National Astronomical Observatory of Japan

The Lion’s Roar: New Telescope Spots Superflare in Leo

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Artist’s impression of the dramatic effect a superflare on a red dwarf star could have on an Earth-like exoplanet orbiting it. (Credit: NAOJ) Original size (1.3MB)

A new telescope in Okayama, Japan observed a superflare on a star in the constellation Leo to better understand how superflares on the Sun can affect technology and life on Earth.

The cold, dark chaos of space is filled with mystery.

Fortunately, the ways in which we can peer into the mists of the void are increasing, and now include Kyoto University’s 3.8 meter Seimei Telescope.

Using this new instrument—located on a hilltop in Okayama to the west of Kyoto—astronomers from Kyoto University's Graduate School of Science and the National Astronomical Observatory of Japan have succeeded in detecting 12 stellar flare phenomena on AD Leonis, a red dwarf star 16 light-years away in the constellation Leo, the Lion. In particular, one of these flares was 20 times larger than those emitted by our own Sun.

“Solar flares are sudden explosions that emanate from the surfaces of stars, including our own Sun,” explains Kosuke Namekata, first author of the paper which appeared in Publications of the Astronomical Society of Japan. “On rare occasions, an extremely large superflare will occur. These result in massive magnetic storms, which when emitted from our Sun can affect the Earth's technological infrastructure.”

Hence understanding the properties of superflares can be vital, but their rareness means that it is difficult to gather data from observing our Sun alone. This has led researchers to look for exoplanets similar to Earth, and to examine the stars they orbit.

In their paper in Publications of the Astronomical Society of Japan, the team reports on a long week of setting the sights of Seimei—along with other observational facilities—to AD Leonis. This M-type red dwarf is cooler than our Sun, resulting in a higher incidence of flares. The team expected a number of these flares to be large, but were still astounded to detect a superflare on their very first night of observations.

“Our analyses of the superflare resulted in some very intriguing data,” Namekata explains.

Light from excited hydrogen atoms in the superflare indicated that there were roughly 10 times more high-energy electrons than seen in typical flares from our Sun.

“This is the first time this phenomenon has been reported, and it’s thanks to the high precision of the Seimei Telescope,” says Namekata.

The team also observed flares where light from excited hydrogen atoms increased, but did not correspond with an increase in brightness across the rest of the visible spectrum.

“This was new for us as well, because typical flare studies have observed the continuum of the light spectrum—the broad range of wavelengths—rather than energy coming from specific atoms,” continues Namekata.

The high-quality of these data was thanks to the new telescope, which the team hopes will open doors to new revelations regarding extreme space events.

Kazunari Shibata, leader of the study, concludes, “More information on these fundamental stellar phenomena will help us predict superflares, and possibly mitigate magnetic storm damage here on Earth. We may even be able to begin understanding how these emissions can affect the existence—or emergence—of life on other planets.”

These results appeared as Namekata, et al. “Optical and X-ray observations of stellar flares on an active M dwarf AD Leonis with Seimei Telescope, SCAT, NICER and OISTER” in Publications of the Astronomical Society of Japan on July 10, 2020.

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