The most common type of star is a(n) ____
a. white dwarf
b. lower-main-sequence star
c. upper-main-sequence star
d. giant
e. supergiant
b
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Discrete spectral lines are observed when excitation occurs in a
A) solid. B) liquid. C) gas. D) superconductor. E) all of the above
There is a direct correlation between the absorption and emission spectra of a particular gas
a. True b. False Indicate whether the statement is true or false
Imagine that you are trying to stop neutrinos with a lead shield. How thick would you need to make this shield to ensure that it can stop a neutrino?
A) about 700,000 kilometers (the radius of the Sun) B) about 150 million kilometers (the size of an astronomical unit) C) about 14 billion light years (the size of the observable universe) D) about one light year E) about one meter
Which of the following is true about the ages and masses of spiral and elliptical galaxies?
A) Ellipticals are all older and more massive than spirals. B) Spirals are older, and much more massive than ellipticals. C) Both types are about the same age, but spirals vary less in mass. D) Spirals are younger and much more massive than any elliptical. E) Ellipticals are older, and show a far wider range of masses than do spirals.