This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outside the atmosphere of Earth. The field of astronomy features an extensive vocabulary and a significant amount of jargon.
Syrtis Major (center) is a prominent dark albedo feature on Mars.
Circumstellar debris disks as detected by the Hubble Space Telescope, and artist's impressions of the disks' orientations around their host stars
A luminous red galaxy (LRG) acting as a gravitational lens, distorting the light from a much more distant blue galaxy into an Einstein ring
The bright center of the Milky Way Galaxy is visible in dark skies on clear nights, in the direction of the constellation Sagittarius.
Luminosity is an absolute measure of radiated electromagnetic energy (light) per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a star, galaxy, or other astronomical objects.
The Sun has an intrinsic luminosity of 3.83×1026 watts. In astronomy, this amount is equal to one solar luminosity, represented by the symbol L⊙. A star with four times the radiative power of the Sun has a luminosity of 4 L⊙.
