Composition:
* Primarily gas and ice: They are composed mainly of hydrogen and helium, with varying amounts of heavier elements like methane, ammonia, and water ice.
* Rocky cores: They are thought to have small, dense, rocky cores at their centers.
Size and Density:
* Massive: They are significantly larger and more massive than the inner, terrestrial planets.
* Low density: Due to their gaseous composition, they have lower densities than the inner planets.
Atmosphere:
* Thick atmospheres: They possess thick, extensive atmospheres that extend far beyond their solid cores.
* Strong winds and storms: The rapid rotation of the outer planets and their deep atmospheres create powerful winds and storms.
Rings:
* Ring systems: All four outer planets have ring systems, though they vary in size, composition, and prominence.
Moons:
* Numerous moons: The outer planets have a large number of moons, many of which are quite large and complex.
Distance from the Sun:
* Farther from the Sun: They orbit much farther away from the Sun than the inner planets, receiving significantly less solar radiation.
Temperature:
* Cold temperatures: The outer planets are extremely cold due to their distance from the Sun.
Internal Structure:
* Differentiated interiors: They have layered internal structures with distinct layers of gas, liquid, and possibly solid material.
Note: While these are common characteristics, each outer planet also has its own unique features. For example, Jupiter has a Great Red Spot, Saturn has extensive rings, Uranus has an axial tilt of 98 degrees, and Neptune has strong winds and storms.
