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Friday, March 22, 13
HW 6-7: (196) RQ 16-18; Supp 14-16
RQ16: Why is it difficult to find out how common the most
luminous stars are? The least luminous?
The most luminous stars are easy to over-count. They stand out
in the sky because they are so bright, but really they are very
rare.
The least luminous stars are easy to under-count. They are hard
to see because they are so dim, but really they are very common.
You have to be careful if you want an honest sample.
RQ17 What is the most common type of star?
Red Dwarfs are the most common type of star.
Friday, March 22, 13
HW 6-7: (196) RQ 16-18; Supp 14-16
RQ18 If you look only at the brightest stars in the night sky, what
type of star are you likely to be observing? Why?
You are probably looking at one of these:
• a Supergiant,
• a “Blue Giant” (upper-left main sequence)
• a Giant
These stars are so exceedingly bright that they
appear as the brightest stars in the sky, even
though they are actually quite rare and usually
fairly far away.
Friday, March 22, 13
HW 6-7: (196) RQ 16-18; Supp 14-16
SQ14 Look at the bottom right figure on page 193 and compare it
to Figure 9-16 on page 183. What is the luminosity class of red
dwarf stars?
Red dwarf
stars are part
of the main
sequence
and
therefore
they are
Luminosity
Class V.
Friday, March 22, 13
HW 6-7: (196) RQ 16-18; Supp 14-16
SQ15 Look at figure 2a on page 193. It says that “O and B stars,
supergiants and giants are so rare their bars are not visible on this
graph.” But when I look at
stars in the sky, most of the
stars that I first look at are
one of these supposedly rare
stars. How do I reconcile
these seemingly
contradictory pieces of data?
They are rare but so
exceedingly bright that, even
though they tend to be very
far away, they appear much
brighter than the abundant
and nearby red dwarfs.
Friday, March 22, 13
HW 6-7: (196) RQ 16-18; Supp 14-16
SQ16 Look at figure 2a on page 193. It says that “Red dwarfs
and white dwarfs are the most common kinds of stars.” But when
I look at stars in the sky, none
of the stars I can see are red
dwarfs or white dwarfs. How
do I reconcile these
seemingly contradictory
pieces of data?
Red dwarfs and white
dwarfs are so exceedingly
dim that, even though many
are quite close to us, they
can only be seen with a
telescope.
Friday, March 22, 13