Existing thinking among astronomers is that a lot of elliptical galaxies formed from the crashes and subsequent mergers of spiral galaxies. The normal ages of the excellent populations of elliptical and spiral galaxies supply proof for this theory, due to the fact that the stars in elliptical galaxies are usually much older and redder than those in spiral galaxies. Whilst spiral galaxies have abundant tanks of the dust and gas that fuel star formation, elliptical galaxies appear to have essentially tired that fuel, and so there is really little raw material for the formation of brand-new stars. It seems most likely that elliptical galaxies are mainly populated by stars that formed within active spiral galaxies.
Elliptical galaxy NGC 4150. Credit: NASA, ESA, R.M. Crockett (University of Oxford, U.K.), S. Kaviraj (Imperial College London and University of Oxford, U.K.), J. Silk (University of Oxford), M. Mutchler (Space Telescope Science Institute, Baltimore, USA), R. OConnell (University of Virginia, Charlottesville, USA), and the WFC3 Scientific Oversight Committee
Elliptical galaxies have an even, ellipsoidal shape. They typically contain a much greater proportion of older stars than spiral galaxies do.
4 classes are used to categorize galaxies: spiral; disallowed spiral; irregular and elliptical. Elliptical galaxies have a smooth ellipsoidal or round look, and they have far less structure than spiral galaxies do. Elliptical galaxies are typically discovered in galaxy clusters.
There is a typical misconception that astronomers utilized to think that elliptical galaxies were the evolutionary forerunners to spiral galaxies, since Hubble himself referred to elliptical galaxies as early-type and spiral galaxies as late-type. Hubble simply utilized those names to suggest the differences in structure in between elliptical and spiral galaxies, and he himself was not sure how the different types of galaxies evolved.
Elliptical galaxies have an even, ellipsoidal shape. They usually include a much greater proportion of older stars than spiral galaxies do. Credit: ESA/Hubble, NASA, ESA, R.M. Crockett (University of Oxford, U.K.), S. Kaviraj (Imperial College London and University of Oxford, U.K.), J. Silk (University of Oxford), M. Mutchler (Space Telescope Science Institute, Baltimore, USA), R. OConnell (University of Virginia, Charlottesville, USA), and the WFC3 Scientific Oversight Committee
Existing thinking among astronomers is that most elliptical galaxies formed from the accidents and subsequent mergers of spiral nebula. The typical ages of the outstanding populations of elliptical and spiral galaxies offer evidence for this theory, since the stars in elliptical galaxies are typically much older and redder than those in spiral nebula. Whilst spiral galaxies have rich reservoirs of the dust and gas that fuel star formation, elliptical galaxies appear to have virtually tired that fuel, and so there is extremely little raw product for the formation of new stars. It seems likely that elliptical galaxies are mainly populated by stars that formed within active spiral galaxies. Due to their really low rate of star development and their populations of old, red stars, elliptical galaxies are sometimes colloquially described as red and dead by astronomers.
Elliptical Galaxy. Credit: NASA, ESA, R.M. Crockett (University of Oxford, U.K.), S. Kaviraj (Imperial College London and University of Oxford, U.K.), J. Silk (University of Oxford), M. Mutchler (Space Telescope Science Institute, Baltimore, USA), R. OConnell (University of Virginia, Charlottesville, USA), and the WFC3 Scientific Oversight Committee
Just recently, the Hubble Space Telescope and ESOs Very Large Telescope (VLT) were utilized to help fix an astrophysical mystery that had actually fixated the most enormous elliptical galaxies. These gigantic dead and red galaxies were not always so inactive. In reality, previously in the history of the Universe, the evolutionary precursors to these huge galaxies were complete of gas and forming stars at a prodigious rate. Thanks to Hubble and the VLT, astronomers had the ability to show for the very first time how star formation in these dead galaxies actually sputtered out billions of years earlier. Hubble has also caught stunning images of elliptical galaxies throughout its more than 30-year history. This includes in-depth views of the elliptical galaxies NGC 4150 (see image at the top of this page) and NGC 2768.