Chapter 11

What is the primary source of information needed to make stellar measurements? a. cosmic rays b. magnetic fields c. electric charge d. light e. atomic structure

True/False: A standard candle is useful for determining distance but not orbital velocity.

What is the definition of a standard candle? a. an object whose luminosity remains the same throughout its life b. an object whose age is known c. an object whose luminosity is equal to the Sun's d. an object whose luminosity is known e. a star within a cluster

Wien's law tells us that a. wavelength is related to frequency. b. blackbodies are essentially black. c. blackbodies radiate light at all wavelengths and absorb light at all wavelengths. d. temperature is regulated by spectral class and luminosity. e. in blackbodies, temperature and peak radiation wavelength (color) are related.

Two neighboring stars are seen with significant differences in composition. What is not likely to be true of these stars? a. They were born together. b. They are of different spectral types. c. One or both migrated from other locations. d. They are of different ages. e. They are from different generations of stars.

Which definition of proper motion is correct? a. motion due to the rotation of the galaxy b. observed motion of an object against very distant background objects c. motion that does not follow Newton's laws d. motion around the Sun e. motion due to the stretching of space-time

Astronomers must take many factors into account when modeling individual stars. Which of the following is not a factor? a. limitations of computers b. star mass c. star composition d. distance between stars e. stellar energy generation

Choose the correct list of spectral classes in ascending order of temperature. a. \(\mathrm{O} \mathrm{B}\) A \(\mathrm{FG}\) KM b. \(A B F G K M O\) c. \(\mathrm{M} \mathrm{K} \mathrm{G} \mathrm{F} \mathrm{A} \mathrm{B}\) O \(\mathrm{d} . \mathrm{O} \mathrm{A} \mathrm{G} \mathrm{M} \mathrm{B} \mathrm{F} \mathrm{K}\) e. \(M G A O K F B\)

A star on the upper right of the HR diagram is a. a giant. b. cool and small. c. hot and small. d. a dwarf. e. hot and large.

A star's position on the main sequence does not tell us a. its chemical composition. b. its mass. c. its luminosity. d. its temperature. e. its exact age.

The more massive the star, a. the longer it remains on the HR diagram. b. the lower it is on the HR diagram. c. the longer it stays on the main sequence. d. the hotter it is as a main-sequence star. e. the higher its apparent magnitude is.

Which of the following is true for low-mass stars? Choose all that apply. a. They may be spectral class \(\mathrm{O}\). b. They are not found on the main sequence. c. They are hotter than intermediate-mass stars. d. Their mass must be at least 8 percent of the mass of the Sun. e. Their life expectancies are in the billions or trillions of years.

What does the HR diagram of a cluster not tell astronomers? a. the age of the cluster b. the highest mass of cluster stars still on the main sequence c. the rotation of the cluster d. which stars are similar to the Sun in size and mass e. the highest luminosity among the remaining stars on the main sequence

Binary stars detectable by direct observation of the proper motion are called a. astrometric binaries. b. spectroscopic binaries. c. eclipsing binaries. d. visual binaries. e. a symbiotic binary system.

Which of the following is true of stars in binary systems? a. They may evolve without interfering with each other. b. They will eventually merge into a single star. c. They are rare. d. They may not be gravitationally related. e. They almost always have identical masses.

Choose the statement about variable stars that is not true. a. They have unstable outer layers. b. They change temperature. c. They change luminosity. d. They may be useful as standard candles. e. Their luminosity may be continually increasing.

How would parallax measurements of stars made from Jupiter differ from those made from Earth? a. The stars would appear to be at greater distances. b. The stars would appear to be closer. c. Parallax for a given star would be greater. d. Parallax for a given star would be less. e. All stars would appear to have greater radii.

True/False: A star with a mass 10 times that of the Sun would have a life span one-tenth as long.

Define the following terms: parallax, energy transport, luminosity, bydrostatic equilibrium, correlation.

What is a standard candle, and how is it used to determine distance?

What information in a star's spectrum indicates the star's surface temperature?

What information in a star's spectrum indicates its chemical composition?

Doppler shift can provide information on which characteristics of a star's motion through space?

A star is observed with a repeating pattern of redshifted spectral lines followed by blueshifted lines. What does this pattern tell you about the star?

Explain what the main sequence on the HR diagram indicates. What is the difference between a star that falls higher and to the left on the main sequence and a star that falls lower and to the right?

What is going on in the core of a star that is on the main sequence?

What is meant by cluster turnoff mass?

Name and describe three categories of binary stars.

You observe that a star's wavelength of maximum intensity is a very reddish \(770 \mathrm{nm}\). What temperature is the surface of that star, in kelvins, and how does it compare to the Sun?

A star has a mass of \(55 M_{\text {sun }} .\) What is the ratio of its expected lifetime to that of the Sun?

What is the distance, in parsecs, to a star whose parallax is \(2^{\prime \prime}\) ? Compare this distance with the closest known star. Why would discovering a star with this parallax be a surprise?

How far from Earth, in parsecs, is a star whose parallax is \(0.43^{\prime \prime} ?\)

A star is known to be 25 pc from Earth. What is its parallax? Would such a change in position be easily visible to the human eye?