ljuskurva

In Swedish astronomy, ljuskurva refers to the light curve of an astronomical object—a graph showing how the object's brightness changes over time. Brightness is typically expressed as flux or apparent magnitude and is corrected for instrumental effects and atmospheric extinction. The horizontal axis represents time (often in Julian date, Modified Julian Date, or Barycentric Julian Date), while the vertical axis shows the brightness measure, commonly on a logarithmic scale when using flux or in magnitudes.

Ljuskurvor are used to study a wide range of phenomena. Periodic variables such as Cepheid variables, RR Lyrae stars, and eclipsing binaries produce regular light curves that help determine intrinsic luminosity, stellar dimensions, and orbital parameters. Transient events like supernovae, novae, and gamma-ray burst afterglows develop evolving light curves that provide insight into explosion mechanisms and energy release. In exoplanet science, transit light curves reveal the dip in brightness as a planet crosses its star, enabling estimation of the planet's radius, orbital period, and, in some cases, atmospheric properties.

Data for ljuskurvor come from photometry with ground-based telescopes or space missions (for example OGLE, Kepler, and TESS). Analysis includes period finding (such as Lomb-Scargle), phase folding, and model fitting to extract physical parameters. Challenges include uneven sampling, observational gaps, extinction, crowding, and instrumental systematics, all of which can affect accuracy and interpretation. Ljuskurvor are central to time-domain astronomy, supporting distance indicators, the study of stellar and planetary physics, and the characterization of transient phenomena.