Our solar system consists of our star, the Sun, and everything bound to it by gravity — the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, dwarf planets such as Pluto, dozens of moons and millions of asteroids, comets and meteoroids. The most recent definition of a planet was adopted by the International Astronomical Union in 2006. It says a planet must do three things: The Sun, and everything that orbits it, is located in the Milky Way galaxy. Must orbit a star (in our cosmic neighborhood, the Sun). It must be big enough to have enough gravity to force it into a spherical shape. It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun. This is a partial list of Solar System objects by size, arranged in descending order of mean volumetric radius, and divided into several size classes. These lists can also be sorted according to an object’s mass and, for the largest objects, volume, density and surface gravity, insofar as these values are available.
1.Jupiter
In our solar system Jupiter is at nearly 11 times the size of Earth and 317 times its mass with a radius of 43,440.7 miles (69,911 kilometers). Despite its size, Jupiter has the shortest day of any other planet; it only takes about 10 hours for a complete rotation. In 1610, astronomer Galileo Galilei used a new invention called the telescope to look at Jupiter and discovered the first moons known to exist beyond Earth. The discovery ended incorrect, ancient belief that everything, including the Sun and other planets, orbited the Earth. From an average distance of 484 million miles (778 million kilometers), Jupiter is 5.2 astronomical units away from the Sun. Jupiter is the largest planet in the solar system – more than twice as massive as all the other planets combined. Jupiter’s familiar stripes and swirls are actually cold, windy clouds of ammonia and water, floating in an atmosphere of hydrogen and helium. Jupiter’s iconic Great Red Spot is a giant storm bigger than Earth that has raged for hundreds of years. Jupiter is the fifth planet from our Sun. Jupiter is surrounded by dozens of moons. Jupiter also has several rings, but unlike the famous rings of Saturn, Jupiter’s rings are very faint and made of dust, not ice. Jupiter spins nearly upright and does not have seasons as extreme as other planets do. Jupiter has a central core of solid material or if it may be a thick, super-hot and dense soup. It could be up to 90,032 degrees Fahrenheit (50,000 degrees Celsius).
Jupiter has the same ingredients as a star, but it did not grow massive enough to ignite. Jupiter doesn’t have a true surface. The planet is mostly swirling gases and liquids. It may also have a rocky core of heavier elements. While a spacecraft would have nowhere to land on Jupiter. Jupiter’s appearance is a tapestry of colorful cloud bands and spots. With four large moons and many smaller moons, Jupiter forms a kind of miniature solar system. Jupiter has 53 confirmed moons and 26 provisional moons awaiting confirmation of discovery. Jupiter’s four largest moons—Io, Europa, Ganymede and Callisto. Jupiter’s environment is probably not conducive to life as we know it. The temperatures, pressures and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to. It is on average the third-brightest natural object in the night sky after the Moon and Venus. it was named after the king of the gods in Roman mythology. In a similar manner, the ancient Greeks named the planet after Zeus, the king of the Greek pantheon. Jupiter’s immense volume could hold more than 1,300 Earths. That means that if Jupiter were the size of a basketball, Earth would be the size of a grape.
2.Saturn
Saturn is the sixth planet from our Sun (a star) and orbits at a distance of about 886 million miles (1.4 billion kilometers) from the Sun. The rings we see are made of groups of tiny ringlets that surround Saturn. They’re made of chunks of ice and rock. Twice every 29 and a half years the great planet Saturn appears ringless. Saturn is heavily present in pop culture. Like Jupiter, Saturn is mostly a ball of hydrogen and helium. Saturn is unique among the planets with a radius of 36,183.7 miles (58,232 kilometers)and 9 times wider than Earth. If Earth were the size of a nickel, Saturn would be about as big as a volleyball. It is Surrounded by more than 60 known moons. The Saturn system is a rich source of scientific discovery and still holds many mysteries. From an average distance of 886 million miles (1.4 billion kilometers), Saturn is 9.5 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 80 minutes to travel from the Sun to Saturn.
Saturn has the second-shortest day in the solar system. It’s hard to imagine, but Saturn is the only planet in our solar system whose average density is less than water. The planet is mostly swirling gases and liquids deeper down. While a spacecraft would have nowhere to land on Saturn, it wouldn’t be able to fly through unscathed either. The extreme pressures and temperatures deep inside the planet crush, melt and vaporize spacecraft trying to fly into the planet. The planet is many different shades of yellow, brown and grey. Saturn’s magnetic field is smaller than Jupiter’s but still 578 times as powerful as Earth’s. Saturn’s rings are thought to be pieces of comets, asteroids or shattered moons that broke up before they reached the planet, torn apart by Saturn’s powerful gravity. Saturn’s ring system extends up to 175,000 miles (282,000 kilometers) from the planet, yet the vertical height is typically about 30 feet (10 meters) in the main rings. Saturn’s environment is not conducive to life as we know it. The temperatures, pressures and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to.
