It is most likely that the tight time line given to the publisher was responsible for their inability to correct all the problems which we found. The page numbers are given for each entry so that teachers can cross-reference our information with that given in the textbook. It was comet Shoemaker-Levy 9 which hit Jupiter. It might be helpful if you explained what causes seasons. Rigel is blue.
All stars have mass, therefore all are massive.
Not all nebulae are areas of star formation. Only elements up to iron are formed inside the stars. The space between stars is not full of clouds of dust and gas. They were discovered by John Goodricke in 1784. Henrietta Leavitt discovered the relationship between their periods and luminosity, allowing astronomers to measure the distances between galaxies for the first time.