Exoplanets are planets outside our solar system. The first one was confirmed in 1995 and since then we’ve discovered over 5000 more.

Tanno and Iguda visited the Trappist system. This has seven exoplanets really close to their star. If you look closely at this picture, you’ll see the Trappist1 system has been enlarged here 25 times. All seven Trappist1 planets would be well inside the orbit of Mercury if they were in our solar system.

Image credit: NASA/JPL-Caltech

kepler 1649c surface image
This is an artist’s idea of what the surface of exoplanet Kepler 1649c might look like.
Image Credit: NASA/Ames Research Center/Daniel Rutter

How do we find exoplanets?

Telescopes looking at a star can check how bright it is. If the brightness drops regularly, it’s likely that a planet is passing in front of the star, blocking some of the light, each time it orbits. This is called the ‘transit method’.

Image credit: NASA/Ames

This diagram shows how the light of the dim red ultra cool dwarf star TRAPPIST-1 fades as each of its seven known planets passes in front of it and blocks some of its light. The larger planets create deeper dips and the more distance ones have longer lasting transits as they are orbiting more slowly. These data were obtained from observations made with the NASA Spitzer Space Telescope.

How do we find exoplanets?

This diagram shows how the brightness of the Trappist star changes as each of its planets moves in front of it. If the line on the graph drops for a long time, that means a planet is further away from the star.

The more the line drops down, the bigger the star is – it’s blocking more light because it’s bigger. Which Trappist planet is the biggest? You can check your answer by looking back up at the first image on this page.

Measurements taken by the Spitzer Space Telescope.

Image credit: ESO/M. Gillon et al.

There are several different ways of finding exoplanets, but so far, most of them have been found by the transit method.

Watch how NASA celebrated going over 5000 confirmed exoplanets by making music with a note to represent each one found:


Scientists do experiments. You can do a simple experiment that is just like the way a space telescope searches for exoplanets.

Bonus Activity

NASA have an exoplanet travel bureau to show you all sorts of great information about exoplanets in a really fun way. It’s designed as if you were going to go on holiday to an exoplanet – how would you choose which one to visit?

You can download their exoplanet advertising posters to colour in yourself. Click here to go to the NASA website.

You can go to the previous DeepSpace secret pages by clicking the places below.

Distant UniverseBlack HoleDark Matter
GalaxiesSupernovasNeutron Stars
These delicate wisps of gas make up an object known as SNR B0519-69.0, or SNR 0519 for short. The thin, blood-red shells are actually the remnants from when an unstable progenitor star exploded violently as a supernova around 600 years ago. There are several types of supernova, but for SNR 0519 the star that exploded is known to have been a white dwarf star — a Sun-like star in the final stages of its life. SNR 0519 is located over 150 000 light-years from Earth in the southern constellation of Dorado (The Dolphinfish), a constellation that also contains most of our neighbouring galaxy the Large Magellanic Cloud (LMC). Because of this, this region of the sky is full of intriguing and beautiful deep sky objects. The LMC orbits the Milky Way galaxy as a satellite and is the fourth largest in our group of galaxies, the Local Group. SNR 0519 is not alone in the LMC; the NASA/ESA Hubble Space Telescope also came across a similar bauble a few years ago in SNR B0509-67.5, a supernova of the same type as SNR 0519 with a strikingly similar appearance. A version of this image was submitted to the Hubble’s Hidden Treasures Image Processing Competition by Claude Cornen, and won sixth prize.
Blue Ring NebulaBetelgeuse