Monday, February 27, 2012

Facts About Our Sun

I did go out and cross country ski again yesterday, but didn't take any pictures. How many photos can you take of the ski trails anyway?

I have been using my DVR to record all of the Universe and How the Universe Works shows. Yesterday I watched the one about our Sun. We perceive that the Sun rises each morning, shines all day, and sets each evening. But actually, the Sun does not rise or set. It just looks like it does because the Earth is moving. For the most part we take our Sun for granted.  Do we think about how important the sun is?

The Sun is by far the largest object in the solar system. It contains more than 99.8 percent of the total mass of the Solar System (Jupiter contains most of the rest).  It is often said that the Sun is an "ordinary" star. It certainly is not one of the larger stars in the universe, but the Sun is in the top ten percent by mass.

Our Sun developed 4.6 billion years ago along with the rest of our solar system when material from a supernova explosion was recycled. Like other stars, our Sun has a specific life cycle. Currently the Sun is a little more than half way through its expected life span. At present the Sun comprises about 70 percent hydrogen,28 percent helium,and 2 percent heavier elements. This changes slowly over time as the Sun converts hydrogen to helium in fusion reactions in its core. Here are a couple of shots from How the Universe Works representing the fusion reactions. Since the formation of the solar system the Sun's output has increased by about 40 percent.

One interesting fact is that the different parts of the Sun, which is a million miles wide, rotate at different rates. 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.

Conditions at the Sun's core (approximately the inner 25 percent of its radius) are extreme. The temperature is 432 million Fahrenheit. At the center of the core the Sun's density is more than 150 times that of water.

The Sun's power (about 386 billion billion megaWatts) is produced by nuclear fusion reactions. 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. For the last 20 percent of the way to the surface the energy is carried more by convection than by radiation.

The surface of the Sun is at a temperature of about 9980 F (5527 C).  Sunspots are "cool" regions, only 6300 F (3482 C). They look dark only by comparison with the surrounding regions. Sunspots can be very large, as much as 31,068 miles in diameter (50,000 km). Sunspots are like hurricanes, except rather than rain and wind, they are intense magnetic storms caused by twisting tubes of magnetic energy that pop out to the surface from deep inside. Because they are magnetic in nature, sunspots always occur in pairs with opposite magnetic polarity. The Sun's magnetic energy is so powerful that it exerts its influence well beyond the orbit of Pluto.

The region above the Sun, called the corona, extends millions of miles into space but is visible only during a total solar eclipse.

Since its birth the Sun has used up about half of the hydrogen fuel. It will continue to radiate "peacefully" for another 5 billion years or so (although its luminosity will approximately double in that time).

The Sun’s diameter is about 870,000 miles wide (1.4 billion km). The Sun is 109 times wider than Earth, and is 333,000 times heavier. Over a million Earths could fit inside the Sun.

Without the Sun, Earth could not support life. The Sun gives off heat and light that the Earth needs to support life (us).

Sun loops are large loops caused by the Sun’s magma (molten rock) shooting off of the Sun’s surface. These loops can fly millions of miles into space. Our Sun is approximately 25,000 light-years from the galactic core of our galaxy (the Milky Way). 

Stars vary in size. They can be as small as 7,000 miles in diameter (11,265 km), or as large as 900 billion miles in diameter (1448 billion km). No two stars are exactly alike. The number of stars in the known Universe exceeds one billion.

1 comment:

  1. Sun diameter = 1.4 million km, not 1.4 billion km.
    Typo below the 2nd last picture above.