01. |
(a) Find the average density of a 1-M⊙
white dwarf having the same diameter as the Earth. (b) What speed is
required to eject gas from the white dwarf's surface? (This is also the
speed with which interstellar gas falling from a great distance would
strike the star's surface.)
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02. |
(a) What kinds of stars would you monitor if you wished to observe a
supernova explosion from its very beginning? (b) Examine Appendices
4 and
5,
which list the nearest and
brightest stars, respectively. Which, if any, of these stars are possible
supernova candidates? Explain.
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03. |
Suppose that the red-supergiant star Betelgeuse, which lies some 1400
light-years from the Earth, becomes a Type II supernova. (a) At the height
of the outburst, how bright would it appear in the sky? Give your answer
as a fraction of the brightness of the Sun (b⊙).
(b) How would it compare with the brightness of Venus (about 10-9
b⊙)?
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04. |
In July 1997, a supernova named SN 1997cw exploded in the galaxy NGC
105 in the constellation Cetus (the Whale). It reached an apparent
magnitude of +16.5 at maximum brilliance, and its spectrum showed an
absorption line of ionized silicon. Use this information to find the
distance to NGC 105. (Hints: Inspect
the light curves of SNe
to find the absolute magnitudes
of typical supernovae at peak brightness.)
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