Dark Matter
Delve into the enigmatic realm of dark matter through historic discoveries by Zwicky and Rubin, explore gravitational anomalies, and investigate the elusive nature of dark matter candidates like MACHOs and WIMPs. Discover the invisible force shaping our universe.
Dark Matter
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Presentation Transcript
Zwicky’s Coma • In 1933 Fred Zwicky measured the speed of Coma cluster galaxies. • Too fast for the visible stars • Cluster would fly apart • Either stars and physics are different, or there is dark matter. Image: D. Rowe
Vera’s Spin • In the 1970’s Vera Rubin studied the speed of stars in distant galaxies. • Outer stars too fast • Galaxies stayed together • Dark matter must be greater than visible stars. • Law of gravity same • Dark matter about 10 times larger
Orbital Check • The Sun orbits the center of the Milky Way. • 90 billion M inside orbit • Distant clusters should show lower speeds after the known mass ends. • Gas with high velocity outside Milky Way Sun’s orbit Mass within interstellar gas
Dark Halo • To account for the speed there must be mass outside the luminous part of the Milky Way. • Not visible in any wavelength dark matter hyperphysics.phy-astr.gsu.edu
Einstein Rings • Gravity bends light like a lens. • More mass = more bending • Dark matter is needed to account for the bending.
MACHOs • One candidate for dark matter sources were massive compact halo objects. • Dwarf stars • Brown dwarfs • Observable by microlensing • Observations rule out MACHOs.
WIMPs • The other possibility for dark matter are weakly interacting massive particles. • Heavier than atoms • Hard to detect • Dedicated experiments still haven’t seen WIMPs. 2004 experimental limits
