Four Centuries of Discovery. Visions of the Universe. torms. on thes. supplemental materials

Transcription

1 Visions of the Universe ~ Four Centuries of Discovery S torms on thes un supplemental materials

2 Storms on the Sun Table of Contents - Exhibit Overview... 3 Science Background... 4 Science Misconceptions... 7 Glossary... 8 Related Educational Resources... 10

3 Exhibit Overview In turning his telescope to the heavens in 1609, Galileo embarked upon a journey that would revolutionize science and culture alike, profoundly changing our view of our place in the universe. Our views of the universe, and how they have evolved over time, are portrayed in the images and text of the Visions of the Universe: Four Centuries of Discovery exhibit. In recognition of the International Year of Astronomy, this exhibit includes six twosided panels that feature key astronomical discoveries from the past 400 years. The exhibit also highlights the technological advancements that made these discoveries possible. Exhibit topics range from celestial objects within our own cosmic backyard to those beyond the realm of our solar system. Featured objects include the Sun, the Moon, Saturn, Mars, comets, stars, nebulae, and galaxies. Images are accompanied by captions that highlight relevant, historical discoveries. The Visions of the Universe: Four Centuries of Discovery exhibit is supported by supplemental resource documents available online, in PDF format, for each panel. These twelve documents include science background information in the form of Q&As, related science misconceptions, a glossary, and links to additional resources on NASA s Amazing Space Web site. In addition, each exhibit panel is available as a downloadable, poster-size file. These materials are available from: The Visions of the Universe: Four Centuries of Discovery exhibit was produced in December 2008 by the Space Telescope Science Institute, the American Library Association, and the Smithsonian Astrophysical Observatory, through funding from the National Aeronautics and Space Administration. 3

4 Science Background Q1: What are the parts of the Sun? The interior of the Sun consists of its core, where the energy is produced. Next to the core is the radiation zone, then the convection zone. Energy from the core travels outward through these zones. The surface of the Sun is called the photosphere, where most visible light is released. The outer layers, or atmosphere of the Sun, are the chromosphere and corona, which also emit some visible light, but generally radiate in higher-energy light. The outer layers become prominent during a solar eclipse. Q2: What causes outbursts from the Sun? Outbursts from the Sun are created by energy released from the Sun s magnetic field. The exact cause is not well understood, but it appears to come from the tangling of the magnetic field. The Sun rotates faster at the equator than it does at the poles. This rotation carries the magnetic field with it, and over time it becomes wrapped and twisted. As this happens, the Sun becomes active and shows more and more sunspots, solar flares, and coronal mass ejections. After about 11 years, the magnetic field resets itself, the Sun calms down, and the cycle begins again. Q3: What is a sunspot? A sunspot is a dark area on the surface of the Sun. Sunspots are regions where the Sun s magnetic field has broken through the surface. This causes the convection or mixing to be reduced, which in turn lowers the temperature of this area. The lower temperature causes the sunspot to look dark. Sunspots generally occur in pairs, with one acting like the North Pole of a magnet and the other the South Pole. Q4: What is a solar flare? A solar flare is a violent explosion of the atmosphere (corona and chromosphere) of the Sun. During the flare, the Sun s plasma (charged particles) is heated to high temperatures that accelerate the electrons, protons, and heavier ions to close to the speed of light. Solar flares also produce electromagnetic energy at all wavelengths from low-energy radio waves to high-energy gamma rays. Continued 4

5 Science Background, continued Q5: What are coronal mass ejections? Coronal mass ejections (or CMEs) are huge bubbles of plasma consisting primarily of electrons and protons (in addition to small quantities of heavier elements such as helium, oxygen, and iron) that are ejected from the Sun over the course of several hours. Although frequently associated with sunspots, both solar flares and CMEs can occur independently of either sunspots or each other. Q6: What does high-energy mean? The term high-energy can be used to describe a portion of the electromagnetic spectrum or high-speed charged particles. Both can cause damage to living systems. The high-energy portion of the electromagnetic spectrum consists of X-rays and gamma rays. High-energy charged particles or plasma consist of protons and electrons moving at speeds close to the speed of light. High-energy radiation and plasma can be released during solar flares and coronal mass ejections on the Sun. Q7: Who was George Ellery Hale? George Ellery Hale ( ) began studying the Sun as a teenager in Chicago. He invented the spectroheliograph as an undergraduate at the Massachusetts Institute of Technology. This instrument allowed him to photograph the Sun in broad daylight and discover that sunspots are places of strong magnetic fields. Further research showed that the polarity of sunspot pairs follows a regular pattern. First, the North Pole leads during one solar cycle; then the South Pole leads during the next cycle. As an adult, Hale founded three famous observatories each one larger than the previous one. His first big project was to build the 40-inch (1-meter) Yerkes refractor for the University of Chicago in It remains the largest working refractor in the world. Next, Hale founded the Mount Wilson Observatory, where he had several telescopes built, including a 60-inch (1.5-meter) reflector, a 100-inch (2.5-meter) reflector, and the Snow Telescope, the first solar telescope. His last observatory was a 200-inch (5-meter) reflector built on Mount Palomar. He was instrumental in establishing the astrophysics branch of astronomy and also founded the Astrophysical Journal, which remains the leading publication in its field. Q8: How did Hale find magnetic fields on the Sun? Hale used his spectroheliograph to discover the magnetic fields in sunspots. The stronger the magnetic field, the greater the effect, as seen with the spectroheliograph. Hale used this relationship to discover that sunspots are areas of intense magnetic fields. 5

