The smallest planet in the solar system, according to the International Astronomical Union's classification, is Mercury, with a radius of approximately 1,516 miles, which is 38 percent the size of Earth. The next smalles... More » Science Astronomy Planets

Mercury is the smallest planet in our solar system; Jupiter is the largest.Pluto was once considered to be the smallest planet, but since Pluto is no longer thought to be a planet, Mercury now takes the title. More »

Only a little larger than Earth's moon, Mercury is the smallest of the eight planets in the Solar System and is also the closest to the Sun. With a surface area of 28,879,000 square miles, Mercury's circumference at its ... More » Science Astronomy Planets

In 2006, the International Astronomical Union decided that Pluto was not a planet in the Earth's solar system. Pluto was named a dwarf planet after a discovery of a similar-sized object deeper in the Kuiper belt, which w... More » Science Astronomy Planets

Jupiter is the largest planet in the solar system, with a radius of 43,441 miles. That is more than 10 times Earth's 3,359-mile radius, but it is also about 16 times smaller than the Sun's radius. Mercury is the smallest... More »

Mercury has a radius of 2,439.7 kilometers, making it smaller than some moons and the smallest planet in the solar system. Its mass is equal to 0.055 of Earth's. More »

The fastest-moving planet in the solar system is Mercury. The planet whizzes around the sun at an orbital velocity of 1.6 times that of Earth's orbital velocity. This amounts to 107,700 miles per hour. More »