solar system

1. Our solar system is made up of the sun and everything that travels around it. This includes eight planets and their natural satellites such as Earth's moon; dwarf planets such as Pluto and Ceres; asteroids; comets and meteoroids
2. The sun is the center of our solar system. It contains almost all of the mass in our solar system and exerts a tremendous gravitational pull on planets and other bodies.
3. Our solar system formed about 4.6 billion years ago.
4. The four planets closest to the Sun - Mercury, Venus, Earth, and Mars - are called the terrestrial planets because they have solid, rocky surfaces.
5. Two of the outer planets beyond the orbit of Mars - Jupiter and Saturn - are known as gas giants; the more distant Uranus and Neptune are called ice giants.
6. Most of the known dwarf planets exist in an icy zone beyond Neptune called the Kuiper Belt, which is also the point of origin for many comets.
7. Many objects in our solar system have atmospheres, including planets, some dwarf planets and even a couple moons.
8. Our solar system is located in the Orion Arm of the Milky Way Galaxy. There are most likely billions of other solar systems in our galaxy. And there are billions of galaxies in the universe.
9. We measure distances in our solar system by Astronomical Units (AU). One AU is equal to the distance between the sun and the Earth, which is about 150 million km (93 million miles).
10. NASA's twin Voyager 1 and Voyager 2 spacecraft are the first spacecraft to explore the outer reaches of our solar system

1. Mercury is the smallest planet in our solar system - only slightly larger than the Earth's moon.
2. It is the closest planet to the sun at a distance of about 58 million km (36 million miles) or 0.39 AU.
3. One day on Mercury (the time it takes for Mercury to rotate or spin once) takes 59 Earth days. Mercury makes a complete orbit around the sun (a year in Mercury time) in just 88 Earth days.
4. Mercury is a rocky planet, also known as a terrestrial planet. Mercury has a solid, cratered surface, much like Earth's moon.
5. Mercury's thin atmosphere, or exosphere, is composed mostly of oxygen (O2), sodium (Na), hydrogen (H2), helium (He), and potassium (K). Atoms that are blasted off the surface by the solar wind and micrometeoroid impacts create Mercury's exosphere.
6. Mercury has no moons.
7. There are no rings around Mercury.
8. Only two spacecraft have visited this rocky planet: Mariner 10 in 1974-5 and MESSENGER, which flew past Mercury three times before going into orbit around Mercury in 2011.
9. No evidence for life has been found on Mercury. Daytime Temperatures can reach 430 degrees Celsius (800 degrees Fahrenheit) and drop to -180 degrees Celsius (-290 degrees Fahrenheit) at night. It is unlikely life (as we know it) could survive on this planet.
10. Standing on on Mercury's surface at its closest point to the sun, the sun would appear more than three times larger than it does on Earth.

1. VENUSVenus is only a little smaller than Earth.
2. Venus is the second closest planet to the sun at a distance of about 108 million km (67 million miles) or 0.72 AU.
3. One day on Venus lasts as long as 243 Earth days (the time it takes for Venus to rotate or spin once). Venus makes a complete orbit around the sun (a year in Venusian time) in 225 Earth days.
4. Venus is a rocky planet, also known as a terrestrial planet. Venus' solid surface is a cratered and volcanic landscape.
5. Venus' thick and toxic atmosphere is made up mostly of carbon dioxide (CO2) and nitrogen (N2), with clouds of sulfuric acid (H2SO4) droplets.
6. Venus has no moons.
7. There are no rings around Venus.
8. More than 40 spacecraft have explored Venus. The Magellan mission in the early 1990s mapped 98 percent of the planet's surface.
9. No evidence for life has been found on Venus. The planet's extreme high temperatures of almost 480 degrees Celsius (900 degrees Fahrenheit) make it seem an unlikely place for for life as we know it.
10. Venus spins backwards (retrograde rotation) when compared to the other planets. This means that the sun rises in the west and sets in the east on Venus.

1. If the sun were as tall as a typical front door, Earth would be the size of a nickel.
2. Earth is the third planet from the sun at a distance of about 150 million km (93 million miles) or one AU. One day on Earth takes 24 hours (this is the time it takes the Earth to rotate or spin once). Earth makes a complete orbit around the sun (a year in Earth time) in about 365 days.
3. Earth is a rocky planet, also known as a terrestrial planet, with a solid and dynamic surface of mountains, valleys, canyons, plains and so much more. What makes Earth different from the other terrestrial planets is that it is also an ocean planet: 70 percent of the Earth's surface is covered in oceans.
4. The Earth's atmosphere is made up of 78 percent nitrogen (N2), 21 percent oxygen (O2) and 1 percent other ingredients -- the perfect balance for us to breathe and live. Many planets have atmospheres, but only Earth's is breathable.
5. Earth has one moon. Another name for a moon is satellite.
6. Earth has no rings.
7. Many orbiting spacecraft study the Earth from above as a whole system and together aid in understanding our home planet.
8. Earth is the perfect place for life.
9. Earth's atmosphere protects us from incoming meteoroids, most of which break up in our atmosphere before they can strike the surface as meteorites.

