Light curve
Graph of celestial light intensity over time.
A light curve is a chart that plots the brightness of a celestial object or region against time, with the magnitude of light (usually in a specific frequency band) on the vertical axis and time on the horizontal axis. These curves can be periodic—seen in eclipsing binaries, Cepheid variables, other periodic variables, and transiting exoplanets—or aperiodic, as with novae, cataclysmic variable stars, supernovae, microlensing events, or binaries observed during occultations. Studying a light curve alongside other observations can reveal a lot about the physical process behind it or help test related theories.
For variable stars, light curves are common tools to visualize and analyze behavior. While spectral properties increasingly define variable star types, the amplitude, period, and regularity of brightness changes remain key factors. Some types, like Cepheids, have extremely regular light curves with identical period, amplitude, and shape each cycle. Others, such as Mira variables, show less regular curves with large amplitudes of several magnitudes, while semiregular variables are even less regular and have smaller amplitudes. The shape of a variable star’s light curve offers clues about the underlying physics: for eclipsing binaries, it reveals the degree of totality, the stars’ relative sizes and surface brightnesses, and can indicate orbital eccentricity or distortions in stellar shape. For pulsating stars, the amplitude or period can relate to the star’s luminosity, and the curve’s shape can point to the pulsation mode.
Supernova light curves help indicate the type of supernova. Though supernova types are defined by spectra, each has typical light curve shapes. Type I supernovae have a sharp maximum followed by a gradual decline, while Type II supernovae have less sharp maxima. Light curves are useful for classifying faint supernovae and determining sub-types. For instance, type II-P (plateau) supernovae have spectra similar to type II-L (linear) but are distinguished by a light curve where the decline flattens for weeks or months before resuming.
In planetary science, light curves can derive the rotation period of a minor planet, moon, or comet nucleus. From Earth, small Solar System objects often appear smaller than a single pixel in even the most powerful telescopes, so astronomers measure brightness over time. The time between peaks in the light
- field
- Astronomy
- used_for
- Studying brightness variations of celestial objects
- types
- Periodic and aperiodic
- applications
- Variable stars, supernovae, planetary astronomy, exoplanet discovery, microlensing
Lore & Background
Light curves can be periodic, as in eclipsing binaries, Cepheid variables, and transiting exoplanets, or aperiodic, like those of novae, supernovae, and microlensing events. The study of a light curve yields information about the physical process producing it. For variable stars, the shape, amplitude, and period of the light curve indicate properties such as stellar sizes, orbital eccentricity, and pulsation modes.
Reader's Guide
Light curves are essential for classifying supernovae: Type I have a sharp maximum and gradual decline, while Type II have less sharp maxima. Type II-P supernovae are distinguished by a plateau in the light curve. In planetary astronomy, light curves derive rotation periods of asteroids, moons, and comets from peak separations, and amplitude differences reveal shape or surface features. The Asteroid Lightcurve Database uses a quality code (U) from 0 to 3 to assess period solutions. Light curve inversion models surfaces of rotating objects, such as starspots or asteroid albedos. Microlensing events produce brief brightness increases, and their light curve shapes allow inference of lensing object properties.
Did You Know?
- Light curves can be periodic, as in eclipsing binaries, Cepheid variables, and transiting extrasolar planets.
- The Asteroid Lightcurve Database uses a quality code U from 0 (incorrect) to 3 (well-defined) for period solutions.
- Occultation light curves can show steps if the occulting or occulted body is double, or gradual transitions if the occulted body is large or has an atmosphere.
- Periodic dips in a star's light curve can indicate an exoplanet passing in front of it, known as the transit method.
More in Stars And Stellar Phenomena 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record