- Sun is a huge, bright sphere of mostly ionized gas, about 4.5 billion years old, and is the closest star to Earth at a distance of about 150 million km. The next closest star - Proxima Centauri - is nearly 268,000 times farther away. There are millions of similar stars in the Milky Way Galaxy (and billions of galaxies in the universe).
- Our Sun supports life on Earth. It powers photosynthesis in green plants and is ultimately the source of all food and fossil fuel. The connection and interaction between the Sun and the Earth drive the seasons, currents in the ocean, weather, and climate.
- The Sun is some 333,400 times more massive than Earth and contains 99.86 percent of the mass of the entire solar system. It is held together by gravitational attraction, producing immense pressure and temperature at its core (more than a billion times that of the atmosphere on Earth, with a density about 160 times that of water).
- At the core, the temperature is 16 million degrees kelvin (K), which is sufficient to sustain thermonuclear fusion reactions. The released energy prevents the collapse of the Sun and keeps it in gaseous form. The total energy radiated is 383 billion trillion kilowatts, which is equivalent to the energy generated by 100 billion tons of TNT exploding each second.
- Mercury is named for the Roman messenger god because it quickly appears and disappears from the morning and evening skies. It's only visible a few days out of the year, and does not rise very far above the horizon.
- The small and rocky planet Mercury is the closest planet to the Sun; it speeds around the Sun in a wildly elliptical (non-circular) orbit that takes it as close as 47 million km and as far as 70 million km from the Sun. Mercury completes a trip around the Sun every 88 days, speeding through space at nearly 50 km per second, faster than any other planet.
- Temperatures on its surface can reach a scorching 467 degrees Celsius. But because the planet has hardly any atmosphere to keep it warm, nighttime temperatures can drop to a frigid -183 degrees Celsius. If you were on the side of the planet facing towards the Sun, you would quickly melt, as the temperature would be around 700 degrees! The "daytime" temperature on Mercury varies, depending on how close it is to the Sun. At the other extreme, the temperature on the "nighttime" side of the planet (the side away from the Sun) can be over 300 degrees below zero! Mercury is not a very pleasant place
- Because Mercury is so close to the Sun, it is hard to see from Earth except during twilight. Until 1965, scientists thought that the same side of Mercury always faced the Sun. Then, astronomers discovered that Mercury completes three rotations for every two orbits around the Sun. If you wanted to stay up for a Mercury day, you'd have to stay up for 176 Earth days.
- Mercury does not spin as fast as Earth, though, so a Mercurian day (the time it takes a planet to rotate once) is 59 Earth days!
- Mercury is the second smallest planet in the solar system. Pluto is the only planet that is smaller
- Earth is about 7,200 miles in diameter, while tiny Mercury is less than half that size at about 3,000 miles in diameter.
- Mercury is so small that Ganymede, one of Jupiter’s moons, and Titan, one of Saturn's moons, is both larger.
- Mercury is one of the rocky planets of the solar system, along with Earth and Venus. Mercury is made up mostly of iron, with a thin rocky layer on the planet surface.
- On the surface of Mercury, you will see that there are many craters on its surface. The planet has been hit many, many times through the years by asteroids and other objects. These impacts are responsible for all the craters on the surface. Earth probably had this many craters at one time, but our weather has worn the down over the years.
- At first glance, if Earth had a twin, it would be Venus. The two planets are similar in size, mass, composition, and distance from the Sun. Venus is almost the same size as Earth, with a diameter of a little over 7200 miles. .But there the similarities end. Venus has no ocean
- Venus is covered by thick, rapidly spinning clouds that trap surface heat, creating a scorched greenhouse-like world with temperatures hot enough to melt lead and pressure so intense that standing on Venus would feel like the pressure felt 900 meters deep in Earth's oceans. These clouds reflect sunlight in addition to trapping heat. Because Venus reflects so much sunlight, it is usually the brightest planet in the sky.
