Click the mouse to advance

1. Click the mouse to advance

2. with new images and information from NASA/ESA’s SOHO spacecraft The Solar andHeliosphericObservatory created by Steele Hill at Goddard Space Flight Center Greenbelt, MD

3. The Sun as photographed by the SOHO spacecraft in 1997 The Sun as revealed in extreme ultraviolet light. Differences in the Sun’s densities cause the uneven appearance on its surface.

4. The Sun viewed in different ultraviolet wavelengths • The Sun is revealed in three different wavelengths, each one showing cooler material than the one before it. These images were taken at nearly the same time on the same day. • Note how certain features are revealed or hidden in different wavelengths. Click on the image to view the clip

5. The Sun’s Rotation • Video of the Sun covering 12 days shows its rotation and some regions of activity. The Sun rotates about every 27 days. • The green color is added so that scientists can easily know which filter was used here. Click on the image to view the clip

6. Earth’s size in relation to Sun The black dot represents the approximate size of the Earth. • Question: • About how many Earth’s do you think could fit inside the Sun? The Sun is 865,000 miles in diameter or 110 Earths across.

7. The parts of the Sun

8. Real facts about the Sun • is 93 million miles from the Earth • 1 second of its energy = U.S. energy needs for 90,000 years • light from the Sun gets to the Earth in 8 minutes • consists of 92% Hydrogen, 7% Helium, and 1% other gases • has an 11-year cycle of solar activity • is 5 billion years old, another 5 billion to go • is a medium-size star, one of about 2 billion in our galaxy Click the mouse to add each bullet

9. Fun facts about the Sun • The ancient Mayan, Egyptian, and other cultures worshipped the Sun. • We measure time by and base our calendar on the Sun. How long does it take for the Earth to go around the Sun? • Answer: 365 days or 1 year • If you drove a car at 100 miles per hour to the Sun, how many years would it take to get there? 5, 50 or 100. • Answer: About 100 years. Now that’s a long drive! Most of us know that radiant energy from the Sun heats and lights the Earth, but did you know that: Click the mouse to add each bullet

10. Solar Eclipses • Eclipses occur when the moon blocks our view of the Sun from specific areas of the Earth. Here you see a relatively rare total eclipse, which lasted only about five minutes or less but reveals a detailed view of the corona.

11. Stonehenge and the Sun • Stonehenge in England, built about 3,000 years ago, is composed of 30 upright stones, each over ten feet tall, aligned in a circle, with horizontal stones perched upon them. There is also an inner circle composed of similar stones. A mysterious site, many believe it served as a prehistoric astronomical observatory, especially for charting the Sun’s movements.

12. The Sun is the source of all our energy • Every second, millions of protons in the Sun's corecollide with other protons due to powerful pressures to produce helium nuclei in a fusionreaction that releases energy. Neutrons + protons Helium nucleus + light and energy = + Without the Sun’s heat and light, life on Earth would not be possible.

13. What about solar energy? • Solar energy is the least polluting and most inexhaustable of all energy sources, with great potential but still somewhat costly. The two most common systems heat buildings and create electricity. Most spacecraft use solar power for their instrumentation and communication. The concept The reality: solar panels

14. Radiation in the Sun’s interior • This animation illustrates how the energy created by the extremely powerful fusion process in the Sun’s core radiates out through the radiation zone (bright yellow) to the convection zone (gold). Click on the image to view the clip again

15. Convection in the Sun In the Sun’s outer layers, matter rises up and transports its energy from a hotter, lower level to a cooler, higher one. Thus, there is a constant circular rising and falling of gases in its convection zone. Illustration of solar convection

16. The Solar Corona • The corona is the area just above the surface. While the surface is about 5,000o Celsius, the temperature in the corona reaches about 2 million degrees Celsius. What causes this rapid increase in temperature is not well understood. 5,000o C 2,000,000 o C The black circle divides two images.

17. Granulation on the Sun’s surface • The Sun’s surface pattern looks like rice grains. Large convection cells cause this granulation, since each cell has a column of hot gas rising and cool gas descending. Granules the size of Earth and larger constantly evolve and change in a churning kind of motion. This clip represents about four hours of activity. Click on the image to view the clip

18. Sounds of the Sun • Waves of motion pushing out from within the Sun have actually been recorded as sound and converted to audible levels. Since we could not hear them as they are (too low a sound), they have been greatly raised in pitch. Listen closely . . . The Sun hums along! Click there to play the sound. (The volume on your computer must be turned up.)

