Discovering exoplanets can be difficult. The star which they orbit, whether it's a red dwarf or a star much larger than our sun, can be millions, even billions of times brighter than the planet which orbits it. Astronomers cannot detect exoplanets through direct observation, yet. Scientists use other methods, such as the radial velocity method. This method uses the Doppler effect. Imagine a police car speeding towards you with its sirens on. As the car approaches you, the pitch of the siren goes up. This is because as the police car is moving away from you, the sound waves are being compressed. As the police car moves away from you, the pitch goes down. This is because the sound waves are being stretched as the car moves away. Light, like sound, is a wave, so the same principle applies. When an object is moving towards you, its light waves are compressed. The light is shifted toward the blue side of the spectrum, so the object appears blue. If the object moves away from you, its light stretched and is shifted to the red side of the spectrum, so the object appears red. This is the Doppler effect, and scientists use it to detect planets around other stars. A planet which orbits its star gravitationally tugs on the star. As the planet orbits the star, the star swings back and forth due to the gravity of the planet. Although it would be impossible to directly observe this, scientists can determine whether a planet is orbiting the star based on its light. As the planet orbits around the star, its gravity pulls the star slightly away or towards us. So the light from the star will slightly be shifted toward the blue or red side of the spectrum. By measuring the shift in light from the star, astronomers can determine if there's a planet in orbit. Scientists can also determine how massive the planet is and how far away from its star it's located.
#astronomy #astronomer #astrophysics #space #cosmos #science #physics #universe #stars #planet #astronaut #constellation #interstellar #spacetravel #outerspace #chandra #instalike #instafollow #astrobiology #nasa #hubble #telescope #galaxy #stargazing #starstuff #astrophotography #photography #amazing #hst #nasabeyond