Physics
Scientific paper
May 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996aps..may..f401k&link_type=abstract
American Physical Society, APS/AAPT Joint Meeting, May 2-5, 1996, abstract #F4.01
Physics
Scientific paper
Supernova explosions lead to luminous optical objects which can be used to measure distances in the Universe. Supernova 1987A in the nearby Large Magellanic Cloud provides a direct geometric distance to this galaxy, and a check on the Cepheid variable star distance scale. Using observations of SN 1987A with the Hubble Space Telescope, we find a distance of 51 ± 3 kiloparsec which is consistent with the Cepheid scale. Type II supernovae, which result from the core collapse of a massive star, emit a spectrum which can be accurately modeled. Based on understanding of the radiation transport through the expanding atmospheres, observations of SN II provide distances to 18 galaxies at redshifts up to 14500 km s-1. These distances agree within the errors with distances found from Cepheids, and correspond to a value of the Hubble Contant of 72 ± 7 km s-1Mpc-1. Finally, the Type Ia supernovae, thought to arise from the thermonuclear incineration of a carbon-oxygen white dwarf, provide the best and the brightest tools for measuring extragalactic distances. Careful study shows that these supernovae are not identical, but that there is a well-determined relation between the supernova luminosity and the time history of its light emission: the supernova light curve. Recent work on the ``Multicolor Light Curve Shape Method'' accounts for this effect in an optimal way, and allows an independent determination of the absorption by dust along the line of sight for each object. Using a sample of 20 SN Ia, and calibrating this with distances determined by Hubble Space Telescope observations of Cepheids yields a Hubble Constant of 65 ± 6 km s-1Mpc-1. This corresponds to an age of the Universe (for Ω = 0 ) of about 15 billion years, which is consistent with the age of the elements and the age of globular cluster stars.
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