Kepler Space Telescope

The Kepler Space Telescope was a NASA spacecraft that searched for planets around other stars. It launched in 2009 and worked for almost 10 years. Kepler discovered over 2,600 confirmed exoplanets. It showed us that planets are very common in our galaxy and that many could be similar to Earth.

How Kepler Found Planets

Kepler stared at one patch of sky with over 150,000 stars. It watched for tiny dips in a star's brightness. When a planet passes in front of a star, it blocks a little bit of light. This is called a transit. By measuring these dips, scientists could figure out the size of the planet and how far it is from its star.

What Kepler Taught Us

Before Kepler, scientists were not sure how common planets were. Kepler showed that most stars have at least one planet. It found rocky planets, gas giants, and even planets orbiting two stars at once. Some planets are in the habitable zone, where liquid water could exist. Kepler changed our understanding of the universe forever.

Fun Facts

• Kepler discovered that there are more planets than stars in our galaxy.
• The smallest planet Kepler found is about the size of our Moon.
• Kepler ran out of fuel and was retired in 2018 after discovering over 2,600 planets.

Did You Know?

Kepler found a planet called Kepler-452b that is sometimes called Earth's cousin. It is about the same size as Earth and orbits a star similar to our Sun in the habitable zone.