Exo-planets are planets that are orbiting a star outside our Solar System.
They are extremely difficult to detect. In fact it is only very big planets that can be detected.
Exo-planets are detected by a couple of methods.
One method is to measure the brightness of a star.
When a large planet passes in front of it the brightness of the star is slightly dimmed.
Obviously the larger the planet the more the planet dims the light of the star it passes in front of.
Astronomers call this the transit method.
Another method is to catch a star wobbling.
The star`s gravitational field will pull the star whilst the planet`s gravitational field will pull the star!
This pulling by the star and planet will cause a wobble which astronomers can measure.
The first exo-planet was discovered in 1995, the total number of confirmed exo-planets are 473.
Will these planets be habitable? Only if they exist in a special zone around the star called the Goldilocks Zone.
Find out more here:
- Extrasolar Planets: BBC
- PlanetQuest NASA
- Exoplanet Database
- The Royal Observatory Edinburgh