In general, galaxies are typically divided into the barred spirals, spirals and elliptical. The "S0s" are called lenticular galaxies which are ones that sit between elliptical and spiral. Another class which does not fit the tuning fork are the irregular galaxies, these are usually satellites galaxies small galaxies which orbit larger ones and don't usually hold an elliptical or spiral shape.
Two examples of non barred spirals are: The whirlpool galaxy, and:. An of example of a barred spiral galaxy is:. Quite clearly, NGC has a large bar across its center which is absent in the other two examples. Barred spirals typically form when stars deviate from their typical circular orbit and instead end up in an elliptical orbit around the galactic center. More and more stars will gather around this orbit locked into it most likely due to the gravitational attraction of the stars already there thereby forming a bar.
Whatever causes the initial deviation is still up for dispute. What are the different types of spiral galaxies besides barred? Andrew I. The elliptical scale varies from E0 to E7. Elliptical galaxies have no particular axis of rotation.
Spiral galaxies have three main components: a bulge, disk, and halo see right. The bulge is a spherical structure found in the center of the galaxy. This feature mostly contains older stars. The disk is made up of dust, gas, and younger stars. The disk forms arm structures. Our Sun is located in an arm of our galaxy, the Milky Way. The halo of a galaxy is a loose, spherical structure located around the bulge and some of the disk.
The halo contains old clusters of stars, known as globular clusters. Spiral galaxies are classified into two groups, ordinary and barred. In normal spirals as seen at above left the arms originate directly from the nucleus, or bulge, where in the barred spirals see right there is a bar of material that runs through the nucleus that the arms emerge from.
The other galaxies are even further away from us and can only be seen through telescopes. The smallest galaxies may contain only a few hundred thousand stars and be several thousand light years across, while the largest galaxies have trillions of stars and may be hundreds of thousands of light years across.
Galaxies can be found by themselves, in small groups and in large clusters. It is very rare to find stars in the space in between galaxies. Galaxies sometimes collide with each other, with interesting results. These collisions can trigger bursts of star-formation in addition to changing the shapes of the galaxies that collide. However, when galaxy collisions occur, individual stars do not collide, due to the vast distances between them.
Interacting galaxies imaged by the Hubble Space Telescope. Ford JHU , G. Galaxies are classified by shape. There are three general types: elliptical, spiral, and irregular. Perhaps the most familiar kind of galaxy are spiral galaxies.
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