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