•Q 1: If
the inner accretion disk around a black hole has a temperature of 1 million K, at what wavelength will it radiate the most
energy?
•Use Wien’s Law: λpeak = 3 million nm K/T = 3 million nm/1 million
•
λpeak
= 3 nm
–
•Q 2: Which of the below sequences shows objects
with increasing densities?
•Density is mass/volume, so...
•Red
Giant -- White Dwarf -- Neutron Star -- Black Hole
•
•Q 3: The black hole in the center of our Milky
Way galaxy seems to be about 2.6 million
times the mass of the sun. What is the radius of its event horizon?
•Rs = 2GM/c2
•Rs
= 7.8 million km, which is about 11
times the solar radius and 5% of an AU.
•
•Q 4: Assume a white dwarf and neutron star have
the same temperatures. White dwarfs
are hard to spot because they are small (about the size of Earth). Neutron stars are smaller. How much fainter are they?
•Use Steffan-Boltzmann Law, or just the Scaling law
for stars: L = 4πR2T4
•LWD/LNS = (RWD/RNS)2 = (radius earth=6000 km/10 km)2
•LWD/LNS = (600 x
600) = 360000 times (round to 400000)
•
•Q 5: Why the "millisecond
pulsars“? Because the
neutron star:
•1.
Is spinning hundreds of times per second.