- Venus is the second planet from the Sun, located in between Mercury and Earth. The orbit, or path, Venus follows around the Sun is nearly circular, so the planet's distance from the Sun averages about 65 million miles
- Being closer to the Sun, a Venusian year, the time it takes for it to complete a trip around the Sun, is just 225 days. Venus spins more slowly than Earth, though, so a day on Venus, the time it takes for the planet to turn once, is 243 days, which means that a day on Venus is longer than it's year! Even stranger is the fact that Venus rotates from East to West, which is just the opposite of Earth and most of the other planets.
- Venus is the second-brightest object in the sky, being outshone only by the Moon. You would never guess that something that is so beautiful could be so unpleasant in reality
- Venus is a very unpleasant place, with winds that blow constantly at hundreds of miles per hour and extremely high temperatures. This planet is an example of a runaway greenhouse effect on a planetary scale
- Venus was named for the goddess of love and beauty. This is definitely a case of beauty being only skin deep, as Venus is a very unpleasant place, with winds that blow hundreds of miles an hour, and temperatures that are hot enough to melt most metals!
- Venus is one of the solar system's rocky planets, along with Earth and Mercury. The planet has an iron core, which is covered by a rocky layer. This rocky layer has a lot of lava, which has been generated by the many volcanoes on its surface.
- The bright white light that we see from Earth is a result of sunlight being reflected off the clouds that completely cover the planets surface. These clouds are made of sulfuric acid, which is an extremely dangerous substance. When you get to the planet's surface, things get even worse. The temperature on Venus averages around 900 degrees Fahrenheit, which is hot enough to melt lead! That's not all, the clouds on Venus have created at atmosphere that is the same as being half a mile underwater here on Earth The air pressure would be enough to crush some submarines. Finally the winds on Venus are almost always faster than a tornado, averaging around 240 miles per hour! The few spacecraft that have managed to land on Venus have lasted less than an hour before the heat and air pressure have melted and crushed them.
Venus has a surface that has many mountains (some higher than Mount Everest), volcanoes and plains filled with lava.
- Earth The air pressure would be enough to crush some submarines. Finally the winds on Venus are almost always faster than a tornado, averaging around 240 miles per hour!
- Mars is much smaller than Earth, but recent research shows that it once had flowing rivers. Mars also has a canyon that stretches over 2000 miles.
- Mars is the fourth planet from the Sun, located in between Earth and Jupiter, with an average distance of around 140 million miles. The orbit, or path, the planet takes around the Sun is an mild ellipse, or stretched circle, with Mars being about 128 million miles from the Sun at its closest and 154 millions away at its furthest.
- Since Mars is so much further away from the Sun than Earth, a Martian year, which is the time it takes to go around the Sun once, is much longer at 687 Earth days. A Martian day, which is the time it takes the planet to spin around once, is a little longer than an Earth day, at 24 hours and 37 minutes.
- Mars, with a diameter of about 4070 miles, is a little more than half the size of Earth. To put it another way, if Earth was the size of a baseball, Mars would be about the size of a golf ball.
- Mars has two very tiny moons, Phobos (top) and Deimos (bottom). The two Martian moons are among the smallest moons in the solar system. Phobos is only about eighteen miles in diameter, while Deimos is even smaller at around nine miles in diameter. The two Martian moons are actually asteroids, which are small rocky bodies that are scattered throughout our solar system. A very long time ago, the two asteroids that are the moons came close enough to Mars that they were "captured" by Mars gravity. They have been circling the planet ever since.
- Mars has a central core, like that of a golf ball, made if iron. In this way, the Red Planet is similar to Earth. On top of the iron core, Mars has a layer of rock, again like Earth, but Mars' rock layer is much thicker than that of Earth. Finally, Mars has a very thin atmosphere, or layer of air, that covers the planet. The atmosphere of Mars is much thinner than that on Earth, but Mars still has weather, including dust storms
- Mars has a rocky, dusty surface, complete with clouds and dust storms that can cover the whole planet at once. The weather on Mars is very cold, with an average temperature of around ten below zero. During the Martian winter, the temperature gets even colder, and can drop to 160 degrees below zero! During the Martian winter, the planet has ice caps at the north and south poles like Earth does. The difference is that these caps are made of frozen carbon dioxide, or "dry ice".
