The habitable zone refers to ________.

A main-sequence star twice as massive as the sun would last __________.

According to current evidence, pluto is best explained as ______.

Among discovered meteorites, we have found some with all the following origins except _________.

Comets falling into the inner solar system from the ____ are called long-period comets.

Gaps in the asteroid belt (often called kirkwood gaps) are caused by ______.

Venus's atmosphere has much more carbon dioxide than earth's because ________.

To estimate the central temperature of the sun, scientists _________.

To calculate the masses of stars in a binary system, we must measure their ________.

The sum of the characteristics that hold a mass in place is referred to as __________.

Our sun is all of the following except ____.