Sun
The Sun is by far the largest object in the solar system. It contains more than 99.8% of the total mass of the Solar System. The Sun is, at present, about 70% hydrogen and 28% helium by mass everything else (“metals”) amounts to less than 2%. This changes slowly over time as the Sun converts hydrogen to helium in its core. The outer layers of the Sun exhibit differential rotation: at the equator the surface rotates once every 25.4 days; near the poles it’s as much as 36 days. This odd behavior is due to the fact that the Sun is not a solid body like the Earth.
Close
Mercury
Named for the Roman god, Mercury is the closest planet to the sun. However, Mercury’s orbit is not a perfect circle. The planet can pass as close as 29 million miles and as far away as 43 million miles. Mercury is the fastest planet in the solar system, speeding along at about 29 miles per second and completing each orbit around the sun in just 88 Earth days. Mercury is also the smallest planet in the solar system, measuring just 3,032 miles wide at its equator. That makes it only slightly larger than Earth’s moon.
Close
Venus
Although the planet is the second closest planet to the sun, it's by far the hottest of the eight worlds in our solar system. Its thick atmosphere is mostly made of carbon dioxide with clouds of sulfuric acid, which creates a greenhouse effect. Thanks to this blanket, temperatures on Venus' surface can soar over 880 degrees Fahrenheit. The surface pressure is around 90 times that on Earth, which would feel like standing under about a half a mile of water. Wintertime doesn't even provide a reprieve from the heat. With an axial tilt of three degrees, Venus has just one season: hot.
Close
Earth
Earth, our home planet, is a world unlike any other. The third planet from the sun, Earth is the only place in the known universe confirmed to host life. With a radius of 3,959 miles, Earth is the fifth largest planet in our solar system, and it's the only one known for sure to have liquid water on its surface. Earth is also unique in terms of monikers. Every other solar system planet was named for a Greek or Roman deity, but for at least a thousand years, some cultures have described our world using the Germanic word “earth,” which means simply “the ground.”
Close
Mars
Mars, named for the Roman god of war, has long been an omen in the night sky. And in its own way, the planet’s rusty red surface tells a story of destruction. Billions of years ago, the fourth planet from the sun could have been mistaken for Earth’s smaller twin, with liquid water on its surface—and maybe even life. Now, the world is a cold, barren desert with few signs of liquid water. But after decades of study using orbiters, landers, and rovers, scientists have revealed Mars as a dynamic, windblown landscape that could—just maybe—harbor microbial life beneath its rusty surface even today.
Close
Asteroid Belt
Scattered in orbits around the sun are bits and pieces of rock left over from the dawn of the solar system. Most of these objects, called planetoids or asteroids — meaning "star-like" — orbit between Mars and Jupiter in a grouping known as the Main Asteroid Belt. The Main Asteroid Belt lies more than two-and-a-half times as far as Earth does from the sun. It contains millions of asteroids, according to NASA. Most of these are relatively small, from the size of boulders to a few thousand feet in diameter. But some are significantly larger.
Close
Jupiter
The fifth planet from the sun, Jupiter is what watercolor dreams are made of. Vibrant bands of clouds ripple around its thick atmosphere, making up a world so large that more than 1,300 Earths could fit inside. Its Great Red Spot seems to look like an enormous eye in the face of a striped giant. Though seemingly serene when viewed from the relative safety of our home world, Jupiter is a chaotic and stormy place. The gas giant planet's spots come from massive storms that whip up prevailing winds as fast as 335 miles an hour at the equator—faster than any known winds on Earth.
Close
Saturn
Saturn is made mostly of hydrogen and helium. Its volume is 755 times greater than that of Earth. Winds in the upper atmosphere reach 1,600 feet (500 meters) per second in the equatorial region. (In contrast, the strongest hurricane-force winds on Earth top out at about 360 feet, or 110 meters, per second.) These superfast winds, combined with heat rising from within the planet's interior, cause the yellow and gold bands visible in the atmosphere. Saturn's ring system is the most extensive and complex in the solar system, extending hundreds of thousands of kilometers from the planet.
Close
Uranus
Uranus, the seventh planet from the sun, may initially look like a bland, blue-green ball. But there's a lot to love about the icy giant, from its 13 rings to its 27 known moons to the fact that it may even rain diamonds from its hazy atmosphere. Like Saturn, Jupiter, and Neptune, Uranus is a big ball of gas, often called a jovian or gas giant world. Uranus owes its vibrant blue-green hues not from unusual oceans but from an upper atmosphere flush with methane, which absorbs the sun's red light and scatters blue light back to our eyes.
Close
Neptune
Neptune may seem like a serene sapphire world at first glance. But don't let its quiet azure hues fool you: The eighth planet from the sun is a wild child. Neptune is the windiest planet in our solar system, whipping up momentous gusts that can reach more than 1,200 miles an hour. That soothing sapphire expanse does reveal some of the whirling chaos below in the form of cloudy bands and massive gyres that look like dark smudges on its surface.
Close
Pluto
It orbits in a disc-like zone beyond the orbit of Neptune called the Kuiper belt, a distant region populated with frozen bodies left over from the solar system's formation. The dwarf planet is a whopping 3.7 billion miles (5.9 billion kilometers) from the sun, and its average temperature hovers around -356 degrees Fahrenheit (-215 degrees Celsius). Pluto's surface is composed of a mixture of frozen nitrogen, methane, and carbon monoxide ices. The dwarf planet also has polar caps and regions of frozen methane and nitrogen.
Close