- Mars also has mountains, sandy deserts and many inactive volcanoes. Mars has the largest volcano in the solar system, Olympus Mons, which is over 45,000 feet tall, much higher than Mount Everest, and is over 600 miles wide at its base.
- Its largest planet in our solar system. Jupiter is so large that over 1300 Earths would fit inside it! Jupiter is over 85 thousand miles in diameter, dwarfing Earth, which is a little over 7,600 miles in diameter.
- It also makes up its own miniature solar system with its family of at least sixteen Moons! Galileo would be astonished at what we have learned about Jupiter and its moons in the past 30 years. Io is the most volcanically active body in our solar system. Ganymede is the largest planetary moon and has its own magnetic field. Ganymede is made up of rocky ice.
- A liquid ocean may lie beneath the frozen crust of Europa. An icy ocean may also lie beneath the crust of Callisto. Callisto is covered with thousands of craters, which are the result of collisions with other objects in space. In 2003 alone, astronomers discovered 23 new moons orbiting the giant planet. Jupiter now officially has 63 moons - by far the most in the solar system. Many of the outer moons are probably asteroids captured by the giant planet's gravity.
- Jupiter is the most massive planet in our solar system, and in composition it resembles a small star. In fact, if Jupiter had been between fifty and one hundred times more massive, it would have become a star rather than a planet
- Jupiter is the fifth planet from the Sun, located in between Mars and Saturn. Jupiter is the first gas planet in our solar system, as well as being the first of what are called the Outer Planets.
- It's average distance from the Sun is almost 470 million miles. Its orbit, or path it follows, around the sun is nearly a perfect circle. The closest it comes to the sun is about 460 million miles, and the furthest away it gets is a little over 500 million miles. Since Jupiter is so much further away from the Sun than Earth, its year, which is the time it takes to go around the sun once, is very long. A year on Jupiter is almost twelve Earth years!
- A day on Jupiter, which is the amount of time it takes to spin around once, is much shorter than a day here on Earth. The giant planet's day is only about ten hours long, less than half as long as a Earth day.
- The two largest moons are both bigger than the planets Pluto and Mercury, and the largest of them is almost the size of Mars! In addition to being very large, these four moons of Jupiter are also very interesting.
- Many of the planet's moons have been named for Jupiter's daughters.
- Jupiter is a gas planet, which means that is not solid at all, but instead is a giant cloud made up mostly of the gas elements hydrogen and helium. You may be wondering "If Jupiter is just gas, how can it be so large and what holds it together?". These are both excellent questions. Most things in the universe are not solid, but are giant balls or clouds of gas, and Jupiter is the same. Our Sun is a ball of gas that also gives us heat and light. What holds Jupiter together is the same thing that makes something drop to the ground here on Earth.
- Since Jupiter is a gas planet, it doesn't have a surface. This means that if you tried to land on the planet, you would not be able to find anything solid to land on. This does not mean that Jupiter does not have its own strange kind of "weather". The clouds that make up Jupiter are constantly swirling around the planet, driven by winds that average over two hundred miles per hour. The winds create an ever-changing pattern of what we call storms on Earth. The most famous of these storms is the Great Red spot.
- The Ringed Planet is probably the most visually stunning planet in our planetary neighborhood. Saturn's giant rings are actually made of thousands of small particles of dust and ice. The divisions in the rings we see from Earth are caused by some of Saturn's smaller moons.
- In 1610, Italian Galileo was the first astronomer to gaze at Saturn through a telescope. To his surprise, he saw a pair of objects on either side of the planet, which he later drew as "cup handles" attached to the planet on each side. In 1659, Dutch astronomer Christiaan Huygens announced that this was a ring encircling the planet. In 1675, Italian-born astronomer Jean Dominique Cassini discovered a gap between what are now called the A and B rings.
