7 ways to discover exoplanets

  Since the discovery of the first exoplanet in 1992, scientists have discovered thousands of exoplanets. Here is a brief introduction to the 7 methods they used to discover exoplanets.

Observe transit

  Transit refers to a situation in which a planet obscures part of the star’s light during the period when the planet passes in front of the star (transit), causing the brightness of the star to decrease. Since the launch of NASA’s “Kepler” space telescope in March 2009, more than 2,700 exoplanets have been discovered by observing transits. Scientists often find other planets orbiting the same star by looking for changes in the transit time of a particular planet.

Swaying star

  The radial velocity method looks for the slight shaking of the star caused by the planet orbiting the star when a star approaches and leaves the earth. This method measures the stellar light shift caused by gravitational pull. Using this method, scientists have discovered many exoplanets with the help of a spectrometer.

Gravitational lens

  Using this method, scientists are observing what happens when we look from the earth and a nearby massive celestial body passes directly in front of a distant star. The gravitational field of this massive celestial body will distort and amplify the stellar light like a lens. The light curve produced by this action (it describes how the stellar light becomes brighter and darker over time) will tell scientists about this massive celestial body. (Often also a star) a lot of information. If this massive celestial body is a star, and it is surrounded by planets, then the planet will also produce a secondary light curve, and scientists can determine the existence of a planet. Transit technology requires the planetary orbit to be relatively close to the star, but the gravitational lensing method does not have this requirement. Using gravitational lensing, scientists discovered “wandering planets” cruising in deep space without a parent star.

Direct shooting

  A coronagraph is used to block the starlight of the parent star, and a powerful telescope can directly photograph distant planets. NASA’s Hubble Space Telescope and some ground-based telescopes directly captured many exoplanets.
Pulse timing

  This technique is used to discover planets orbiting pulsars. As super-compact small remnants left after a star explodes, pulsars emit radio waves at regular intervals during their rotation. If this interval becomes abnormal, it may indicate a planet orbiting a pulsar. Scientists used this method when they discovered exoplanets in 1992.

Use special relativity

  Using this new method, scientists are looking for a kind of brightening of stars: the planet’s gravitational drag on the parent star will cause the star’s photons to accumulate energy, and the stellar light will be focused in the direction of the star’s motion due to the relativistic effect. The exoplanet “Kepler-76b” known as the “Einstein planet” was discovered through this technique. As the method continues to improve, it is likely that more exoplanets will be discovered through it.


  Scientists discover planets orbiting stars by ultra-precisely tracking the movement of stars in the sky. This method is similar to the radial velocity method, but there are also differences. Scientists have used this method to find exoplanets for decades.