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Evolution of the Universe

Evolution of the Universe. From the Big Bang to the Big Chill. Dan Caton. What we will look at. The Big Bang Star formation (with or without planets) Stellar evolution and death The Big Chill ------------- Questions and Break -----------

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Evolution of the Universe

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  1. Evolution of the Universe From the Big Bang to the Big Chill Dan Caton

  2. What we will look at • The Big Bang • Star formation (with or without planets) • Stellar evolution and death • The Big Chill • ------------- Questions and Break ----------- • The search for (intelligent?) life in the Universe

  3. The Smoking Gun: Galaxies and their motions • Several hundred billion stars • Their motions revealed the expansion of the Universe

  4. Billions of Galaxies • Hubble Ultra-Deep Field • 11.3 days of exposure time • 3 arc-minutes in size • 10,000 galaxies • Seeing back to within 800 million years of Big Bang • Let’s look at galactic motions….

  5. Vesto M. Slipher • In 1914 found 11 of 15 spiral 'nebulae' spectra showed spectral lines Doppler shifted toward the red.........

  6. Milton Hummason • In 1920's, worked his way up at Mt. Wilson to be night assistant and observer. • Photographed spectra of many galaxies using...

  7. … the 100-inch Mt. Wilson telescope These interpreted by...

  8. Edwin Hubble, who found that velocity proportional to distance

  9. Plot means expansion • Uniform expansion means velocities are proportional to distance • No “center”—every location looks like center!

  10. Back up the Expansion: Big Bang Big Bang!

  11. Remnants of BB were Predicted In 1960 it was predicted that we should see the remnants of the Big Bang, Princeton physicists Robert Dicke and P. J. Peebles

  12. Discovery! • Penzias and Wilson discover it in 1965 • Bell Labs / satellite communications • detected isotropic static • got 1978 Nobel prize in physics

  13. Spectrum: 3o Kelvin “Blackbody”

  14. Origin of the 3o Cosmic Background

  15. Evidence of initial structure Wilkinson Microwave Anisotropy Probe (launched 6/01) – more details later…

  16. The Stellar Era (now) • Current era of star formation will continue • 100 trillion (1014) years: stellar era ends • Let’s make some stars…

  17. Star Formation: the Nurseries • Stars began to form in areas of gas and dust very soon • Some fraction form with planets

  18. Triggers needed for star formation • Shock wave from passage of spiral arm in galaxy. • Hot young blue stars define formation regions

  19. Triggers for star formation • Supernovae – either the death of massive stars or explosion of accreted material in a binary star system, create shock waves in the region Outshines the rest of the galaxy Used as a “standard candle” for finding galactic distances

  20. Triggers for star formation • Energetic ultraviolet light from new, hot stars generate shock waves that trigger other stars to form.

  21. Proto-stars form in collapse… • Seen in visible and infrared images from HST here. • Initially heat from energy of gravitational collapse • Then …

  22. Stars’ energy source: fusion

  23. Proton-proton cycle Converts hydrogen to helium: • Two protons combine to deuterium + positron + neutrino • Another proton combines with this to make isotope of helium + gamma ray • Two of these He combine to make He plus two protons • Final mass less than ingredients by E = mc2 • Products ….

  24. Products: gamma rays and neutrinos • Gamma rays take random walk out of star, absorbed and re-emitted at lower temperatures and longer wavelengths • Neutrinos leave directly with little interaction with matter. Used as a probe of solar nuclear process…

  25. Subsequent Evolution These processes replenish the Universe with gas and dust…

  26. Stellar Evolution The Lightweights

  27. Structure of evolving Low-Mass stars • Core heats up and starts burning He • Outer atmosphere expands and cools Firewood and the fireplace…

  28. M57: the Ring Nebula Outer atmosphere is gently puffed off in a so-called “planetary” nebula Remaining core becomes a “white dwarf,” like these…

  29. … White dwarfs

  30. Real White dwarfs • Very dense—stellar mass within planet size • Supported from collapse by electron degeneracy • Mass must be less than the Chandrasekhar limit of 1.4 solar masses Subrahmanyan Chandrasekhar.

  31. High mass stars’ fate Grows to become a red supergiant….

  32. Fusing iron… Endothermic reactions

  33. Stages of Evolution Type II

  34. What will happen to falling matter? • A) both balls (all matter) will bounce to their combined heights • B) The big ball (core) will stop the small ball • C) The small ball (ejecta) will bounce out more Core

  35. Rebound is violent! • Infalling matter rebounds dramatically due to conservation of momentum • Outer material is still falling in while inner core is already rebounding outward Core

  36. Prominent Historical Supernovae

  37. Supernova 1054 • Seen by Chinese in 1054 AD • Possibly recorded by native Americans in Chaco Canyon • Not seen in Europe? • Visible in daylight for weeks • Today …

  38. Crab Nebula (M1) “supernova remnant”

  39. Tycho’s Star’s SNR • 1572 • X-ray image from Chandra satellite

  40. SN1987A in the Large Magellanic Cloud • Ian Shelton, Univ. Toronto, working in Chile • LMC satellite of Milky Way Galaxy, 170kly away • Important: first ‘nearby’ SN in modern times

  41. The Future What can we tell from measurements of the expansion of the Universe?

  42. Recent data.. Look at details at upper end…

  43. Models vs. data scatter

  44. Our new fate? Let’s look at current model of the future… three more eras

  45. The Degenerate Era • Most of the mass is locked up in degenerate stars, those that have blown up and collapsed into black holes and neutron stars, or have withered into white dwarfs. • Energy in this era is generated through proton decay and particle annihilation. • Ends in 1037 years.

  46. The Black Hole Era • Protons have decayed (t >1033 yr? undetected yet) and black holes have evaporated. • After the epoch of proton decay, the only stellar-like objects remaining are black holes of widely disparate masses, which are actively evaporating during this era. • Ends at ~10100 years

  47. The Dark Era • Only the waste products from these processes remain: mostly photons of colossal wavelength, neutrinos, electrons, and positrons. • For all intents and purposes, the universe as we know it has dissipated… the truly Big Chill

  48. The (real) end.

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