Saturn is the sixth planet in the solar system, located in between Jupiter and Uranus. Its average distance from the Sun is over 850 million miles, compared to Earth's which is 93 million miles. Saturn's orbit, the path it follows around the Sun, is nearly a circle. The closest the as planet comes to the Sun is around 840 million miles, while the furthest away it gets is around 930 million miles.
- Since Saturn is so far away from the Sun, it takes a very long time for it to go around the Sun once. A year on Saturn, the amount of time it takes for this trip, is twenty-nine and one-half Earth years! A day on Saturn though is much shorter than one of our Earth days. The giant planet spins around, or rotates, once every ten and one-half hours.
- Saturn is the second-largest planet in the solar system. Jupiter is the only planet that is bigger. The gas giant is 72 thousand miles in diameter; almost ten times the size of Earth. In spite of its huge size, though, Saturn weighs very little. It is a very light gas planet. Saturn is so light, in fact, that it would float in water, assuming you had a very large swimming pool.
- The beautiful rings that are Saturn's most famous feature are absolutely huge. The rings are over 160 thousand miles in diameter. That is two-thirds of the distance from Earth to the Moon! The rings are very, very thin when compared to their width. They average less than fifty feet thick! This explains why the rings seem to disappear when we are looking at Saturn from the edge.
- There are several gaps in the rings. If you could get even closer, you would see that even the parts that appear to be solid are not solid at all, but are made up of billions of snowballs, ranging in size from the snowball you throw in winter to ones that are bigger than a house!. Many moons that circle the giant planet cause the gaps in Saturn’s rings. The moons act as "shepherds" that keep the rings lined up in the beautiful patterns. One of the bands in Saturn's rings is even braided, much like a pigtail. The Voyager mission sent back pictures of this amazing feature.
- Saturn has at least eighteen moons, more than any other planet in our solar system. The many moons of Saturn play an important part in keeping the shape of Saturn's spectacular rings. One of Saturn's most interesting moons is Titan. Titan has a very thick atmosphere, or blanket of air, surrounding it. The atmosphere on Titan contains a lot of the gas nitrogen, like what we have here on Earth. Scientists believe that Titan may liquid water on its surface, which would be an exciting discovery if it turns out to be true.
- In Roman mythology Saturn was the father of Jupiter. In our solar system, this is a case where the son outgrew the father.
- Saturn is a lot like Jupiter, in that it is a gas planet, made of mostly of the elements hydrogen and helium. Saturn is a lot lighter, or less dense, than Jupiter. The combination of its lightweight and speedy rotation causes Saturn to spread out, or oblate, at its center.
- Jupiter spreads out at its center, too, like the rest of the gas planets, but not nearly as much as Saturn. What's It Like on the Surface, Since Saturn is a gas planet, and it does not have a solid surface like Earth does. Landing a spacecraft on Saturn would be like trying to land an airplane on a cloud. The clouds we see when we look at Saturn are just the top layer of a very deep Saturn.
- Saturn is a lot like Jupiter, in that it is a gas planet, made of mostly of the elements hydrogen and helium. Saturn is a lot lighter, or less dense, than Jupiter. The combination of its lightweight and speedy rotation causes Saturn to spread out, or oblate, at its center.
- Jupiter spreads out at its center, too, like the rest of the gas planets, but not nearly as much as Saturn. What's It Like on the Surface, Since Saturn is a gas planet, and it does not have a solid surface like Earth does. Landing a spacecraft on Saturn would be like trying to land an airplane on a cloud. The clouds we see when we look at Saturn are just the top layer of a very deep layer that covers a center of liquid hydrogen. The clouds on Saturn are blown by constant winds that can blow at speeds up to one thousand miles per hour at the equator, or center, of the planet. Saturn does have different colored spots, or features, in its clouds, but nothing that is as spectacular as the Great Red Spot on Jupiter.
