Whats going on in the Universe

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Whats going on in the Universe?

• Jocelyn Bell Burnell
• University of Oxford Astrophysics
• Mansfield College

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Contents

• Pluto an update
• The Milky Way scene setting
• Dark matter and the rotation of galaxies
• Dark matter and clusters of galaxies
• The Big Bang review
• Dark energy

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Pluto no longer a planet!

• Pluto much less massive than other planets
• As we get better telescopes, finding other
  Pluto-like objects further away from Sun
• Pluto seems to be the first-discovered and
  nearest of a new type of object
• Sun has eight planets smaller objects like
  Pluto (dwarf planets) lumps of rock and ice
  (small solar system bodies)

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• The Milky Way our galaxy

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Rotating, spiral galaxy
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Andromeda Galaxy
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Our Galaxy the Milky Way

• Our Sun is one of 100 thousand million stars that
  make up the Milky Way.
• It is an average star, located two-thirds of the
  way out from the centre.
• Galaxy is disk-shaped, 100,000 light years
  diameter.
• Sun rotates round centre of galaxy at 200 km/s

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Orion and Milky Way
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The Milky Way in other languages

• Celtic The Silver Street (Arianrod)
• China The Celestial River
• Cree Indian The Path of the Spirits
• Kalahari The Backbone of the Night
• Maori - The Long Fish
• Siberia Silicon River
• Sweden The Winter Road

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• Dark matter and the rotation of galaxies

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Spiral galaxies
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Wheres the edge of the galaxy?

• As the edge of the visible galaxy is reached you
  would expect this rotation curve to start
  dropping it should follow Keplers Third Law.
• It doesnt! Besides the visible material there
  must be dark material which contributes gravity

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• Clusters of galaxies
• and dark matter

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Perseus Cluster of Galaxies

• Galaxies moving so fast the cluster should break
  up.
• We see no sign of clusters breaking up.
• Does extra, dark material in cluster provides
  gravity to bind cluster?

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Dark matter

• To prevent galaxies and clusters of galaxies
  centrifuging apart we postulate the existence of
  dark matter.
• This material has gravity, but does not shine.
• There may be several kinds of dark matter.
• All of them must be totally different from the
  material know about already.

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• The history of the universe

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The Beginning of the Universe

• The Universe began 13.7 billion years ago with a
• BIG BANG
• All the universe, all of space, matter, energy,
  time started with a huge explosion from a tiny
  size.

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Evidence for Big Bang

• Galaxies moving apart they appear to have been
  all together at one point in past.
• Cosmic microwave background radiation left
  over from Big Bang now cooled to about 3 K.
  2006 Nobel prize for physics.
• The abundance of deuterium

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The Evolution of the Universe
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• Dark energy accelerating the expansion of the
  universe

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An accelerating phase?
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An accelerating universe

• Something is causing the expansion of the
  Universe to accelerate.
• We dont know what it is, but we feel better if
  we give it a name dark energy.
• The acceleration shows in the Universe today, but
  was not noticeable in the earlier universe.

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The Content of the Universe

• Of the mass-energy that makes up our Universe
• 4 is ordinary matter (the stuff we and our world
  are made out of)
• 23 is dark matter
• 73 is dark energy

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We are exceptional!

• Live in an exceptionally dense part of the
  Universe
• Live in a chemically atypical part of the
  Universe
• We are made of matter, not antimatter we owe
  our existence to a ninth decimal place anomaly!
• We are made of baryons, particles which make up
  only 4 of the mass-energy of the universe.

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In conclusion

• We have had to invent dark matter to stop
  galaxies and clusters of galaxies from flying
  apart.
• We have had to invent dark energy to explain
  why the expansion of the universe is getting
  faster not slower.

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• The End
• Questions welcome!

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Our Galaxy the Milky Way

• Our Sun is one of 100 thousand million stars that
  make up the Milky Way.
• It is an average star, located two-thirds of the
  way out from the centre.
• Galaxy is disk-shaped, 100,000 light years
  diameter.
• Sun rotates round centre of galaxy at 200 km/s
• Monty Python Galaxy Song

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Carl Sandburg

• USA poet, Pullitzer prize winner. 1878 1967
• Remember who you are. Remember you are one of the
  latest products of millions of years of toil and
  play and regurgitation of universal forces. The
  rain and stars and dust of a thousand worlds that
  have perished have contributed to the making of
  you.
• Part of A Little Sermon, 1907.