Astronomy Practice Exam

Which of the following statements about comets is true?

1. They are primarily composed of metal and rock

2. They travel in circular orbits around the Sun

3. They typically have a nucleus, coma, and tail

4. They are larger than asteroids

The correct answer is: They typically have a nucleus, coma, and tail

Comets are indeed characterized by having a nucleus, coma, and tail, making this description accurate. The nucleus of a comet is made of ice, dust, and rocky materials. When a comet approaches the Sun, the heat causes the nucleus to sublimate, leading to the formation of a glowing cloud of gas and dust known as the coma. The solar wind and radiation pressure then push this material away from the Sun, creating a tail that always points away from the Sun due to the solar wind influence. This distinct structure of a nucleus, coma, and tail differentiates comets from other celestial bodies such as asteroids. In contrast, while asteroids are primarily composed of metal and rock, comets have a different composition, largely involving ice and organic compounds. Comets also do not typically travel in circular orbits; their orbits can be highly elliptical. Finally, while some comets can be large, many asteroids are significantly larger, particularly the larger ones found in the asteroid belt between Mars and Jupiter.