THE PLANETS IN OUR SOLAR SYSTEM
Our solar system is made up of a star—the Sun—eight planets, 146 moons, a bunch of comets, asteroids and space rocks, ice, and several dwarf planets, such as Pluto. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Mercury is closest to the Sun. Neptune is the farthest.Planets, asteroids, and comets orbit our Sun. They travel around our Sun in a flattened circle called an ellipse. It takes the Earth one year to go around the Sun. Mercury goes around the Sun in only 88 days. It takes Pluto, the most famous dwarf planet, 248 years to make one trip around the Sun.
Moons orbit planets. Right now, Jupiter has the most named moons—50. Mercury and Venus don't have any moons. Earth has one. It is the brightest object in our night sky. The Sun, of course, is the brightest object in our daytime sky. It lights up the moon, planets, comets, and asteroids.
Our solar system’s eight planets come in two flavors: smaller rocky planets with solid ground (Mercury, Venus, Earth and Mars) and larger gas giants (Jupiter, Saturn, Uranus, and Neptune).
• You can spot six of the solar system’s planets with the naked eye from Earth—and all eight if you have binoculars or a telescope.
• Astronomers have discovered hundreds of worlds beyond our solar system and are spotting more every day. Scientists believe some of these “exoplanets” may support alien life. Who knows. Maybe an alien kid elsewhere in the galaxy is wondering if you exist.
Thousands of years before the invention of the Internet or Super Mario Kart, people entertained themselves by peering into the night sky and connecting the stars to create pictures—called constellations—of animals, objects, and legendary heroes. But these ancient stargazers noticed that some stars didn’t cooperate with the constellations. These oddball balls of light followed their own paths across the night sky, so the ancient Greeks called them “planetes,” meaning wanderers. By 1930, nine planets had been discovered: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
But what exactly is a planet? It seems like an easy question. After all, you’re standing on one right now! But the scientific definition was fairly loose until recently. The discovery of other solar-system “wanderers” rivaling Pluto in size suddenly had scientists asking what wasn’t a planet. They put their heads together in 2006 and came up with three conditions for planethood: A planet must orbit the sun, be large enough so that its own gravity molds it into a spherical shape, and it must have an orbit free of other small objects. Unfortunately for Pluto, our one-time “ninth planet” failed to meet the third condition. It was downgraded to a “dwarf planet,”
Moons orbit planets. Right now, Jupiter has the most named moons—50. Mercury and Venus don't have any moons. Earth has one. It is the brightest object in our night sky. The Sun, of course, is the brightest object in our daytime sky. It lights up the moon, planets, comets, and asteroids.
Our solar system’s eight planets come in two flavors: smaller rocky planets with solid ground (Mercury, Venus, Earth and Mars) and larger gas giants (Jupiter, Saturn, Uranus, and Neptune).
• You can spot six of the solar system’s planets with the naked eye from Earth—and all eight if you have binoculars or a telescope.
• Astronomers have discovered hundreds of worlds beyond our solar system and are spotting more every day. Scientists believe some of these “exoplanets” may support alien life. Who knows. Maybe an alien kid elsewhere in the galaxy is wondering if you exist.
Thousands of years before the invention of the Internet or Super Mario Kart, people entertained themselves by peering into the night sky and connecting the stars to create pictures—called constellations—of animals, objects, and legendary heroes. But these ancient stargazers noticed that some stars didn’t cooperate with the constellations. These oddball balls of light followed their own paths across the night sky, so the ancient Greeks called them “planetes,” meaning wanderers. By 1930, nine planets had been discovered: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
But what exactly is a planet? It seems like an easy question. After all, you’re standing on one right now! But the scientific definition was fairly loose until recently. The discovery of other solar-system “wanderers” rivaling Pluto in size suddenly had scientists asking what wasn’t a planet. They put their heads together in 2006 and came up with three conditions for planethood: A planet must orbit the sun, be large enough so that its own gravity molds it into a spherical shape, and it must have an orbit free of other small objects. Unfortunately for Pluto, our one-time “ninth planet” failed to meet the third condition. It was downgraded to a “dwarf planet,”