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NASA/MSFC/NSSTC The Closest Star Mitzi Adams The Sun:

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Presentation on theme: "NASA/MSFC/NSSTC The Closest Star Mitzi Adams The Sun:"— Presentation transcript:

1 NASA/MSFC/NSSTC The Closest Star Mitzi Adams 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! The Closest Star NASA/MSFC/NSSTC Mitzi Adams The Sun: The Sun is an average star, similar to millions of others in the Universe. It is a prodigious energy machine, manufacturing about 4.0E023 kilowatts of energy per second. In other words, if the total output of the Sun was gathered for one second it would provide the U.S. with enough energy, at its current usage rate, for the next 9,000,000 years. The basic energy source for the Sun is nuclear fusion, which uses the high temperatures and densities within the core to fuse hydrogen, producing energy and creating helium as a byproduct. The core is so dense and the size of the Sun so great that energy released at the center of the Sun takes about 50,000,000 years to make its way to the surface, undergoing countless absorptions and re-emissions in the process. If the Sun were to stop producing energy today, it would take 50,000,000 years for significant effects to be felt at Earth! Variability: n X-radiation - a minor feature of the solar spectrum, arising in the tenuous corona - things are entirely different. The variability can be huge: in the SXT band, many factors of ten. For hard X-rays and gamma-rays, the natural emission of the Sun must be close to zero, and the minimum brightness would be set by cosmic-ray albedo somehow. The total variability for gamma-rays at one MeV might be a factor of 108 or so, and if one could make an image of the sky at such a wavelength, the Sun would normally be as dark as the Moon, darker than the background radiation from the rest of the universe. An eclipse would be completely unspectacular. But we digress badly.

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 Solar X rays discovered from rocket flight This was first done at White Sands missile range in New Mexico with a V2 rocket in X-rays from the Sun were detected by the Navy's experiment on board. OSO - primary mission objectives were to measure the solar electromagnetic radiation in the UV, X-ray, and gamma-ray regions. There were eight of these. The University of Minnesota Gamma-ray Experiment, was designed to provide preliminary measurements of the intensity and directional properties of low-energy gamma-rays in space. The detector operated in the 50 keV - 3 MeV range. For the keV range, a NaI(Tl) scintillation crystal monitored radiation through a lead shield. The detector operating in the MeV and MeV energy regions used two scintillators connected as a Compton coincidence telescope. OSO 8 launched on June 21, 1975 (2-60KeV)... primary objective was to observe the Sun, four instruments were dedicated to observations of other celestial X-ray sources brighter than a few milliCrab. OSO-8 ceased operations on 1 October 1978. 1962 OSO 1 launched -- OSO 8 ceased operations in 1978 Skylab -- produced 35,000 images in 9 mos.

4 1949 X rays from the Sun discovered
Herbert Friedman 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. By 1950, he had switched to the newly emerging field of observations from space using sounding rockets. Friedman's first experiment, a V-2 rocket launched from the White Sands Missile Range in 1949, involved observing solar x-ray and ultraviolet radiation using Geiger counters to reveal the source of the ionization of the upper atmosphere. During the next 10 years, Friedman continued his program of solar and atmospheric investigations. He arranged for campaigns of shipboard rocket launches to study solar x rays. He obtained the first x-ray image of the Sun with a pinhole camera; flew the first Bragg spectrometer for measuring hard x rays; and developed and flew SOLRAD, the first satellite dedicated to long-term monitoring of the Sun.

5 Skylab 4 major instruments, 2 X-ray telescopes
May 14, July 11, 1979 4 major instruments, 2 X-ray telescopes Skylab, a science and engineering laboratory, was launched into Earth orbit by a Saturn V rocket on 14 May Three crews of 3 men each visited the station, with their missions lasting 28, 59, and 84 days. Circling 50 degrees north and south of the equator at an altitude of 435 km, Skylab had an orbital period of 93 minutes. There were a plethora of UV astronomy experiments done during the Skylab lifetime, as well as detailed X-ray studies of the Sun. Skylab fell from orbit on 11 July 1979. Skylab included eight separate solar experiments on its ApolloTelescope Mount: two X-ray telescopes (S-054 sponsored byAmerican Science and Engineering and S-056 sponsored by Marshall Space Flight Center); an X-ray and extreme ultraviolet camera (S-020 sponsored by the Naval Research Laboratory); an ultraviolet spectroheliometer (S-055 sponsored by Harvard College Observatory); an extreme ultraviolet spectroheliograph and an ultraviolet spectroheliograph (S-082A and S-082B sponsored by the Naval Research Laboratory); a white light coronagraph (S-052 sponsored by the High Altitude Observatory); and two hydrogen-alpha telescopes (H-alpha no. 1 sponsored by Harvard College Observatory and H-alpha no. 2 sponsored by Marshall Space Flight Center). The ATM canister was as large as any solar observatory spar on Earth at the time, measuring 3 meters long and 2 meters in diameter. Solar Flare Alert monitor went off each time Skylab orbit went through the S. Atlantic Anomaly -- led to “Cry Wolf” problem. Xray Images of Coronal Holes Magnetic Structure of Corona Seen Even in Quiet Areas 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 Frequency varies with an 11-year solar cycle
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  I < 10-2 M  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 and definitely more powerful that the famous 6 March 1989 flare which was related to the disruption of the power grids in Canada.


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