NASA’s Swift satellite picked up one of the brightest solar flares ever seen — not from our own sun, but a star 16 light-years away. This flare packed the power of thousands of solar flares combined, and a flare of this magnitude from our own sun would have stripped Earth's atmosphere and sterilized the planet. Astronomers say the flare would have been visible to the naked eye on April 25, 2008 if the star had been easily observable in the night sky at the time. As it was, the flare's brightness caused Swifts' Ultraviolet/Optical Telescope to shut down for safety reasons. But Swift was able to study the flare for over 8 hours with its X-ray capabilities.
The Swift satellite normally searches for gamma ray bursts, and is surrounded with detectors that look for bursts of light. The spacecraft then "swiftly" and autonomously re-points itself to the location of the burst. However, this was no gamma ray burst, just a solar flare. But what a solar flare!
The star, EV Lacertae, is a basic red dwarf, 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. It's one of our closest stellar neighbors, but normally is not visible with the naked eye, as it holds a magnitude of -10.
"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," says Rachel Osten, from NASA’s Goddard Space Flight Center. "Flares like this would deplete the atmospheres of life-bearing planets, sterilizing their surfaces."
Astronomers say EV Lacertae is like an unruly child that throws frequent temper tantrums. It's a relatively young star at a few hundred million years of age. But it’s a fast rotating star which generates a strong magnetic field, about 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 in X-ray, as the star remained bright in x-rays for about 8 hours. "This gives us a golden opportunity to study a stellar flare on a second-by-second basis to see how it evolved," says Stephen Drake of NASA Goddard.
Flares release energy across the electromagnetic spectrum, but the extremely high gas temperatures produced by flares can only be studied with high-energy telescopes like those on Swift. Swift's wide field and rapid repointing capabilities, designed to study gamma-ray bursts, make it ideal for studying stellar flares. Most other X-ray observatories have studied this star and others like it, but they have to be extremely lucky to catch and study powerful flares due to their much smaller fields of view.