Author Question: The major presence of water detected on the Moon is in A) the puffs of steam seen coming from ... (Read 69 times)

awywial · **on:** Jul 27, 2018

The major presence of water detected on the Moon is in

A) the puffs of steam seen coming from some still active lunar volcanoes.
B) the floors of deep craters in the polar regions, as ice deposits that never thaw.
C) faint clouds of ice in the thin lunar atmosphere.
D) the flows of mud seen on the walls of some craters.
E) the mare.

Question 2

Explain why stars more massive than the Sun live shorter main sequence lives than stars less massive than the Sun, despite having more fuel available for nuclear reactions.

What will be an ideal response?

janieazgirl · **Reply #1 on:** Jul 27, 2018

Answer to Question 1

B

Answer to Question 2

The main sequence lifetime of a star is its fuel supply (its mass) divided by the rate at which it uses up this fuel (its luminosity). The luminosities of main sequence stars increase dramatically with mass and this leads to shorter lifetimes. For example, a 2 solar mass star has a luminosity approximately 16 times that of the Sun, and therefore its main sequence lifetime is approximately (2/16 ) or 1/8 that of the Sun's.