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