14 DAY TRIAL // On April 25, a red dwarf star in the EV Lacertae constellation, known as Lacerta, ejected a massive solar flare equivalent to about a thousand solar flares emitted by the Sun. It was the brightest burst of light created by a normal star ever seen in the universe. The emission was first detected by NASA's Wind satellite, followed two minutes later by the Swift X-ray Space Telescope. After the initial burst of light in the visible spectrum, Lacerta remained bright in the X-ray spectrum before returning to normal brightness levels.
Lacerta is a red dwarf star with brightness only one percent of that of the Sun and a mass of about 30 percent of the latter. It is located 16 light-years away from Earth, meaning that in fact the flare was ejected more than 16 years ago. It is usually visible only a few hours during the spring season in the Northern Hemisphere, albeit the massive flare on April 25 would have made it visible to the naked eye, if the observation conditions had been optimal of course.
"Here's a small, cool star that shot off a monster flare. Flares like this would deplete the atmospheres of life-bearing planets, sterilizing their surfaces", said researcher Rachel Osten from the University of Maryland, NASA's Goddard Space Flight Center and investigator for Hubble.
The tiny star is only a couple of hundred million years old and has been regularly generating solar flares, although not as bright as the latest. According to Osten, this particularly powerful solar flare is probably the result of the release of surplus energy from the star's powerful magnetic field. Because it is so small, it rotates around its axis once every four days which enables it to generate a powerful localized magnetic field some 100 times stronger than that of our Sun.
"These flares are ultimately related to the twisting and tangling of magnetic fields that are poking out of the surface of the star, and stars like it", Osten said. Most likely, similarly to the Sun, Lacerta is also covered by sunspots moving rapidly across its surface during a solar flare.
"If we could look at the surface of the star as it was undergoing this flare, we would probably see that the spots on the surface rearrange themselves. The spots on the star cover a much larger fraction of the surface than they do on the sun, so the resulting change of the spots would be even more dramatic", said Osten.
The EV Lacertae, being much younger than our Sun, offers us the opportunity to study the solar system's early history. Young stars often produce powerful flares during the first billion years of their lives, which could also have happened to the Sun.