Use the information on Page 181 of Croswell to calculate, approximately, the density of stars in the giant sphere surrounding the Sun. Express your answer both in stars/l.y.3 and stars/pc3. From this number estimate the average distance between stars in the Solar Neighborhood. [Hint: to do this it might help to imagine that every star is at the center of a cube in space with the same distance to the next star]. How does the average distance between stars compare to the distance between the Sun and the Alpha Centauri system?
Orbital periods of visual binary stars
Refer to your midterm to answer this question: Suppose a new planet was found in the Trappist-1 system in a 1 AU orbit. What would be the period of this planet?
SECOND: Check a reference and make some adjustments to your graph if needed. (OK to draw a new graph)
THIRD: Suppose someone says to you "Yellow stars are intrinsically brighter than red stars." Use your graph (and Wein's Law) to argue for or against this opinion. Draw one or two lines on the graph to make your point.
Assume, instead, that the Sun is powered by nuclear reactions, and that 10% of the Sun's mass is available. If the Sun's nuclear reactions have an efficiency of converting mass to energy of about 1%, then estimate the lifetime of the Sun, in years, clearly stating in words the reasoning behind your approach.
Is this consistant with the present age of the Sun?