19. What is the solar wind? • A constant stream of particles flows from the Sun’s corona, with a temperature of about a million degrees and with a velocity of about 450 kilometers per second. The solar wind reaches out beyond Pluto's orbit (about 5900 million kilometers). The drawing showshow it pushes onand shapes the Earth’s magnetosphere(the dotted line).

20. The Sun’s magnetic field • The Sun is strongly affected by magnetic forces. The redarrows show open magnetic field lines emerging from the poles. The grayarrowsrepresent solar wind particles which carry field lines with it. The bright active regions have closed magnetic field lines (orange).

21. The Sun’s extended magnetic lines • Some of the Sun’s magnetic field lines are closed (yellow, but others from the poles are open (red. Most are carried out into space by the solar wind (light dotted lines.

22. Sun Spots • Darker and cooler areas are caused by a concentration of the Sun's magnetic field lines, which last from several hours to several months. Their frequency varies with the solar cycle (11 years), in 1997 near its minimum. Light and dark in this magnetic scan of the Sun indicate concentrated areas of intense magnetic field lines. Close-up of sunspots

23. Polar coronal holes • Shown with special filters in extreme ultraviolet light (the green tint is a false color). Hot gas flows out from the coronal holes (where magnetic field lines are open to space) into the solar wind.

24. Multiple solar prominences • A fairly common occurrence, these eruptions are caused by magnetic forces. Cooler gases above the photosphere can often be seen flowing along magnetic field lines. This is an active region.

25. Prominences and magnetic loops • This image is tinted blue to identify to scientists which filter was used to create it.

26. Large Solar Prominence • This is the largest prominence observed by SOHO. Twisting magnetic fields forced this huge eruptive prominence 100,000 kilometers above the Sun. The plasma is heated to about 150,000 degrees C. 28 Earths high August 27, 1997

27. Video clip showing solar activity • The Sun is surprisingly active. The motion captured here occurred over a 12-hour period. The sliding movement of gases follows the lines of magnetic forces. You can also see the boiling type of motion on the surface. Click on the image to play the video

28. Comet Hale-Bopp and Aurora Borealis • Both these dramatic events, rarely seen together, are directly influenced by the Sun. Keep on going to find out how!

29. Comets and the solar wind • By studying the tails of comets, scientists determined there must be a solar wind pushing out from the Sun because the tails always head away from the Sun. (Note the comet’s blue ion tail as well.) Hale-Bopp Sun

30. Sun grazing comet as it approaches the Sun • A comet is seen entering from the lower left streaks towards the Sun on Dec. 23, 1996, and is presumably consumed by the heat soon after this image was taken. Solar particles can also be seen blowing out into space on the right side. Click on the image to play the video The clip spans about 3 days. Note: the Sun is blocked by a disk but represented by the white circle.

31. Auroral Lights • They are also Northern or Southern lights. These often brilliant and colorful phenomena, seen in the night sky usually closer to the poles, are caused by the impact of solar wind particles and magnetic forces on the Earth’s magnetosphere. Click on this image to play the video

32. Aurora as seen from space Aurora taken from the space shuttle

33. Large coronal mass ejection (CME) sequence • CMEs are clouds of million degree Celsius gases ejected from the Sun at hundreds of miles per second. This one clearly heads off to the right. CMEs are caused by the breaking apart of magnetic forces. This sequence occurred over an 8-hour period in 1996.

