Washington, May 20 : NASA's Swift satellite has detected an extremely bright flare coming from a considerably small star - a red dwarf.
The flare, which is the brightest ever seen from a normal star other than our Sun, packed the power of thousands of solar flares. In fact, it would have been visible to the naked eye if the star had been easily observable in the night sky at the time.
But the star, known as EV Lacertae, is a run-of-the-mill red dwarf, by far the most common type of star in the universe. It shines with only one percent of the Sun's light, and contains only a third of the Sun's mass.
At a distance of only 16 light-years, EV Lacertae is one of our closest stellar neighbors. But with its feeble light output, its faint magnitude-10 glow is far below naked-eye visibility.
"Here's a small, cool star that shot off a monster flare. This star has a record of producing flares, but this one takes the cake," said Rachel Osten, a Hubble Fellow at the University of Maryland, College Park and NASA's Goddard Space Flight Center in Greenbelt, Maryland.
"Flares like this would deplete the atmospheres of life-bearing planets, sterilizing their surfaces," he added.
The star remained bright in X-rays for 8 hours before settling back to normal.
The star is relatively young, with an estimated age of a few hundred million years. The star rotates once every four days, which is much faster than the sun, which rotates once every four weeks.
EV Lacertae's fast rotation generates strong localized magnetic fields, making it more than 100 times as magnetically powerful as the Sun's field. The energy stored in its magnetic field powers these giant flares.
The flare's incredible brightness enabled Swift to make detailed measurements.
"This gives us a golden opportunity to study a stellar flare on a second-by-second basis to see how it evolved," said Stephen Drake of NASA Goddard.
Since EV Lacertae is 15 times younger than our Sun, it gives us a window into our solar system's early history.
Younger stars rotate faster and generate more powerful flares, so in its first billion years, the sun must have let loose millions of energetic flares that would have profoundly affected Earth and the other planets.