our solar system
Our solar system consists of the sun, the planets and their moons, and other smaller objects that revolve around the sun.
Our solar system revolves around the sun. In other words, it is heliocentric -- in which Earth and all the other planets orbit the sun. All of our planets orbit our sun in ellipses. There are 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto) in our solar system, and they are divided into two groups - terrestrial plants and gas giants.
Our solar system revolves around the sun. In other words, it is heliocentric -- in which Earth and all the other planets orbit the sun. All of our planets orbit our sun in ellipses. There are 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto) in our solar system, and they are divided into two groups - terrestrial plants and gas giants.
Terrestrial Planets
The four terrestrial planets are Mercury, Venus, Earth, and Mars. These planets are small, dense, and have rocky surfaces.
Mercury: The surface of Mercury has many flat plains and craters, and its surface has not been changed in billions of years. Because no wind or water has altered Mercury's surface, Mercury must have virtually no atmosphere. Because of its close proximity to the sun, Mercury has high daytime temperatures, and these temperatures cause gas particles to move very fast. Also, Mercury has a small mass and weak gravity, so these fast moving gas particles easily escape into space. Temperatures on Mercury are extreme, ranging from 430 degrees Celsius in the daytime to -170 degrees Celsius at night.
Venus: Venus has a similar density and internal structure compared to Earth, but in many ways, Venus is very different. Venus's atmosphere is so thick it is always cloudy there. Its sky is covered with sulfuric clouds, and the air is mostly carbon dioxide. Also, the pressure of Venus's atmosphere is 90 times greater than the pressure of Earth's atmosphere. Venus also reflects most sunlight and radiation.
Mars: Mars's atmosphere is 95 percent carbon dioxide, like Venus's, except much thinner. Mars's surface is uneven, containing a variety of features that seem as if they were made by ancient streams, lakes, or floods. There are huge canyons and ancient coastlines. Because of these seemingly water-carved remains, scientists believe that a large amount of liquid water flowed on Mars's surface in the distant past. They also believe that Mars was warmer, and had a much thicker atmosphere, which would prevent water from turning into gas. Now, scientists believe that water is frozen under Mars's surface.
Earth: Earth has four main layers, the crust, the mantle, the outer core, and the inner core. The inner core is solid magnetic elements, such as nickel, and the outer core is liquid. Above the outer core is the mantle, which contains magma, or hot melted rock. Above the mantle is the crust, a solid rocky surface.
Mercury: The surface of Mercury has many flat plains and craters, and its surface has not been changed in billions of years. Because no wind or water has altered Mercury's surface, Mercury must have virtually no atmosphere. Because of its close proximity to the sun, Mercury has high daytime temperatures, and these temperatures cause gas particles to move very fast. Also, Mercury has a small mass and weak gravity, so these fast moving gas particles easily escape into space. Temperatures on Mercury are extreme, ranging from 430 degrees Celsius in the daytime to -170 degrees Celsius at night.
Venus: Venus has a similar density and internal structure compared to Earth, but in many ways, Venus is very different. Venus's atmosphere is so thick it is always cloudy there. Its sky is covered with sulfuric clouds, and the air is mostly carbon dioxide. Also, the pressure of Venus's atmosphere is 90 times greater than the pressure of Earth's atmosphere. Venus also reflects most sunlight and radiation.
Mars: Mars's atmosphere is 95 percent carbon dioxide, like Venus's, except much thinner. Mars's surface is uneven, containing a variety of features that seem as if they were made by ancient streams, lakes, or floods. There are huge canyons and ancient coastlines. Because of these seemingly water-carved remains, scientists believe that a large amount of liquid water flowed on Mars's surface in the distant past. They also believe that Mars was warmer, and had a much thicker atmosphere, which would prevent water from turning into gas. Now, scientists believe that water is frozen under Mars's surface.
Earth: Earth has four main layers, the crust, the mantle, the outer core, and the inner core. The inner core is solid magnetic elements, such as nickel, and the outer core is liquid. Above the outer core is the mantle, which contains magma, or hot melted rock. Above the mantle is the crust, a solid rocky surface.
gas giants
The four outer planets -- Jupiter, Saturn, Uranus, Neptune -- are called gas giants. They are larger and more massive than Earth, and do not have solid surfaces.
the role of gravity in the solar system
Gravity is the force that holds the our galaxy together - with a black hole at its center, the gravity holding all the stars, gas and dust together is immense. Inside our individual solar system, the sun holds the planets in elliptical orbits around this. Gravity is the key force that holds solar systems, stars, planets, and galaxies together. Without it, planets would drift apart, and nothing would hold the universe together.
the moon
When the Earth, sun, and other planets emerged, a planetismal the size of Mars struck Earth, ejecting large amounts of matter into space. A disk of orbiting material formed, and this matter eventually reshaped into the Moon. The moon is rough, rocky, and cold. Daytime temperatures can hit 123 Degrees Celsius, but drop down to -153 degrees Celsius at night. Temperatures can reach so high because the moon does not have an atmosphere to protect it. The absence of atmosphere means no wind, which means that no forces change the moon's surface. Therefore, the moon's terrain is rough, rocky, and littered with craters. These landmarks have been on the moon for billions of years, and will continue to remain there for maybe forever.
Movement of earth in space
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Earth revolves around the Sun in an elliptical orbit. One full revolution around the Sun takes approximately 365 1/4 days, or 1 year. Because we only count the 365 days and disregard the 1/4 of a day, every four years, we add an extra day to the year (the 29 of February) in a leap year. While the Earth orbits the Sun, it rotates on its own axis. One day is one full rotation on its own axis, which takes approximately 24 hours.
But how does the Earth stay in orbit? Two factors combine to keep the Earth in orb it around the sun, and the moon is orbit around Earth: inertia and gravity. Earth's gravity keeps pulling the moon toward it, preventing the moon from traveling in a straight line, while the moon keeps moving ahead because of its inertia. Earth's gravity keeps the moon from drifting off in to space in a straight line. Similarly, the Sun keep the Earth from drifting off in a straight line with gravity.
But how does the Earth stay in orbit? Two factors combine to keep the Earth in orb it around the sun, and the moon is orbit around Earth: inertia and gravity. Earth's gravity keeps pulling the moon toward it, preventing the moon from traveling in a straight line, while the moon keeps moving ahead because of its inertia. Earth's gravity keeps the moon from drifting off in to space in a straight line. Similarly, the Sun keep the Earth from drifting off in a straight line with gravity.
comets, asteroids, and meteors
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Comets: Comets are loose collections of ice, dust, and rocks, and orbits in long, narrow ellipses. Comets have four main parts: the coma, which is the fuzzy outer layer of dust and gas, the nucleus, the solid inner core, the dust tail, which is a trail of dust left behind the comet, and the gas tail, a stream of gas in space.
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Asteroids: Asteroids are rocky objects too small and too numerous to be considered planets. Most asteroids revolve in the asteroid belt in a fairly circular orbit between Maris and Jupiter. Most asteroids are less than a kilometer in diameter, and only Ceres, Pallas, Vesta, and Hygiea are over 300 kilometers across.
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Meteors: Meteoroids are chunks of rock or dust in space that come from comets or asteroids. Some meteoroids are created by the collision of two asteroids, or from the disintegration of a comet. When a meteoroid enters Earth's atmosphere, friction with the air creates heat and produces a streak of light in the sky called a meteor. Most meteoroids disintegrate, but some pass through the atmosphere and strike Earth's surface. These meteoroids are called meteorites.