•Question 4 (1 point) Which of the
following is *not* true?
You will want to refer to Appendix A -- the information is available in tables A-7 and A-9.
a.Aside from the
sun, Sirius (the "dog star") is the brightest star in our sky. b. Aside from the
sun, the nearest
star is Proxima Centauri. c. Aldebaran, the brightest star in Taurus, is a relatively cool K5
star. d. Most of the nearby stars are type A or B
stars. e. Vega, a future North Star, is one of the six
brightest stars in
the sky, about the same brightness (magnitude) as Capella.
• Question
5 (1 point) If a star cooled by a factor of 2 but expanded by a factor of 10 the ratio of its new luminosity to its old luminosity would be
a.0.125 b.1.412 c.6.250 d.64.0 e.100.0
•L = 4πR2σT4 so then L (new) = (0.5)4(10)2 or 100/16
•L = 6.25 solar luminosities