© 2010 Pearson Education, Inc. Dark Universe: Dark Matter Dark Energy and the Fate of the Universe

© 2010 Pearson Education, Inc. The Universe is huge, filled with many many bright stars …

© 2010 Pearson Education, Inc. Rotation curve A plot of orbital velocity versus orbital radius The solar system’s rotation curve declines because the Sun has almost all the mass. There are something dark out there …

© 2010 Pearson Education, Inc. The rotation curve of the Milky Way stays flat with distance. Mass must be more spread out than in the solar system. There are something dark out there …

© 2010 Pearson Education, Inc. The visible portion of a galaxy lies deep in the heart of a large halo of dark matter. There are something dark out there …

© 2010 Pearson Education, Inc. 85% dark matter 13% hot gas 2% stars I am telling you, What we can see is nothing!

© 2010 Pearson Education, Inc. Ordinary Dark Matter (MACHOS) –Massive Compact Halo Objects: dead or failed stars in halos of galaxies Extraordinary Dark Matter (WIMPS) –Weakly Interacting Massive Particles: mysterious neutrino-like particles What could be the Dark Matter? Two Basic Options

© 2010 Pearson Education, Inc. MACHOs occasionally make other stars appear brighter through lensing… … but there are not enough lensing events to explain all the dark matter. Search for MACHOs …

© 2010 Pearson Education, Inc. There’s not enough ordinary matter. WIMPs could be left over from Big Bang. Models involving WIMPs explain how galaxy formation works. Why do we believe in WIMPs?

© 2010 Pearson Education, Inc. WIMP Dark matter effects …

© 2010 Pearson Education, Inc. The Fate of the Universe … Dark Energy Big Bang: The birth of everything

© 2010 Pearson Education, Inc. Will the universe continue expanding forever? Or, will it re-collapse (Big Crunch)? Philosophers lose sleep on this question …

© 2010 Pearson Education, Inc. The fate of the universe depends on the amount of dark matter. Which one you like the most?

© 2010 Pearson Education, Inc. The brightness of distant white dwarf supernovae tells us how much the universe has expanded since they exploded. Insert TCP 6e Figure This is how scientists do to find the answer

© 2010 Pearson Education, Inc. In fact, the expansion appears to be speeding up! Dark Energy Big surprise !

© 2010 Pearson Education, Inc. This is what in our Universe

© 2010 Pearson Education, Inc. Dark Universe Dark Matter, Dark Energy Enjoy in the darkness!

© 2010 Pearson Education, Inc. And, South Dakota is the perfect place to entertain ourselves in the darkness!

© 2010 Pearson Education, Inc. SDSMT is also part of it

© 2010 Pearson Education, Inc. Questions

© 2010 Pearson Education, Inc. Spiral galaxies all tend to have flat rotation curves, indicating large amounts of dark matter.

© 2010 Pearson Education, Inc. Nova – Standard candle for cosmology

© 2010 Pearson Education, Inc. An accelerating universe best fits the supernova data. The “fact” is …

© 2010 Pearson Education, Inc. Summary-1: What do we mean by dark matter and dark energy? –Dark matter is the name given to the unseen mass whose gravity governs the observed motions of stars and gas clouds. –Dark energy is the name given to whatever might be causing the expansion of the universe to accelerate.

© 2010 Pearson Education, Inc. “Ordinary” matter: ~ 4.4% –Ordinary matter inside stars:~ 0.6% –Ordinary matter outside stars:~ 3.8% Dark matter: ~ 23% Dark energy~ 73% Summary-2: Contents of Universe Now you know this is indeed almost nothing!