[Music] Rachel Osten: When I got the
news on April 23rd, earlier this year,
that a flare had been detected by Swift and it
was coming from a nearby flare star called
DG CVn, I was initially very surprised.
Swift doesn't normally detect flares
from nearby flare stars, and DG CVn
is a relatively unknown star.
Narrator: There are a few things we know about DG CVn. It is an
M-class star, also called a red dwarf, and is located only about
60 light years away. Rachel: It's a dim little red star, it has
a luminosity that's about one-thousandth the luminosity of the sun.
It has a mass that's about one-third the mass of the sun,
and a radius that's about one-third
the radius of the sun. Narrator: The largest solar flare
ever recorded happened on November 4th, 2003.
It was so powerful that it overloaded the sensors measuring it, but
later calculations put it at an an X45.
Flares are classified according to their strength. The smallest ones are
B-class, followed by C, M, and X, the largest.
An X45 flare is a very powerful flare.
DG CVn's flare, however, was much
larger. Rachel: We can estimate
how big the flare on DG CVn was with respect to
the solar scale; it would have been an
X100,000. So this is several orders of
magnitude larger than the biggest solar flare we've ever seen.
The flare that Swift triggered on from DG CVn
was only the beginning of what turned out to be
a fairly extended series of flares,
a flare "event" if you will, that lasted
almost 20 days. Steven Drake: This was a
very different star than the sun, so we don't really have to worry about this happening
in the present-day sun. The young sun, such large events may have
occurred. In the present-day sun the activity levels are much
lower. The fundamental reason that DG CVn is more active than the sun
is it's a very young star--30 million years--it's rapidly rotating,
young stars are born that way, and rapid rotation
is one of the key ingredients which powers activity. The faster the rotation,
the greater the activity. Narrator: While not a threat to us,
the massive flares of red dwarf stars can help us better understand the flares produced
by our own sun. They are also of interest because red dwarf stars
a often orbited by planets. Some data suggest
that 40 percent of red dwarfs have "super-Earth" type planets orbiting
in a habitable zone, where liquid water is possible.
If this is true, then they are good candidates for supporting life.
However, the habitable zone around a cool, dim star like
DG CVn is much closer to the star than the Earth is to the sun.
Rachel: When planets are closer to their star,
they're more susceptible to anything the star does. For instance,
if the star flares, the planet is much closer to the
star, and it can be hit by
the radiation or the particles that get ejected
from the star when this flare process happens. If you happened
to be on a planet around an M dwarf,
when one of these large flares went off, you'd be
having a very bad day. [Beeping]
[Beeping]