3.Uranus
Uranus was discovered in 1781 by astronomer William Herschel. The planet was named for Uranus, the Greek god of the sky. The seventh planet from the Sun with the third largest diameter in our solar system, Uranus is very cold and windy. The ice giant is surrounded by 13 faint rings and 27 small moons as it rotates at a nearly 90-degree angle. This unique tilt makes Uranus appear to spin on its side, orbiting the Sun like a rolling ball. One day Uranus takes about 17 hours to rotate and Uranus makes a complete orbit around the Sun in about 84 Earth years. Uranus is the only planet whose equator is nearly at a right angle to its orbit. With a radius of 15,759.2 miles (25,362 kilometers), Uranus is 4 times wider than Earth. If Earth was the size of a nickel, Uranus would be about as big as a softball. From an average distance of 1.8 billion miles (2.9 billion kilometers), Uranus is 19.8 astronomical units away from the Sun. It takes sunlight 2 hours and 40 minutes to travel from the Sun to Uranus.
Uranus is also one of just two planets that rotate in the opposite direction than most of the planets (Venus is the other one), from east to west. Uranus is slightly larger in diameter than its neighbor Neptune. Most (80 percent or more) of the planet’s mass is made up of a hot dense fluid of “icy” materials—water, methane and ammonia—above a small rocky core. Near the core, it heats up to 9,000 degrees Fahrenheit (4,982 degrees Celsius). Uranus gets its blue-green color from methane gas in the atmosphere. Sunlight passes through the atmosphere and is reflected back out by Uranus’ cloud tops. Uranus doesn’t have a true surface. The planet is mostly swirling fluids. While a spacecraft would have nowhere to land on Uranus, it wouldn’t be able to fly through its atmosphere unscathed either. Uranus’ atmosphere is mostly hydrogen and helium, with a small amount of methane and traces of water and ammonia. The methane gives Uranus its signature blue color. Uranus has an unusual, irregularly shaped magnetosphere. Uranus’ environment is not conducive to life as we know it. Uranus has been visited only once by a spacecraft: Voyager 2.
4.Neptune
Dark, cold and whipped by supersonic winds, ice giant Neptune is the eighth and most distant planet in our solar system. Neptune has 14 known moons. Neptune’s largest moon Triton was discovered on October 10, 1846, by William Lassell. More than 30 times as far from the Sun as Earth, Neptune is the only planet in our solar system not visible to the naked eye. Neptune is our solar system’s windiest world. Neptune is the farthest planet from our Sun. Neptune is very similar to Uranus. It’s made of a thick soup of water, ammonia, and methane over an Earth-sized solid center. Its atmosphere is made of hydrogen, helium, and methane. The methane gives Neptune the same blue color as Uranus. Neptune has six rings, but they’re very hard to see. The warm light we see here on our home planet is roughly 900 times as bright as sunlight on Neptune. The ice giant Neptune was discovered in 1846. With a radius of 15,299.4 miles (24,622 kilometers), Neptune is about four times wider than Earth.
If Earth were the size of a nickel, Neptune would be about as big as a baseball. From an average distance of 2.8 billion miles (4.5 billion kilometers), Neptune is 30 astronomical units away from the Sun. From this distance, it takes sunlight 4 hours to travel from the Sun to Neptune. Neptune takes about 16 hours to rotate or spin once. And Neptune makes a complete orbit around the Sun in about 165 Earth years (60,190 Earth days). Pluto is closer to the Sun than Neptune. Scientists think there might be an ocean of super hot water under Neptune’s cold clouds. It does not boil away because incredibly high pressure keeps it locked inside. Neptune does not have a solid surface. Its atmosphere extends to great depths, gradually merging into water and other melted ices over a heavier, solid core with about the same mass as Earth. Neptune is a more vivid, brighter blue. Neptune’s winds can be three times stronger than Jupiter’s and nine times stronger than Earth’s. Neptune’s environment is not conducive to life as we know it. The temperatures, pressures and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to.
