Last November, a satellite named Mauve made history as the first private space telescope to reach orbit. It’s already hitting its stride, recently clocking its first star discovery. But Mauve isn't just star-gazing; it’s on a hunt for exoplanets.
But what exactly is an exoplanet, and how do we find things that are trillions of miles away?
Simply put, “An exoplanet is a planet that orbits a star other than the sun,” says John Gianforte, director of the Observatory at the University of New Hampshire. While our solar system has eight planets, the universe is teeming with billions of others — we just have to know how to spot them.
How to catch a planet
Since planets don't give off their own light, finding them is like trying to spot a moth buzzing around a massive searchlight from miles away. Scientists primarily use two clever "detective" methods:
1. The Radial Velocity Method (The "Wobble")This method looks at the star's movement. If a star has a planet, that planet’s gravity pulls on the star. As the planet orbits, it causes the star to "wobble" back and forth.
2. The Planetary Transit MethodThink of this as a mini-eclipse. When a planet crosses between us and its host star, it blocks a tiny fraction of the star's light—often 1% or less. By measuring that dip in brightness, we know something is there.
You might wonder why we need two different ways to look at the same thing. It turns out, they tell us different parts of the story:
- The Wobble (Radial Velocity): Tells us the minimum mass of the planet (how heavy it is).
- The Transit: Tells us the size (how big it is).
"If we know the size of the planet and we know an approximation of its mass, we can calculate the density of that planet," Gianforte explains. "In layman's terms: Can we walk around on that planet, or is it a gas giant like Jupiter? That’s really important when you’re trying to determine if that planet could host life."
By combining these data points, scientists can figure out if a world is rocky, watery, or just a massive ball of gas.Cosmically Curious is a partnership between UNH, St. Anselm College, the McAuliffe Shepard Discovery Center and NHPR.
Have a space related question? Email us at Cosmic@NHPR.org
