The Reason Astronomers Are Watching This Hypergiant Star As It Dies

One of the most famous hypergiant stars is Betelgeuse, located in the constellation of Orion. Betelgeuse has been the subject of a lot of interest recently because of its strange behavior: Beginning in 2019, the star dimmed dramatically, losing as much as two-thirds of its normal brightness (via NASA). Then, by 2020, it appeared to be back at its previous brightness. While it is normal for stars to dim or brighten over time, this is typically a process that happens much more slowly.

Originally, some observers thought that Betelguese might be about to go supernova. Others thought that the star could be covered in dark patches like sunspots. But research using the Hubble Space Telescope found that the cause of the dimming was something different: The star had produced a large amount of gas in an eruption, which had formed a dust cloud. This cloud was blocking some of the star’s light from reaching us, hence why it appeared to look dimmer.

A similar process happens on VY Canis Majoris, but on a larger scale. “Think of it as Betelgeuse on steroids,” said Ziurys. “It is much larger, much more massive and undergoes violent mass eruptions every 200 years or so.”

The researchers observed VY Canis Majoris using tools like the Atacama Large Millimeter Array in Chile to look at the gas that the star is ejecting. They have spotted sulfur oxide, sulfur dioxide, silicon oxide, phosphorous oxide, and sodium chloride, and also gathered information on how well these chemicals are mixed within the gas. They also found that different ejections gave off different mixes of chemicals, helping to understand how stars like this one shed their mass over time (via the University of Arizona).

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