ASTRONOMY

Helium is very common in the Sun and calcium is rare. Why are helium lines weak and calcium lines strong in the visible spectrum of the Sun?
How would a star regain its state of equilibrium if the energy generation rate of a star were to become slightly smaller than its equilibrium?

Why do metal poor stars have the most elliptical orbits? From where do they obtain their metals?

why do so few visual binary star systems been fully analyzed to reveal individual masses?

When we look at light curve for an eclipsing binary system with total eclipses, how can we tell which star is hotter?

Why do extremely cool stars look fainter than we might expect from their luminosities and distances?

Why can't we use solar type stars as spiral tracers? what type of stars make good spiral tracers? why? What characteristics do they have to perform this function?

in some old, dense stars, a few blue stars, known as blue stragglers are seen. why are blue stars unexpected in such clusters? If stars that stick together mix their material thoroughly when they collide, how might you explain such blue stars?

Supposed you jumped into a black hole feet first? what would happen to you? what would your friends who stayed behind actually see?

Why are there different types of galaxies?

what is the eventual fate of the milky way galaxy? what process will lead to this fate? can anything change this?

What are the processes that are responsible for the formation of an elliptical galaxy in comparison to a spiral galaxy? Why cannot galaxies evolve from elliptical to spiral and from spiral to elliptical?

Is it surprising that a pulsar is not seen in every supernova remnant? why?

How do we form the conclusion that quasars are so vary far away? 

How many times longer does a .50 - M star fuse hydrogen at it's core than does a 1.5 - M star?

How many 0.75 - M main sequence stars would it take to equal the luminosity of one 15 - M star?