Size really doesn’t matter: A tiny star—of about 8 percent the Sun’s mass—has been caught emitting an enormous “super flare” of X-rays.
In a matter of minutes, the celestial body released 10-plus times more energy than even the most intense bursts by our Sun.
Exciting stuff, right?
Not quite.
The dramatic eruption (like a child’s unexpected tantrum in the cereal aisle of the grocery store) poses a problem for astronomers, who didn’t think it possible for such small bodies to act so big.
The culprit, known as J0331-27, is an L dwarf: a star with so little mass that it barely qualifies as a star. Any less mass, according to the European Space Agency (ESA), and it wouldn’t be able to generate its own energy.
Astronomers spotted the flare in data recorded nearly 12 years ago by the European Photon Imaging Camera (EPIC), onboard ESA’s XMM-Newton X-ray observatory.
Artist’s impression of XMM-Newton (via European Space Agency/C. Carreau)
Flares are caused when the magnetic field in a star’s atmosphere becomes unstable and collapses, releasing an explosive emission of stored energy that creates a sudden brightening.
“This is the most interesting scientific part of the discovery, because we did not expect L-dwarf stars to store enough energy in their magnetic fields to give rise to such outbursts,” according to Beate Stelzer, from the University of Tübingen’s Institute for Astronomy and Astrophysics in Germany and the National Institute for Astrophysics (INAF) in Italy.
Energy can only be placed in a star’s magnetic field by charged particles created in high-temperature environments, the ESA explained. L dwarf J0331-27, however, has a low surface temperature for a star (2100K compared to the Sun’s roughly 6000K). So how is a super flare even possible on such an orb?
“That’s a good question,” Stelzer said. “We just don’t know—nobody knows.”
Understanding this new, and so far unique, phenomenon on the L dwarf has become a priority for researchers, who must now find more examples.
“There is still much to be discovered in the XMM-Newton archive,” project leader Andrea De Luca of INAF said in a statement. “In a sense, I think it is only the tip of the iceberg.”
Read more about the findings in a paper published this month by the journal Astronomy & Astrophysics.
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