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Video:What Is the Definition of the Sun?

with Michael Shara

There is a lot of information available about the defintion of a star. See this basic definition of the sun if you'd like to learn more about our greatest light source.See Transcript

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Transcript:What Is the Definition of the Sun?

Hi, I'm Michael Shara, Curator of Astrophysics at The Museum of Natural History, here for About.com. Today, I'm going to tell you all about the sun.

Facts About Our Sun

The Sun is by far the largest object in our solar system. Both the biggest and the most massive. It is a star. Must brihter than all the other stars in the sky because it's much closer to us. But, still a huge distance. About 93 million miles away. The reason the sun shines, the reason it's so bright is because it's really a nuclear reactor. All of the hydrogen inside the core of the Sun and at the inner part of the Sun is at a stupendous 17 million degrees Kelvin in temperature. And the protons that make up the hydrogen are crashing into each other at enormous speed. Some of those protons fuse together to make helium. And, when they do they release energy. That energy is mostly bottled up in the core of the sun, but over millions of years it trickles out to the surface, makes the surface hot. And that's why the Sun shines.

Age of Our Sun

We know that the sun is about 4 ½ billion years old . The Sun has an eleven year or twenty-two year cycle of activity when the number of sun spots is almost zero at the beginning, and then rises to a maximum, and then, decreases again. And, the magnetic field of the Sun. Or, the direction in which the north and south poles, in the magnetic fields of the sun spots of the sun flip, change sides. This happens over and over again.

Sun Spots

There are times when the Sun has dozens or even a hundred sun spots on its surface. The Sun gives off light of all wave lengths. Very, very long wavelength light, or radio waves, come from the Sun and sometimes, we can hear them, with our radio telescopes.

Light From the Sun

The Sun also gives off infra-red or heat light as well as visible and ultra-violet light. There are x-rays given off by storms on the surface of the sun. So, all the elctro-magnetic spectrum, all the possible wave lengths of light that we can detect are given off by the Sun.

We're pretty sure the Sun has another 4 ½ billion years to go as a hydrogen burning star.

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