Our star, the Sun is a big ball of gasAnd it's 99 percent of our solar system's massIt's an average star in our Milky WayWarming 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 conclusionIt changes Hydrogen to Helium by nuclear fusion When fusion takes place light is createdAnd it makes its way out (although rather belated)Through the Photosphere that's the part that we seeThe light comes out and shines on you and me About a million Earths could fit in the SunBut if you were there you wouldn't have much funIt's six thousand degrees at the photosphereAnd much hotter inside the solar atmosphere There are a few places where it's not so hotLike at the center of a big sunspotBut heat is relative it's still pretty warmSitting on a sunspot would do you great harm

Galileo discovered sunspotsWhat are those things, those funny dots?They're cooler parts, scientists feelCaused by a stronger magnetic field Those spots move around the face of the SunProving to all... solar rotation!A strange kind of movement, to do a full roll25 days in the middle, 36 at the poles

What about flares? I've heard of them hereThey're like giant explosions in the ChromosphereThe magnetic fields above those sunspotsReconnecting again after being in knots

Above the Chromosphere the Corona is placedIt's millions of degrees and reaches way into spaceIt's very thin, but read my lipsThat's the part that you see in a solar eclipse That's the end of our song about Mr. SunWe hope that you find that learning is funBut never look at the Sun, you could go blindJust keep on enjoying that warm sunshine!

The Sun:

The Closest StarMitzi AdamsNASA/MSFC/NSSTC

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

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 discoveredfrom rocket flight

1973-74 Skylab -- produced 35,000 images in 9 mos.

1962 OSO 1 launched -- OSO 8ceased operations in 1978

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.

1949 X rays from the Sun discovered

4 major instruments, 2 X-ray telescopes

Observations of Coronal Mass Ejections

Xray Images of Coronal Holes

Magnetic Structure of CoronaSeen Even in Quiet Areas

SkylabMay 14, 1973 - July 11, 1979

• 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.

The Sun’s Structure

Sunspots

Light and dark in this magnetic scan of the Sun indicate concentrated areas of intense magnetic field.

Darker areas (umbra, penumbra)Strong magnetic fields

Inhibit energy transport from solar interiorThese areas cooler, therefore darker

Frequency varies with an 11-year solar cycle

Solar Cycle

Maunder minimum

the Sun's magnetic field is generated by a dynamo within the Sun the Sun's magnetic field changes dramatically over just a few yearsthe magnetic field continues to be generated within the Sun,

it’s produced in interface layer between radiative and convective zone

The Solar Dynamo

Flares and Things

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

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.