Small ‘Micronova’ Stellar Explosion Is Still Mighty Enough to Wreak Big Havoc – CNET


This artist’s impression shows a white dwarf stealing material from a companion star, triggering a micronova explosion at one of its poles. 

Mark Garlick

Astronomers have spotted a new type of thermonuclear explosion on the surface of distant stars. It’s called a “micronova,” and it’s smaller than a classical nova or dazzling supernova but still powerful enough to burn through entire mountain ranges in a few hours.

Researchers led by Simone Scaringi at Durham University’s Center for Extragalactic Astronomy spent months puzzled by data from NASA’s Transiting Exoplanet Survey Satellite. TESS is used to search for planets around other stars by taking a close look at the light from those stars for dips in brightness that could be caused by other worlds passing in front. 

But at least three stars TESS observed showed unusual bursts in brightness lasting for just a few hours at a time. 

“We couldn’t explain it until we made, finally, a connection that these may be thermonuclear explosions happening on accreting white dwarfs,” explains Scaringi, who’s lead author on a study published in the latest issue of the journal Nature

A white dwarf is a star that’s as powerful as the sun, but only about the size of the Earth. In a two-star system, a white dwarf can often suck up, or accrete, hydrogen and other material from its companion star. This gas can build up around the white dwarf until it triggers an explosion, or nova, that can make the star system shine up to a million times more brightly. The gas could even spur the much more spectacular supernova, which could make the system shine as brightly as an entire galaxy for several weeks.

Micronovas appear to start the same way, but are smaller, faster and happen on white dwarfs with strong magnetic fields that push stolen material toward the star’s poles. The result is a big blast around the pole that’s only one millionth the size of a nova explosion. Hence the name “micronova.”

While a micronova might seem small on the scale of the cosmos, you still wouldn’t want to be caught up in one. Explosions like those the researchers observed in TESS data are still powerful enough to burn through over 124,000 mountains the size and mass of Mount Everest in less than a day. 

“It just goes to show how dynamic the universe is,” Scaringi said in a statement. “These events may actually be quite common, but because they are so fast they are difficult to catch in action.”  

He says micronovas challenge astronomers’ understanding of how stellar thermonuclear explosions occur. Next, the team hopes to use more large-scale sky surveys to spot the elusive events and then make quick follow-up observations with powerful telescopes for a more detailed look at the new phenomenon.

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