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RW Cephei

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description RW Cephei Overview

RW Cephei is an orange hypergiant star located in the constellation Cepheus. It is classified as an irregular variable star and ranks among the largest known stars in the Milky Way, with an estimated radius exceeding 1,500 times that of the Sun. The star's substantial size and mass place it near the theoretical upper limit for stellar stability. In late 2022 and early 2023, astronomers observed a significant dimming event, sometimes called a great dimming, which was likely caused by the formation of a temporary dust cloud.

help RW Cephei FAQ

How large would RW Cephei be if it replaced the Sun?

Published estimates put its radius at roughly 900 to 1,760 times the Sun's, reflecting uncertainty in its distance and atmosphere. At the larger end of that range, its surface would reach approximately to Jupiter's part of the Solar System.

What caused the great dimming of RW Cephei?

Observations suggest that RW Cephei expelled material which cooled into dust and partly blocked its visible surface. CHARA Array images revealed an asymmetric disk with a conspicuous dark region during the event.

Is RW Cephei the same kind of star as Betelgeuse?

Both are enormous, cool, evolved stars capable of mass loss and dramatic dimming, but RW Cephei is usually classified as a hypergiant. Its recent fading was explicitly compared with Betelgeuse's 2019 to 2020 great dimming.

Can RW Cephei be seen without a telescope?

RW Cephei sits near the traditional naked-eye limit and becomes fainter when its semiregular variability or dust obscuration increases. Binoculars or a small telescope are therefore much more reliable for observing it in Cepheus.

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