Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
EXOPLANETS: Real or IMPOSTORS?
.MPhys Public Research Summary: Decide which candidate is more likely to be a planet!.
.Aiza Kenzhebekova.
Start
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
What is an Exoplanet?
An exoplanet is any planet outside of our Solar System. We can find some exoplanets by taking a picture with powerful telescopes (like the James Webb Space Telescope), and taking out the starlight until only the planet remains! This is called
Direct Imaging.
But, there's a problem...
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
The Impostor Problem
Once we remove the starlight, what remains is not always an exoplanet! Sometimes, a far away background star or distant galaxy can line up with or next to the star we're looking at. These are called background objects and they act as exoplanet impostors. So, how do we know the difference?
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Your Mission
Your mission is to decide which of the two cases is more likely to be a real exoplanet and which is more likely to be the impostor!
See Cases
What is the Evidence?
Click on the exclamation marks to explore the clues! When you feel confident in your answer, press "Ready to Decide?" below and find out if you're right!
Ready to Decide?
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Good work, Detective!
You have correctly identified that Case One is more likely to be the impostor! Since Case Two is closer to its star, there is a smaller probability of a random alignment. Additionally, since it's faint and red, Case Two looks more like what a real exoplanet would look like! BUT! This doesn't mean that Case Two is definitely a planet, only that it is more likely to be one than Case One. We have to be careful about making absolute statements like this!
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Not Quite... Try Again!
Think carefully about the clues. A farther separation means that background objects are more likely, and bright and blue objects are more likely to be stars and galaxies. BUT! Just because Case One is more likely to be an impostor, doen't mean that it definitely is. We have to be careful when making absolute statements like this!
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
An Important Detail!
Even if one object is more likely to be a real exoplanet, astronomers still have to confirm these objects, usually by watching how the potential planet moves over time. If it moves with its star, it is likely to be a planet. If it doesn't move much or moves away from its star, it is likely a background object.
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Mission complete!
You just used the colour, magnitude, and separation of an object to decide which case was more likely to be an exoplanet. That's real science! In my MPhys project, I am building a tool that does excatly this (with a couple of extra steps)! Although we can't say for certain if either case is an exoplanet without more observations, we can find which objects are most likely to be exoplanets. This helps us prioritise the objects we want to follow-up with in the future!
Start over
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Are you sure you want to exit?
You will lose your progress
Back
exit
Clue Two: What colour is it?
Colour is the difference between how bright an object is in two filters. The colour depends on the temperature of the object, its chemical make-up, and how far away it is from Earth. Generally, hotter objects are more blue, and cooler objects are more red (which sounds backwards!). Planets are cooler than stars and galaxies and hence appear redder.
- Planets don't make their own visible light like stars, but they can glow because of their temperature
- Colour helps astronomers classify what kind of objects they're looking at
Credit: Chris North/Cardiff University
Direct Imaging
You can take the starlight out of the original image, either physically with something called a coronagraph, or digitally by post-procesing techniques. Slide the bar to reveal the planet! (from: Galicher & Mazoyer 2023)
Clue One: How bright is it?
Apparent magnitude is how bright an object looks in the sky. This depends on how bright an object is inherently, how far away it is from Earth, and the telescope you're looking at it with. Remember: astronomers are weird, so the smaller the magnitude, the brighter the object.
- Bright far away objects like stars and galaxies might look like they have the same brightness as closer and dimmer objects like planets
- There are many more dim objects in space than bright ones, but because they are dim, they can be more difficult to detect from Earth
Clue Three: How close is it?
Separation is the distance between the star and the potential exoplanet. Astronomers usually measure this as an angle since it depends on how far away the planet is from its star, but also how far away the star is from Earth.
Exoplanet
- Imagine drawing a circle around your star. The bigger the circle, the more background stars and galaxies could fit inside it
- More area means there is a bigger probability that a star or a galaxy might accidentally line up there
Credit: Lagrange et al. (2025)
Which case is more likely to be an exoplanet?
VS
Case Two
Case One
A fainter red object close to its star
A bright blue object far away from its star
EXOPLANETS: Real or IMPOSTORS?
Aiza Kenzhebekova
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Transcript
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
EXOPLANETS: Real or IMPOSTORS?
.MPhys Public Research Summary: Decide which candidate is more likely to be a planet!.
.Aiza Kenzhebekova.
Start
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
What is an Exoplanet?
An exoplanet is any planet outside of our Solar System. We can find some exoplanets by taking a picture with powerful telescopes (like the James Webb Space Telescope), and taking out the starlight until only the planet remains! This is called
Direct Imaging.
But, there's a problem...
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
The Impostor Problem
Once we remove the starlight, what remains is not always an exoplanet! Sometimes, a far away background star or distant galaxy can line up with or next to the star we're looking at. These are called background objects and they act as exoplanet impostors. So, how do we know the difference?
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Your Mission
Your mission is to decide which of the two cases is more likely to be a real exoplanet and which is more likely to be the impostor!
See Cases
What is the Evidence?
Click on the exclamation marks to explore the clues! When you feel confident in your answer, press "Ready to Decide?" below and find out if you're right!
Ready to Decide?
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Good work, Detective!
You have correctly identified that Case One is more likely to be the impostor! Since Case Two is closer to its star, there is a smaller probability of a random alignment. Additionally, since it's faint and red, Case Two looks more like what a real exoplanet would look like! BUT! This doesn't mean that Case Two is definitely a planet, only that it is more likely to be one than Case One. We have to be careful about making absolute statements like this!
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Not Quite... Try Again!
Think carefully about the clues. A farther separation means that background objects are more likely, and bright and blue objects are more likely to be stars and galaxies. BUT! Just because Case One is more likely to be an impostor, doen't mean that it definitely is. We have to be careful when making absolute statements like this!
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
An Important Detail!
Even if one object is more likely to be a real exoplanet, astronomers still have to confirm these objects, usually by watching how the potential planet moves over time. If it moves with its star, it is likely to be a planet. If it doesn't move much or moves away from its star, it is likely a background object.
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Mission complete!
You just used the colour, magnitude, and separation of an object to decide which case was more likely to be an exoplanet. That's real science! In my MPhys project, I am building a tool that does excatly this (with a couple of extra steps)! Although we can't say for certain if either case is an exoplanet without more observations, we can find which objects are most likely to be exoplanets. This helps us prioritise the objects we want to follow-up with in the future!
Start over
Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre
Are you sure you want to exit?
You will lose your progress
Back
exit
Clue Two: What colour is it?
Colour is the difference between how bright an object is in two filters. The colour depends on the temperature of the object, its chemical make-up, and how far away it is from Earth. Generally, hotter objects are more blue, and cooler objects are more red (which sounds backwards!). Planets are cooler than stars and galaxies and hence appear redder.
Credit: Chris North/Cardiff University
Direct Imaging
You can take the starlight out of the original image, either physically with something called a coronagraph, or digitally by post-procesing techniques. Slide the bar to reveal the planet! (from: Galicher & Mazoyer 2023)
Clue One: How bright is it?
Apparent magnitude is how bright an object looks in the sky. This depends on how bright an object is inherently, how far away it is from Earth, and the telescope you're looking at it with. Remember: astronomers are weird, so the smaller the magnitude, the brighter the object.
Clue Three: How close is it?
Separation is the distance between the star and the potential exoplanet. Astronomers usually measure this as an angle since it depends on how far away the planet is from its star, but also how far away the star is from Earth.
Exoplanet
Credit: Lagrange et al. (2025)
Which case is more likely to be an exoplanet?
VS
Case Two
Case One
A fainter red object close to its star
A bright blue object far away from its star