Star clusters are important to our study of stars because
a. all stars formed in star clusters.
b. the Sun was once a member of a globular cluster.
c. they give us a method to test the our theories and models of stellar evolution.
d. they are the only objects that contain Cepheid variables.
e. All of the other choices are correct.
c
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What actually "controls" Saturn's rings?
a. Saturn's magnetic field b. Saturn's tidal heating c. Saturn's moons d. Saturn's rapid rotation e. Saturn's metallic core
The oxygen molecules and the nitrogen molecules at any one place in our atmosphere are at the same temperature. How do the root-mean-square speeds of the two molecules compare?
A) same B) N2 > O2 C) O2 > N2
The Doppler technique can be used to measure the eccentricity of a planet's orbit by
A) measuring the amount by which the starlight is reduced when the planet transits. B) measuring the asymmetries in the velocity curve. C) measuring the time it takes for the star's line-of-sight velocity to cycle from peak to peak, and using Newton's version of Kepler's Third law. D) measuring the speed at which the star orbits the mutual center-of-mass of the star and planet, and using Newton's theory of gravity.
Which of the following is the most basic definition of a greenhouse gas?
A) a gas that absorbs infrared light B) a gas that makes a planet much hotter than it would be otherwise, even in small amounts C) a gas that keeps warms air from rising, and therefore warms the surface D) a gas that reflects a lot of sunlight