Dark Universe: Dark Matter Dark Energy and the Fate of the Universe © 2010 Pearson Education, Inc.
Download ReportTranscript Dark Universe: Dark Matter Dark Energy and the Fate of the Universe © 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.
There are something dark out there …
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.
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There are something dark out there …
The rotation curve of the Milky Way stays flat with distance.
Mass must be more spread out than in the solar system.
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There are something dark out there …
The visible portion of a galaxy lies deep in the heart of a large halo of dark matter.
© 2010 Pearson Education, Inc.
© 2010 Pearson Education, Inc.
I am telling you, What we can see is nothing!
85% dark matter 13% hot gas 2% stars
What could be the Dark Matter? Two Basic Options
• 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 © 2010 Pearson Education, Inc.
Search for MACHOs …
MACHOs occasionally make other stars appear brighter through lensing… … but there are not enough lensing events to explain all the dark matter.
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Why do we believe in WIMPs?
• There’s not enough ordinary matter.
• WIMPs could be left over from Big Bang.
• Models involving WIMPs explain how galaxy formation works.
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WIMP Dark matter effects …
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The Fate of the Universe … Dark Energy
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Big Bang: The birth of everything
Philosophers lose sleep on this question …
• Will the universe continue expanding forever?
• Or, will it re-collapse (Big Crunch)? © 2010 Pearson Education, Inc.
Which one you like the most?
The fate of the universe depends on the amount of dark matter.
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This is how scientists do to find the answer
Insert TCP 6e Figure 20.14
The brightness of distant white dwarf supernovae tells us how much the universe has expanded since they exploded.
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Big surprise !
In fact, the expansion appears to be speeding up!
Dark Energy
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This is what in our Universe
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Dark Universe Dark Matter, Dark Energy Enjoy in the darkness!
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And, South Dakota is the perfect place to entertain ourselves in the darkness!
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SDSMT is also part of it
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© 2010 Pearson Education, Inc.
Questions
Spiral galaxies all tend to have flat rotation curves, indicating large amounts of dark matter.
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Nova – Standard candle for cosmology
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The “fact” is …
An accelerating universe best fits the supernova data.
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Summary-1: What do we mean by dark matter and dark energy?
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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.
Summary-2: Contents of Universe
• “Ordinary” matter: ~ 4.4% – Ordinary matter inside stars: ~ 0.6% – Ordinary matter outside stars: ~ 3.8% • Dark matter: • Dark energy ~ 23% ~ 73% Now you know this is indeed almost nothing!
© 2010 Pearson Education, Inc.