Spacetelescopeorgabouthistorythe man behind the name

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Unformatted text preview: life and work of Edwin Hubble on this website: http://www.spacetelescope.org/about/history/the man behind the name/ 2 See the essay by Hubble’s student, Alan Sandage at http://antwrp.gsfc.nasa.gov/diamond jubilee/d 1996/sandage hubble.html 1 1 PHSC12000 V1.0 2 will find evidence for the existence of dark matter in the universe - one of the most intriguing mysteries of modern cosmology. In this first part of the labs, you will explore the morphological types of galaxies and the overall shapes and features of their spectra, including the features in the spectra called “spectral lines.” You will count galaxies in randomly chosen patches of the sky to see how homogeneous their distribution over the sky really is. You will then measure the wavelengths of spectral lines in real galaxy spectra. To determine galaxy redshifts you will compare the measured redshifted galaxy lines to laboratory measurements of the line wavelength on Earth. Morphological types of galaxies Hubble classified galaxies into a sequence, now called the tuning-fork Hubble diagram (due to its resemblance to a tuning fork viewed horizontally) based on their visual appearance: shape, smoothness, and presence of features such as bars and spiral arms. All this collectively is called “galaxy morphology” and the classification scheme is called “morphological classification.” Hubble had conjectured that the sequence represented the path of galaxy evolution. Although this was not confirmed by further observations, the classification is still widely used by astronomers. What properties of the galaxies indicate that the classification scheme is not an evolutionary sequence? Consult your textbook and discuss with your TA. Hubble’s classification contains many sub-classes of galaxies3 , but the two main classes of galaxies are elliptical and spiral galaxies. Ellipticals tend to be smooth in their light distribution and roundish in their appearance. Spiral galaxies tend to have features such as bars and spiral arms. To famili...
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