- Uranus is the seventh planet in our solar system, located in between Saturn and Neptune. Uranus is very far away from the Sun. Its average distance from the Sun is about one and three-quarters billion miles, or about twenty times the distance from the Sun to Earth. The path, or orbit, Uranus follows around the Sun is an ellipse, or stretched out circle, which means that Uranus’ distance from the Sun varies from about 1.7 billion (1,700,000,000) miles at its closest to about 1.87 billion (1,870,000,00) miles at its furthest away.
- Uranus has been revealed as a dynamic world with some of the brightest clouds in the outer solar system and 11 rings. Uranus gets its blue-green color from methane gas above the deeper cloud layers (methane absorbs red light and reflects blue light).
- Since Uranus is so far away from the Sun, it takes it a very long to go around the Sun once. A year on Uranus, the amount of time it takes for this trip, is 84 Earth years. A day on Uranus, which is the amount of time it takes for the plant to spin around, or rotate, once is shorter than a day here on Earth. The blue-green planet spins around once in a little over seventeen hours.
- One of the many odd facts about Uranus is that it is "lying on its side" as it faces the Sun. Earth faces the sun standing almost straight up, with the north and south poles at the top and bottom as it looks at the Sun. For some reason, Uranus has rolled over, so what we would think of as the south pole is facing the Sun. Scientists don't know why the planet does this, but it may be the result of a collision with some other body in space. Also, the planet rotates, or spins, from East to West, which is the exact opposite of the way that Earth spins.
- The planet will appear as a faint blue-green light
- Uranus is about four times the size of Earth, but it is still much smaller than either Saturn or Jupiter. Uranus is a little over 30 thousand miles in diameter, compared to Earth's diameter of around 7,600 miles. Even though Uranus is much larger than our Earth, it is dwarfed when compared to mighty Jupiter, which is over 85 thousand miles in diameter.
- Rings of Uranus are a very faint imitation of the spectacular rings that surround Saturn. While the rings of Saturn are made up of fairly small pieces of bright white ices, the rings of Uranus for the most part are made of larger chunks of very dark, rocky material. The darkness of the chunks that make up the rings help explains why we cannot see them from Earth.
- it has an interesting collection of at least fifteen moons. they are Miranda, Ariel, Umbriel, Titania and Oberon. In case you are wondering where such unusual names came from, they are named after characters in the stories of William Shakespeare and Alexander Pope. The remaining ten moons in the collection are much smaller and a lot closer to the planet. Some of the smaller moons act as "shepherds", helping to keep some order in some of the rings. The others may be comets or asteroids that have been "captured" by the planet as they attempted to fly by.
- Uranus is another member of the family of gas planets that live in our solar system, but it is quite a bit different from Jupiter and Saturn. First, it has methane gas mixed in with the hydrogen and helium that make up most of the giant planets. Methane is what gives Uranus its unusual color. Second, Uranus appears to have a core, or center, of melted rock, which changes into a dirty ocean made of of water, ammonia and other elements the further from the center you go. Finally, the dirty ocean changes into the blue-green cover of clouds that we see in the pictures. Scientists believe that the layer of the planet are not separate, like those of an onion, but gradually blend with one another.
- By carefully studying the pictures sent back by the Voyager spacecraft, scientists were able to see that there are winds blowing at over four hundred miles an hour.
- Neptune is the eighth, or next to last, planet in our solar system. It is located in between Uranus and Pluto, and is a very long way away from the Sun. Its average distance from the Sun is almost 2.8 billion (2,800,000,000) miles, or over thirty times the distance from Earth to the Sun. The orbit, or path, Neptune follows around the Sun is almost a perfect circle. The closest Neptune gets to the Sun is about 2.7 billion miles, and the furthest away it gets is a little over 2.8 billion miles. At this distance, our Sun is just another bright light in Neptune's sky. Since Neptune is so far away from the Sun, one of its years, which is the amount of time it takes for the planet to go around, or orbit, the Sun once is a very long time.
- A year on Neptune lasts for 165 of our Earth years! A day on Neptune, though, is shorter than a day here on Earth. The gas planet spins, or rotates, once every sixteen hours.
