The appearance of the spiral arms also changes between the a, b, and c subclasses. This is labeled on the SINGS Tuning Fork. In Sa galaxies, the bulge dominates the galaxy, while in Sc galaxies, the bulge is much smaller. The subclasses are divided based on the dominance of the bulge component of the galaxy. SpiralsĪ spiral galaxy is classified as an S galaxy with subclassification a, b, or c, so for example, M51 above is classified as an Sb galaxy. Within each of these groups, there are also sub-classifications. You can find many, many more images of galaxies at a variety of websites, but here is one source at the National Optical Astronomy Observatory with an excellent sample of many of the well-known types.Įdwin Hubble classified galaxies using the types that you see illustrated on the two tuning fork images the one above and the SINGS image.Irregular I galaxy Large Magellanic Cloud.Sb spiral M51 (note, M51 has a companion galaxy, and it is the main object that is classified as an Sb spiral).Hubblesite image of a dwarf irregular galaxy: NGC 4449 image tourįinally, if you want to look at images of galaxies of a specific type, below is a list of galaxies with their types in Hubble's classification scheme:.Hubblesite image of a barred spiral: NGC 1300 image tour.Hubblesite image of a normal spiral: M51 Image tour.Next, study some specific examples in detail to familiarize yourself with their differences: Keep a mental list of the similarities and differences between these 7 objects.When you center on the galaxy, using the zoom tool, zoom in so that you can see the image at a reasonable level of detail.Using the find tool, locate galaxies, M51, M81, M95, M61, M87, M49, M59 one at a time.So, if you have that version, you will have to skip this part of the exercise): First, open Starry Night, and do the following (Note: The Digital Download core application does not have galaxy images. You should investigate the images of several galaxies, and then compare and contrast their features. You should repeat some of what Hubble did when he developed his tuning fork classification system.
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