Star profile: Betelgeuse

The famous red giant will soon be coming to an explosive end

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Betelgeuse, or Alpha Orionis, has had an eventful 8.5 million years, and astronomers predict it has less than a million years left. If you were to go outside and stare out at the night sky, you’d recognise Betelgeuse quite easily within Orion, shining with an apparent magnitude of +0.5. However, this figure has been known to vary due to the star’s instability, which causes pulsations in the star’s outer layers and in turn expells material into its surrounding environment.

The star is relatively nearby at just 642 light-years away, and exists as an enormous red supergiant star. If it were placed in the centre of our Solar System, its outer surface could stretch to around the orbit of Jupiter. This Herculean size is due to an imbalance within the star’s interior. Towards the end of any star’s life, a lifetime of nuclear fusion – the process in which hydrogen fuses into helium within a stellar core and releases energy – has inevitably depleted the hydrogen fuel source that keeps the fire burning. This results in overpowering gravity putting strain on the core, which is experiencing a depleting radiation pressure output. This ignites nuclear fusion in the outer layers of the star, and the core then begins to convert helium into heavier elements such as carbon, oxygen and so on. The resultant radiation pressure within Betelgeuse’s outer layers has pushed the surface of the star outwards, bloating it into its current supergiant status.