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Our Sun: Our Turbulent Active Star •The Sun is not a static body, but very active. QuickTime™ and a YUV420 codec decompressor are needed to see this picture. •Solar activity can have dramatic effects on the Earth Why Study the Sun? • Understand how the Sun affects the Earth and the solar system SOHO • Understand how stars work • Understand more about the laws of nature QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. SDO STEREO The Sun is the only star known to grow vegetables. (Dr.Philip Scherrer, Stanford University) Ask Students: “How does the Sun Change?” • Answers (selected answers from and 8th grade classroom) – – – – Changes height in the sky Changes in intensity Changes in temperature Changes distance from the Earth • Many of these are “changes” of the Earth • Students consider the Sun itself to be pretty constant. – Not a bad assumption but certainly not correct – Solar Constant: 1300 - 1400 W/m2 What makes the Sun hot? Fusion in the Sun’s core produces heat/energy 6 protons -> He + 2 protons + 2 electrons + 2 neutrinos + energy The Sun’s Roiling Surface QuickTime™ and a YUV420 codec decompressor are needed to see this picture. Size of Earth, for comparison Like fudge or oatmeal cooking, the Sun’s surface boils up with heat, then crashes down As the Sun turns QuickTime™ and a YUV420 codec decompressor are needed to see this picture. QuickTime™ and a YUV420 codec decompressor are needed to see this picture. Approximately 5 months worth of images from 2001 Like the Earth, the Sun rotates. However, unlike the Earth, the Sun has a complex rotation mechanism. Sunspots Sunspots denote regions of strong magnetic fields. They appear dark because they are relatively cooler than the surface. QuickTime™ and a YUV420 codec decompressor are needed to see this picture. What color is the Sun? 1 The Sun appears white to us but it radiates in all wavelengths (visible and nonvisible “colors”) The electromagnetic spectrum The Sun in Another Light QuickTime™ and a YUV420 codec decompressor are needed to see this picture. Extreme Ultraviolet image of the Sun at 195 Angstroms Visible Light has wavelengths between 4000 and 7000 Angstroms Seeing Magnetic Field lines QuickTime™ and a Cinepak decompressor are needed to see this picture. Plasma emission traces out magnetic fields in the solar corona Solar Eruptions Common during the Sun’s active periods QuickTime™ and a YUV420 codec decompressor are needed to see this picture. Huge flare of 28 October 2003 Solar prominence dwarfs Earth in size The 11 year sunspot cycle The amount of magnetic activity on the Sun varies in an 11 year cycle. A regular cycle of sunspot numbers over the past 300 years. Dramatic changes occur during the solar cycle X-ray and magnetic activity compared CoronagraphsArtificial Eclipses Explosions on the Sun (Coronal Mass Ejections) A billion tons of hot gas being launched from the Sun. White circle in image indicates size and location of Sun, which is blocked by a metal disk in the instrument. A solar “wind” streams into the solar system and shapes Earth’s magnetosphere The Sun generates Space Weather in our solar system Solar activity can have a dramatic impact on communications, satellites, and astronauts. Solar activity causes colorful aurorae Space Weather affects the Moon and other planets we hope to explore. Mars Aurorae on Neptune, Saturn, and Jupiter Solar and Space Weather Links on the Web • NASA Link – SOHO: http://sohowww.nascom.nasa.gov/ – SDO: http://sdo.gsfc.nasa.gov/ – STEREO: http://stereo.gsfc.nasa.gov/ • Stanford Solar-Center: http://solar-center.stanford.edu/ – SID home page: http://solar-center.stanford.edu/SID/ • CISM Home Page: http://www.bu.edu/cism/ • Windows to the Universe: http://www.windows.ucar.edu/ • Exploritorium: http://www.exploratorium.edu/spaceweather/index.html • SWPC: http://sec.noaa.gov/