Глоссарий - G

Galactic nucleus or core is the region at the center of a galaxy that is usually host to a tight concentration of stars and gas. It almost always includes a supermassive black hole, which, when active, can generate a much higher luminosity in a compact region than its surroundings. This excess luminosity is known as an active galactic nucleus, and the brightest such active galaxies are called quasars.

Galactic tide is the tidal force experienced by objects subject to the gravitational field of a galaxy such as the Milky Way.

Galilean moons are the moons of Jupiter that were discovered by Galileo Galilei in 1610. They consist of the moons Io, Europa, Ganymede, Callisto, and were the first objects found to orbit another planet.

Geometric albedo is the ratio of the brightness of an astronomical body at a phase angle of zero to an idealized flat, fully reflecting, diffusively scattering (Lambertian) disk with the same cross-section. It is a measure of how much of the incoming illumination is being scattered back toward an observer and has a value between zero and one.

Globular cluster is a tight, spherical conglomeration of many thousands stars that are gravitationally-bound to each other and orbit a galactic core as a satellite. They differ from open clusters in having a much higher combined mass, with a typical life span extending for billions of years.

A gravitational lens is a large distribution of mass, such as a galactic cluster, that can bend passing light from a distant source by a noticeable degree. The effect can make background objects take on a ring or arc shape.