1. If the sun were as tall as a typical front door, Earth would be the size of a nickel, and Mars would be about as big as an aspirin tablet.
2. Mars orbits our sun, a star. Mars is the fourth planet from the sun at a distance of about 228 million km (142 million miles) or 1.52 AU.
3. One day on Mars takes just a little over 24 hours (the time it takes for Mars to rotate or spin once). Mars makes a complete orbit around the sun (a year in Martian time) in 687 Earth days.
4. Mars is a rocky planet, also known as a terrestrial planet. Mars' solid surface has been altered by volcanoes, impacts, crustal movement, and atmospheric effects such as dust storms.
5. Mars has a thin atmosphere made up mostly of carbon dioxide (CO2), nitrogen (N2) and argon (Ar).
6. Mars has two moons named Phobos and Deimos.
7. There are no rings around Mars.
8. More than 40 spacecraft have been launched for Mars, from flybys and orbiters to rovers and landers that touched surface of the Red Planet. The first true Mars mission success was Mariner 4 in 1965.
9. At this time in the planet's history, Mars' surface cannot support life as we know it. A key science goal is determining Mars' past and future potential for life.
10. Mars is known as the Red Planet because iron minerals in the Martian soil oxidize, or rust, causing the soil -- and the dusty atmosphere -- to look red.

1. If the sun were as tall as a typical front door, the Earth would be the size of a nickel and Jupiter would be about as big as a basketball. Jupiter orbits our sun, a star. Jupiter is the fifth planet from the sun at a distance of about 778 million km (484 million miles) or 5.2 AU.
2. One day on Jupiter takes about 10 hours (the time it takes for Jupiter to rotate or spin once). Jupiter makes a complete orbit around the sun (a year in Jovian time) in about 12 Earth years (4,333 Earth days).
3. Jupiter is a gas-giant planet and therefore does not have a solid surface. However, it is predicted that Jupiter has an inner, solid core about the size of the Earth.
4. Jupiter's atmosphere is made up mostly of hydrogen (H2) and helium (He).
5. Jupiter has 50 known moons, with an additional 17 moons awaiting confirmation of their discovery that is a total of 67 moons.
6. Jupiter has a faint ring system that was discovered in 1979 by the Voyager 2 mission.
7. Many missions have visited Jupiter and its system of moons. The Juno mission will arrive at Jupiter in 2016.
8. Jupiter cannot support life as we know it. However, some of Jupiter's moons have oceans underneath their crusts that might support life.
9. Jupiter's Great Red Spot is a gigantic storm (about the size of two to three Earths) that has been raging for hundreds of years.

1. If the sun were as tall as a typical front door, the Earth would be the sizeof a nickel and Saturn would be about as big as a basketball. Saturn orbits our sun, a star. Saturn is the sixth planet from the sun at a distance of about 1.4 billion km (886 million miles) or 9.5 AU.
2. One day on Saturn takes 10.7 hours (the time it takes for Saturn to rotate or spin once). Saturn makes a complete orbit around the sun (a year in Saturnian time) in 29 Earth years.
3. Saturn is a gas-giant planet and does not have a solid surface.
4. Saturn's atmosphere is made up mostly of hydrogen (H2) and helium (He).
5. Saturn has 53 known moons with an additional 9 moons awaiting confirmation of their discovery.
6. Saturn has the most spectacular ring system of all our solar system's planets. It is made up of seven rings with several gaps and divisions between them.
7. Five missions have been sent to Saturn. Since 2004, Cassini has been exploring Saturn, its moons and rings.
8. Saturn cannot support life as we know it. However, some of Saturn's moons have conditions that might support life.
9. When Galileo Galilei looked at Saturn through a telescope in the 1600s, he noticed strange objects on each side of the planet and drew in his notes a triple-bodied planet system and then later a planet with arms or handles. Thehandles turned out to be the rings of Saturn.

1. If the sun were as tall as a typical front door, Earth would be the size of a nickel and Uranus would be about as big as a baseball. Uranus orbits our sun, a star. Uranus is the seventh planet from the sun at a distance of about 2.9 billion km (1.8 billion miles) or 19.19 AU.
2. One day on Uranus takes about 17 hours (the time it takes for Uranus to rotate or spin once). Uranus makes a complete orbit around the sun (a year in Uranian time) in about 84 Earth years.
3. Uranus is a gas giant and therefore does not have a solid surface. The bulk (80 percent or more) of the mass of Uranus is made up of a hot dense fluid of "icy" materials (water (H2O), methane (CH4). and ammonia (NH3)), above a small rocky core.
4. Uranus has an atmosphere which is mostly made up of hydrogen (H2) and helium (He), with a small amount of methane (CH4).
5. Uranus has 27 moons. Uranus' moons are named after characters from the works of William Shakespeare and Alexander Pope.
6. Uranus has faint rings. The inner rings are narrow and dark and the outer rings are brightly colored.
7. Voyager 2 is the only spacecraft to have visited Uranus.
8. Uranus cannot support life as we know it.
9. Like Venus, Uranus has a retrograde rotation (east to west). Unlike any of the other planets, Uranus rotates on its side, which means it spins horizontally.

1. If the sun were as tall as a typical front door, the Earth would be the size of a nickel and Neptune would be about as big as a baseball. Neptune orbits our sun, a star. Neptune is the eighth planet from the sun at a distance of about 4.5 billion km (2.8 billion miles) or 30.07 AU.
2. One day on Neptune takes about 16 hours (the time it takes for Neptune to rotate or spin once). Neptune makes a complete orbit around the sun (a year in Neptunian time) in about 165 Earth years (60,190 Earth days).
3. Like the other gas giants, Neptune does not have a solid surface. Neptune is mostly made of a very thick, very hot combination of water (H2O), ammonia (NH3), and methane (CH4) over a possible heavier, approximately Earth-sized, solid core.
4. Neptune's atmosphere is made up mostly of hydrogen (H2), helium (He) and methane (CH4).
5. Neptune has 13 moons. Neptune's moons are named after various sea gods and nymphs in Greek mythology.
6. Neptune has six rings.
7. Voyager 2 is the only spacecraft to have visited Neptune.
8. Neptune cannot support life as we know it.
9. At times during the course of Neptune's orbit, dwarf planet Pluto is actually closer to the sun, and us, than Neptune. This is due to the unusual elliptical (egg) shape of Pluto's orbit.