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How Galaxies are Classified by Type (Infographic)

Infographic: How types of galaxies are identified.
Astronomer Edwin Hubble devised a method for identifying kinds of galaxies. (Image credit: by Karl Tate, Infographics Artist)

Astronomer Edwin Hubble, after whom the space telescope is named, classified galaxies according to shape. 

The Hubble scale chart takes a wishbone, or tuning fork shape. Armless, elliptical galaxies are on the left. Spirals are divided into those with a central bar and those without one. Looser arm windings are toward the right.

Even distant galaxies, seen as they were billions of years ago, fall into the Hubble shape classifications.

The deeper astronomers look into the universe, the more they see that the expansion of the universe has stretched light, shifting it toward the red end of the spectrum. By measuring the amount of redshift, astronomers can determine how far away a given galaxy is. 

A map of 220,000 galaxies produced by the 2dF Galaxy Redshift Survey Team shows the universe has a filamentary structure, seen when it is considered on a large scale.

Karl Tate
