Lesson 5 Multiple Choice Flashcards
(31 cards)
What celestial objects are used as spiral-arm tracers?
O and B type stars
H II regions
Population I cepheid variable stars
The emission from jets is thought to be in synchrotron in origin. This requires that
there be magnetic fields in the jets
high-speed electrons must be present
A major assumption made when judging distances to galaxies by the “smallness means farness” criterion is that
all galaxies of the same type are about the same size
List the galactic regions in correct order of increasing metal content of stars found in each region
halo, nuclear bulge, disk, spiral arms
What is NOT violent activity in the Milky Way and other galaxies?
The nuclei of galaxies spin very rapidly
Collisions between galaxies… (frequency of occurrence and what they cause)
cause a burst of star formation in the galaxies
occur once in a while, but the stars in the galaxies almost never collide
A problem astronomers face when figuring out the structure of the galaxy is that…
we can only see a small region of the galaxy with optical telescopes because of interstellar dust
The radio emission from radio galaxies typically comes from what regions of the galaxy?
two large regions beyond and on opposite sides of the galaxy
Which galaxy type consists of mostly young, Population I stars?
irregular galaxies
The main advantage a radio astronomer has over an optical astronomer when determining the Galaxy’s spiral arm structure is that
radio waves penetrate interstellar dust more readily than light
Which galaxy type contains the lowest percentage of gas and dust?
Elliptical galaxies
Stars in open clusters tend to be ______ than stars in globular star clusters?
younger and bluer
The sun’s orbit around the Galaxy is….
nearly a circular orbit lying the the plane of the Galaxy’s disk (Population I star)
One possible energy source for quasars may be
electron collisions
One characteristic of the radio emission from active galaxies that distinguishes them from normal galaxies is
extreme brightness in one or more areas of the electromagnetic spectrum
Megaparsecs do NOT tell…
distance
Which type of galaxy has the greatest range in diameter, mass, and luminosity?
elliptical galaxies
In a typical spiral galaxy, stars in the disk have what kind of orbits?
nearly circular
To evaluate Hubble’s constant for distant galaxies, what quantities must you measure?
Redshift and distance
The distances to most distant clusters of galaxies are determined by
using the value of Hubble’s constant and the measured redshifts
Observations that tell us about the Milky Way disk are measured at what wavelengths?
Radio
Objects you would NOT find in a spiral arm are
Globular clusters
Quasars are galaxies that are
early in their lives
Possible errors in estimating distances to galaxies using the Hubble relation are…
uncertainties in the value of the H
using a straight-line extrapolation of the Hubble relation
inaccurate distances to galaxies used to evaluate Hubble’s constant
