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
thought to be very rare in the universe.
usually violent sources of energy that can destroy galaxies.
only found in distant galaxies.
found at the centre of nearly every galaxy.
3. The best evidence of black holes comes from
direct observation of black areas in space.
signs of the effect of strong gravitational fields.
evidence of their extreme magnetic fields.
x-ray sources which are always black holes.
4. Pulsars typically spin
about once a year.
many times per second.
many thousands of times per second.
about once a day.
5. Neutron degeneracy
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.
causes supernova explosions.
6. An emission nebula is
internally heated by stars.
blue as it scatters the light from stars.
red as it scatters the light from stars.
usually dark as it blocks 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
stay approximately constant in size.
are hydro-dynamically unstable.
are continuously contracting.
are continuously cooling.
9. If 4 hydrogen nuclei fuse to form a helium nucleus
the mass-energy increases by about 1 %.
the mass is conserved.
the mass drops by about 1 %.
energy is absorbed.
10. Given that the radius of the Sun is about 700,000 km
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.
energy from fusion appears almost instantly at the photosphere.
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