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For Active Galaxies, the topic in 2011, please see Astronomy/Active Galaxies.

Galaxies is expected to be the topic for Astronomy in the upcoming 2019 season along with Stellar Evolution, and was previously the topic in the 2010 season.


A galaxy is a gravitationally bound group of stars, dust and stellar remnants. In Astronomy, teams are tested over their knowledge of galaxies, various DSOs (deep sky objects), and mathematical relationships.

This year's galaxies fall into two categories: normal galaxies, and starburst galaxies.

Normal Galaxies

Normal galaxies are classified by the Hubble system as being either elliptical or spiral. Elliptical Galaxies are generally older and larger than spiral galaxies. Spiral galaxies consist of an inner core of old stars moving slowly and outer arms of faster-moving younger stars. They also have a separate classification, as some spirals are barred, or they have a horizontal bar of stars protruding out from the galactic core. The normal galaxies include the Milky Way Galaxy, the Andromeda Galaxy and the Triangulum Galaxy.

Starburst Galaxies

Main article: Astronomy/Starburst Galaxies

Starburst galaxies are typified by significantly greater levels of star formation than normal galaxies. They are often normal galaxies that have collided with each other, causing gravity ripples and star formation. The starburst galaxies in 2010's DSOs included M82, M84, M101, the Cartwheel Galaxy, and C153.

Galaxy Groups and Clusters

Galaxies are usually located close to other galaxies. A galaxy group is the smallest group classification, and it refers to a group of about 30-50 galaxies. The Milky Way is located in the Local Group, along with the Andromeda and Triangulum Galaxies. Galaxy clusters are slightly larger than groups. Although they seem to be held together by gravity, there is no set structure to galaxy clusters. The largest classification is that of galaxy superclusters, which are groups of other groups and clusters. The Milky Way is located in the Virgo (or Local) Supercluster.

Deep Sky Objects

See Astronomy/DSOs for more information.

Although the focus of this year's event is galaxies, many of the DSOs are other stellar objects including: M15 the globular cluster, Sag A* the black hole, Epsilon Aurigae the eclipsing binary, G1 (Mayall II) the globular cluster, NGC 604 the stellar nursery, and M33 x-7 the x-ray binary. Most of these are prominent objects located in the other galaxies studied.