Sun Facts - to help clarify some questions this week

Solar Snippets: 

          source - http://www.lawrencehallofscience.org/pass/passv12/WheresEast.pdf

The Sun's name: Egyptians called it Ra; the Greeks

called it Helios; the Romans called it Sol. There are

many other names—each culture is different.

Sun's Age: 4.5 billion years (happy birthday!)

Sun's size: Diameter is about 1.4 million km (870

million mi), or 109 times Earth Diameter. In terms of

volume, the Sun could contain 1.3 million Earths

Sun's Rotation Rate: at the equator the surface

rotates once every 25.4 days; near the poles it's as

much as 36 days. This odd behavior is due to the fact

that the Sun is not a solid body like the Earth.

Similar effects are seen in the gas planets.

Surface Temperature of the Sun: about 5,800°K

(5,430°C, or 9,800°F)

Core Temperature of the Sun: 15,600,000°K

(28,000,000°F)

Temperature of the Sun's atmosphere (called the

corona): Over 1,000,000K° (The fact that this is so

much higher than the Sun's surface temperature was

a puzzlement for a long time. We are only beginning

to understand the reason for this—it has to do with

activity on the surface of the Sun.

The Sun is made of about 75% hydrogen and 25%

helium. This changes slowly over time as the Sun

converts hydrogen to helium in its core.

Sunspots are "cool" regions, only 3800 K (they look

dark only by comparison with the surrounding

regions). Sunspots can be very large, as much as

50,000 km in diameter—larger than Earth! Sunspots

are caused by complicated, not very well

understood changes in the Sun's magnetic field.

Pressure at the Sun's core: 250 billion times Earth

atmospheric pressure.

Density at the Sun's core: > 150 times that of water.

Energy output of the Sun: 386 billion billion

megawatts. Each second about 700,000,000 tons of

hydrogen are converted to about 695,000,000 tons of

helium and 5,000,000 tons of energy in the form of

gamma rays. As it travels out toward the surface, the

energy is continuously absorbed and re-emitted at

lower and lower temperatures so that by the time it

reaches the surface, it is primarily visible light. Since

its birth it has used up about half of the hydrogen in

its core. It will continue to radiate "peacefully" for

another 5 billion years or so (although its luminosity

will approximately double in that time). But

eventually it will run out of hydrogen fuel. It will

then be forced into radical changes which, though

commonplace by stellar standards, will result in the

total destruction of the Earth (and probably the

creation of a planetary nebula).