•Question 6 (1 point) If the O6 V star in
the Orion Nebula is magnitude 5.4,
how far away is the nebula? (Hint: Use spectroscopic parallax and look at plots of the HR diagram showing absolute
magnitudes on one axis.)
Choose the best answer below.
a.10 parsecs. b.120 parsecs.
c.300 parsecs d.1600 parsecs e.10000 parsecs
•an
HR diagram, estimate M = -6 or so.
So d = 10 (m-M+5)/5 is roughly 10^3+ and we are done since only one answer is
between 1000 and 10000. –
I’ll work
on the board.
•
• Question
7 (1 point) In my novel Star Dragon, the characters fly to a distant binary star system, SS Cygni. SS Cygni is a
type of binary system in
which a white dwarf star is consuming a main sequence K star. If the average separation of the stars is 1.5 million km,
and the orbital period is 6.6
hours, what is the combined mass of the stars? (Hint: it will help to immediately convert 6.6 hours to years and 1.5
million km to AU.)
a.0.6 solar masses. b.6 solar
masses. c.1.8 solar masses. d.18 solar masses e.1.3 solar masses.
•Either
solve from basic considerations (mass of KV star and white dwarf) or from Kepler’s Law: Mass = a^3/P^2, with unit conversions
to AUs and
years. Get 1.8 solar masses. I’ll work on the board.
•