Astronomers are nonetheless making new discoveries concerning the pink supergiant star Betelgeuse, which skilled a mysterious “dimming” a number of years in the past. That dimming was ultimately attributed to a chilly spot and a stellar “burp” that shrouded the star in interstellar mud. Now, new observations from the Hubble Space Telescope and different observatories have revealed extra concerning the occasion that preceded the dimming.

It appears Betelgeuse suffered an enormous floor mass ejection (SME) occasion in 2019, blasting off 400 instances as a lot mass as our Sun does throughout coronal mass ejections (CMEs). The sheer scale of the occasion is unprecedented and means that CMEs and SMEs are distinctly several types of occasions, in accordance with a new paper posted to the physics arXiv final week. (It has been accepted for publication in The Astrophysical Journal.)

Betelgeuse is a vivid pink star within the Orion constellation—one of many closest large stars to Earth, about 700 light-years away. It’s an previous star that has reached the stage the place it glows a uninteresting pink and expands, with the recent core solely having a tenuous gravitational grip on its outer layers. The star has one thing akin to a heartbeat, albeit an especially sluggish and irregular one. Over time, the star cycles by durations when its floor expands after which contracts.

One of those cycles is pretty common, taking a bit over 5 years to finish. Layered on that could be a shorter, extra irregular cycle that takes wherever from beneath a yr to 1.5 years to finish. While the cycles are straightforward to trace with ground-based telescopes, the shifts do not trigger the kind of radical modifications within the star’s mild that will account for the modifications seen throughout the dimming occasion.

As we have reported beforehand, astronomers first seen the unusual, dramatic dimming within the mild from Betelgeuse in December 2019. The star dimmed a lot that the distinction was seen to the bare eye. The dimming endured, reducing in brightness by 35 p.c in mid-February earlier than brightening once more in April 2020.

Astronomers puzzled over the phenomenon and puzzled whether or not it was an indication that the star was about to go supernova. Several months later, they’d narrowed the almost certainly explanations to 2: a short-lived chilly patch on the star’s southern floor (akin to a sunspot) or a clump of mud making the star appear dimmer to observers on Earth. Last yr, astronomers decided that mud was the major wrongdoer, linked to the transient emergence of a chilly spot. 

The ESO staff concluded {that a} fuel bubble was ejected and pushed additional out by the star’s outward pulsation—kind of like a stellar “burp.” When a convection-driven chilly patch appeared on the floor, the native temperature lower was ample to condense the heavier components (like silicon) into strong mud, forming a veil that obscured the star’s brightness in its southern hemisphere.

According to the authors of this newest paper, the occasion was considerably greater than a mere stellar burp. A big convective plume with a diameter of over 1 million miles bubbled up from deep within the pink big’s inside. The ensuing shocks and pulsations had been highly effective sufficient to provide an SME, blasting an enormous chunk of the star’s photosphere into area. That produced the chilly patch coated by the mud cloud, which explains the dimming.

The pink big has solely simply begun to heal from that catastrophic occasion. “Betelgeuse continues performing some very uncommon issues proper now; the inside is kind of bouncing,” stated co-author Andrea Dupree of the Harvard-Smithsonian Center for Astrophysics, likening the exercise to a plate of Jell-O. Its trademark pulsation has additionally stopped—hopefully quickly—maybe as a result of the inside convection cells “are sloshing round like an imbalanced washer tub” because the photosphere begins the sluggish means of rebuilding itself.

“We’ve by no means earlier than seen an enormous mass ejection of the floor of a star,” stated Dupree. “We are left with one thing happening that we do not fully perceive. It’s a completely new phenomenon that we will observe immediately and resolve floor particulars with Hubble. We’re watching stellar evolution in actual time.” The Webb Space Telescope might be able to detect the ejected materials in infrared mild because it continues transferring away from the star, which could inform astronomers much more about what occurred—and its implications for different related stars.

DOI: arXiv, 2022. 10.48550/arXiv.2208.01676  (About DOIs).

Listing picture by ESO/P. Kervella/M. Montargès et al.