The total number of galaxies in our observable universe is
A) about ten million
B) about a hundred billion
C) infinite
D) a few trillion
B
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Which of the following are typically found in the halo of our galaxy?
A) open star clusters B) stars of spectral types O and B C) globular star clusters D) cold gas and dust E) all of the above
Algol consists of a 3.7 MSun main-sequence star and a 0.8 MSun subgiant. Why does this seem surprising, at least at first?
A) A star with a mass of 3.7 MSun is too big to be a main sequence star. B) The two stars should be the same age, so we'd expect the subgiant to be more massive than the main-sequence star. C) It doesn't make sense to find a subgiant in a binary star system. D) The two stars in a binary system should both be at the same stage of life; that is, they should either both be main sequence stars or both be subgiants.
An airplane flying faster than the speed of sound of 340 m/s produces a shock wave that makes an angle of 50° with the direction the plane is flying. What is the speed of the plane?
A) 490 m/s B) 530 m/s C) 390 m/s D) 440 m/s E) 405 m/s
When a hunter fires a rifle, the hunter feels a force against her shoulder. Explain why
What will be an ideal response?