Mastering Astronomy Timed quiz 4 Flashcards
Approximately, what basic composition are all stars born with?
90 percent hydrogen, 10 percent helium, no more than 1 percent heavier elements one-quarter hydrogen, three-quarters helium, no more than 2 percent heavier elements three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements 98 percent hydrogen, 2 percent helium half hydrogen, half helium, no more than 2 percent heavier elements
three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements
Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?
mass they are formed with time they are formed location where they are formed color they are formed with luminosity they are formed with
mass they were formed with
What are the standard units for luminosity?
joules Newtons kilograms watts per second watts
watts
What are the standard units for apparent brightness?
Newtons watts watts per square meter joules watts per second
watts per square meter
Which of the following correctly states the luminosity-distance formula?
distance = apparent brightness = luminosity × 4π × (distance)2 luminosity = apparent brightness =
apparent brightness = luminosity / 4pie x (distance)^2
Why do astronomers often measure the visible-light apparent brightness instead of the total apparent brightness of a star?
Astronomers are lazy. All stars put out most of their light in the visible range of the spectrum. They are identical for most stars. Most stars do not put out light in other ranges of the spectrum. In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths.
In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths.
The most distant stars we can measure stellar parallax for are approximately
5,000 parsecs away. halfway across the Milky Way Galaxy. 50 parsecs away. 500 parsecs away. in the Andromeda Galaxy.
50 parsecs away.
Which of the following statements about apparent and absolute magnitudes is true?
A star with apparent magnitude 1 is brighter than one with apparent magnitude 2. A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth. The absolute magnitude of a star is another measure of its luminosity. The magnitude system that we use now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared. All of the above are true.
all of the above are true
The spectral sequence sorts stars according to
surface temperature. mass. radius. core temperature. luminosity.
surface temperature
The spectral sequence in order of decreasing temperature is
OBAFGKM. BAGFKMO. OBAGFKM. ABFGKMO. OFBAGKM.
OBAFGKM
Why is the spectral sequence of stars not alphabetical?
Because there is still uncertainty over what generates the energy in stellar cores. The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered. Because it refers to stellar masses and these were difficult to measure accurately. The letters refer to the initials of the original discovers. They were chosen to fit a mnemonic.
The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered.
Which of the following statements about spectral types of stars is true?
The spectral type of a star can be used to determine its color. A star with spectral type F2 is hotter than a star with spectral type F3. A star with spectral type A is cooler than a star with spectral type B. The spectral type of a star can be used to determine its surface temperature. All of the above are true.
all of the above are true
Which of the following persons reorganized the spectral classification scheme into the one we use today and personally classified over 400,000 stars?
Annie Jump Cannon Williamina Fleming Henry Draper Cecilia Payne-Gaposchkin Edward Pickering
Annie Jump Cannon
On a Hertzsprung-Russell diagram, where would we find stars that are cool and luminous?
upper right lower right upper left lower left
Upper right
On a Hertzsprung-Russell diagram, where would we find stars that have the largest radii?
upper right lower right upper left lower left
Upper right
On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have the greatest mass?
upper right lower right upper left lower left
Upper left
On a Hertzsprung-Russell diagram, where would we find red giant stars?
upper right lower right upper left lower left
Upper right
You observe a star in the disk of the Milky Way, and you want to plot the star on an H-R diagram. You will need to determine all of the following, except the
spectral type of the star. apparent brightness of the star in our sky. distance to the star. rotation rate of the star.
Rotation rate of the star
A star of spectral type G lives approximately how long on the main sequence?
100 million years 10,000 years 10 billion years 1 million years 1,000 years
10 billion years
Which of the following luminosity classes refers to stars on the main sequence?
II V III I IV
V
Cluster ages can be determined from
main sequence turnoff. main sequence fitting. visual binaries. pulsating variable stars. spectroscopic binaries.
main sequence turnoff.
