The Allure of Betelgeuse
BETELGEUSE, THAT ORANGE BEACON shining from the shoulder of Orion, the Hunter, is one of the best-studied stars out there. Yet despite all we’ve learned, virtually everything we know — or think we know — about this aged, highly volatile red supergiant remains uncertain. This includes everything from its distance and mass to the question that astronomers can’t reliably answer without getting a better handle on those and other basic stellar parameters: When will this amber-glowing behemoth go supernova?
The suspicion is, it could explode anytime. Increasingly frustrated by the uncertainties, astronomers are trying every tool in their toolkits to improve their understanding of this nearby supernova progenitor.
What we know
Betelgeuse — Alpha (α) Orionis — was born roughly 10 million years ago, condensing out of a molecular cloud probably in the area of Orion’s Belt. It’s thought to be a runaway star from that region, possibly forced out by a supernova. Today Alpha Ori is hurtling away from the Belt at a speed of 30 kilometres per second (108,000 kph).
Betelgeuse is a star of superlatives. It’s the ninth-brightest star in the night sky, but if we could perceive all the wavelengths of radiation it emits, it would be the brightest star of all. With an average apparent angular diameter of about 44 milliarcseconds — equivalent to a lunar crater 80 metres wide as seen from Earth — Alpha Ori is also one of the largest stars in our sky. It’s so near to us that we can actually resolve its surface like we can that of our own Sun. With sophisticated enough scopes, the red supergiant appears as a disk rather than a point, and like a planet it doesn’t twinkle. It’s not. If Betelgeuse were placed at the centre of our Solar System, it would extend out beyond the asteroid belt, engulfing Mercury, Venus, Earth, Mars and possibly even Jupiter.
