Astronomers call alien worlds "exoplanets." An exoplanet is a planet orbiting a star other than our sun.
For centuries, people assumed that other worlds existed, but only recently did astronomers detect exoplanets for real.At first, the detection techniques and equipment could only spot huge planets (as big or bigger than Jupiter) that tugged hard on its star.
 |
| Image from the course "Astrobiology: Exploring Other Worlds" from the University of Arizona |
Imagine you are spinning around while holding a bucket of English peas covered in squeeze cheese. As you spin, the bucket tugs on you, and you have to lean back to make up for the weight.
The same happens when an exoplanet (the bucket) spins around a star (you). The heavier the planet, the more the star is tugged. The star actually wobbles through space!
Astronomers can measure a star's wobble using a "radial velocity" technique.
They started by finding big Jupiter-size planets. Then they got better and started finding smaller Neptune-sized planets. Nowadays, the techniques and equipment have improved, and astronomers are finding Earth-sized planets that exert a tiny tug on the star.
The tiny star wobble is exciting since it means that planets like ours may be common. Could it mean that these planets also have alien creatures? I bet some of them do!
 |
| I like to paint exoplanets. Here are two companions floating along the dusty arm of a spiral galaxy. |
