1. The SUN!!!!!!! The Facts Just the Facts:
1. Center of our Solar System.
2. Spinning ball of hot gas and nuclear reactions.
3. Lights up the Earth and provides us with heat.
4. The sun's absolute magnitude (its intrinsic brightness) is
5. Its stellar type is G (a star that absorbs strong metallic lines in its spectrum).
6. A medium-sized yellow star
It’s 149,680,000 km or 1 Astronomical Unit from the Earth. .
discovery.nasa.gov/ images/sun.jpe

2. How Close is Close?
The Earth is closest to the Sun (this is called perihelion) around January 2 each year (147.1 million km.)
It is farthest away from the Sun (this is called aphelion) around July 2 each year ( million km).

3. How Hot is Hot?
The Sun's core can reach 10 to 22.5 million°F. The surface temperature is approximately 9,900°F (5,500°C). The outer atmosphere of the Sun (which we can see during a solar eclipse) gets extremely hot again, up to 1.5 to 2 million degrees. At the center of big sunspots the temperature can be as low as 7300 °F (4300 K, 4000 °C). The temperature of the Sun is determined by measuring how much energy (both heat and light) it emits.

5. What makes up the Sun?
The Sun is made up of about 2 x 1030 kilograms of gas. It is composed of about 75% hydrogen and 25% helium. About 0.1% is metals (made from hydrogen via nuclear fusion). This ratio is changing over time (very slowly).
Since the Sun formed 4.5 billion years ago, it has used up about half of its initial hydrogen supply.

6. Star Type
Our Sun is a second or third generation star. Second generation stars do not just burn hydrogen, they also burn heavier elements, like helium and metals (elements heavier than hydrogen and helium).
The element helium was named after the Sun (called "Helios" in Greek) because it was first discovered on the Sun. Helium is plentiful on the Sun but rare on Earth.

7. How does the Sun Produce Energy?
At the Sun's core, nuclear fusion produces enormous amounts of energy, through the process of converting hydrogen nuclei into helium nuclei (nuclear fission).

8. Each second the Sun converts about 600,000,000 tons of hydrogen nuclei into helium nuclei. These fusion reactions convert part of these atoms' mass (roughly 4 million tons) into energy, and release an enormous amount of this heat and light energy into the Solar System.

9. How long will the Sun continue to Burn?
In these fusion reactions, the Sun loses 4 million tons of mass each second. The Sun will run out of fuel in about 5 billion (5,000,000,000) years. When this happens, the Sun will explode into a planetary nebula, a giant shell of gas that will destroy the planets in the Solar System (including Earth).

11. From the center out, the layers of the Sun are as follows: the solar interior composed of the core (which occupies the innermost quarter or so of the Sun's radius), the radiative zone, and the convective zone, then there is the visible surface known as the photosphere, the chromosphere, and finally the outermost layer, the corona.
The energy produced through fusion in the Sun's core powers the Sun and produces all of the heat and light that we receive here on Earth.

12. All of the energy that we detect as light and heat originates in nuclear reactions deep inside the Sun's high-temperature "core." This core extends about one quarter of the way from the center of Sun to its surface where the temperature is around 15 million Kelvin (K).
In the innermost shell, right above the core, energy is carried outwards by radiation. This "radiative zone" extends about three quarters of the way to the surface.

13. In the outermost of the two shells, where the temperature drops below 2,000,000 K (3.5 million degrees F) the plasma in the Sun's interior is too cool and opaque to allow radiation to pass. Instead, huge convection currents form and large bubbles of hot plasma move up towards the surface (similar to a boiling pot of water that is heated at the bottom by a stove).

14. The radiation does not travel directly outwards - in this part of the Sun's interior, the plasma density is very high, and the radiation gets bounced around countless numbers of times, following a zig-zag path outward. It takes about 170 thousand years for radiation to make its way from the core to the top of the radiative zone!

15. The Sun's Outer Layers
Collectively referred to as the solar 'atmosphere‘.
The photosphere, the chromosphere, and the corona. These three regions have substantially different properties from each other, with regions of gradual transition between them.

16. The Photosphere There is not really a "surface" to the Sun.
The Sun is a bunch of gas which gets denser and denser as you move from space toward the solar core.
In general is has a pressure about a few hundredths of the sea-level pressure on Earth, a density of about a ten-thousandth of the Earth's sea-level atmospheric density, and a temperature in the range Kelvin.

17. The Chromosphere
The gases which extend away from the photosphere make up the chromosphere.
The chromosphere is about 2500 km thick
The density of the gases decreases as you move away from the photosphere into the chromosphere, but the temperature increases! From the bottom to the top of the chromosphere, the average temperature goes from 4500 to 10,000 Kelvin!

19. The Corona The outermost region of the Sun's atmosphere.
Extends for millions of miles into space above the photosphere.
During a total solar eclipse, the corona shines beautifully against the dark sky.
The corona has a density about times that of the Earth's sea-level atmosphere.
It is very hot - millions of Kelvin. Because of this high temperature, the bulk of the radiation from the corona is emitted at ultraviolet and X-ray wavelengths.

20. Other Solar Features
Solar Wind: a stream of charged particles flowing outward from the Sun with an average velocity of about 400 km/sec.

21. Sunspots and Their Cycle:
Sunspots are cooler regions on the Sun's photosphere (about 1500 K cooler) and so appear to be darker than the photosphere. A given sunspot can have a lifetime ranging from a few hours to a few months. It consists of two parts - the dark inside region called the umbra the surrounding less dark region called the penumbra. Their sizes vary over a wide range, with a few having been measured to be 50,000 km in diameter!
Sunspot Courtesy of ASASand

22. Sun spots were first observed telescopically in late 1610 by Frisian astronomers Johannes and David Fabricius, who published a description in June At the latter time Galileo had been showing sunspots to astronomers in Rome, and Chrisoph Scheiner had probably been observing the spots for two or three months. The ensuing priority dispute between Galileo and Scheiner, neither of whom knew of the Fabricius' work, was thus as pointless as it was bitter.

23. A German amateur astronomer, Heinrich Schwabe, published a paper in 1851 which stated that the number of sunspots visible on average varied with a period of about 10 years. This conclusion has been substantiated by observations over the 140 years since. The period of repetition on average is 11.1 years, but has been as short as 8 years and as long as 16 years.

24. During the maximum of the cycle, more than 100 sunspots can be seen on the Sun at once. During the minima, the Sun sometimes has no spots at all. This cycle is closely related to the magnetism of the Sun. In fact, it is the changing magnetic field of the Sun which governs many aspects of solar activity.

25. Facts
The Sun has 333,400 times more mass than the Earth and contains 99.86% of the mass of the entire Solar System - this means Jupiter and all the other planets and asteroids only make up 0.14% of the mass of the Solar System! In fact just a pinhead of the Sun's core material could kill a person 160 kilometres away.

26. More Facts
    Each second the Sun loses 4.5 million tons of material - this means that in 42 million years it would lose enough material to make the Earth. However this high loss of mass is really rather insignificant when compared to the total mass of the Sun - over the past 4,500 million years it has barely lost a few hundredths of a percent of its total mass.

27. A Few More Facts
Interestingly, all the light we see from the Sun comes from a layer 500km deep (the top 0.1%) and takes about 8.3 minutes to reach us down here on Earth. The radiation does however take about 170,000 years to make its way out from the Sun's core.

28. The End