Exoplanets and the Search for Life
Thousands of planets orbit other stars.
About this topic
Exoplanets orbit other stars; over 5,500 have been confirmed. Methods of detection: the transit method (a star dims as a planet crosses it, used by Kepler and TESS) and the radial velocity method (star wobbles). Planets range from hot Jupiters to rocky super-Earths.
The habitable zone is the region where liquid water could exist. Telescopes analyse atmospheres for biosignatures such as oxygen and methane. Astrobiology also searches icy moons like Europa and Enceladus. So far, no confirmed life beyond Earth.
A transit example: when Jupiter-sized planets pass in front of a Sun-like star, the starlight dims by about 1 percent, while an Earth-sized planet dims it by only about 0.01 percent, which is why finding Earth twins is hard. Kepler watched about 150,000 stars and discovered thousands of planets, showing that planets are common, and on average there is at least one per star. The radial velocity method measures tiny Doppler shifts in starlight as the star is tugged by an orbiting planet; it gave the first planet around a Sun-like star, 51 Pegasi b, in 1995.
The habitable zone, sometimes called the Goldilocks zone, depends on star type; it is closer for cool red dwarfs, such as the TRAPPIST-1 system with seven Earth-sized worlds. The James Webb telescope can study atmospheres as light filters through them during transit. Students should remember that a planet in the habitable zone is not necessarily habitable, and that finding biosignatures needs several lines of evidence because non-biological processes can also make oxygen or methane.
Key ideas
- Transit and wobble methods
- Habitable zone
- Biosignatures
Quick check
Use cases: where Exoplanets and the Search for Life helps
- Homework: review the key idea behind Exoplanets and the Search for Life before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Exoplanets and the Search for Life without notes.
- Visual learning: play with the interactive lab to see how Exoplanets and the Search for Life changes when you adjust its inputs.
- Teaching a friend: explain Exoplanets and the Search for Life in your own words, then compare your version with the key ideas.
Earth science helps with weather forecasts, natural hazards, energy and climate planning.
Frequently asked questions
What is Exoplanets and the Search for Life?
Thousands of planets orbit other stars.
What will I learn in Exoplanets and the Search for Life?
Transit and wobble methods. Habitable zone. Biosignatures.
Is Exoplanets and the Search for Life part of Earth & Space?
Yes. It is one of 60 Earth & Space topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Exoplanets and the Search for Life lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Exoplanets and the Search for Life?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.