The correct answer is option 2: Comet. A comet is a collection of gas and dust that appears as a bright ball of light in the sky with a glowing tail.

Let`s review the other options to understand why they are not the correct answer:

1. Star: A star is a celestial object made up of hot gases that produces its own light and heat through nuclear reactions. It does not typically have a glowing tail like a comet.

3. Constellation: A constellation is a group of stars that appear to form a pattern in the sky. While constellations are made up of stars, they do not have the characteristics of a bright ball of light with a glowing tail like a comet.

4. Galaxy: A galaxy is a vast system of stars, gas, and dust held together by gravity. While galaxies can contain comets, a galaxy by itself does not appear as a bright ball of light in the sky with a glowing tail.

In conclusion, a collection of gas and dust that appears as a bright ball of light in the sky with a glowing tail is called a comet.