An Astronomer's Dilemma: Finding Planets among the Stars.
Presented by Science@NASA.
Strange but true: When it comes to finding new planets, stars can be an
incredible nuisance. It's a matter of luminosity.
Stars are bright, but their planets are not. Indeed, when astronomers peer
across light years to find a distant Earth-like world, what they often find
instead is an annoying glare. The light of the star itself makes the star's dim
planetary system nearly impossible to see. How would you like to be an
astronomer who's constantly vexed by stars? Bummer!
Fortunately, there may be a solution. It comes from NASA's Galaxy Evolution
Explorer or "GALEX' for short, an ultraviolet space telescope that has been
orbiting Earth since 2003.
In a new study, researchers say GALEX is able to pinpoint dim stars that might
not overwhelm their own planets.
"We've discovered a new technique of using ultraviolet light to search for
young, low-mass stars," says David Rodriguez, a graduate student of astronomy at
UCLA, and the study's lead author. "These M_class stars, also known as red
dwarfs, are excellent targets for direct imaging of exoplanets."
Young red dwarfs produce a telltale glow in the ultraviolet part of
electromagnetic spectrum that GALEX can sense. Because dwarf stars are so
numerous — as a class, they account for more than 2/3 of the stars in the galaxy
— astronomers could reap a rich bounty of targets.
In many ways, these stars represent a best-case scenario for planet hunting.
their low mass means they are dimmer than heavier stars, so their light is less
likely to mask the feeble light of a planet. And because they are young, their
planets are freshly formed, and thus warmer and brighter than older planetary
Astronomers know of hundreds of distant planets, but very few have actually been
seen. Many exoplanets are detected indirectly by means of their "wobbles" the
gravitational tugs they exert on their central stars. Some are found when they
transit the parent star, momentarily dimming the glare, but not dimming it
enough to reveal the planet itself.
This new GALEX technique might eventually lead to planets which can be seen
directly. That would be good because, as Rodriguez points out, "seeing is
believing." And it just might make astronomers feel a little better about the
For more information about distant planets and the stars they circle, visit