![]() NCG 6872's enormous size and odd appearance are the consequence of its gravitational interaction with a neighbor galaxy called IC 4970, which contains just 20 percent of NGC 6872's mass, researchers said.Ĭomputer simulations suggest that IC 4970 made its closest approach about 130 million years ago, stirring up a burst of activity in certain parts of NCG 6872. The sun is in a finger called the Orion Spur. ![]() ![]() This includes detailed views of the elliptical galaxies NGC 4150 and NGC 2768.The Milky Way Galaxy is organized into spiral arms of giant stars that illuminate interstellar gas and dust. Hubble has also captured beautiful imagery of elliptical galaxies throughout its more than 30-year history. Thanks to Hubble and the VLT, astronomers were able to show for the first time how star formation in these ‘dead’ galaxies actually sputtered out billions of years ago. In fact, earlier in the history of the Universe, the evolutionary precursors to these massive galaxies were full of gas and forming stars at a prodigious rate. These gigantic ‘red and dead’ galaxies were not always so inactive. Recently, the Hubble Space Telescope and ESO's Very Large Telescope (VLT) were used to help solve an astrophysical mystery that had centred on the most massive elliptical galaxies. Due to their very low rate of star formation and their populations of old, red stars, elliptical galaxies are sometimes colloquially referred to as ‘red and dead’ by astronomers. Therefore, it seems likely that elliptical galaxies are largely populated by stars that formed within active spiral galaxies. Whilst spiral galaxies have rich reservoirs of the dust and gas that fuel star formation, elliptical galaxies appear to have virtually exhausted that fuel, and so there is very little raw material for the formation of new stars. The typical ages of the stellar populations of elliptical and spiral galaxies provide evidence for this theory, because the stars in elliptical galaxies are typically much older and redder than those in spiral galaxies. Current thinking amongst astronomers is that most elliptical galaxies formed from the collisions and subsequent mergers of spiral galaxies. In fact, Hubble just used those names to indicate the differences in structure between elliptical and spiral galaxies, and he himself was not sure how the different types of galaxy evolved. There is a common misconception that astronomers used to think that elliptical galaxies were the evolutionary forerunners to spiral galaxies, because Hubble himself referred to elliptical galaxies as ‘early-type’ and spiral galaxies as ‘late-type’. Elliptical galaxies are typically found in galaxy clusters. Elliptical galaxies have a smooth ellipsoidal or spherical appearance, and they have far less structure than spiral galaxies do. They typically contain a much greater proportion of older stars than spiral galaxies do.įour classes are used to classify galaxies: spiral barred spiral elliptical and irregular. Elliptical galaxies have an even, ellipsoidal shape.
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