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Observing the Universe QuickTime™ and a YUV420 codec decompressor are needed to see this picture. The Scale of Things… QuickTime™ and a YUV420 codec decompressor are needed to see this picture. You are Here - Star-filled skies The night sky may appear to be serene and unchanging but… Nova Stellae “New Stars” Nova “RS Ophiuchi” in February 2006 Before the Telescope “Star” of Bethlehem? Far Eastern Star Gazers Star of Wonder Tycho Brahe (1546 – 1601) Johannes Kepler (1571 – 1630) Tycho’s Nova Tycho Brahe noticed a bright star in the constellation of Cassiopeia in 1572… “On the 11th day of November in the evening after sunset, I was contemplating the stars in a clear sky. I noticed that a new and unusual star, surpassing the other stars in brilliancy, was shining almost directly above my head; and since I had, from boyhood, known all the stars of the heavens perfectly, it was quite evident to me that there had never been any star in that place of the sky, even the smallest, to say nothing of a star so conspicuous and bright as this… A miracle indeed, one that has never been previously seen before our time, in any age since the beginning of the world.” The Great Debate of 1920 Harlow Shapley Heber Curtis “The scale of the universe” Shapley argued that “spiral nebulae” (like Andromeda) were just nearby gas clouds inside our own Galaxy. Curtis believed them to be galaxies in their own right lying far outside our own Galaxy. Novae part of the problem 1885: S And, a nova in the Andromeda Nebula. “Standard Candle” led to distance estimate within our Galaxy, the Milky Way. 1920’s: Edwin Hubble used these Standard Candles (Cepheid Variable stars) to get a much larger distance to Andromeda. Hence S And was 20,000 times brighter than a “normal” nova… Baade therefore dubbed these objects “super-novae”. Supernovae Two main classes: Type II Explosion of massive stars at end of their lives Type Ia Explosion of white dwarf star near its limiting mass of 1.4x the mass of the Sun QuickTime™ and a YUV420 codec decompressor are needed to see this picture. Novae and Supernovae We see a few ordinary novae per year in our galaxy. Supernovae are much rarer, a typical galaxy may only have one every 30 years. We know of 6 Supernovae in our galaxy in the last 1000 years. Year Type 1006 I Crab 1054 II 1181 Tycho 1572 I Kepler 1604 I Cas A 1667 II Over 400 years since last one was actually observed in our galaxy The remnant of Tycho’s nova Composite: X-ray (Chandra), IR (Spitzer) & optical (Calar Alto) Supernova 1987A in the Large Magellanic Cloud More Distant Supernovae