Other galaxies

Andrew Conway

The Andromeda Galaxy

The Andromeda Galaxy

Source: Adam Evans CC-BY 2.0

Andromeda galaxy facts

Galaxy naming

Galaxies are assigned a number according to several schemes:

M objects are mostly in NGC, but IC is an extension to NGC. All these catalogues include star clusters, galaxies, nebulas, but galaxies were not distinguished from galaxies until the early 20th century.

Messier objects

Messier objects

Source: NASA Public domain

Hubble classification

Hubble classification

Source: NASA/ESA Public Domain

Classification limitations

Classification schemes like Hubble's are useful, but limited:

M33 - photograph


Source: Hewolooks CC-BY SA 3.0

M33 - facts

M51 Whirlpool galaxy - drawing

M51 drawing

Source: Lord Rosse, 1845 Public Domain

M51 - photograph

M51 photograph

Source: NASA/ESA Public Domain

M51 - facts

M87 - an elliptical galaxy

M87 photograph

Source: NASA/Hubble Public Domain

M87 facts

Irregular galaxies

There are two types of irregular galaxy according to the Hubble classisfaction:

M82 - photograph


Source: NASA/ESA/Hubble Public Domain

M82 - facts

Galaxy statistics

These statistics are broadly correct for all galaxies we can see, but there is noticeable variation throughout space:

The Local Group

The Local Group

Source: Richard Powell CC BY-SA 2.5

Local Group facts