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Lecture 35 Extragalactic Astronomy

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Lecture 35 Extragalactic Astronomy. Summary so far. Still ... Every 50 100 Mpc. Virgo cluster, p601. 20 Mpc. Neighbor small ... Characteristics ... – PowerPoint PPT presentation

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Title: Lecture 35 Extragalactic Astronomy


1
Lecture 35 Extragalactic Astronomy
  • Summary so far

2
More general formula for the redshift
  • Reason If d 1000 Mpc, then v H0d gives v
    70,000 km/sec 0.25 c. More distant galaxies
    have v c? Whats up?

Figure 24.3
3
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4
An interludeRadio Astronomywill make sense later
  • To remind you of what you already know.
  • Radio astronomy study of universe with EM waves
    having wavelength from about 1 millimeter to 50
    meters
  • Comparison optical astronomy studies wavelengths
    between 4E-07 to 7E-07 meters

5
The Radio Sky
Radio sources many associated with giant
elliptical galaxies
6
Radio Galaxies, e.g. 3C296
Radio galaxies shine by a mechanism called
synchrotron radiation
7
What is synchrotron radiation?
Accelerated electrons radiate EM waves DEMO
8
History of Radio Astronomy, circa 1960
  • Some of the brightest radio sources, 3C48, 3C273,
    did not seem to be associated with galaxies, but
    with star-like objects

9
Spectra of these sources showed highly redshifted
lines great distances
Z (w-w0)/w0 0.16, 0.48, 1.7, 4.42 !! Quasar
Quasi-Stellar Radio Sources
10
With Hubble Space Telescope, we have imaged
Quasars
11
Summary of Quasar Characteristics
  • Clearly are a brilliant, energetic phenomenon in
    centers of galaxies
  • Quasars are very distant. We see them as they
    were long ago
  • Lets look at the distribution of quasar
    redshifts

12
Question what does this mean?
7236 quasars
13
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