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Dr. Laura Peticolas Space Sciences Laboratory University of California at Berkeley 2009 International Year of Astronomy The Sun-Earth Connection Slide 2 Tonights main talking points We learn about our connection to the Sun through careful observations. Tools (such as telescopes, satellites, computers) help us to understand this connection. The Sun emits light of many different colors (wavelengths/frequencies) known as the electromagnetic spectrum. Slide 3 Tonights main talking points The Sun is a magnetic and dynamic star, ever changing in its output of light and particles. Earth is a giant electromagnet. The northern and southern lights (auroras) are global, dynamic glowing light displays originating at the boundary between Earths atmosphere and space. The Suns particles affect the magnetic field surrounding Earth in a dynamic way. Slide 4 1600s:Birth of the Telescope Telescopes increased the ability of people to see details in astronomical objects such as the moons around Jupiter and spots on the Sun. Johannes Hevelius observing with one of his telescopes (from galileo.rice.edu) Galileos telescopes (from galileo.rice.edu) Slide 5 Sunspots: Observations In 1612 during the summer months, Galileo made a series of sunspot observations which were published in Istoria e Dimostrazioni Intorno Alle Macchie Solari e Loro Accidenti Rome (History and Demonstrations Concerning Sunspots and their Properties, published 1613). Galileos sunspot drawing (from galileo.rice.edu) Slide 6 Sunspots: Observations Because these observations were made at approximately the same time of day, the motion of the spots across the Sun can easily be seen. Conclusion: the Sun rotates on its axis. Movie made from Galileos sunspot drawings from June 2, 1613 July 8, 1613 (from galileo.rice.edu) Slide 7 Sunspots: A modern understanding Sunspots are about 2,000 degrees Kelvin cooler than the average temperature on the photosphere (5,000 degrees Kelvin). They are bright but appear to be dark only in comparison to their very bright surroundings. Following long-lived sunspots through time allows one to determine the rotation rate of the Sun (25-36 days). The Sun spins faster at the equator (25 days) than at the poles (36 days). Slide 8 What is the Sun? The Sun is a Star, but seen close-up. The Stars are other Suns but very far away. Stars, including the Sun, are giant balls of very hot, mostly ionized gas that shine under their own power (from nuclear fusion). Radius696,000 km (109 times Earths radius) Rotation Rate27 days (equator) to 31 days (poles) Luminosity (Power Output) 3.8 x 10 26 watts (10 trillion times the power consumption of all Earths nations combined) Surface Temperature5,800 K (average) Mass2 x 10 30 kg (300,000 times Earths mass) Composition70% Hydrogen, 28% Helium, 2% heavier elements (by percentage of mass) Age5 billion years (expected to live another 5 billion) Distance from EarthThe Sun is 150 million kilometers away from Earth. This is defined as 1 Astronomical Unit (AU) Slide 9 Modern Solar Science: Careful Observations In 2006 NASA launched the STEREO (Solar Terrestrial Relations Observatory) spacecraft to continue our study of the Sun in ways not possible on Earth. To understand why the scientific instruments (tools) on the spacecraft needed to be above Earths atmosphere and magnetic field, we need a little more background. Slide 10 Light: Careful Observations 1666 A.D. Sir Isaac Newton used a prism to show that white light from the Sun disperses to form a series of colors called the spectrum Prism with white light shining through the prism, shown at the top of the image, and the rainbow of colors (spectrum) coming out of the prism, shown at the bottom of the image. Slide 11 Electromagnetic Spectrum 1800 A.D. Fredrick W. Herschel used a prism and thermometers to measure the temperature of each color of light. During this experiment he placed a thermometer to one side of the spectrum and discovered infrared light. Slide 12 The Multiwavelength Sun Looking at the Sun in different wavelengths of light reveals different parts of the Sun with different temperatures. 2 dark spots Visible light (white light): Wavelength = 400-700 nm T = 5,800 K 2 bright spots He II Extreme Ultraviolet light: Wavelength = 30.4 nm T = 60,000- 80,000 K 2 bright spots Fe XII Extreme Ultraviolet light: Wavelength = 19.5 nm T = 1.5 million K 2 bright spots Fe IX, X Extreme Ultraviolet light: Wavelength = 17.1 nm T = 1 million K Slide 13 The Multiwavelength Sun The Extreme Ultraviolet Light (EUV light) is blocked by our atmosphere we have to go to space to get these images. 