This page is about The Sun, the specific star that the Earth orbits. For the sun of any other system, see Star and Interstellar Terrain.

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Basic Information

Our Sun is a main sequence yellow star, rated as G2V on the Morgan-Keenan Stellar Classification system. It has an average surface temperature of 5,510 oC (9,950 oF). The core, however, is believed to be over 13 million degrees celsius, and certain portions of the Corona surrounding the sun heat up to 1 to 3 million degrees. The energy output of the sun has been compared to detonating one million one-megaton nuclear bombs every second.

The sun has a very complex magnetic field, with from 1 to 10 million magnetic poles at any given time. The entire field reverses itself frequently, and follows an 11 year cycle. The last period of great solar activity (known as a Solar Maximum) was in 2001, it is anticipated the next such period will be in 2012, and it's expected to be a doozy.

Relative Position

Our sun (and the entire Solar System) is located in the Orion Arm of the Milky Way Galaxy, and is currently moving through the Local Interstellar Cloud region of the Local Bubble zone. We are near the inner rim of the Orion arm, in what is known as Local Fluff or the Gould Belt. We are roughly 24,800 lightyears from the Galactic Center, and about 6,500 lightyears from the Perseus Arm. It takes over 200 million years for our sun to complete one orbit of the galaxy, so in it's entire life it has only made 20-25 orbits, and done far less than 1% of an orbit since the birth of man.

Sunlight is the primary source of energy for life on the planet Earth. On average (over the course of the year), it takes 8 minutes and 19 seconds for sunlight to travel from the sun to the earth. The distance between them is about 93 million miles. See also Movement of the Earth.

The Bleak Far Future

Our sun is 4.57 billion years old. It's primary fuel is hydrogen, which it turns into helium by means of nuclear fusion. Eventually, it will run out of hydrogen, and have to burn Helium. When this happens, it will balloon up into a Class C Red Giant. Approximately 5 billion years from now, it is likely to grow as large as the orbit of Mars, and the heat will devestate the Earth. Our oceans will boil off, and our atmosphere will escape the Earth's gravity. Long after that happens, the Sun will transition again, this time throwing off particles to form a Planetary Nebula while simultaneously collapsing into a White Dwarf.

See Also:


3. Non-Fiction Book: Hyperspace by Michio Kaku
4. TV Show: The Universe on the History Channel.
5. Music: Why Does the Sun Shine? by They Might Be Giants

Game and Story Use

  • Technically, we're on a time schedule, and eventually must spread off this rock or die. Not that 5 billion years is really putting much pressure on us, though, and The End Of The World As We Know It will probably come from some other means than the rapidly-expanding Red Giant Sun. Still, for a game set far enough into the future, it's a cool visual.
  • Explorers and Mad Scientists in a Speculative Fiction campaign might just fly a vessel out to the corona for one reason or another. Don't be fooled by the statement that the surface of the sun is just a few thousand degrees - parts of the Corona get to the millions. Depending on the phases of the sun's 11-year cycle, however, there are times when large holes appear in the Corona, especially over the poles. During such a time, a spacecraft may be able to get very close without being destroyed by million+ degree temperatures, but it's still risky. An unexpected solar flare could do you in. This is the sort of scenario where the Spaceship Engineer shines. (Or, fails a critical roll and burns up.)
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