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 the heat from a red giant.
caused by radioactive decay in a Type-II supernova.
a feature of radiation from a neutron star.
2. Supermassive black holes are
only found in distant galaxies.
thought to be very rare in the universe.
found at the centre of nearly every galaxy.
usually violent sources of energy that can destroy 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.
many times per second.
about once a year.
about once a day.
5. Neutron degeneracy
causes supernova explosions.
prevents the collapse of a white dwarf in a supernova.
leads to the formation of heavy metals like gold in supernovae.
stops collapse in a supernova.
6. An emission nebula is
red as it scatters the light from stars.
blue as it scatters the light from stars.
usually dark as it blocks the light from stars.
internally heated by 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 low density region containing hydrogen.
collapse of a high density region of gas.
8. Main sequence stars
are hydro-dynamically unstable.
are continuously contracting.
are continuously cooling.
stay approximately constant in size.
9. If 4 hydrogen nuclei fuse to form a helium nucleus
energy is absorbed.
the mass is conserved.
the mass drops by about 1 %.
the mass-energy increases 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.
it takes a few hours for light to travel from the core to the photosphere.
energy from fusion appears almost instantly at the photosphere.
light takes 2 to 3 seconds to travel from the core to the photosphere.
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