5.Earth
The name Earth is a Germanic word with a radius of 3,959 miles (6,371 kilometers), which simply means “the ground. “Our home planet is the third planet from the Sun, and the only place we know of so far that’s inhabited by living things. While Earth is only the fifth largest planet in the solar system. it is the only world in our solar system with liquid water on the surface. Just slightly larger than nearby Venus, Earth is the biggest of the four planets closest to the Sun, all of which are made of rock and metal. Earth is the only planet that has a single moon. Our Moon is the brightest and most familiar object in the night sky. The Moon is an average of 238,855 miles (384,400 kilometers) away from Earth. From an average distance of 93 million miles (150 million kilometers), Earth is exactly one astronomical unit away from the Sun. It takes about eight minutes for light from the Sun to reach our planet.
As Earth orbits the Sun, it completes one rotation every 23.9 hours. It takes 365.25 days to complete one trip around the Sun. That extra quarter of a day presents a challenge to our calendar system, which counts one year as 365 days. To keep our yearly calendars consistent with our orbit around the Sun, every four years we add one day. That day is called a leap day, and the year it’s added to is called a leap year. Earth is composed of four main layers, starting with an inner core at the planet’s center, enveloped by the outer core, mantle and crust. It has a solid and active surface with mountains, valleys, canyons, plains and so much more. Earth is special because it is an ocean planet. Water covers 70 percent of Earth’s surface. Earth’s atmosphere is made mostly of nitrogen and has plenty of oxygen for us to breathe. The atmosphere also protects us from incoming meteoroids, most of which break up before they can hit the surface. Earth’s global ocean, which covers nearly 70 percent of the planet’s surface, has an average depth of about 2.5 miles (4 kilometers) and contains 97 percent of Earth’s water. Earth has an atmosphere that consists of 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases such as argon, carbon dioxide and neon.
6.venus
Similar in size and structure to Earth, Venus has been called Earth’s twin. These are not identical twins, however – there are radical differences between the two worlds. Venus is the second planet from the Sun, and is Earth’s closest neighbor in the solar system. Venus is the brightest object in the sky after the Sun and the Moon, and sometimes looks like a bright star in the morning or evening sky. Average diameter of Venus is about 7,500 miles. Surface temperature is 864 degress Fahrenheit. Venus has a thick, toxic atmosphere filled with carbon dioxide. It’s perpetually shrouded in thick, yellowish clouds of mostly sulfuric acid that trap heat, causing a runaway greenhouse effect. It’s the hottest planet in our solar system.
The surface of Venus is not where you’d like to be, with temperatures that can melt lead, an atmosphere so thick it would crush you, and clouds of sulfuric acid that smell like rotten eggs. you couldn’t breathe the air, you would be crushed by the enormous weight of the atmosphere, and you would burn up in surface temperatures high enough to melt lead. The atmosphere traps the small amount of energy from the sun that does reach the surface along with the heat the planet itself releases. It is always found near the Sun. It rises and sets each day, so it has the nicknames Morning and Evening Star! Scientists found that Venus rotates backwards. This means that on Venus the Sun rises in the west and sets in the east.
7.Mars
Mars has a thin atmosphere made up mostly of carbon dioxide, nitrogen and argon gases. It is frequently called the “Red Planet” because iron minerals in the Martian dirt oxidize, or rust, causing the surface to look red. Today, a science fleet of robotic spacecraft study Mars from all angles. With a radius of 2,106 miles (3,390 kilometers), Mars is about half the size of Earth. If Earth were the size of a nickel, Mars would be about as big as a raspberry. From an average distance of 142 million miles (228 million kilometers), Mars is 1.5 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 13 minutes to travel from the Sun to Mars. As Mars orbits the Sun, it completes one rotation every 24.6 hours, which is very similar to one day on Earth (23.9 hours). Like Earth, Mars has distinct seasons, but they last longer than seasons here on Earth since Mars takes longer to orbit the Sun. On Mars the seasons vary in length because of Mars’ elliptical, egg-shaped orbit around the Sun. Mars has a dense core at its center between 930 and 1,300 miles (1,500 to 2,100 kilometers) in radius. It’s made of iron, nickel and sulfur. Surrounding the core is a rocky mantle between 770 and 1,170 miles (1,240 to 1,880 kilometers) thick, and above that, a crust made of iron, magnesium, aluminum, calcium and potassium. This crust is between 6 and 30 miles (10 to 50 kilometers) deep.
