1.Who first calibrated the Cepheid variable stars for use in : 1777256
1.Who first calibrated the Cepheid variable stars for use in determining distance?
2.Which of the following is not a characteristic of the stars of the disk component of our galaxy?
B.randomly inclined orbits
C.higher metal abundance
E.star formation regions
3.A group of 10 to 100 stars that formed at the same time but are so widely scattered in space their mutual gravity cannot hold them together is called
A.a globular cluster.
B.an open cluster.
D.a spherical component
E.an accretion disk.
4.Our galaxy is suspected to be surrounded by a galactic halo or corona because the disk of the galaxy
A.rotates faster than expected in its outer region.
B.rotates more slowly than expected in its outer region.
C.is only visible during a total eclipse of our sun
D.is surrounded above, below and well beyond by the brightly glowing corona.
5.Younger stars have more heavy elements because
A.old stars destroy heavy elements as they age.
B.young stars burn their nuclear fuels faster.
C.the heavy elements were made in previous generations of stars.
D.heavy elements haven't had time to settle to the core of these younger stars.
E.all of these
6.The first stars to form in our galaxy
A.had circular orbits.
B.had highly elongated elliptical orbits.
C.were population I stars.
D.all had orbits in the same plane.
E.formed the galactic clusters we see today.
7.Good tracers of the spiral tracers are all
moving with large radial velocities.
A.I & III
B.I & IV
C.II & III
D.II & IV
E.I, III, & IV
8.Radio maps of our galaxy show spiral arms because
A.the arms have larger Doppler shifts.
B.the gas in the spiral arms is very hot.
C.the dust in spiral arms is denser.
D.the gas in spiral arms is denser.
E.the stars in the spiral arms emit most of their energy at radio wavelengths.
9.If the spiral density wave were the only thing producing spiral arms, it would be expected that
A.all spiral arms would be gas and dust free.
B.all galaxies would have only two smooth spiral arms.
C.the Milky Way would show and irregular pattern of short arms
D.the Milky Way wouldn't have any spiral arms.
E.the halo component of the Milky Way would show spiral arms as well.
10.____ galaxies have a great many short spiral segments branching from the spiral arms.