• Scientists discovered a completely new type of stellar explosion that they've dubbed micronova.
  • The findings challenge our understanding of how cosmic blasts happen in some stars, researchers say.
  • Micronova could be common in the universe, but they're difficult to detect.

An international team of astronomers have observed and identified a never before seen type of stellar explosion they have dubbed micronova.

In a paper published Wednesday in the journal Nature, researchers describe a small, but mighty cousin of a typical nova, or stellar outbursts in which the surface of certain dead stars, called white dwarfs, blow up. But unlike nova, the previously unknown blasts detailed in the new study are smaller and faster, burning through the equivalent of around 3.5 billion Great Pyramids of Giza worth of stellar material in only a few hours. 

"We have discovered and identified for the first time what we are calling a micronova," Simone Scaringi, astronomer and assistant professor at Durham University in the United Kingdom, who led the study, said in a statement. The finding challenges current understanding of how cosmic blasts occur in some stars, according to Scaringi.

"We thought we knew this, but this discovery proposes a totally new way to achieve them," Scaringi said of stellar explosions. "It just goes to show how dynamic the universe is."

Micronova are small, localized explosions, distinct from a full-fledged nova, where thermonuclear flares engulf the entire white dwarf. Foto: Mark Garlick/ESO

Looking at data from NASA's Transiting Exoplanet Survey Satellite, researchers detected rapid bursts of energy coming from a white dwarf — small, dense remnants of sun-like stars that have burned up all their fuel. These flashes only lasted 10 hours before the outburst fizzled out. Searching further, they found two similar events. Using the European Southern Observatory's Very Large Telescope in Chile's Atacama Desert, the team confirmed that these small explosions were a new class of nova occurring in specific regions of white dwarfs.

Scientists think these mini versions of energetic nova occur in binary systems — meaning systems where two stars are gravitationally bound to each other — where the magnetic fields of white dwarfs are strong enough to pull in material from a nearby star to its poles. That triggers small, localized explosions, distinct from a full-fledged nova, where thermonuclear flares engulf the entire white dwarf. 

"For the first time, we have now seen that hydrogen fusion can also happen in a localized way. The hydrogen fuel can be contained at the base of the magnetic poles of some white dwarfs, so that fusion only happens at these magnetic poles," Paul Groot, an astronomer at Radboud University in the Netherlands, who coauthored the paper, said in a statement.

While novas shine brightly for several weeks, micronova only last a few hours, according to the researchers. The study authors suspect these small pyrotechnic displays could be plentiful throughout the universe.

The next step is to use large-scale surveys to find and study more micronova and other elusive cosmic events in our galaxy. "Because they are so fast, they are difficult to catch in action," Scaringi said. 

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