Monday, May 19, 2008

Brightest flare ever from normal star other than Sun

On April 25, NASA's Swift satellite picked up the brightest flare ever seen from a normal star other than our Sun. The flare on EV Lacertae packed the power of thousands of solar flares and would have been visible to the naked eye if the star had been easily observable in the night sky at the time. EV Lac is a run-of-the-mill red dwarf, by far the most common type of star in the universe, shining with only one percent of the Sun's light and having 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 at 10 mag. far below naked-eye visibility - that changed for one or two hours last month, though there are no reports of anyone actually seeing it (Lac is poorly placed right now).

The flare was first seen by the Russian-built Konus instrument on NASA's Wind satellite in the early morning hours of April 25. Swift's X-ray Telescope caught the flare less than two minutes later, and quickly slewed to point toward EV Lacertae. When Swift tried to observe the star with its Ultraviolet/Optical Telescope, the flare was so bright that the instrument shut itself down for safety reasons. The star remained bright in X-rays for 8 hours before settling back to normal. 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 for which EV Lac is well known.

In other news rare mutual occultations of the satellites of 2003 EL61, one of the largest and most unusual Kuiperoids, are under way right now, and observers scramble to get large telescopes - including Hubble - in line. • Here are early follow-up observations of comet Wirtanen triggered by Cosmos4U's report of a possible outburst. • The brightest star with a transiting exoplanet in the Southern hemisphere has been found in WASP-7. • Alert #1: Mars will be near the Beehive stellar cluster May 21-24 and right inside it on May 23. • Alert #2: Jupiter can be seen without any satellites (Galilean moons, that is) visible in the night May 21/22 - a rare but not extremely rare telescopic sight: Another such view will come in Sep. 2009.

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