10 Things You Should Know About the Sun

[b]1. The sun is by far the largest object in the solar system[/b]

[url=http://z.about.com/d/space/1/0/q/6/1/prominence.gif][img]http://z.about.com/d/space/1/6/q/6/1/prominence.gif[/img][/url]NASA
The sun contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest).
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[*]Equatorial Radius: 695,500 km
[*]Equatorial Circumference: 4,379,000 km
[*]Volume: 1,142,200,000,000,000,000 km[sup]3[/sup]
[*]Mass: 1,989,000,000,000,000,000,000,000,000,000 kg
[*]Density: 1.409 g/cm[sup]3[/sup]
[*]Surface Area: 6,087,799,000,000 km[sup]2[/sup]
[*][b]2. Our Sun is actually the closest star to Earth[/b]

[url=http://z.about.com/d/space/1/0/y/6/1/coronaloop_trace_big.jpg][img]http://z.about.com/d/space/1/6/y/6/1/coronaloop_trace_big.jpg[/img][/url]NASA
Our
Sun is an average star, meaning its size, age, and temperature fall in
about the middle of the ranges of these properties for all stars. While
some in our galaxy are nearly as old as the universe, about 15 billion
years, our sun is a 2nd-generation star, only 4.6 billion years old.
Some of its material came from former stars.
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[*]Spectral Type: G2 V
[*]Synodic Period: 27.2753 days
[*]Velocity Relative to Near Stars: 19.7 km/s
[*]Solar Constant (Total Solar Irradiance): 1.365 - 1.369 kW/m[sup]2[/sup]
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[b]3. We've always known the sun[/b]

[url=http://z.about.com/d/space/1/0/r/6/1/sun2_trace.jpg][img]http://z.about.com/d/space/1/6/r/6/1/sun2_trace.jpg[/img][/url]NASA/ESA
Unlike
many other objects in our solar system, the sun has been known to
humans since the dawn of time. There is no discovery date or discoverer.

[b]4. Since its creation, the sun has used up about half of the hydrogen in its core[/b]

[url=http://z.about.com/d/space/1/0/s/6/1/PIA03149.jpg][img]http://z.about.com/d/space/1/6/s/6/1/PIA03149.jpg[/img][/url]SOHO/Extreme Ultraviolet Imaging Telescope (EIT) consortium
Over
the next 5 billion years or so, it will grow steadily brighter as more
helium accumulates in its core. As the supply of hydrogen dwindles, the
Sun's core must keep producing enough pressure to keep the Sun from
collapsing in on itself. The only way it can do this is to increase its
temperature. Eventually it will run out of hydrogen fuel. At that
point, it will go through a radical change which will most likely
result in the complete destruction of the planet Earth.

[b]5. The Greeks named the sun Helios[/b]

[url=http://z.about.com/d/space/1/0/u/6/1/174608main_Image1A.jpg][img]http://z.about.com/d/space/1/6/u/6/1/174608main_Image1A.jpg[/img][/url]NASA
However,
the Romans used the name Sol, which is still in use today. Because of
the important role the sun plays in our lives, it has been studied,
perhaps, more than any other object in the universe, outside out own
planet Earth. Our Sun has inspired mythology in almost all cultures,
including ancient Egyptians, Aztecs, Native Americans, and Chinese.

[b]6. Ulysses was the first spacecraft to study our Sun's poles[/b]

[url=http://z.about.com/d/space/1/0/t/6/1/174607main_Image1.jpg][img]http://z.about.com/d/space/1/6/t/6/1/174607main_Image1.jpg[/img][/url]NASA
Launched
aboard the Space Shuttle Discovery and sent towards Jupiter with
powerful booster rockets. After studying Jupiter for 17 days, Ulysses
used the giant planet's gravity to hurl it into an orbit out of the
Ecliptic Plane, where planets orbit our Sun. The other primary
Solar mission is SOHO. The international Solar and Heliospheric
Observatory (SOHO) has been keeping a steady watch on the Sun since
April 1996.

[b]7. The sun's strong gravitational pull holds Earth and the other planets in place[/b]

[url=http://z.about.com/d/space/1/0/v/6/1/174602main_FullDisk3D.jpg][img]http://z.about.com/d/space/1/6/v/6/1/174602main_FullDisk3D.jpg[/img][/url]NASA
It keeps the planets orbiting inside the solar system:
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[*]Equatorial Surface Gravity: 274.0 m/s[sup]2[/sup]
[*]Escape Velocity: 2,223,720 km/h
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[b]8. The sun is made up of distinctive areas[/b]

[url=http://z.about.com/d/space/1/0/p/6/1/Sun_Earth.jpg][img]http://z.about.com/d/space/1/6/p/6/1/Sun_Earth.jpg[/img][/url]NASA
In
addition to the energy-producing solar core, the interior has two
distinct regions: a radiative zone and a convective zone. From the edge
of the core outward, first through the radiative zone and then through
the convective zone, the temperature decreases from 8 million to 7,000
K. It takes a few hundred thousand years for photons to escape from the
dense core and reach the surface.

[b]9. How does the sun's "surface" and "atmosphere" compare to planets?[/b]

[url=http://z.about.com/d/space/1/0/x/6/1/Ecliptic.jpg][img]http://z.about.com/d/space/1/6/x/6/1/Ecliptic.jpg[/img][/url]NASA
The
"surface," known as the photosphere, is just the visible 500-km-thick
layer from which most of the Sun's radiation and light finally escape,
and it is the place where sunspots are found. Above the photosphere
lies the chromosphere ("sphere of color") that may be seen briefly
during total solar eclipses as a reddish rim, caused by hot hydrogen
atoms, around the Sun. Temperature steadily increases with altitude up
to 50,000 K, while density drops to 100,000 times less than in the
photosphere.

[b]10. One unsolved mystery of the sun involves the corona ("crown")[/b]

[url=http://z.about.com/d/space/1/0/w/6/1/Venus_Transit.jpg][img]http://z.about.com/d/space/1/6/w/6/1/Venus_Transit.jpg[/img][/url]NASA
Above
the chromosphere lies the corona ("crown"), extending outward from the
Sun in the form of the "solar wind" to the edge of the solar system.
The corona is extremely hot - millions of degrees kelvin. Since it is
physically impossible to transfer thermal energy from the cooler
surface of the Sun to the much hotter corona, the source of coronal
heating has been a scientific mystery for more than 60 years.

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good information and every1 has 2 know it [img]https://2img.net/i/fa/i/smiles/icon_biggrin.png[/img]