Exploring the Cosmos - Degree Exam 2012 - Life and Death of Stars (Part 2)
1. Synchrotron radiation is
a pulsed source of radio interference.
caused by radioactive decay in a Type-II supernova.
a feature of the heat from a red giant.
a feature of radiation from a neutron star.
2. Supermassive black holes are
only found in distant galaxies.
found at the centre of nearly every galaxy.
usually violent sources of energy that can destroy galaxies.
thought to be very rare in the universe.
3. The best evidence of black holes comes from
signs of the effect of strong gravitational fields.
evidence of their extreme magnetic fields.
x-ray sources which are always black holes.
direct observation of black areas in space.
4. Pulsars typically spin
about once a day.
about once a year.
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.
red as it scatters the light from stars.
internally heated by stars.
7. A protostar forms due to
changes in the early stage of a main sequence star.
collapse of a low density region containing hydrogen.
collapse of a high density region of gas.
gravitational attraction due to a nearby star.
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
the mass-energy increases by about 1 %.
energy is absorbed.
the mass drops by about 1 %.
the mass is conserved.
10. Given that the radius of the Sun is about 700,000 km
energy from fusion appears almost instantly at the photosphere.
light takes 2 to 3 seconds to travel from the core to 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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