Book 8, Question 112
Why Can Astronomers Find Planets They Can’t See?
Astronomers can find planets they can't see by looking for wobbles and dips! A planet's gravity tugs its star, making it wobble. A planet crossing in front of the star blocks a little of its light. Thousands of planets were found this way.
More fun facts
- When a planet passes in front of its star, it blocks a little starlight and the star looks slightly dimmer.
- How much the star dims can give astronomers a rough idea of the planet's size.
- A planet's gravity tugs its star back and forth a tiny bit, and astronomers can measure that wobble.
- A planet can also bend and magnify the light of a star far behind it. This is called microlensing.
- Microlensing can find planets thousands of light-years away, while other methods work only for nearby stars.
- Not every signal is real. One study found that up to 35 percent of some planets flagged in telescope data might not exist.
Sources: NASA, Smithsonian Magazine
Questions kids ask
How can you find a planet you can't see?
By watching its star dim as the planet passes in front of it, or wobble from the planet's pull.