Go looking for planets that travel around other stars.
An exoplanet travels around a star other than the Sun. Scientists often spot one when it passes in front of its star and blocks a tiny part of its light.
A fly passing in front of a lamp hides a little light: a planet can do something similar in front of its star.
An exoplanet is outside our Solar System.
Most are found thanks to the effect they have on their star.
No evidence of life beyond Earth has been found yet.
How much light is blocked, and how often it happens, help estimate the size and orbit of the planet. Other methods measure the small wobble of a star caused by the pull of its planet.
Choose an exoplanet. Compare its size, its year and its star with those of the Earth.
Answer two questions about the lesson to stamp your passport.
Question 1 of 2
An exoplanet is a planet that goes around a star other than the Sun! Thousands have been found since 1995, thanks to telescopes such as Kepler and James Webb.
The “habitable zone” is the area around a star where the temperature could allow liquid water. That does not prove a planet is habitable: its atmosphere and surface matter too.
In 1995, Michel Mayor and Didier Queloz discovered the first exoplanet around a Sun-like star. The very first known exoplanets had been found around a pulsar in 1992.
Telescopes almost never see exoplanets directly. Here are the scientists’ tricks:
When the planet passes in front of its star, the brightness drops a little. Like a fly passing in front of a lighthouse!
The planet makes its star wobble a little as it goes around. We measure this wobble in the star’s light.
We photograph the planet itself. It is hard, because its star is much brighter.
The gravity of a star and its planet bends the light of a more distant star, like a magnifying glass.
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The closest known exoplanet goes around Proxima Centauri. It is in the star’s habitable zone, but we do not know whether it has water.
Its light takes more than four years to reach us. A spacecraft today would need thousands of years to make the trip.
It is one of the seven rocky planets of the TRAPPIST-1 system. It is close to Earth’s size.
These seven planets orbit very close to their small star, yet some receive about as much energy as Earth does.
Its year lasts 385 days and its star looks like the Sun. But it is bigger than Earth and its surface is still unknown.
Being in the habitable zone is not enough: we also need to know about its atmosphere and whether there is water.
Discovered in 1995, it is the first confirmed exoplanet around a Sun-like star.
It goes around its star in only four days and is far too close to it for life as we know it.
This planet looks blue, but it is very hot and its winds are extremely fast.
Models suggest that silicate particles could form a rain of glass blown sideways by the winds.
This planet passes so close to its star that it is stretched out of shape and slowly loses material.
It reflects very little visible light: observations show it absorbs almost all of it.
The European Space Agency’s cartoon about our neighbourhood in space.
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