2 dark spots Visible light (white light): Wavelength = 400-700 nm T = 5,800 K 2 bright spots He II Extreme Ultraviolet light: Wavelength = 30.4 nm T = 60,000- 80,000 K 2 bright spots Fe XII Extreme Ultraviolet light: Wavelength = 19.5 nm T = 1.5 million K 2 bright spots Fe IX, X Extreme Ultraviolet light: Wavelength = 17.1 nm T = 1 million K Earth-based image Space-based image (STEREO) Slide 14 Observations of the Sun Zoom in images of the Sun in ultraviolet light reveal loops of hot ionized gas (plasma) trapped in magnetic fields above the locations of Sunspots. Images from NASA TRACE Slide 15 SN Left: Magnetic field tracing using a compass around two magnetic poles Above: Magnetic field tracing above sunspots on the visible Sun. The Magnetic Sun Slide 16 STEREO Views: June 2007 STEREO camera BSTEREO camera A STEREO Viewing geometry. http://stereo-ssc.nascom.nasa.gov Slide 17 The Sun in 3D Slide 18 STEREO Views: April 2009 SOHO cameraSTEREO camera BSTEREO camera A STEREO Viewing geometry. SOHO is located near Earth between Earth and the Sun (i.e. looking straight to the Sun from Earth) http://stereo-ssc.nascom.nasa.gov Now we can study the sides of the Sun we cannot normally take images of. Slide 19 Atmosphere of the Sun During a total eclipse of the Sun, the very bright Photosphere is blocked and the Suns outer atmosphere becomes visible (in white light). We call it the Corona. Spacecraft, like SOHO and STEREO, place a disk in front of their cameras to create an eclipse. They are then able to take images with a larger view of the Suns Corona. It extends far out into the Solar System, in fact we live in it! Slide 20 Solar flares are enormous explosions in the atmosphere of the Sun. Solar flares are enormous explosions in the atmosphere of the Sun. They release energy in the form of light, heat, and the movement of large amounts of plasma. Coronal Mass Ejections (CMEs) are literally ejections of mass from the Suns corona. CMEs occur when large-scale magnetic fields break and release energy and enormous amounts of matter into space. Solar Flares & CMEs Slide 21 Coronal Mass Ejections (CMEs) are literally ejections of mass from the Suns corona. CMEs occur when large-scale magnetic fields break and release energy and enormous amounts of matter into space. STEREO CMEs new! CME continues into the solar system Slide 22 We have turned the data from these charged particles and magnetic fields into sounds and put the sounds with a movie of the outermost atmosphere of the Sun from STEREO. We are watching the Suns outer atmosphere from far away while listening to the solar wind data nearby the spacecraft. Find out more here http://cse.ssl.berkeley.edu/impact/sounds.html The Solar Wind The solar wind is a stream of mostly charged particles that emanate from the Sun and blow throughout the Solar System. The Suns Magnetic field flows with these particles. Slide 23 Earth Slide 24 Earths Magnetic Field: Careful Observations In the late 1500's, William Gilbert realized that the compass was a tiny magnet and it was interacting with a larger magnetic field in order to point north. In 1600, he published "De Magnete" explaining that "the globe of the earth is magnetic, a magnet," Chapter 17, Book 1. Slide 25 Satellite observations: Earths Magnetosphere The solar wind is electrically and magnetically connected to Earths magneto- sphere Satellite data (from sophisticated compasses and particle detectors) out into space compared with computer models gives us this model for Earths Magnetosphere. Slide 26 Aurora Observations in 1800s La Recherche Expedition, 1838-1840 (woolgathersome.blogspot.com) Slide 27 August 28, 1859 Galveston, Texas: August 28 as early as twilight closed, the northern sky was reddish, and at times lighter than other portions of the heavens. At 7:30 PM a few streamers showed themselves. Soon the whole sky from Ursa Major to the zodiac in the east was occupied by the streams or spiral columns that rose from the horizon. Spread over the same extent was an exquisite roseate tint which faded and returned. Stately columns of light reaching up about 45 degrees above the horizon moved westward. There were frequent flashes of lightning along the whole extent of the aurora. At 9:00 PM the whole of the streaking had faded leaving only a sort of twilight over the northern sky. Slide 28 Aurorae are found in an oval around the North and South Magnetic Poles. These ovals are always present. Cusp Aurora South Oval North Oval Both Ovals Images on the left are from the IMAGE satellite in 2001 and 2004 (UV Light) with continents drawn on image. Image on the right is from the Polar Satellite, 2001 (UV Light.) Observations from Space Slide 29 Aurora observed in 2008 from the ground Aurora observed in 2008 from the ground (aurora oval detail) THEMIS All-sky camera mosaic image of aurora across the Northern American Continent. The cameras looking up using cameras with a wide field-of-view. Slide 30 Sun-Earth Connection (1128 A.D.) In 2001, Astronomers drew a link between the earliest known record of sunspots, drawn by John of Worcester in England in AD 1128, and the aurora borealis (northern lights) recorded in Korea five days later. http://www.abc.net.au/science/articles/2001/07/18/330954.htm Slide 31 Energy from Solar Flares and CMEs can damage satellites and change orbits. Disrupt radio communications CME particles traveling near the speed of light threaten Astronauts. CMEs can intensify auroras (Northern and Southern Lights) Electric currents from intense aurora can cause power surges and blackouts. Electric currents from intense aurora create interesting magnetic field variations detectable on Earth. Space Weather Effects Slide 32 When a CME passes Earth, it can drag the magnetic tail far out into space. Stretched magnetic lines can break and then reconnect into a different shape. Electrons, guided by the magnetic field, speed up towards Earth and enhance auroras. Magnetic Reconnection Model confirmed for one case in 2008