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