Transcript Age of the Universe

Age of the Universe
by
Robert Nemiroff
Michigan Tech
Physics X: About This Course
• Officially "Extraordinary Concepts in Physics"
• Being taught for credit at Michigan Tech
o Light on math, heavy on concepts
o Anyone anywhere is welcome
• No textbook required
o Wikipedia, web links, and lectures only
o Find all the lectures with Google at:
 "Starship Asterisk" then "Physics X"
o
http://bb.nightskylive.net/asterisk/viewforum.php?f=39
Expanding Universe:
Determining Hubble’s Constant
• What is Ho?
o
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Major astronomical quest of recent years
Hubble Space Telescope “Key Project”
• Measure distance and redshift of nearby
galaxies
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Trouble: peculiar velocities
• Today: Ho = 71 (+/- 5) km / sec / Mpc
• d=v/Ho
o
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Say v = 7100 km/sec, then
D = 100 Mpc
Universe Expansion:
Cosmological Distance Ladder
• Sun
o
How: timing radar bounces
• Nearest stars
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How: parallax shift over six months
• Open star clusters
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How: parallax, main sequence fitting
• Cepheids
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How: found in star clusters
The Cepheids of M100
Credit: NASA, HST, W. Freedman (CIW), et al.
APOD: 1996 January 10
Universe Expansion:
Cosmological Distance Ladder
• Nearest Galaxies
o
How: Cepheid variable stars
• Supernovas
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How: Inside galaxies with Cepheids
• Distant Galaxies
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How: supernovas calibrate redshifts
M3: Inconstant Star Cluster
Credit & Copyright: J. Hartman & K. Stanek (Harvard CfA)
APOD: 2004 October 12
A Nearby Supernova in M51
Credit & Copyright: R Jay GaBany (Cosmotography.com)
APOD: 2005 July 19
Supernova Factory NGC 2770
Credit: A. de Ugarte Postigo (ESO) et al.,
Dark Cosmology Centre (NBI, KU),
Instituto de Astrofísica de Andalucía (CSIC),
University of Hertfordshire
APOD: 2008 January 18
Universe Expansion:
The Age of the Universe
• The universe must be older than things in it
• Three old things:
• Age of the Earth
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Oldest rocks are 3.5 billion years old
• Age of the oldest white dwarf stars
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Faint white dwarfs: 12.5 +/- 1 billion years old
• Age of the oldest globular star clusters
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14.6 +/- 1.7 billion years
White Dwarf Stars Cool
Credit: H. Richer (UBC) et al., WFPC2, HST, NASA
APOD: 2000 September 10
M55: Color Magnitude Diagram
B.J. Mochejska, J. Kaluzny (CAMK), 1m Swope Telescope
APOD: 2001 February 23
Universe Expansion:
New method: Microwave background
• Spot size and distribution on the
microwave background correlates with
universe age.
• Universe age 13.7 +/- 0.1 billion years old
A Year of Resolving Cosmology
Credit: WMAP Science Team, NASA
APOD: 2003 December 31