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A system of about 100 billion stars. Our Sun is a member of the Milky Way Galaxy. There are billions of galaxies in the observable universe, most of them are to far in order to be seen with the unaided eye. Galaxies are classified in three main groups; spirals, ellipticals and irregulars. The Milky Way galaxy is spiral in shape.

Galaxy cluster

A collection of dozens to thousands of galaxies bound together by gravity

Gas giant

A large planet with a small, rocky core and a deep atmosphere composed mostly of hydrogen and helium. Our solar system contains four gas giants: Jupiter, Saturn, Uranus, and Neptune. This group is also known as Jovian planets.


תמסורת רגילה


An adjective meaning “centered on the Earth.” Most early civilizations had a geocentric view of the universe

Globular Cluster

Spherical grouping of hundreds of thousands of stars. Globular clusters are composed of older stars,
and are usually found around the central regions of a galaxy.

Guide star

A star that a telescopes guidance system locks onto to ensure that a celestial object is followed and observed as the telescope moves. The telescope uses one of its sensors to detect and lock onto a guide star.