The four outer planets in our solar system (Jupiter, Saturn, Uranus, and Neptune) are all gas giants.

Here's why:

* Composition: They are primarily composed of hydrogen and helium, with smaller amounts of heavier elements.

* No solid surface: They don't have a solid surface like the inner planets (Mercury, Venus, Earth, and Mars).

* Large size: They are significantly larger than the inner planets.

* Ring systems: All four outer planets have ring systems, though Saturn's are the most prominent.

* Many moons: Each gas giant has a large number of moons.

Let me know if you'd like to learn more about any of these characteristics!