An elliptical galaxy is a type of galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile. They are more three-dimensional, without much structure, and their stars are in somewhat random orbits around the center.
Elliptical galaxies are the most abundant type of galaxies found in the universe.
Elliptical galaxies have a broader range in size than other types of galaxies. The smallest are dwarf elliptical galaxies, which can be less than 10 percent the size of the Milky Way and contain only ten million times the mass of the sun. But ellipticals can also stretch to more than a million light-years across, and contain more than ten trillion stars.
Elliptical galaxies are the most abundant type of galaxies found in the universe.
Elliptical galaxies have a broader range in size than other types of galaxies. The smallest are dwarf elliptical galaxies, which can be less than 10 percent the size of the Milky Way and contain only ten million times the mass of the sun. But ellipticals can also stretch to more than a million light-years across, and contain more than ten trillion stars.
History and Formation
Because elliptical galaxies contain older stars and less gas, scientists think that they are nearing the end of the evolution line for galaxies. The universe is a violent place, and collisions between galaxies are frequent — indeed, the Milky Way is due to crash into the Andromeda Galaxy in a few billion years. When two spirals collide, they lose their familiar shape, morphing into the less-structured elliptical galaxies.
A supermassive black hole is thought to lie at the center of these ancient galaxies. These gluttonous giants consume gas and dust, and may play a role in the slower growth of elliptical galaxies.
Born from collision, elliptical galaxies are more commonly found around clusters and groups of galaxies. They are less frequently spotted in the early universe, which supports the idea that they evolved from the collisions that came later in the life of a galaxy.
Because elliptical galaxies contain older stars and less gas, scientists think that they are nearing the end of the evolution line for galaxies. The universe is a violent place, and collisions between galaxies are frequent — indeed, the Milky Way is due to crash into the Andromeda Galaxy in a few billion years. When two spirals collide, they lose their familiar shape, morphing into the less-structured elliptical galaxies.
A supermassive black hole is thought to lie at the center of these ancient galaxies. These gluttonous giants consume gas and dust, and may play a role in the slower growth of elliptical galaxies.
Born from collision, elliptical galaxies are more commonly found around clusters and groups of galaxies. They are less frequently spotted in the early universe, which supports the idea that they evolved from the collisions that came later in the life of a galaxy.
Structure
Elliptical galaxies are also named because of their shapes. Elliptical galaxies range from circular (remember, a circle is an ellipse!) to long, narrow, and cigar-shaped.
Elliptical galaxies are denoted by the letter E. They are also given a number from 0 to 7. An E0 galaxy looks like a circle. An E7 galaxy is very long and thin. Astronomers have specific mathematical definitions for each number, but these definitions are beyond the scope of this project. With some practice, you can learn to visually tell what type of elliptical galaxy you are observing.
Elliptical galaxies are also named because of their shapes. Elliptical galaxies range from circular (remember, a circle is an ellipse!) to long, narrow, and cigar-shaped.
Elliptical galaxies are denoted by the letter E. They are also given a number from 0 to 7. An E0 galaxy looks like a circle. An E7 galaxy is very long and thin. Astronomers have specific mathematical definitions for each number, but these definitions are beyond the scope of this project. With some practice, you can learn to visually tell what type of elliptical galaxy you are observing.
Elliptical galaxies have a large range of sizes. The largest elliptical galaxies can be over a million light-years in diameter. The smallest "dwarf elliptical" galaxies are less than one-tenth the size of the Milky Way!
Elliptical galaxies have very little gas and dust. Since stars form from gas, little star formation occurs in elliptical galaxies. Most of their stars are old and red.
Note: Many galaxies take the form of ellipsoids, with no spiral structure or flattened disks. Elliptical galaxies constitute approximately 10% of observed galaxies.
Elliptical galaxies have very little gas and dust. Since stars form from gas, little star formation occurs in elliptical galaxies. Most of their stars are old and red.
Note: Many galaxies take the form of ellipsoids, with no spiral structure or flattened disks. Elliptical galaxies constitute approximately 10% of observed galaxies.
Properties of Elliptical Galaxies
The masses of elliptical galaxies cover a large range: from about 107 up to 1013 solar masses. The corresponding range of diameters is about 1/10 kpc up to about 100 kpc, and the absolute blue magnitude varies over a correspondingly large range from -8 to -23. Thus, the smallest of the elliptical galaxies, which are called dwarf ellipticals, may be only a little larger than globular clusters, while the giant elliptical galaxies like M87 are among the largest galaxies in the Universe. This is a much larger range in size than is seen for the spiral galaxies.
*Note: Elliptical galaxies exhibit far less evidence for young stars, gas, or dust than do spiral galaxies, and have larger random motion of stars than in spiral galaxies where the motion is a more ordered rotation.
The masses of elliptical galaxies cover a large range: from about 107 up to 1013 solar masses. The corresponding range of diameters is about 1/10 kpc up to about 100 kpc, and the absolute blue magnitude varies over a correspondingly large range from -8 to -23. Thus, the smallest of the elliptical galaxies, which are called dwarf ellipticals, may be only a little larger than globular clusters, while the giant elliptical galaxies like M87 are among the largest galaxies in the Universe. This is a much larger range in size than is seen for the spiral galaxies.
*Note: Elliptical galaxies exhibit far less evidence for young stars, gas, or dust than do spiral galaxies, and have larger random motion of stars than in spiral galaxies where the motion is a more ordered rotation.