et al.