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YSS - Intro. to Observational Astrophysics (ASTR 205) Class #13 Dark Matter, Dark Energy, and the Fate of the Universe (Chapter 16). Professor : Jos é Maza July 5, 2011. Dark Matter Dark Energy.
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YSS - Intro. to Observational Astrophysics (ASTR 205)Class #13Dark Matter, Dark Energy, and the Fate of the Universe(Chapter 16) Professor: José Maza July 5, 2011
Dark Matter • Dark Energy
Dark matter is the name given to mass that we infer to exist through its gravitational effects but that emits no detectable radiation. • Dark energy is the name given to an unseen influence that may be causing the expansion of the Universe to accelerate with time.
Evidence for dark matter • Distribution of mass in the Milky Way
A rotation curve plots the orbital speeds of objects in a galaxy against their distances from the center of the galaxy. • The flatness of the Milky Way’s rotation curve indicates that a large amount of dark matter lies beyond our galaxy’s visible regions.
Orbits of Galaxies in Clusters • Hot Gas in Clusters
What might dark matter be made of? • Baryonic dark matter • Non-baryonic dark matter • Ordinary Dark Matter: • MACHOs (Massive Compact Halo Objects)
Extraordinary Dark Matter • The dark matter in galaxies cannot be made of neutrinos, because these very low mass particles travel through the universe at enormous speeds and can easily escape a galaxy’s gravitational pull. • WIMPs (weakly interacting massive particles). WIMPs are subatomic particles so the “massive” in their nature is relative.
WIMPs are often called “cold dark matter” to set them apart from the fast moving neutrinos. • WIMPs could make up most of the mass of a galaxy or cluster of galaxies, but they would be completely invisible in all wavelengths of light. • WIMPS are like neutrinos but more massive.
Structure Formation • What is the role of dark matter in galaxy formation? • What are the largest structures in the Universe?