Apparent size of Quasar = d = v t
After we correct for the distance to the quasar, we find that
QSO 3C273 was the size of a large star!
How could the energy of 100 to 1000 galaxies be produced by an object the size of a large star ?
How could this energy be produced from such a small volume?
V r C*delta lamda/ Lamda lab
V = H o
D = V/H o
The mechanism of a Quasar
- Quasars are usually found in groups of galaxies.
- The quasars and the galaxies have similar redshifts
o Similar velocities
o Similar distances
o An association
- “Fuzz” around Quasars shows stellar absorption spectra
- Quasars are very luminous centers of distant, young galaxies.
- Quasar energy is radiated by matter swirling in an accretion disk around a supermassive
Summary of Quasar Properties
- Small, compact, blue objects (x-rays are the dominant wavelength)
- Looks like faint stars in photographs
- X-ray emission
- Large redshifts such that UV spectral lines appear in visible portion of the spectrum
- Spectra are dominated by emission lines
Know the names of the three spectra and how they are generated for the test (refer to
- ~10% are radio sources
- Optical luminosities are 100 to 1000 times that of normal galaxies
- Many vary in intensity over days or weeks - Some quasars exhibit jets (optical or radio)
30 multiple choice questions
5 of them require use calculators
Review from Bergmann’s lecture notes
Photon: burst of energy Class 10
Material for Test 2
Unit 4: Birth of Stars…Lives of Stars
- This is dust and gas that occupy space between the stars
- Stars form in the dust/gas clouds in space
- Dust is ~1% of the total visible mass in space
- Obscures our view of distant objects
- Is a mixture of
o Elongated, tiny grains of dirty ice
o Grains of graphite (carbon)
o Silicate particles
o Complex molecules
- Light from a star passes through the dust
- The dust particles are ~same length as blue wavelength’s
- The dust scatters blue wavelengths more than red wavelengths
- More red photons pass unhindered through the dust and reach the observer.
- Star appears redder than it actually is
There exists ~100 times more gas mass than dust mass in the universe