Why is an absorption spectrum especially useful for astronomers? O It helped astronomers to understand the rainbows we see on Earth after storms
O It shows that the stars are transparent; we can see right through them
O It has bright lines in it which allow astronomers to determine how bright the star is
O It has dark lines in it that allow astronomers to determine what elements are in the
star

The answer should be vaporization 

You would do 1500/4 and the answer is 375

1. why does the same side of the moon always face earthc.the rotational period of the moon is equal to one revolution around earth2. which is greater the moons period of rotation or its period of revolution  b.the moons revolution period around earth3.what was the major accomplishment of the apollo missions  d.landing on and exploring the moon4. which of these space missions involved the deployment of lunar rovers d.apollo5. which scientists are going to explore next on kepler-186fd. evidence of existence of life6.which mission is not going to explore the outside of the solar systemb.safir7.which technology limit the future of space exploration b. scientist must first develop certain technologies before missions can be completed.