3.1 cosmic distance ladder. from these methods: determine distance (see p 615 including fig 20.16)
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3.1 Cosmic Distance Ladder
From these methods: Determine distance (see p 615 including Fig 20.16)
From these methods: Determine distance (see p 626 including Fig 20.16)
From these methods: Determine distance (see p 626 including Fig 20.16)
Given luminosity infer distance (see p 626 including Fig 20.16)
Use surface temperature of “main sequence stars” to infer Luminosity.
Use pulsation period of variable starts (“Cepheids”) to infer luminosity
Given luminosity infer distance (see p 626 including Fig 20.16)
Given luminosity infer distance (see p 626 including Fig 20.16)
Use “Tully-Fisher relation” to infer galaxy luminosity from rotation speed
Given luminosity infer distance (see p 626 including Fig 20.16)
Use “Tully-Fisher relation” to infer galaxy luminosity from rotation speed
From these methods: Determine distance (see p 641)
3.2 The Redshift
Fig 20.15A redshifted galaxy spectrum
observed rest
rest
z
Redshift:
For small z v c z
3.3 The Hubble law
Putting together info about speed v and distance d reveals
remarkably simple behavior:
0v H d
0 65H Km/Sec/Megaparsec
1 Megaparsec = 3.3 million lightyears
Special feature of the Hubble law: It looks the same from any position:
The Big Bang