(Image credit: NASA, ESA and The Hubble Heritage Team (STScI/AURA)) History and formationīecause elliptical galaxies contain older stars and less gas, scientists think that they are nearing the end of the evolutionary line for galaxies. Elliptical galaxies host less (or no) star birth than spiral galaxies like the Milky Way.
TWO CHARACTERISTICS OF A SPIRAL GALAXY FULL
M87, identified as one of the largest galaxies in the universe, is classified as an E0 elliptical galaxy.Īn elliptical galaxy, full of dark lanes of gas, likely formed in the merger of two other galaxies.
But ellipticals can also stretch to more than a million light-years across, and contain more than ten trillion stars. The smallest are dwarf elliptical galaxies, which can be less than 10 percent of the size of the Milky Way. A galaxy having the E7 shape but seen head on would appear as an E0, for instance, because observers would not see its stretched shape, which lies "behind" it.Įlliptical galaxies have a broader range in size than other types of galaxies. A galaxy's appearance is related to how it lies on the sky when viewed from Earth. Galaxies classified as E0 appear to be almost perfect circles (remember, a circle is an ellipse), while those listed as E7 seem much longer than they are wide. Under this organization, elliptical galaxies are classified by how stretched out they are.
Known as the Hubble sequence, or the "Hubble tuning-fork," it organizes galaxies based on their shape. In 1926, Edwin Hubble devised a system to classify galaxies.
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