. Get acquainted with our star. The Solar System belongs to the Sun. More than 99% of all the matter in the Solar System is in the Sun. Everything else - planets, moons, asteroids, icy bodies, comets - is made from stuff left over from making the Sun. It's the Sun's gravity that holds everything together. And, of course, it makes. life on Earth possible.
. Mercury is close enough to the Sun for lead to melt during the day. Yet there is ice at the poles. Before we had space probes, Mercury was a mystery hidden in the Sun's glare, but that's changed now.
An international mission to Mercury is currently in progress. It's called Bepi-Colombo. Two spacecraft riding together will orbit and study the planet from unique vantage points. The European Space Agency (ESA) provided one orbiter, and the Japan Aerospace Exploration Agency (JAXA) supplied the other. BepiColombo made its first flyby of Mercury on Oct. 1, 2021, and sent back several images. But several more planetary flybys will be used to steer the craft into orbit around Mercury in December 2025.
. The Moon has no air, no sound, no weather and no liquid water. It even has places that are colder than Pluto. But since gravity is weaker there, you could throw a ball a long way, and the footprint you left might last a hundred thousand years or more.
. Mars has no little green men, but it's a fascinating place. It has a mountain three times the height of Everest and a deep valley that dwarfs the Grand Canyon. Although Mars has no liquid water on the surface, if the southern polar icecap melted, it could cover the planet 36 feet deep in water.
Earth's moon is "the Moon” because it was the only one people had ever seen until 1610. That's when Galileo discovered moons orbiting Jupiter. Why did it take until 1877 for someone to find the moons of our neighbor Mars?
Beyond Mars, there is a belt of material, called the Asteroid Belt. It contains a dwarf planet and lots of small irregular bodies.
Observers used to call them 'vermin of the skies". Asteroids weren't interesting and their streaks ruined sky photos. But no more! They can tell us about the early Solar System. One of them may have finished off the dinosaurs, and more could be coming our way.
. NASA's Dawn mission spent 14 months orbiting the asteroid Vesta. Vesta's an unusual object, too small to be a dwarf planet. Yet it has the Solar System's tallest mountain, and canyons as big as Earth's Grand Canyon. And it may help scientists to understand the early Solar System.
, When Ceres was discovered in 1801, astronomers assumed it was a planet. But when many more of these bodies were found, they were all finally listed as asteroids. In 2006 Ceres became the only asteroid also to be listed as a dwarf planet.
. Three beautiful planets - Mars, Jupiter and Saturn - are all visible to the unaided eye. If you have binoculars or a telescope, you can also see some of the moons and other features. Here's a beginner's look at the planets which lie beyond Earth.
. Jupiter has at least 79 moons. Some of them are only half a mile long, but one is bigger than the planet Mercury. Which moon has hundreds of volcanoes, and which one has a deep ocean under an icy surface? Find out here.
. Everybody recognizes Saturn's rings, but that isn't all that circles the planet. There are shepherd moons, a moon with cold volcanoes erupting, a planet-sized moon, and more. And it took nearly two hundred years for the first seven known moons to get named.
. Even being the Saturn's second biggest moon doesn't make Rhea very big. We could set three Rheas down on the USA and have room to spare. It whizzes around Saturn so quickly that a month is only four and a half Earth days long. It's so cold there that ice is as hard as rock.
Mimas is named for a giant in Greek mythology, but Saturn's moon is no giant. It's less than 400 km (245 mi) across and the smallest body we know of that's rounded by gravity. The moon also has a bizarre resemblance to the Death Star in George Lukas's Star Wars films.
Titan was a mystery for three and a half centuries. It's a giant moon shrouded in impenetrable clouds, and has only recently begun to share its secrets. Why do scientists say it's like Earth? Is it time to book a vacation to visit the lakes and mountains of Titan?
Rhea was Saturn's wife in classical mythology. Rhea the moon zips around Saturn in four and a half days. Although it has an oxygen atmosphere, we won't be moving there anytime soon. Even in direct sunlight, it's -281 degrees Fahrenheit and the "atmosphere" is similar to a vacuum on Earth.
. This ice giant is twenty times farther from the Sun than we are. It circles the Sun lying on its side, so each half the planet is dark for over twenty years at a time. It's the planet Uranus, discovered in 1781 by William Herschel who named it George.
William Herschel discovered the planet which was named Uranus after the ancient Greek sky god. Although Uranus has at least 27 moons, most of them weren't discovered until at least the twentieth century.
, You can see planets without a telescope. People have been seeing Mercury, Venus, Mars, Jupiter and Saturn for thousands of years. Even though Uranus was the first planet discovered by telescope, sometimes it can be seen without one.
, Far beyond Uranus is another blue planet, one named for the Roman sea god. It could well have been named for a god of winds as it's the windiest place in the Solar System. And it has a captured moon that was a Kuiper Belt object like Pluto.
. Neptune is the last planet out from the Sun. It has fourteen known moons and they're a mixed bag. One of them – Triton – has over 99% of the total mass of Neptune's moons. Thirteen little moons share what's left. Only two of the moons were discovered before 1981.
Neptune, named for the Roman sea god, was discovered in 1846. And 17 days later, William Lassell found a moon. Its moon is probably a captured Kuiper Belt object, similar to Pluto, but colder than Pluto. It's a strange object. Nasa is considering a mission to Neptune and Triton to have a look.
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