In the context of a planetary atmosphere, what is a bar?
A) the surface pressure on any planet
B) a description of the atmospheric composition on Earth
C) a place where lawyers can get sodas and other drinks
D) a unit of pressure roughly equal to the atmospheric pressure at sea level on Earth
D
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When a fixed amount of ideal gas goes through an adiabatic expansion,
A) its internal (thermal) energy does not change. B) the gas does no work. C) no heat enters or leaves the gas. D) its temperature cannot change. E) its pressure must increase.
What two observable properties of a Cepheid variable are directly related to one another?
A) the period between its peaks of brightness and its luminosity B) the period between its peaks of brightness and its distance C) its luminosity and its mass D) its mass and its distance
Why do astronomers conclude that the spiral arms are places of active star formation?
What will be an ideal response?
The diagram above shows the life track of a 1 MSun protostar from the time it first begins to form until it reaches the main sequence, with four stages labeled. What is happening to the protostar's surface temperature and luminosity during Stage 2, when it is undergoing convective contraction, and its life track moves almost straight down on the HR diagram?
A) Its surface temperature and luminosity increase. B) Its surface temperature remains the same and its luminosity decreases. C) Its surface temperature and luminosity decrease. D) Its surface temperature decreases and its luminosity increases. E) Its surface temperature and luminosity remain the same.