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The Solar System

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Solar System

The word "solar" refers to the sun; the sun is one of the 150 billion stars of the Milky Way. It moves through space taking with it a larger family of objects. The whole group is called the solar system. Our solar system is elliptical in shape. The sun is the center of the solar system. Solar system is always in motion. Its largest and most important members are the nine known planets and their moons, along with smaller objects called comets, asteroids, and meteoroids that orbit the sun. The sun is the biggest object in our solar system. It contains 99.8% of the solar system's mass. Many scientists believe that our Solar System is over 4.6 billion years old.

Scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, may be by the explosion of a nearby star called SUPERNOVA. This explosion made waves in space that squeezed the cloud of gas and dust. Squeezing made the cloud start to collapse, as gravity pulled the gas and dust together, forming a solar nebula. The sun's nuclear fires ignited at the dense center of this nebula. The planets were born in the swirling currents of the great cloud.

The planets Mercury, Venus, Earth, and Mars, evolved as globes of rock that are present near the Sun. They were too small and their gravitational fields too weak to capture. However, far from the sun, the massive planets Jupiter and Saturn, with powerful gravitational fields, did attract and hold thick gaseous atmospheres of Hydrogen and Helium.


The Sun

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The Sun

The Sun is our closest star. It is a member of the Milky Way galaxy. The diameter of the Sun is 1,392,000 kilometers. It is believed to be over 4 billion years old. The Sun is a medium sized star known as a yellow dwarf. The Sun spins slowly on its axis as it revolves around the galaxy.

The Sun is a large ball of gas consisting mostly of hydrogen and helium. The Sun is about 109 times larger than Earth.

The center, or core, of the Sun is very hot. The temperature in its core is estimated to be over 15,000,000 degrees Celsius. A process called "nuclear fusion" takes place there. Nuclear fusion produces a lot of energy. Some of this energy travels out into space as heat and light. Some of it reaches the Earth!

We can see storms on the Sun's surface called as "sunspots" because they look like dark spots on the Sun's surface. The Sun also produces big explosions of energy called solar flares. These flares shoot fast moving particles off the Sun's surface. These particles can hit the Earth's atmosphere and cause a glow called an Aurora.

The Sun has several layers: the core, the radiation zone, the convection zone, and the photosphere (which is the surface of the Sun). In addition, there are two layers of gas above the photosphere called the chromosphere and the corona. The following are the events that occur on the Sun frequently: sunspots, solar flares, solar wind, and solar prominences.

Without the Sun, the Earth would be a lifeless ball of rock and ice. The Sun warms our planet, creates our weather, and gives energy to plants providing food and energy to support life on Earth. The Sun is a large ball of gas consisting mostly of hydrogen and helium. The Sun is about 109 times larger than the Earth. Scientists estimate that the temperature at the center of the Sun is about 15 million degrees Celsius. This is similar to exploding a hydrogen, or nuclear, bomb. Large explosions on the Sun's surface cause solar flares that shoot up high into space. The surface temperature is about 4000 degrees Celsius. Energy released from the Sun radiates in all directions, reaching the Earth and other planets. The further the planet is from the Sun, the less energy it receives.


Other Objects in the Solar System

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Asteroids: Asteroids are rocky and metallic objects that orbit the Sun but are too small to be considered as planets. They are known as minor planets. Most of the asteroids in our solar system can be found orbiting the Sun between the orbits of Mars and Jupiter. This area is sometimes called the "asteroid belt". A few asteroids approach the Sun more closely. None of the asteroids have atmospheres.

Asteroid belt: The asteroid belt is a doughnut-shaped concentration of asteroids orbiting the Sun between the orbits of Mars and Jupiter, closer to the orbit of Mars.


Other objects in the solar system

Comets: A comet is made of dirty ice, dust, and gas. Scientists believe that comets are made up of material left over when the Sun and the planets were formed. When a comet gets close to the Sun, part of the ice starts to melt. Scientists think about 100,000 million comets orbit the Sun. There are some comets orbiting the Sun like planets. Their orbits take them very close to and very far away from the Sun.

A comet can be seen only when it comes close to the Sun. The Sun's heat melts the comet's ice to form glowing gases. The gases stream out into a long tail that can extend to millions of kilometers.



Meteorites: Besides asteroids some smaller pieces of rocks and dust also orbit the Sun. These pieces of rock or dust enter the Earth's atmosphere. As they pass they encounter great friction, which causes them to heat up and burn out. These burning pieces of rock or dust are called as meteors. Although they are not stars, people call them as shooting stars, because they flash light across the sky. Most of the meteors burn up before they reach the Earth. Some are so large that a part of it reaches the ground as a meteorite.

Any leftover part that does strike the Earth is called a meteorite. A meteorite can make a hole or crater in the ground when it hits it. The larger the meteorite, the bigger the hole.


Books about the Sun

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Links to other sites on the Sun

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The Virtual Sun http://www.michielb.nl/sun/
The Starry Sky http://starryskies.com/solar_system/sun_html/sun.html
All About the Sun http://www.windows.ucar.edu/cgi-
Beginning of the Solar System


Exploring the Solar System http://www.kidsastronomy.com/solar_system.htm
Future of the Solar System http://www.windows.ucar.edu/cgi-bin/tour.cgi?link=/our_solar_system/solar_system_fate.html

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