W9

What was the first evidence that gravity outside our solar system worked the same way as it does inside?

Herschel measured the two stars that make up the Castor system moved around each other

Who was the astronomer who is the "H" in H-R diagram?

Hertzsprung

Which law do astronomers use to determine the masses of the stars in a spectroscopic binary system?

Kepler's third law

Which of the following has the smallest mass?

a planet

One of your good friends who is on a diet asks you to point out the stars with the smallest mass on an H-R diagram that you are studying. Where are you sure to find the stars with the lowest mass on any H-R diagram?

among the stars at the bottom right of the main sequence

A star that is quite cool and has a very small radius compared to most stars is called

an M-type star

Two stars that are physically associated (move together through space) are called

binary stars

Stars that do not have what it takes to succeed as a star (i.e. do not have enough mass to fuse hydrogen into helium at their centers) are called:

brown dwarfs

Stars on the main sequence obey a mass-luminosity relation. According to this relation,

luminosity is proportional to mass to the fourth power (luminosity increases strongly with mass)

Ninety percent of all stars (if plotted on an H-R diagram) would fall into a region astronomers call:

main sequence

A team of astronomers discovers one of the most massive stars ever found. If this star is just settling down in that stage of its life where it will be peacefully converting hydrogen to helium in its core, where will we find it on the H-R diagram?

near the very top of the main sequence, in the upper left

Where on the H-R Diagram would we find stars that look red when seen through a telescope?

only on the right side of the diagram and never on the left

Why can astronomers not measure the diameters of stars directly?

stars are so far away, we cannot resolve (distinguish) their diameters

An H-R Diagram plots the luminosity of stars against their:

surface temperature

I am measuring the spectrum of the stars in a spectroscopic binary system. When one of the stars is moving toward the Earth in its orbit, we observe

that the lines in its spectrum show a blue-shift