Astronomers have detected a new type of thermonuclear explosion on the surface of distant stars. It's known as a "micronova," and while it's smaller than a conventional nova or spectacular supernova, it's still powerful enough to burn up whole mountain ranges in a matter of hours.
Researchers at Durham University's Center for Extragalactic Astronomy, led by Simone Scaringi, spent months deciphering NASA's Transiting Exoplanet Survey Satellite data. TESS searches for planets circling other stars by looking for brightness dips in the light from those stars that could be due to other celestial objects passing in front of them.
However, at least three of the stars spotted by TESS had unexpected bursts of brilliance that lasted just a few hours at a time. Researchers detailed their study, "Localized thermonuclear bursts from accreting magnetic white dwarfs," in the journal Nature.
This artist’s impression shows a two-star system where micronovae may occur. The blue disc swirling around the bright white dwarf in the centre of the image is made up of material, mostly hydrogen, stolen from its companion star. Towards the centre of the disc, the white dwarf uses its strong magnetic fields to funnel the hydrogen towards its poles. As the material falls on the hot surface of the star, it triggers a micronova explosion, contained by the magnetic fields at one of the white dwarf’s poles.
Micronovae Explained
CNET said a white dwarf is a star with the same brightness as the sun but is only approximately the size of Earth. In a two-star system, a white dwarf may frequently absorb hydrogen and other materials from its partner star, known as accretion. The gas can pile up around the white dwarf until it causes an explosion, known as a nova, brightening the star system a million times. The gas might trigger a more spectacular explosion, causing the system to light as brilliantly as an entire galaxy for weeks.
Micronovas appear to begin in the same way as supernovas. Still, they are smaller, quicker, and occur on white dwarfs with strong magnetic fields that force stolen material toward the star's poles. The consequence is a massive explosion around the pole that is just one-millionth the magnitude of a nova. As a result, the term "micronova" was coined.
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Even if a micronova appears little in the grand scheme of things, you wouldn't want to be trapped in one. Explosions as intense as those shown in TESS data can still destroy nearly 124,000 mountains the size and mass of Mount Everest in less than a day.
Astronomer Nathalie Degenaar of the University of Amsterdam in the Netherlands, a co-author of a study describing the new micronova observations, said in an ESO press release that detonations cause the white dwarf's whole surface to glow intensely for several weeks.
Experts Using NASA TESS Mission Finds Microexplosions From Stars
After looking over data provided by NASA's planet-hunting Transiting Exoplanet Survey Satellite (TESS) mission, the study team discovered the microexplosions. The spacecraft is meant to look for exoplanets, but it also scans the sky for planets around nearer stars.
"Looking through astronomical data collected by NASA's TESS, we discovered something unusual: a bright flash of optical light lasting for a few hours," Degenaar said per CNN, citing the same press release. She added that they found very similar signals after searching further.
Two of the micronovae happened on white dwarfs, and scientists used the Very Large Telescope to confirm the third was a white dwarf. As a result, the researchers claimed that their findings were groundbreaking.
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