As of 2015, scientists define dwarf planets as bodies that are similar to planets in that they orbit a star, are large enough to form a round shape and are not moons. However, dwarf planets do not have sufficient gravity... More » Science Astronomy Planets

Jupiter is the biggest planet in the solar system in terms of surface area, mass and volume. While it is significantly larger than Earth, it has only one-fourth of the density of Earth. The composition of Jupiter is most... More » Science Astronomy

Mercury, Venus, Mars, Jupiter and Saturn have been known since prehistory. According to NASA, only two non-dwarf planets in the solar system have official discoverers and dates of discovery. These are Uranus and Neptune.... More » Science Astronomy Planets
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The number of moons is constantly changing for some planets as they are discovered, but at the last official count there are 166 moons, with more than 20 waiting to be recognized as moons. This count is only of the moons... More » Science Astronomy Planets

According to NASA, none of the planets in the solar system are known to have exactly four moons. It is noted that Jupiter has four large moons, known as the Galilean Satellites, but the gas giant might have up to 46 addi... More » Science Astronomy Planets

Not all planets have moons. In the solar system, Mercury and Venus do not have any moons orbiting them. All of the other planets, including the Earth, have one or more natural satellites. More » Science Astronomy Planets

Many other planets have moons. There are 166 natural satellites in the solar system orbiting six different planets, including Earth. Jupiter has 63 orbiting moons, followed by Saturn's 60. Uranus has 27 moons, Neptune ha... More » Science Astronomy Planets