Transit method
An astronomical method for detecting and characterizing planets by measuring the periodic dimming of a star as a planet passes in front of it.
Transit light curve: A graph of a star’s brightness over time that shows the dimming caused by a planetary transit. Its depth, duration, and shape are the measurements from which transit properties are inferred.
Kepler space telescope: NASA’s space observatory that monitored stellar brightness to search for exoplanets, primarily using transits. Its survey established the transit method as a source of large, uniform planet samples.
Radial velocity method: A planet-detection method that measures the periodic motion of a star along the observer’s line of sight. It detects a star’s reflex motion rather than the starlight blocked by a planet.
False positive (exoplanet detection): An apparent exoplanet signal caused by another astronomical or instrumental source. Eclipsing binary stars and blended light can imitate a transit and require validation.
Planetary transit: An event in which a planet crosses the apparent disk of its star as seen by an observer. This alignment produces the brightness dip the method measures.
Transiting Exoplanet Survey Satellite: NASA’s all-sky space survey mission that searches for exoplanets around bright, nearby stars. TESS uses transits to identify planets suited to follow-up observations.
Direct imaging of exoplanets: The detection of an exoplanet by separating its light from the light of its host star. It can reveal planets at wide apparent separations, where transits are unlikely.
Transit surveys and observational bias: The ways survey design and detection limits distort the observed properties of transiting planets. Transit probability, stellar variability, and finite observing time make some planets easier to find than others.
Transit depth: The fractional decrease in a star’s observed brightness during a planetary transit. For a small planet crossing a uniformly bright star, it approximately measures the squared planet-to-star radius ratio.
Hot Jupiter: A gas giant planet orbiting very close to its star, typically completing an orbit in days. Its frequent, deep transits made this class especially accessible to early surveys.