Why Betelgeuse Dimmed

Astronomers have been puzzled by the star Betelgeuse, which is the second-brightest point in the constellation. After starting to dim considerably in October, Belegeuse reached 1/3rd of its normal brightness a few months later. As of February 22nd, it has remained in a normal brightness range. The most likely explanation was a circumstellar dust cloud, not any changes in the star's brightness.

Astronomers used data from the Hubble Space Telescope and other telescopes to conclude that a Surface Mass Ejection was the cause. The star was obscured by a circumsolar dust ring when Betelgeuse released a large amount of material. Betelgeuse ejected roughly 400 billion times as much mass as a typicalCME. This is the first time something like this has been seen in a star.

Betelgeuse is one of the largest stars in the sky and can be seen in the night sky. When stars are no longer in their main phase and begin to grow larger, there is a Red Supergiant. Betelgeuse would swallow up Mercury to Mars if it were located in our Solar System. A semiregular variable star is a star that varies in brightness over time but is subject to cycles and predictable.

backyard observers used small telescopes, binoculars, and even the naked eye to see Betelgeuse's dimming because of its prominence in the night sky The exact cause was determined by the observations from the Hubble Telescope. The first direct image of a star other than the Sun was taken with Hubble in 1996, by Dupree and Ronald L. Gilliland of the Space Telescope Science Institute.

Dupree and her colleagues combined Hubble observations with other data to understand Betelgeuse's behavior before and after the event. This included data from the American Association of Variable Star Observers. Betelegueseblew its stack and released a lot of material into space.

A jet of superheated material bubbling up from deep inside the star is what caused this massive ejection. It is estimated that this is more than a million kilometers across and several times as large as the Moon. It was enough for the shocks and pulsations to blow off a large patch of material from Betelgeuse. The material would have created a large patch on Betelgeuse's surface and cooled to form a large cloud of dust.

The shock caused by this event is something Betelgeuse has yet to fully recover from. Astronomers have not seen a pulsation rate of 400 days in 200 years. The sudden disappearance of the variability in brightness and surface motions is further proof of how disruptive this event was. In a recent NASA press release, Dupree explained.

“Betelgeuse continues doing some very unusual things right now; the interior is sort of bouncing. We’ve never before seen a huge mass ejection of the surface of a star. 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.”

Red stars lose mass late in their lives as their nuclear fuel is slowly exhausted and they end up with a supernova. As they near the end of their Red Giant phase, how much mass they lose would have a big impact on their fate. The way this event dwarfs ejections from the Sun's corona suggests that there is a different class of stellar events. Despite Betelgeuse's recent behavior, there is no reason to think it will go supernova in the near future.

The outer layers of Betelgeuse have returned to normal despite the surface showing signs of activity as the photoosphere rebuilds. Dupree and her colleagues think that the star may be unbalanced. Future observations can be made using the James Webb Space Telescope, which will be able to detect ejected material.

As the ejected material continues to move away from Betelgeuse, there could be more clues as to why the event happened. Who doesn't know? It's important to know what distinguishes SMEs from CMEs in order to make sure planetary defense.

There is further reading on NASA.