How it works
This method is based on the idea that when a planet orbits its star, the planet’s gravitational pull makes the star move in a small circle rather than stay still. We can detect those small movements, or wobbles, by observing the light coming from a star.
**additional information for the kids, that are already familiar with the Doppler effect: we can detect the wobbles by looking at the star’s spectrum (we know what kind of spectrum to expect from a stationary star): if the spectrum shifts towards blue, that means the star is moving towards us, if the spectrums shifts towards red, that means that the star is moving away from us. If the red-to-blue-and-back shifts are periodical, that means the star is moving in a circle. Bingo! We found a planet!
can be detected.
Method name decoding
“Transit” means passage, the word ”photometry” comes from greek words “photo” (meaning light) and “metrio” (meaning measure).
How it works
When the planet passes in front of its star, it blocks a tiny bit of light coming from the star. And we can observe the dips in the star’s brightness!
There are lots of stars that appear to change their brightness when we observe them from Earth, we call them variable stars. Not any change of brightness is interesting to us, but only a periodic change, when the dip repeats at a certain intervals (because the planet orbits its stars periodically). And unfortunately there are many reasons for the star to change its brightness in a pattern. For example:
Gravitational microlensing is another way to find a planet outside the Solar System.
The magic behind the method is this: gravity can bend light!
How it works
For the method to work, we need two stars, the star we study should be at the front, another star should be behind it at the background. Imagine that the light from a distant star moves towards the Earth. As it pases by our study star, it gets bent by the star’s gravity. As a result, we get to see two images of a background star instead of one!
Now let’s imagine there is a planet orbiting the foreground star. The planet’s gravity will also bend the light of the distant star. Just a bit.
As a result, an observer on Earth should see not two, but three images on the background star. Though the third image will be less bright than the other two.
In practice, though, the images appear so close together that it is impossible to see them as three different pictures of a star. Instead, the background star will appear to look brighter and the planet’s input to such temporary brightening will be easily detectable.
How it works
As the name suggests, in this method we try to get a direct image of an exoplanet. Easier said, than done, as normally the dim and relatively small planet will be lost in the glare of its big and bright companion star. To solve this problem coronagraphs can be used. Coronagraphs are disks that can be placed in front of a telescope (ground-based or space telescope) to “hide” the brightest central part of a star.
They are so called because the first such attachments were used to study the corona, the outer layer of the Sun, that is otherwise lost in the light of the very bright central layers of the Sun.
To tell them apart, we now use the terms Solar coronagraphs and Stellar coronagraphs.
Age group: The lesson can be adapted for the different age groups from Y6 all through the secondary school. The technical details of the methods described in the lesson should be fully accessible to the students KS4+.
Time: 60 minutes +
In this lesson, the pupils learn what an exoplanet is, they find out what methods scientists use to detect exoplanets, how these methods work and what types of planets each method can be used to find. They learn about some of the ongoing exoplanet search projects, including TRAPPIST, responsible for the discovery of seven Earth-like planets orbiting one star. They discuss why the search for exoplanets is an important part of the modern space exploration, what kind of planets we are particularly interested in and why. Then the children write down the new concepts they’ve learned during the lesson. At the end of the lesson they design an exoplanet by choosing the type of a star, the planet’s distance from the star, planet’s composition etc and try to determine what kind of life could exist on their made-up planet. If there is time, the children do a drawing/ painting of their planetary system and its inhabitants.
exoplanet in Space.
Tell the children, that now they are going to look at the two ongoing exoplanet
search projects that are actively discovering planets outside our Solar System
Time for some creative work!
End of the lesson!
Exoplanet – a planet orbiting a star other than the Sun.
Hot Jupiter – a Gas Giant exoplanet, similar to Jupiter. Hot Jupiters orbit close to their parent star, therefore they have a very high surface temperature and short orbital period (less than 10 days).
Light Year – measure of distance in Astronomy. It is equal to the distance that light travels in one year, or 9.5 000 000 000 000 km.
Orbital plane (of a planet) – a plane that contains the orbit of a planet around its star.
Radial velocity – how fast an object moves along the line of sight of the stationary observer.
Super Earth – an exoplanet with the mass between 1 and 10 of that of the Earth. Heavier planets are called Mini – Neptunes. The term does not specify the composition, proximity to the star, presence of the atmosphere etc.
www.nasa.gov -The offical NASA website
www.esa.int/ESA – European Space Agency
www.bbc.co.uk – BBC science of space
www.bbc.co.uk/education – BBC KS2 Space education resources
www.bbc.co.uk/education – BBC KS1 Earth and Space resources
www.gov.uk – UK Space Agency
https://principia.org.uk – Tim Peaks Journey to the ISS
www.kidsastronomy.com – Videos and games about the solar system