Planetary transit

A planetary transit is the passage of a planet across the face of its star as seen by an observer. It produces a temporary dip in the star’s observed brightness.

Transit light curve: A graph of a star’s brightness over time that records the dimming caused by a transiting object. Its shape and depth encode the planet’s passage across the stellar disk.
Transit photometry: The measurement of changing stellar brightness to detect and characterize orbiting bodies. It is the observational method that turns a transit into a detectable signal.
Radial velocity method: A planet-detection method that measures periodic shifts in a star’s spectral lines caused by orbital motion. It measures a planet’s gravitational effect, complementing the size information from transits.
HD 209458 b: An exoplanet orbiting HD 209458 and the first known to transit its star. Its observed transits enabled direct measurement of an exoplanet’s radius.
Stellar activity: Time-varying phenomena on a star, including spots, flares, and magnetic activity. Surface features can distort transit light curves and complicate planet measurements.
Transit depth: The fractional decrease in a star’s observed brightness during a transit. For a small planet, the depth approximately measures the squared planet-to-star radius ratio.
Transit spectroscopy: The analysis of a planet’s atmosphere using starlight filtered through it during transit. Wavelength-dependent dimming can reveal atmospheric gases.
Direct imaging of exoplanets: The observation of light emitted or reflected by an exoplanet separately from its star. Unlike transit observations, direct imaging spatially separates the planet from its star.
TrES-1: A transiting hot Jupiter discovered by the Trans-Atlantic Exoplanet Survey in 2004. Its discovery demonstrated that ground-based surveys could find transiting planets.
Exoplanet atmosphere: The gaseous envelope surrounding a planet outside the Solar System. Transit spectra probe atmospheres, but clouds and hazes can obscure their composition.

Linked from 10 pages