Barth and Space Setenee semester 2011

The Expanding Universe

Pre-Test Active

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Which statements describe the outer planets? Select three options

Pluto is one of the outer planets

The outer planets are also called gas giants

The outer planets have thin atmospheres

The outer planets have a high gravity due to their large size

The outer planets formed where temperatures were cooler

The outer planets are also called gas giants; The outer planets have a high gravity due to their large size; The outer planets formed where temperatures were cooler

Explanation:

All planets in our solar system can be divided into two groups; inner and outer planets. Border between these two groups is the asteroid belt. So, all the planets further from the asteroid belt (Jupiter, Saturn, Uranus and Saturn) are called outer planets. They all have some characteristics in common:

- they are huge in size, several times bigger than the Earth, and since they are mostly composed of gases they are referred to as "gas giants"

- since the gravity of a planet is directly proportional to its size, these planets have higher gravity, which is why outer planets have multiple moons and rings

- since they are very far from the heat source, the Sun, they were formed in a cold part of space and their temperature is lower

Although Pluto also is further from the asteroid belt, it does not fulfill all the criteria to be a planet; officially, its status is a dwarf planet.