Unsteady Giant

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Unsteady Giant

Betelgeuse grew dramatically fainter a couple of years ago. The supergiant star blasted out a giant blob of gas, which cooled to form a dust cloud that blocked part of the star from view. And a similar star might recently have gone through the same process.

RW Cephei is at least 900 times the diameter of the Sun, making it one of the larger stars in the galaxy. It’s also hundreds of thousands of times brighter than the Sun. In late 2022, though, it dropped to a third of its usual brightness. By last summer, it was recovering.

Astronomers analyzed some especially sharp images of the star. The pictures showed that it was blobby, with bright and dark regions many times larger than the Sun.

The astronomers later found that RW Ceph had grown brighter than usual in 2019. It may have blown out a huge blob of hot gas not long after that. The gas cooled and condensed to form a cloud of dust grains. The cloud moved in front of the star, causing it to fade. As the cloud dispersed, RW Ceph returned to its usual brilliance.

The hypergiant star is near the end of its life. It’s expected to explode as a supernova sometime in the next million years or so – just like Betelgeuse.

RW Cephei is low in the northeast at nightfall. It’s about halfway between Deneb, the star at the tail of the swan, and W-shaped Cassiopeia. Even at its best, though, you need binoculars or a telescope to see it.

Script by Damond Benningfield

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