Astronomers recently rejoiced after witnessing the eruption of a strange volcanic comet like a “champagne bottle”, spraying gas and ice across the solar system like sparkling wine. The unusual explosion was cause for celebration because it was the first time researchers had successfully predicted it would happen.
The volatile comet, known as 29P/Schwassmann-Wachmann (29P), is about 37 miles (60 kilometers) across and takes about 14.9 years to orbit around sun. Besides being volcanic, 29P has an unusually circular orbit for a a comet and spins much slower than expected. It’s one of about 100 comets known as “centaurs” that have been pushed from the Kuiper belt — a ring of icy comets that lurk beyond Neptune — into a closer orbit around the sun, near Jupiter.
Unlike Earth’s volcanoes, which spew hot magma and ash from the planet’s mantle, 29P spews extremely cold gases and ice from its supercold interior. This unusual type of volcanic activity is known as cryovolcanism or “cold volcanism”.
On April 2, scientists from the British Astronomical Association (BAA) observed a sharp jump in the brightness of 29P, which was caused by light reflected from recently ejected gas and ice, or cryomagma, in the comet’s coma – the cloud of gas that surrounds the comet’s body or core. The eruption was probably quite large, given that the coma overshadowed the core by a factor of more than 10, Spaceweather.com (opens in new tab) reports, but its exact strength has not yet been quantified.
The eruption was “like a cork popping out of a champagne bottle,” according to Spaceweather.com.
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29P is one of the most volcanically active comets in the world solar system, and researchers have seen it hundreds of times before. In November 2022, the icy comet underwent a massive eruption that ejected more than 1 million tons of cryomagma, making it the second largest explosion of its kind recorded in the last 12 years. But as with all other past flares of 29P, astronomers had no idea that a massive eruption was imminent before it happened.
This time, however, researchers strongly suspected that 29P would erupt.
Cryovolcanic bodies, which include a handful of other comets and several solar system moons, such as Saturn’s Enceladus, Jupiter’s Europa, and Neptune’s Triton, have a surface crust surrounding an essentially solid icy core. Richard Miles (opens in new tab), a BAA astronomer who studied 29P, told Live Science last year. Over time, radiation from the sun can cause the comet’s icy interior to sublimate from a solid to a gaseous state, causing pressure to build up beneath the crust, although at the same time some gas is continually escaping. When radiation from the sun weakens the crust, this pressure causes the outer shell to crack and cryomagma is shot into space.
On April 1, BAA astronomers noticed that the light around the comet’s nucleus was “the faintest we’ve ever seen,” Miles wrote in statement (opens in new tab). This is a sign that less gas is escaping from the comet’s outer crust than usual, suggesting that pressure is building up at an increased rate inside the comet, he added. This made it “highly likely that an eruption would occur”.
The latest outburst is proof that 29P’s outbursts can be predicted in advance, which will hopefully help researchers study future outbursts in more detail.