Betelgeuse is the red supergiant at Orion’s shoulder, one of the largest stars visible to the eye, famous for its Great Dimming and its small companion, Siwarha.
At a glance
| type | red supergiant (class M) |
|---|---|
| distance from the Sun | 548 light-years (168 pc) |
| its light left it | 548 years ago |
| luminosity | 90,000 × the Sun |
| radius | 764 × the Sun |
| surface temperature | 3,600 K |
| constellation | Orion (Hunter) |
Read off the piece’s own catalogue, the same values it draws with.
About Betelgeuse
Betelgeuse is a massive star in the last stages of its life, swollen so far that, put in place of the Sun, its surface would reach beyond the orbit of Mars. It was one of the first stars other than the Sun whose disc was imaged directly. It is a semi-regular variable, its brightness rising and falling as its surface pulsates.
In a recent episode called the Great Dimming it faded far more than usual. Observations showed a cloud of dust, formed from gas the star had thrown off, blocking part of its face, together with a cooler patch on its surface. Supernova speculation followed, but the star recovered.
A faint companion, named Siwarha, has been detected very close to it, near the limit of what the largest telescopes can resolve. Its orbit matches a long, slow cycle in the star’s brightness that had long suggested a partner.
What you see in the piece
With HUMAN EYE on it is the orange-red shoulder of Orion, opposite blue Rigel. The WONDERS (W) show it with Siwarha, a tiny point lost against the vast red disc.
Measured or modelled
Siwarha’s nature is inferred: probably a young star more massive than the Sun, though it has been seen only at the edge of detection. The distance of Betelgeuse, and so its size and luminosity, carry real uncertainty. It will end as a supernova, but not on any predictable human timescale.
Questions
Is Betelgeuse about to explode?
Not on any timescale we can predict. It is near the end of its life, but the Great Dimming was caused by dust and a cooler patch on its surface, not an imminent supernova.
How big is Betelgeuse?
Betelgeuse has a radius of 764 × the Sun and a luminosity of 90,000 × the Sun.