Question: how do you find new planets

Leila Battison answered on 10 Mar 2012:

Scientists use loads of different ways of searching for new planets around other stars.

One of the most successful methods has been to look directly at a star with a telescope and measure the tiny movements forward and back, that can be caused by a heavy planet orbiting around it. When a planet travels round its star, the gravity of that planet pulls the star towards it a bit, and you can see this swinging in the light coming from that star. This is called ‘radial velocity’, and it works best for big planets with a big pull on their star.

Another really cool way of finding planets is to look for a long time at a single star, and measure the amount of light coming off it. If there is a dip in the amount of light, then it might be a planet passing infront of the star. If it happens regularly, like every few days, or weeks, then that’s a sign that the planet is orbiting round and round. This is called the ‘transit method’, and you can give it a go yourself at planethunters.org!

There are lots of other techniques, including trying to spot them on their own in telescope images, and we have found over 750 planets around other stars so far.