Mars formed when gravity pulled swirling gas and dust in to become the fourth planet from the Sun. The Red Planet is actually many colors. At the surface we see colors such as brown, gold and tan. Mars is home to the largest volcano in the solar system, Olympus Mons. It’s three times taller than Earth’s Mt. Everest. Mars appears to have had a watery past, with ancient river valley networks, deltas and lakebeds, as well as rocks and minerals on the surface that could only have formed in liquid water. There is water on Mars today, but the Martian atmosphere is too thin for liquid water to exist for long on the surface. The temperature on Mars can be as high as 70 degrees Fahrenheit (20 degrees Celsius) or as low as about -225 degrees Fahrenheit (-153 degrees Celsius). Mars has no global magnetic field today. Mars has two small moons, Phobos and Deimos. Phobos, the innermost and larger moon, is slowly moving towards Mars and will crash into the planet or break apart in about 50 million years. Scientists don’t expect to find living things currently thriving on Mars.
8.Mercury
The smallest planet in our solar system and nearest to the Sun, Mercury is only slightly larger than Earth’s Moon. It doesn’t have any moons. Mercury is the fastest planet, zipping around the Sun every 88 Earth days. With a radius of 1,516 miles (2,440 kilometers), Mercury is a little more than 1/3 the width of Earth. If Earth were the size of a nickel, Mercury would be about as big as a blueberry. From an average distance of 36 million miles (58 million kilometers), Mercury is 0.4 astronomical units away from the Sun. It takes sunlight 3.2 minutes to travel from the Sun to Mercury. Mercury’s highly eccentric, egg-shaped orbit takes the planet as close as 29 million miles (47 million kilometers) and as far as 43 million miles (70 million kilometers) from the Sun. Mercury spins slowly on its axis and completes one rotation every 59 Earth days. Mercury is the second densest planet, after Earth. It has a large metallic core with a radius of about 1,289 miles (2,074 kilometers), about 85 percent of the planet’s radius.
Mercury has a central core, a rocky mantle and a solid crust. It’s actually not the hottest. Along with Venus, Earth, and Mars, Mercury is one of the rocky planets. Mercury spins slowly compared to Earth. Mercury takes 59 Earth days to make one full rotation. It goes around the Sun in just 88 Earth days. Most of Mercury’s surface would appear greyish-brown to the human eye. Temperatures on the surface of Mercury are extreme, both hot and cold. During the day, temperatures on Mercury’s surface can reach 800 degrees Fahrenheit (430 degrees Celsius). Because the planet has no atmosphere to retain that heat, nighttime temperatures on the surface can drop to minus 290 degrees Fahrenheit (minus 180 degrees Celsius). Mercury’s environment is not conducive to life as we know it. The temperatures and solar radiation that characterize this planet are most likely too extreme for organisms to adapt to.
9.Pluto
Pluto is a complex and mysterious world with mountains, valleys, plains, craters, and maybe glaciers. Discovered in 1930, Pluto was long considered our solar system’s ninth planet. Icy Pluto was reclassified as a dwarf planet. Pluto is orbited by five known moons, the largest of which is Charon. Charon is about half the size of Pluto itself. Pluto and Charon are often referred to as a “double planet.” With a radius of 715 miles (1,151 kilometers), Pluto is about 1/6 the width of Earth. If Earth was the size of a nickel, Pluto would be about as big as a popcorn kernel. From an average distance of 3.7 billion miles (5.9 billion kilometers), Pluto is 39 astronomical units away from the sun. It takes sunlight 5.5 hours to travel from the sun to Pluto. Pluto’s orbit around the sun is unusual compared to the planets. Pluto was actually closer to the sun than Neptune. One day on Pluto takes about 153 hours. Pluto is about two-thirds the diameter of Earth’s moon and probably has a rocky core surrounded by a mantle of water ice. Interesting ices like methane and nitrogen frost coat its surface.
Due to its lower density, Pluto’s mass is about one-sixth that of Earth’s moon. Pluto’s surface is characterized by mountains, valleys, plains, and craters. The temperature on Pluto can be as cold as -375 to -400 degrees Fahrenheit (-226 to -240 degrees Celsius). Pluto’s mountains can be as tall as 6,500 to 9,800 feet (2 to 3 kilometers) and are big blocks of water ice, sometimes with a coating of frozen gases like methane. Craters as large as 162 miles (260 kilometers) in diameter dot some of the landscape on Pluto, with some showing signs of erosion and filling. The main constituent is molecular nitrogen, though molecules of methane and carbon monoxide have also been detected. Pluto’s low gravity (about six percent of Earth’s) causes the atmosphere to be much more extended in altitude than our planet’s atmosphere. Pluto has a magnetic field. There are no known rings around Pluto. Pluto has five known moons: Charon, Nix, Hydra, Kerberos and Styx. The surface of Pluto is extremely cold, so it seems unlikely that life could exist there. At such cold temperatures, water, which is vital for life as we know it, is essentially rock-like. Pluto’s interior is warmer, however, and some think there could even be an ocean deep inside.
