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Methods for Detecting Exoplanets

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1. The transit method

A method that detects the presence and size of a planet by measuring the tiny dimming of starlight as the planet passes between its star and the observer; this is the primary detection method used by the Kepler Space Telescope and TESS.

2. The radial velocity method (Doppler method)

A method that detects the presence and mass of a planet by measuring the extremely subtle wobble of a star caused by the planet's gravity, through the Doppler shift in the star's light spectrum.

3. Direct imaging

A method that uses a device to block a star's bright light in order to directly capture the faint light of the planet itself; this is the most technically difficult method, with relatively few successful cases.

4. The achievements of the Kepler Space Telescope

Launched in 2009, the Kepler Space Telescope officially confirmed more than 2,600 exoplanets using the transit method before its mission ended in 2018, marking a turning point in exoplanet exploration.

5. TESS

Launched in 2018 as Kepler's successor, TESS is carrying out a mission to scan the entire sky in search of exoplanets around relatively nearby, bright stars.

6. The James Webb Space Telescope's atmospheric analysis

Launched in December 2021, the James Webb Space Telescope is being used to detect atmospheric components such as water vapor and carbon dioxide by analyzing the spectrum left behind as starlight passes through a planet's atmosphere during a transit.

7. The Goldilocks zone (habitable zone)

This refers to the orbital region where the temperature range is neither too hot nor too cold, allowing liquid water to potentially exist on a planet's surface; it is used as an important criterion for gauging the possibility of life.

How do we find planets around other stars?

Exoplanets don't shine on their own and are obscured by their host star's light, making them extremely difficult to observe directly. That's why astronomers detect the presence of exoplanets through indirect methods that precisely analyze tiny changes in starlight.

The search for habitable places also continues on Mars

If exoplanet exploration is the search for the possibility of habitability elsewhere, Mars is at the center of a similar question within our own solar system. See our complete history of Mars exploration to explore the process of searching for traces of water.

Frequently Asked Questions

How many exoplanets have been discovered so far?

The Kepler Space Telescope alone officially confirmed more than 2,600 exoplanets, and when combined with TESS and ground-based observations, the number of confirmed exoplanets continues to grow.

If a planet is in the Goldilocks zone, does that guarantee it has life?

No. The Goldilocks zone is simply an orbital region with temperature conditions that allow liquid water to exist — determining whether life actually exists requires examining far more factors together, such as atmospheric composition and magnetic field.