- Neptune is about 30 thousand miles in diameter, about four times the size of Earth, which is about 7,600 miles in diameter Neptune and Uranus are almost the same size, but both seem tiny in comparison to mighty Jupiter, which is almost three times as large as either of them.
- The rings of Neptune are made up of fairly small, very dark clumps of rock. Scientists believe that most of these clumps are about the size of a compact car. There is also a large amount of dust in the rings. Even though the rings are very faint, they still had a surprise for us. One of the rings has a twist in it!.
- Neptune has eight moons that we know about and there may be more. The family of moons surrounding Neptune is unusual because Triton, the largest, is over 1,600 miles in diameter and the rest of them are tiny, some as small as twenty miles in diameter.
- Triton was the last solid object Voyager would see before it left our solar system. Saving the one of its best discoveries for last, the spacecraft sent back pictures of nitrogen "geysers" erupting on Triton's surface.
- Neptune has a small central core, or ball, made of up melted rock. Above the rocky center, the planet is covered by extremely cold water, which eventually changes into the top layer of hydrogen and helium, with a little methane mixed in. The methane is what gives Neptune its color.
- Since Neptune is a gas planet, it does not have a solid surface like we do here on Earth. In spite of this, Neptune has some of the most unusual "weather" in the solar system. The winds on Neptune can blow as fast as twelve hundred miles per hour at the planet’s equator!
- PLUTO The most distant planet in our solar system, is so far away that the Sun is not much bigger or brighter than most of the other stars in its sky. Pluto also has a moon, Charon, that is nearly as big as the planet itself.
- This distant region consists of thousands of miniature icy worlds with diameters of at least 1,000 km and is also believed to be the source of some comets.
- Pluto is a very long way from the Sun. Its average distance from the Sun is over 3.5 billion (3,500,000,000) miles. The closest Pluto gets to the Sun is over 2.7 billion (2,700,000,000) miles, and the furthest away it gets is over 4.5 billion (4,500,000,000) miles From Pluto, the Sun is not much brighter than any other star. Not only is Pluto a very long way from the Sun, but its orbit is tilted. If you could look at our solar system from an "edge", most of the planets would be on a line like a table top, with the Sun being in the middle. This line, also called a plane, is the ecliptic, and the rest of the planets' orbits stay on this line. Pluto's orbit though is tilted at an angle to the rest of the solar system. Since Pluto is so far away from the Sun, one of its years, which are the time it takes for the planet to go around the Sun once, is a very long time. A year on Pluto lasts for 248 Earth years.
- A day on Pluto, which is the length of time it takes for the planet to spin around once, is also longer than a day here on Earth. It takes Pluto over six Earth days to spin around once. Pluto is also one of the planets that spins around in the opposite direction from Earth. This means that the dim Sun would rise in the West and set in the East.
- Pluto is the smallest planet in our solar system at a little over 1,300 miles in diameter, or about one-sixth the diameter of Earth. Put another way, if Earth was the size of a basketball, Pluto would be the size of a ping-pong ball. Many of the moons of other planets, including our very own Moon, are larger than Pluto.
- Pluto has one tiny moon, named Charon, that wasn't discovered until 1978. Charon is half the size of Pluto. No other moon in the solar system is as large, when compared to its mother planet, as Charon. Pluto and Charon are so similar in size that some astronomers think of them as a double planet
- The current studies tell us that Pluto is made up of a mixture of rocks and several kinds of "ices". Scientists believe that most of the ices that make up Pluto are frozen methane and ammonia.
- The surface of Pluto is very dark and extremely cold. Since the planet is so far away from the Sun, it gets almost no light or heat. Scientists believe that the temperature on the surface of the ninth planet over four hundred degrees Fahrenheit below zero. At this low temperature, almost everything freezes solid. Scientists here on Earth have determined that Pluto does have a very thin atmosphere, but it is far too thin to support any kind of life. is the ninth, or last, planet in the solar system. The orbit, or path the planet takes around our Sun is an ellipse, or stretched out circle. For this reason there are times when Pluto is the furthest away from the Sun. There are also times when it is closer to the Sun than Neptune.