Astrometry method: A method of detecting exoplanets by precisely measuring a star’s position on the sky and detecting tiny back-and-forth motions caused by orbiting planets. The European Space Agency’s Gaia mission has greatly improved this technique.
Binary star system: A system in which two gravitationally bound stars orbit around their common centre of mass.
Direct imaging method: A technique for detecting exoplanets by blocking a star’s light using a coronagraph or starshade, allowing the much fainter planet to be directly imaged.
Eccentric orbit: An orbit that is elongated rather than circular, often the result of gravitational perturbations during planetary migration or planet–planet scattering.
Emission spectroscopy: A method of analysing planetary atmospheres by observing infrared radiation emitted by a planet as it rotates in and out of view.
Extrasolar planet naming convention: The international convention for naming exoplanets by appending a lowercase letter (b, c, d…) to the star’s name in order of discovery. The first planet discovered is always “b”.
Extrasolar planets: Planets that orbit stars other than the Sun.
Exoplanets: Another term for extrasolar planets.
Gravitational lensing: A general relativistic effect in which light from a distant object is bent by the gravity of a massive foreground object, producing magnification or distortion.
Habitable zone: The region around a star where liquid water could exist on a planet’s surface, assuming suitable atmospheric conditions.
Hot Jupiters: Gas-giant planets that orbit extremely close to their host stars, often completing an orbit in only days.
James Webb Space Telescope (JWST): A space observatory launched in 2021 designed to observe exoplanet atmospheres, star formation, and early galaxies using infrared wavelengths.
Kepler mission: A NASA space telescope launched in 2009 that monitored over 150,000 stars for planetary transits, revolutionizing exoplanet statistics.
Light curve: A graph showing how a star’s brightness changes over time, used to detect planetary transits.
Microlensing method: A detection technique based on the temporary brightening of a background star when a planetary system passes in front of it, bending light through gravity.
Mini-Neptune: A class of planet larger than Earth with a thick atmosphere of hydrogen and helium surrounding an icy or rocky core.
Phase curve: A measurement of how a planet’s brightness changes as different portions of its surface rotate into view, used to infer atmospheric and surface structure.
Pulsar: A rapidly spinning neutron star that emits beams of radiation that sweep across space like a lighthouse.
Pulsar planets: Planets orbiting pulsars, detected through highly precise timing shifts in pulsar pulses rather than traditional Doppler shifts.
Radial velocity method: A method of detecting planets by measuring oscillations in the motion of a star along the line of sight using Doppler shifts in its spectrum.
Rogue planets: Planetary-mass objects that drift freely through space without orbiting a star.
Spectroscopy: The analysis of light by wavelength to determine chemical composition, temperature, and physical conditions.
Super-Earth: A class of rocky planet larger than Earth but smaller than Neptune.
TESS mission: A NASA mission launched in 2018 that scans nearly the entire sky for transiting planets around nearby stars.
Transit method: A detection technique based on observing the small dimming of a star as a planet passes in front of it.
Transit spectroscopy: The study of starlight filtered through a planet’s atmosphere during transit to identify atmospheric molecules.
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