Chapter 11 Flashcards
Based on the nature of the Milky Way Galaxy, select all of the correct statements from the following list.
The sun is 75,000 ly from the center of the galaxy.
Modern observations suggest a disk shape for the galaxy.
The Herschels’ star counts gave us our modern perception of the sun’s place in the galaxy.
There are over 100 billion stars in our galaxy.
The size and shape of our galaxy is obvious from observing the Milky Way.
Shapley determined that the sun is not at the center of the galaxy.
Rotation curves show that much of the galaxy’s mass is unseen.
Modern observations suggest a disk shape for the galaxy.
There are over 100 billion stars in our galaxy.
Shapley determined that the sun is not at the center of the galaxy.
Rotation curves show that much of the galaxy’s mass is unseen.
Based on the origin and evolution of the Milky Way, select all of the correct statements from the following list.
The current theory of galactic formation states that the galactic disk and halo formed together.
Supernovae spread heavy elements throughout the galaxy.
The disk of the galaxy appears to be older than the halo.
The galactic halo is filled with metal-poor stars.
Population I stars formed in the galaxy earlier than Population II stars.
The first stars formed in the galaxy were metal-rich.
Our galaxy may have merged with others in the past.
Supernovae spread heavy elements throughout the galaxy.
The galactic halo is filled with metal-poor stars.
Our galaxy may have merged with others in the past.
With respect to spiral arms, select all of the correct statements from the following list.
Radio telescopes can see through interstellar gas and dust.
Massive stars are found in spiral arms.
The spiral density wave theory does not seem to agree with observations.
Spiral arms are believed to be places of star formation.
The entire galaxy can be mapped by examining the locations of bright O and B type stars.
Spiral arms are stationary; they do not move around the galactic disk.
The formation of massive stars in spiral arms is believed to give rise to further star formation.
Radio telescopes can see through interstellar gas and dust.
Massive stars are found in spiral arms.
Spiral arms are believed to be places of star formation.
The formation of massive stars in spiral arms is believed to give rise to further star formation.
With respect to the galactic nucleus, select all of the correct statements from the following list.
The galactic nucleus is free of dust.
The galactic nucleus emits infrared radiation.
The nucleus of the galaxy cannot be observed in visible light.
Near the very center of our galaxy there are no stars, just hot gas.
Sagittarius A* is a massive X-ray source.
The very center of our galaxy may be a supermassive black hole.
The nucleus of the galaxy has many stars “crowded” together.
The galactic nucleus emits infrared radiation.
The nucleus of the galaxy cannot be observed in visible light.
The very center of our galaxy may be a supermassive black hole.
The nucleus of the galaxy has many stars “crowded” together.
Our sun is located in the _______ of our galaxy, whereas globular clusters are found primarily in the _______.
disk; halo
Who discovered that when viewed through a telescope, the Milky Way is resolved into thousands of individual stars?
Galileo Galilei
What did the Herschels find when they counted stars in 683 regions around the Milky Way?
They saw different numbers of stars in each direction.
What main conclusion did the Herschels draw from their star counts?
The Milky Way is a disk of stars with the sun near the center.
This graph shows the period-luminosity relation for Cepheid variables. If the period of a type I Cepheid is 10 days, what is its absolute magnitude?
–4.3
How are star clusters distributed in the sky?
Open clusters lie along the Milky Way and half of the globular clusters are in or near the constellation Sagittarius.
Estimate the average apparent magnitude of Delta Cephei from the light curve shown here. Combine this apparent magnitude with the absolute magnitude read directly from the graph of the period-luminosity relation for type I Cepheids also shown here. From these two magnitudes, the distance to Delta Cephei is which of the following?
300 pc
What fundamental principle did Shapley use to calibrate the period-luminosity relationship for Cepheid variable stars?
Objects with large proper motion tend to be closer than objects with small proper motion.
What must be measured to determine distance by the Cepheid variable star method?
What must be measured to determine distance by the Cepheid variable star method?
the apparent magnitude and the period of pulsation of the variable star
With the 100-inch telescope, Harlow Shapley could not resolve variable stars in the more distant globular clusters of the Milky Way. What basic assumption did Shapley make about the far-away globular clusters that allowed their distances to be found?
Far-away globular clusters have the same average size as nearby globular clusters.
What main conclusion did Shapley draw from his measurements of the distances to the globular clusters?
The sun is far from the center of the Milky Way.
What is the approximate diameter of the disk component of the Milky Way Galaxy?
80,000 ly
Where are the youngest stars in the Milky Way Galaxy located?
in the flattened disk
Which of these two figures illustrates the orbits of population II stars?
figure b
What measurements are needed to determine the entire mass of the Milky Way Galaxy?
the rotational velocity of a star near the Galaxy’s outer edge and the distance to a star near the Galaxy’s outer edge
Why do astronomers propose that the Milky Way Galaxy contains a lot of dark matter?
The Galaxy’s rotation curve flattens out at great distances.
This globular cluster map (black border) shows the sun far from the center of the galaxy using the distances determined by Shapley in 1918 (units are kiloparsecs). The rotation curve graph on the right shows the sun’s location with corrections made to Shapley’s original measurement. According to these two diagrams, how big was Shapley’s error?
The corrected distance is about half of that of Shapley’s original measurement.
How are population II stars different than the sun?
Population II stars are lower in metals than Population I stars.
What does the observed heavy element abundance tell us about a star?
A low percentage of metals indicates that a star formed long ago.
Which of the following are problems facing the traditional hypothesis of the formation of the Milky Way?
All of these choices are correct.
