Exploring the Cosmos - Degree Exam 2012 - Life and Death of Stars (Part 2)
1. Synchrotron radiation is
caused by radioactive decay in a Type-II supernova.
a feature of radiation from a neutron star.
a feature of the heat from a red giant.
a pulsed source of radio interference.
2. Supermassive black holes are
thought to be very rare in the universe.
found at the centre of nearly every galaxy.
only found in distant galaxies.
usually violent sources of energy that can destroy galaxies.
3. The best evidence of black holes comes from
x-ray sources which are always black holes.
direct observation of black areas in space.
signs of the effect of strong gravitational fields.
evidence of their extreme magnetic fields.
4. Pulsars typically spin
about once a day.
many times per second.
about once a year.
many thousands of times per second.
5. Neutron degeneracy
stops collapse in a supernova.
leads to the formation of heavy metals like gold in supernovae.
prevents the collapse of a white dwarf in a supernova.
causes supernova explosions.
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.
collapse of a high density region of gas.
collapse of a low density region containing hydrogen.
gravitational attraction due to a nearby star.
8. Main sequence stars
are hydro-dynamically unstable.
stay approximately constant in size.
are continuously contracting.
are continuously cooling.
9. If 4 hydrogen nuclei fuse to form a helium nucleus
the mass drops by about 1 %.
the mass is conserved.
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.
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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