Astronomers using NASA's Swift satellite spotted a massive solar flare coming from a tiny star on April 23. The explosion was over 10,000 times more intense than anything that has been recorded from our Sun.
The star, DG CVn, is an M class star located about 26 light years away in the constellation Canes Venatici. Its radius and mass are about a third of that of our Sun and it's about 1/1000 less luminous. DG CVn is a young star at only about 35 million years old, and like most young stars, it spins rather quickly. While this spinning does contribute to an increased level of activity, DG CVn's flares surpass anything astronomers had predicted.
"We used to think major flaring episodes from red dwarfs lasted no more than a day, but Swift detected at least seven powerful eruptions over a period of about two weeks," Goddard's Stephen Drake said in August at a meeting of American Astronomical Society’s High Energy Astrophysics Division. "This was a very complex event."
Solar flares are triggered by a buildup of charged particles in the star's plasma. That energy is sometimes released in huge explosions of radiation, spanning the electromagnetic spectrum. Some stars are known as flare stars, as they have predictable activity levels.
Astronomers at NASA study these stars in order to learn more about the phenomenon. However, DG CVn's flare came as quite a shock.
"This system is poorly studied because it wasn't on our watch list of stars capable of producing large flares," added astronomer Rachel Osten of the Space Telescope Science Institute in Baltimore. "We had no idea DG CVn had this in it."
Interestingly, Swift is typically used to identify gamma ray bursts, which are brief explosions of radiation stemming from certain supernova events or interactions between neutron stars. A solar flare must have occurred from a small star that was so large, the high level of gamma radiation triggered Swift's Burst Alert Telescope (BAT) and alerted astronomers of its presence.
"For about three minutes after the BAT trigger, the superflare's X-ray brightness was greater than the combined luminosity of both stars at all wavelengths under normal conditions," explained Goddard's Adam Kowalski, who is heading up the research into this event.
"Flares this large from red dwarfs are exceedingly rare."
Solar flare events are classified based on intensity. B class flares are the weakest and X class are the most powerful. Within the classes, the solar flare is given a numerical value to describe how powerful it is, relative to other events within the same class.
"The biggest flare we've ever seen from the sun occurred in November 2003 and is rated as X 45," Drake continued. "The flare on DG CVn, if viewed from a planet the same distance as Earth is from the sun, would have been roughly 10,000 times greater than this, with a rating of about X 100,000."