Exploring the Cosmos - Degree Exam 2012 - Life and Death of Stars (Part 2)
1. Synchrotron radiation is
caused by radioactive decay in a Type-II supernova.
a pulsed source of radio interference.
a feature of the heat from a red giant.
a feature of radiation from a neutron star.
2. Supermassive black holes are
usually violent sources of energy that can destroy galaxies.
only found in distant galaxies.
found at the centre of nearly every galaxy.
thought to be very rare in the universe.
3. The best evidence of black holes comes from
direct observation of black areas in space.
evidence of their extreme magnetic fields.
x-ray sources which are always black holes.
signs of the effect of strong gravitational fields.
4. Pulsars typically spin
many thousands of times per second.
about once a day.
about once a year.
many times per second.
5. Neutron degeneracy
stops collapse in a supernova.
causes supernova explosions.
prevents the collapse of a white dwarf in a supernova.
leads to the formation of heavy metals like gold in supernovae.
6. An emission nebula is
blue as it scatters the light from stars.
red as it scatters the light from stars.
internally heated by stars.
usually dark as it blocks the light from stars.
7. A protostar forms due to
gravitational attraction due to a nearby star.
changes in the early stage of a main sequence star.
collapse of a high density region of gas.
collapse of a low density region containing hydrogen.
8. Main sequence stars
are hydro-dynamically unstable.
are continuously cooling.
are continuously contracting.
stay approximately constant in size.
9. If 4 hydrogen nuclei fuse to form a helium nucleus
the mass-energy increases by about 1 %.
the mass drops by about 1 %.
the mass is conserved.
energy is absorbed.
10. Given that the radius of the Sun is about 700,000 km
it takes a few hours for light to travel from the core to the photosphere.
energy from fusion takes about 1 million years to travel this distance.
light takes 2 to 3 seconds to travel from the core to the photosphere.
energy from fusion appears almost instantly at the photosphere.
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