Pluto is the ninth planet from the Sun. It is the smallest planet in the solar system. Pluto is smaller than Earth's moon. If Earth were the size of the ball used in playing Jacks, Pluto would be the size of a peppercorn.
Pluto is one of the outer planets. The other outer planets are Jupiter, Saturn, Uranus, and Neptune. Pluto is the farthest known planet from the Sun. It can only be seen through the largest telescopes. Even through a telescope, Pluto looks like a faint star. It is so far away, no spacecraft has visited it.
Unlike its gas giant neighbors, Pluto has very little atmosphere. It is a small, rocky planet. It is so far away that it doesn't get much heat from the Sun. Pluto is the coldest planet in the solar system.
Pluto's long orbit is very narrow. Its narrow orbit brings it inside Neptune's orbit. This means that part of Pluto's orbit comes closer to the Sun than Neptune's orbit. So, sometimes Pluto is closer to the Sun than Neptune is. Pluto is the only planet with an orbit that crosses inside the orbit of another planet. Pluto and Neptune will never collide, though. They are always thousands of miles apart. Pluto has one moon, Charon. The moon is about half the size of Pluto. Because they are almost the same size, Pluto and Charon are sometimes called a double planet.
Compared to Earth
Pluto is a very small world. It is the smallest planet in the solar system. Its diameter is less than one-fifth of Earth's diameter. About 160 planets the size of Pluto could fit inside the Earth. The surface area of Pluto is a little less than the size of South America. Pluto is a tiny planet. It has a lot less mass than Earth. Pluto's surface gravity is much less than Earth's. If you weighed 100 pounds (45 kg) on Earth, you would weigh 4 pounds (3 kg) on Pluto! Move the slider below to compare weights. The slider shows weight in pounds.
Not much is known about Pluto. It is thought to have a very large, rocky core. The core may take up about four fifths of its diameter. Earth's core is metal and takes up more than half its diameter. Pluto's mantle is probably made of frozen ices and takes up about one fifth of its diameter. Earth's mantle is rock and takes up about half its diameter. Earth has a thin, rocky crust. Pluto may not have a crust. Recently, it was discovered that Pluto has an atmosphere.
Pluto is almost 40 times farther from the Sun than Earth is. From Pluto, the Sun looks like a distant point of light. The Sun wouldn't look any different from any other star in Pluto's sky. It takes more than 5 hours for sunlight to reach Pluto. It takes only 8 minutes for sunlight to reach Earth. Even when Pluto is closest to the Sun in its orbit, it receives little warmth. The average temperature is -382¬°F (-230¬°C). That is hundreds of degrees colder than the coldest temperature recorded on Earth.
