Chapter 17 & 18

The astronomer who, at the turn of the century, measured the spectra of hundreds of thousands of stars, leaving a catalog that astronomers used for the rest of the century, was:

Annie Cannon

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

Hertzsprung

The first astronomer who did photometry in a systematic way (even though he did not have a telescope) was

Hipparchus

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

Keplar''s Third Law of Motion

After a lot of work, a group of graduate students has finally measured the wavelengths of many dozens of lines in the spectrum of a distant star. If a number of the lines come from molecules such as titanium oxide, the star is likely to be which spectral type:

M

Which of the following types of star is the coolest (has the lowest surface temperature)?

M

Which of the following is a failed star , an object with too little mass to qualify as a star?

a brown dwarf

Which of the following has the smallest mass?

a planet

A star moving toward the Sun will show:

a shift in the spectral lines toward the blue end (as compared to the laboratory positions of these lines)

The most common kinds of stars in the Galaxy

are red dwarves

Two stars that are physically associated (rotate around each other in space) are called

binary stars

Which color star is likely to be the hottest?

blue-violet

One key difference that astronomers use to distinguish between brown dwarfs and high-mass planets is that:

brown dwarfs are able to do a little bit of occasional fusion in their cores, while planets can't

For what type of star can astronomers measure the diameter with relative ease?

eclipsing binary stars

When an astronomer rambles on and on about the luminosity of a star she is studying, she is talking about:

how much energy the star gives off each second

Studies of the spectra of stars have revealed that the element that makes up the majority of the stars (75% by mass) is

hydrogen

Which of the following can astronomers learn from studying the spectrum of a star?

its surface temperature; its motion toward or away from us; whether it is rotating slow or fast; whether it is a star the size of the Sun or a giant star all of these can be learned from studying the spectrum

An exhausted-looking astronomer comes off the mountain where her observatory is located and tells you she has been doing photometry all night. What has she been up to?

measuring the brightness of different stars

Two stars have the same luminosity, but star B is three times farther away from us than star A. Compared to star A, star B will look

nine times fainter

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

on the right side of the diagram with dwarves near the bottom and giants near the top

Astronomers identify the main sequence on the H-R diagram with what activity in the course of a star's life?

peacefully fusing hydrogen into helium in their cores

Astronomers call the motion of a star across the sky (perpendicular to our line of sight) its

proper motion

A white dwarf, compared to a main sequence star with the same mass, would always be:

smaller in diameter

Two stars have the exact same luminosity, but star Y is four times dimmer looking that star X. This means that

star Y is twice as far away as star X

Why can astronomers not measure the diameters of stars directly?

stars are so far away, their diameters all look like pinpoints

An astronomer whose secret hobby is riding merry-go-rounds has dedicated his career to finding the stars that rotate the most rapidly. But the stars are all very far away, so none of them can be seen to spin even when he looks through the largest telescopes. How then can he identify the stars that rotate rapidly?

stars that rotate have much wider lines in their spectra than stars that do not

Stars that appear in different zones on the main sequence of the H-R diagram differ from each other mainly by having different:

starting masses

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

surface temperature/ spectal class

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

the main sequence