How do scientists detect exoplanets?

Scientists detect exoplanets primarily through methods such as the transit and radial velocity techniques. The transit method involves observing the light curve of a star to detect small dips in brightness that occur when a planet passes in front of the star as seen from Earth. This method not only reveals the presence of an exoplanet but can also provide information about the planet’s size and orbital period.

The radial velocity method, also known as the Doppler method, involves monitoring changes in the star's spectrum as the gravitational pull of an orbiting planet causes the star to wobble slightly. As the star moves towards and away from Earth, its light shifts in wavelength due to the Doppler effect, allowing astronomers to infer the presence of a planet and estimate its mass.

These techniques have been instrumental in the discovery of thousands of exoplanets and provide a wealth of data regarding their characteristics. Other methods mentioned, such as the study of a star's temperature, utilizing radio waves from distant galaxies, or measuring photon's energy levels, do not directly lead to the detection of exoplanets in the same effective manner as the transit and radial velocity methods.