The search for exoplanets (planets that we find outside the solar system) has advanced greatly over the years. Scientists have discovered thousands of exoplanets using a wide variety of techniques and have brought us closer to understanding how diverse these planetary environments are. So, how do we detect them?
- Radial Velocity Method
This method involves observing the parent star of the system and looking for a slight “wobble” in its motion. This “wobble” is caused by the gravitational pull of the planet in orbit around it. If we measure the star’s radial velocity over a period of time, we can observe the planet and how much time it takes to complete one orbit around the star.
- Gravitational Microlensing
Exoplanets in the foreground will bend light from a star in the background because of their gravitational fields. Monitoring the brightness of the star over time, scientists can make conclusions about the planet and its characteristics like mass.
- Transit Method
Here, scientists observe small dips in the brightness of a star when a planet passes by in front of it or transits. Measuring the dip in light, and how long that dip persists, we can infer the planet’s size and its orbital period.
- Direct Imaging
As the name implies, this method involves directly taking a picture of the planet rather than relying on information from its effects on other celestial bodies around it. It is a challenging technique because planets are much smaller and fainter than their host stars, and bright light from these stars can often make these exoplanets almost invisible to detect directly.
We have ways to detect them, and have a huge repertoire of information about their formation and characteristics. What have we learned so far?
We know that they are common throughout the universe, and that there are likely billions upon billions in just the Milky Way alone. They come in a wide range of sizes: We’ve discovered Earth sized planets and planets that are more massive than Jupiter.
The search for exoplanets is a rapidly evolving field in both computational and observational astronomy. With the launch of telescopes like the James Webb Space Telescope, we can expect to see more exciting discoveries that will take us closer to understanding exoplanets and their properties.