Outer Planets are Jupiter, Saturn, Uranus, Neptune, and the dwarf planet – Pluto.
The four outer planets, called the gas giants, collectively make up 99% of the mass known to orbit the Sun. They are composed mainly of hydrogen & helium & lack a solid surface. Their moons are, however, solid. The two outermost planets, Uranus and Neptune, are composed of substances called ices, such as water, ammonia and methane, and are often referred to separately as “ice giants”
Jupiter is the largest planet in the solar system, twice as massive as all the other planets, moons, and asteroids in the solar system put together. More than 90 percent of Jupiter’s mass consists of swirling gases, mostly hydrogen and helium. The largest of these storms is the Great Red Spot, which is often visible from Earth through even a small telescope.
A day on Jupiter is only 9 hours 56 minutes which makes it the fastest rotating planet/body in the solar system.
It takes 12 years to complete its revolution.
There are 67 known moons of Jupiter. Some of them are Io, Europa, Ganymede, and Calisto.They are about the size of Earth’s Moon or larger.
Ganymede is the largest moon in the solar system, about one-and-a-half times as wide as Earth’s Moon. It has a very thin atmosphere and its own magnetic field.
Atmosphere of Jupiter
Jupiter’s upper atmosphere is composed of about 88–92% hydrogen and 8–12% helium by percent volume or fraction of gas molecules.
There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, and sulfur.
The outermost layer of the atmosphere contains crystals of frozen ammonia.
Saturn is similar to Jupiter, although about one-third the mass.
A day on Saturn is only 10 hours and 39 minutes long. However, its day is longer than that of Jupiter.
It takes 29.5 years to complete its revolution.
The most spectacular part of Saturn is its magnificent system of planetary rings, which stretch some 300,000 kilometers across.
Saturn has 62 confirmed moons. Also, like Jupiter, many of these are small moons that are likely to be asteroids are captured in Saturn’s gravitational field.
Titan is the largest satellite of Saturn and perhaps the most complex moon in the entire solar system. This is the only satellite in the solar system with a dense atmosphere.
Uranus is the seventh major planet in our solar system and the third of four gas giant planets.
It was discovered by William Hershel in the year 1781.
Its pale blue-green, cloudy atmosphere is made of 83 percent hydrogen, 15 percent helium, and small amounts of methane and other gases.
Uranus gets its color because the methane in the atmosphere absorbs reddish light and reflects bluish-greenish light.
Deep down below its atmosphere, a slushy mixture of ice, ammonia, and methane is thought to surround a rocky core.
Rotation and revolution:
Although it orbits the Sun in a perfectly ordinary, near-circular ellipse every 84 Earth years, Uranus has an extremely odd rotation compared to the other major planets. It rotates on its side, almost like a bowling ball rolling down its lane, and its polar axis is parallel rather than perpendicular to its orbital plane. This means that one end of Uranus faces the Sun for an entire half of its orbit, while the other end faces away during that time. So, one “day” on Uranus is equal to 42 Earth years.
Neptune is the eighth major planet in our solar system, 17 times more massive than Earth and about four times its diameter.
A “day” on Neptune, however, is only 16 Earth hours.
Neptune is bluish-green in color, it is due to the gases in Neptune’s atmosphere reflecting sunlight back into space.
Neptune’s atmosphere consists mostly of hydrogen, helium, and methane.
Before 2006 it was also considered a Planet But now it is considered to be a dwarf planet by the International Astronomical Union.