Andrew Yee[_1_]
May 26th 08, 03:48 PM
Robert Naeye
Goddard Space Flight Center, Greenbelt, Md. May 19, 2008
301-286-4453
The Mouse That Roared: Pipsqueak Star Unleashes Monster Flare
On April 25, NASA's Swift satellite picked up the brightest flare ever seen
from a normal star other than our Sun. The flare, an explosive release of
energy from a star, packed the power of thousands of solar flares. It would
have been visible to the naked eye if the star had been easily observable in
the night sky at the time.
The star, known as EV Lacertae, isn't much to write home about. It's 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," says Rachel Osten,
a Hubble Fellow at the University of Maryland, College Park and NASA's
Goddard Space Flight Center in Greenbelt, Md. "Flares like this would
deplete the atmospheres of life-bearing planets, sterilizing their
surfaces."
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 can be likened to an unruly child that throws frequent temper
tantrums. 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.
EV Lacertae's constellation, Lacerta, is visible in the spring for only a
few hours each night in the Northern Hemisphere. But if the star had been
more easily visible, the flare probably would have been bright enough that
the star could have been seen with the naked eye for one to two hours.
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," says 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.
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.
Says Eric Feigelson of Penn State University in University Park, Pa., "I
find it remarkable that a satellite designed to detect the explosive birth
of black holes in distant galaxies can also detect explosions on stars in
the immediate neighborhood of our Sun."
IMAGE CAPTION:
[http://www.nasa.gov/centers/goddard/images/content/226765main_pipsqueak.jpg
(140KB)]
An artist depicts the incredibly powerful flare that erupted from the red
dwarf star EV Lacertae. Credit: Casey Reed/NASA
Goddard Space Flight Center, Greenbelt, Md. May 19, 2008
301-286-4453
The Mouse That Roared: Pipsqueak Star Unleashes Monster Flare
On April 25, NASA's Swift satellite picked up the brightest flare ever seen
from a normal star other than our Sun. The flare, an explosive release of
energy from a star, packed the power of thousands of solar flares. It would
have been visible to the naked eye if the star had been easily observable in
the night sky at the time.
The star, known as EV Lacertae, isn't much to write home about. It's 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," says Rachel Osten,
a Hubble Fellow at the University of Maryland, College Park and NASA's
Goddard Space Flight Center in Greenbelt, Md. "Flares like this would
deplete the atmospheres of life-bearing planets, sterilizing their
surfaces."
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 can be likened to an unruly child that throws frequent temper
tantrums. 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.
EV Lacertae's constellation, Lacerta, is visible in the spring for only a
few hours each night in the Northern Hemisphere. But if the star had been
more easily visible, the flare probably would have been bright enough that
the star could have been seen with the naked eye for one to two hours.
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," says 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.
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.
Says Eric Feigelson of Penn State University in University Park, Pa., "I
find it remarkable that a satellite designed to detect the explosive birth
of black holes in distant galaxies can also detect explosions on stars in
the immediate neighborhood of our Sun."
IMAGE CAPTION:
[http://www.nasa.gov/centers/goddard/images/content/226765main_pipsqueak.jpg
(140KB)]
An artist depicts the incredibly powerful flare that erupted from the red
dwarf star EV Lacertae. Credit: Casey Reed/NASA