TEMPO.CO, Jakarta – After nova and supernova, a new type of explosion has been found in dead stars, namely micronovae. These explosions are smaller but more frequent than the usual explosions in star systems.
When stars, such as our sun, reach the end of their lives, they shed their outer layers, leaving only their dense core as a dwarf. Thousand dwarf star white dwarfs have been known to exist in our galaxy in pairs with larger stars, where white dwarfs can suck in — or accrete — material from their mates.
Over thousands of years, this accretion process can lead to very powerful explosions known as novae or even supernovae, in which the star disappears completely. Simone Scaringi of the Center for Extragalactic Astronomy, Department of Physics, at Durham University, UK, and colleagues used the proprietary Transiting Exoplanet Survey Satellite (TESS) NASA to find micronova explosions.
“Mikronova is about a million times fainter than a classic nova,” Scaringi said. “The explosion lasts only half a day, compared to several weeks for a nova.”
Their brief period of occurrence may have made them previously unobservable. TESS only revealed it during exoplanet search observations. Three micronovae were found 5,000 light-years from Earth, with the white dwarf appearing bright for a moment before dimming again.
The exact mechanism behind these micronova explosions isn’t clear, but it’s thought to be caused by hydrogen gas accumulating at the star’s poles. Hydrogen reaches temperatures and pressures capable of triggering a fusion reaction and causing a localized thermonuclear explosion, with as much energy being released as the sun does in a single day.
Only a highly magnetic white dwarf might be able to accumulate hydrogen gas at its poles in this way, which means that not all should experience the same. Finding and studying more micronovae is believed to reveal a more definitive sequence of processes, and possibly explain how white dwarfs are capable of accreting enough mass to cause them to explode as supernovas.
“It shows how dynamic our universe is,” Scaringi said. “If you don’t see it at the right time, you might end up going through things like this.” The report of Scaringi et al was published online in the Journal of Nature 20 April 2022.
NEW SCIENTIST, NATURE
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