In general, how does the size and location of a star’s habitable zone depend on the star’s mass?

Which of the following is not considered a potential solution to the question of why we lack any evidence of a galactic civilization?

A___ stands out in a photo of a galaxy because it shines brightly with light from massive young stars and glowing clouds of gas and dust

Scientists think it is very unlikely that complex and large forms of life could evolve on planets that orbit stars that are much more massive than the Sun. Why?

Overall, does the nebular theory seem adequate for describing the origins of other planetary systems?

How can scientists account for the fact that extrasolar planets seem to come in a wider range of types than the planets of our solar system?

What is planetary migration, and how may it account for the surprising orbits of many extrasolar planets?

Directly detecting an Earth-size planet around one of the nearest stars (besides the Sun) is roughly equivalent to trying to take a picture of a ball point from a pen at a distance of about ________ kilometers.