Wide field view of the region of the sky where betelgeuse is located

Did Betelgeuse supernova? Or was it just a dusty fart?

Between November 2019 and March 2020, the star Betelgeuse – the second closest red supergiant to Earth, and a star that’s slowly pulsing towards the end of its lifespan – dimmed visibly, sparking global speculation about the cause.

For many in the astronomical community, it was thought at first that Betelgeuse might be about to supernova – a highly anticipated stellar explosion in which a red giant’s core collapses inwards, before exploding outwards, ejecting elements and debris into space. These supernovae only occur at the deaths of the largest stars in the Universe. When no such explosion was subsequently detected, scientists set out to understand why.

According to a new study published in the journal Nature, the ‘Great Dimming’ was actually caused by a giant, cosmic outrush of dust and gas. That’s right – it was because of cosmic flatulence.

Miguel Montarges, from the Observatoire de Paris, France, and colleagues studied Betelgeuse’s surface before and during the Great Dimming. Using high-angular-resolution observations from the Very Large Telescope in Chile, the team determined that the star’s southern hemisphere was ten times darker than usual during the dimming.

Observations and modelling revealed that a local temperature drop occurred in a cool region of the star’s surface, leading the team to conclude that a dust clump formed in the vicinity of the star as a direct result of the cooling patch. This cooling, dust-ejecting event evolved rapidly over weeks, increasing the dimness of the star, before wrapping up in March 2020. That’s a long toot.

Tough luck for astronomers hoping to catch a glimpse of one of the universe’s most spectacular light shows: when Betelgeuse does eventually explode, within the next 100,000 years, the supernova will probably shine as bright as a half-moon for at least three months, and cast visible shadows on Earth.

The last supernova event visible to the naked eye occurred in 1604. Known as Kepler’s Supernova after its observer and describer Johannes Kepler, at its strongest the exploding star was brighter than Jupiter.

These images, taken with the SPHERE instrument on ESO’s Very Large Telescope, show the surface of the red supergiant star Betelgeuse during its unprecedented dimming, which happened in late 2019 and early 2020. Image credit: Springer Nature

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