Joan Cartan-Hansen: A planet is a large body orbiting a sun. There are 9 planets in our solar system and the Earth is the third planet from the sun. But what lies beyond our solar system? Are there other planets out there, and if there are, is there any life on those planets? Why are exoplanets so hard to find?

Well, planets are very small compared to the stars they orbit. For example, the Earth is 10 billion times fainter than the sun. Scientists use lots of tools to look for exoplanets – computers, telescopes on the ground and telescopes in space. Exoplanet scientists are looking for very slight changes in the light while they look up into the sky.

Light is made up of colors. When an unseen planet pulls a bit on a star, the light from that star shifts slightly to the red as it moves away from you and slightly to the blue as it moves toward you. Exoplanet scientists look for those shifts in light to find a planet. Sometimes a star’s light dims slightly when it passes in front of it and astronomers can measure tiny wobbles of a star against stars in the background to look for planets. Others use special telescopes that block out the light from a central star and take pictures looking for planets.

Scientists found the first Exoplanet in 1995. That planet is named 51 Pegasus. Scientists have found more than 400 Exoplanets ever since. Most are gas giants, planets like Jupiter. They’re so much easier to find because they’re so much bigger than Earth. But so far scientists have only found 1 Exoplanet that might be able to sustain life.

Gliese 581g was found about 20 light years away from Earth. Unlike many other Exoplanets, Gliese 581g’s orbit is in what is called the goldilocks zone. It’s called that because it’s not too close to the star, which would make it too hot for life, or not too far away which would make it too cold. Gliese 581g’s orbit is just right. But scientists don’t know yet if life exists there and they haven’t stopped looking for other exoplanets. Some even look in places where planets are just forming because who knows, some day they might find the ultimate exoplanet - another Earth.

Print Transcript