Our star, the Sun is a big ball of gas And it's 99 percent of our solar system's mass

1. Mitzi Adams The Closest Star NASA/MSFC/NSSTC The Sun: Our star, the Sun is a big ball of gas And it's 99 percent of our solar system's mass It's an average star in our Milky Way Warming the Earth every day What powers our Sun and makes it so bright? Come on and tell me, what makes all that light? Hans Bethe long ago reached the conclusion It changes Hydrogen to Helium by nuclear fusion When fusion takes place light is created And it makes its way out (although rather belated) Through the Photosphere that's the part that we see The light comes out and shines on you and me About a million Earths could fit in the Sun But if you were there you wouldn't have much fun It's six thousand degrees at the photosphere And much hotter inside the solar atmosphere There are a few places where it's not so hot Like at the center of a big sunspot But heat is relative it's still pretty warm Sitting on a sunspot would do you great harm Galileo discovered sunspots What are those things, those funny dots? They're cooler parts, scientists feel Caused by a stronger magnetic field Those spots move around the face of the Sun Proving to all... solar rotation! A strange kind of movement, to do a full roll 25 days in the middle, 36 at the poles What about flares? I've heard of them here They're like giant explosions in the Chromosphere The magnetic fields above those sunspots Reconnecting again after being in knots Above the Chromosphere the Corona is placed It's millions of degrees and reaches way into space It's very thin, but read my lips That's the part that you see in a solar eclipse That's the end of our song about Mr. Sun We hope that you find that learning is fun But never look at the Sun, you could go blind Just keep on enjoying that warm sunshine!

2. The Sun • The Sun is located in a spiral arm of our Galaxy, in the so-called Orionis arm, some 30,000 light-years from the center. • The Sun orbits the center of the Milky Way in about 225 million years. Thus, the solar system has a velocity of 230 km/s (or 830,000 km/hr...or...515,000 mi/hr) • Our galaxy consists of about 100 billion other stars and there are about 100 billion other galaxies • The Sun has inspired mythology in many cultures including the ancient Egyptians, the Aztecs, the Native Americans, and the Chinese. • The Sun is 333,400 times more massive than the Earth and contains 99.86% of the mass if the entire solar system • It consist of 78% Hydrogen, 20% Helium and 2% of other elements • Total energy radiated: 100 billion tons of TNT per second

3. A Few Major Events in Solar Astronomy 1610 Galileo Galilei and Thomas Harriott observe sunspots with a telescope 1908 George Ellery Hale discovers magnetic fields on the Sun 1949 Solar X rays discovered from rocket flight 1962 OSO 1 launched -- OSO 8 ceased operations in 1978 1973-74 Skylab -- produced 35,000 images in 9 mos.

4. 1949 X rays from the Sun discovered Herbert Friedman 1916-2000 flew a geiger counter on a sounding rocket during a solar flare, demonstrated that emission was principally of x ray photons a series of Nike-Asp rockets fired during the 1958 total solar eclipse demonstrated that the x-ray emission extended far beyond the visible disk of the sun and was concentrated in small regions on the surface These series of rocket observations also demonstrated the effect of solar x-rays on the upper atmosphere. During this period of time he also obtained the first image of the sun with a pinhole camera, flew a spectrometer for measuring hard x-rays, and developed and flew the first satellite dedicated to solar observations, SOLRAD, that traced out the solar x-ray flux during a solar cycle.

5. Skylab May 14, 1973 - July 11, 1979 Magnetic Structure of Corona Seen Even in Quiet Areas 4 major instruments, 2 X-ray telescopes Xray Images of Coronal Holes Observations of Coronal Mass Ejections

6. The Sun’s Structure • Core • Where the energy is created. • Every second, nuclear reactions convert about 700 million tons of hydrogen into helium. • Radiation Zone • Where energy is carried by radiation. • Convection Zone • Energy transported by convection (just like boiling soup) where heat is transported to the photosphere.

7. Sunspots • Darker areas (umbra, penumbra) • Strong magnetic fields • Inhibit energy transport from solar interior • These areas cooler, therefore darker Frequency varies with an 11-year solar cycle Light and dark in this magnetic scan of the Sun indicate concentrated areas of intense magnetic field.

8. Solar Cycle Maunder minimum

9. The Solar Dynamo the Sun's magnetic field is generated by a dynamo within the Sun the Sun's magnetic field changes dramatically over just a few years the magnetic field continues to be generated within the Sun, it’s produced in interface layer between radiative and convective zone

10. Flares and Things

11. Physical Characteristics of Flares How are Flares Classified? Flares are classified according to the order of magnitude of the peak burst intensity (I) measured at the Earth in the 0.1 to 0.8 nm wavelength band as follows: Class Flux Ergs/cm2/s B I < 10-3 C 10-3 I < 10-2 M 10-2 I < 10-1 X I  10-1 A multiplier is used to indicate the level within each class. For example, M6 = 6 x 10-5 Watts/m2

12. The Biggest Flare on Record • At 21:51 UT, Monday 2 April 2001, active region 9393 unleashed a major solar flare reclassified as at least an X20 It appears to be the biggest flare on record, most likely bigger than the one on 16 August 1989 and definitely more powerful that the famous 6 March 1989 flare which was related to the disruption of the power grids in Canada.