34. Another CME sequence 1 2 • CMEs release a billion tons of matter at millions miles/hr. • CMEs occur almost every day but few are Earth-directed • a CME wave, moving through space, is preceded by a shock wave of matter pushed ahead of it • the bright spot (lower left in each) is Venus 3 4

35. CME shown in soft X-rays • This dramatic footage taken by the Yohkoh spacecraft shows a very strong storm blasting particles out from the Sun over a 36-hour period. Click on the image to view the clip again

36. Solar flare and CME event • This video of an April 7, 1997 event captures the dynamics of a solar storm building up then flaring out over a 4-day period. • Solar flares are "explosions" on the Sun where tensions in the magnetic field are released. These generate a lot of energy that heats up material and shoots it into outer space. Solar flares are usually associated with active regions. Click on the image to play the video

37. Another view of April 7 CME event • This is a “running difference” video sequence where the imaging highlights the difference between each successive image so that the changes are easier to visualize. The Sun is blocked by a disk but represented by the white circle. Click on the image to play the video

38. Animation of a CME approaching Earth • It takes 2 to 4 days for a CME blast to reach Earth, as it expands up to 30 million miles wide. The white lines represent the shape of Earth’s magnetosphere (magnetic field). Click on the image to view the clip again

39. CME: initial blast and later impact • This illustrates a CMEs progress from a blast on the Sun’s surface (lower left) to its impact on the Earth’s magnetosphere days later (drawing not to scale)

40. Earth’s Magnetosphere and a CME • Normal shape Changed by CME Electrically charged particles from a CME both compress and lengthen Earth’s magnetosphere. The particles are guided by Earth’s magnetic field lines into the polar regions.

41. CME impact on Earth’s magnetosphere • Seen on Earth as aurora, the impact of a CME on Earth’s magnetic field is captured in an ultraviolet video from the perspective of a spacecraft. The red areas indicate the most intense magnetic activity. Click on the image to play the video

42. Some effects of CMEs on Earth • When CME’s interact with our magneto-sphere, strong magnetic changes occur, impacting a wide range of things. A CME knocked out power in Quebec in 1989 and interfered with communications.

43. How do some of these effects occur? As a result of major magnetic storm activity: • When charged particles and radiation from a CME strike satellites, they can disrupt electronic equipment and even cause total failure. The atmosphere also heats and expands, increasing the drag on satellites in orbit around the Earth and changing their orbits. Intense electric currents flow in the Earth’s atmosphere induces currents in pipelines (which act like electric conductors), causing increased corrosion of the pipeline. Irregularities in the ionosphere (about 40-400 km above Earth) occur, disrupting radio signals passing through it to satellites and back, as well as Earth-to-Earth communications.

44. How can we prepare for CMEs? With greater reliance on technology for travel, communications, transportation, and power generation, we need to find ways to avoid damage and disruptions from CMEs. • Further improve space weather predictions • Build stronger satellites and more protected systems • Take operational precautions in response to warnings • NOTE: there is no human health risk from CMEs. Click the mouse to add each bullet

45. The SOHO spacecraft • Is a joint mission of NASA and the European Space Agency (ESA) to study the Sun for over 3 years • Has 12 instruments to study the Sun’s interior, atmosphere,and solar wind • Provided most of the images and video in this presentation Click the mouse to add each bullet

46. SOHO’s orbit • positioned about 1 million miles towards the Sunfrom the Earth • keeps that position as Earth orbits around the Sun • studies the Sun 24 hours a day without interference from the Earth’s atmosphere

47. Sun study spacecraft in orbital positions

48. X-ray images of Sun reveal changes • The 12 x-ray images of the Sun's atmosphere, 1991-95 at 90 day increments, show how the corona changes during the solar cycle. Only very hot gases can emit x rays; the Sun's atmosphere, at millions of degrees, is hot enough to emit x rays; the sun’s surface is not. As the solar activity cycle declines, the Sun's magnetic field changes from a complex structure to a simpler configuration. This represents another way to study the Sun over time. Taken by Yohkoh, an orbiting Japanese sun-study spacecraft.

49. The Sun transformed through 3 wavelengths • This video shows three different views of the Sun in different wavelengths of light captured by another spacecraft’s instrument. Layers are built out from the Sun’s photosphere (surface), to the chromosphere (lower atmosphere), and finally the corona (outer atmosphere). Click on the image to view the clip

50. Ground-based Observatories • Numerous observatories around the world continue to study and capture different images of the Sun. National Solar Observatory (Sacramento Peak, NM) Helium white light image (Kitt Peak Observatory, NM) Coronameter image (Mauna Loa Solar Observatory,Hawaii) H-Alpha white light image (Learmonth, Australia)