6 Science Background, continued Q9: What causes solar weather? Solar weather refers to violent transfers of matter and energy from the Sun to Earth. Activity on the Sun, such as solar flares and coronal mass ejections (CMEs), can cause high levels of radiation in space. This radiation can come as plasma (charged particles) or electromagnetic radiation (light). Solar flares and CMEs are the largest explosions in the solar system. They are caused by the buildup and sudden release of magnetic stress in the solar atmosphere. Q10: Why are we concerned with solar weather? When a solar flare or a coronal mass ejection (CME) is directed toward Earth, high levels of radiation can interact with Earth s magnetic field and interfere with Earth systems. Some of the specific effects of solar weather on Earth systems include interference with short-wave radio communication, problems with electric power grids (such as power failures), the decay of satellite orbits, and radiation hazards for satellites and for astronauts during some phases of space missions. 6

7 Science Misconceptions MYTH 1: The Earth is the largest object in the solar system. FACT: The largest object in the solar system is the Sun. It contains 99 percent of the mass of the solar system. Jupiter is the largest planet in the solar system, and Earth is the fifth-largest. MYTH 2: The Earth is the center of the solar system. FACT: The Sun is at the center of the solar system, and the planets, asteroids, moons, and comets orbit the Sun. The Earth is the third planet from the Sun. MYTH 3: The Sun is not a star because it doesn t shine at night. FACT: The Sun is the closest star to Earth and provides us with most of our energy and light. Earth turns on its axis once every day. When we experience darkness, we are facing away from the Sun. When we experience daylight, we are facing the Sun. We can t see other stars during the day because the Sun s light illuminates Earth s atmosphere. MYTH 4: The Sun is a burning ball of fire. FACT: The Sun is glowing, not burning like a fire. The Sun glows because its temperature is about 5,500 degrees Celsius (about 10,000 degrees Fahrenheit). This heat is not produced by burning (a chemical reaction), but rather by fusion (a nuclear reaction). This nuclear fusion takes place deep in the Sun s core at a temperature of about 15 million degrees. As the heat travels out through the Sun s layers, it becomes much cooler, but still hot enough to glow in visible light. For comparison, the temperature of a wood fire is less than a thousand degrees Fahrenheit. MYTH 5: Other stars and galaxies are part of the solar system. FACT: There is only one star, the Sun, in the solar system. Besides the Sun, the solar system consists of planets, moons, asteroids, and comets. The solar system resides in the Milky Way Galaxy. Many other stars are outside our solar system, but are part of our Milky Way Galaxy. About 50 billion galaxies are outside our galaxy. Galaxies contain from tens of millions to trillions of stars. 7

8 Glossary Chromosphere The layer of the Sun s atmosphere below the corona. Most of the Sun s ultraviolet light is emitted from this region. Corona The outermost layer of the Sun s atmosphere. The corona extends millions of kilometers from the Sun s surface and has a temperature in the millions of degrees. The Sun s corona is visible during a solar eclipse or when special equipment is attached to a telescope. Coronal mass ejection (CME) Huge outburst of plasma (charged particles) emitted from the Sun s atmosphere. CMEs can last for several hours and send plasma streaming past Earth. Electrons A negatively charged elementary particle that typically resides outside the nucleus of an atom but is bound to it by electromagnetic forces. An electron s mass is tiny. It takes the mass of 1,836 electrons to equal the mass of one proton. Gamma rays The part of the electromagnetic spectrum with the highest energy; also called gamma radiation. Gamma rays can cause serious damage when absorbed by living cells. Ion An atom with one or more electrons removed (or added), giving the atom a positive (or negative) charge. Magnetic field A region of space in which magnetic forces may be detected or may affect the motion of an electrically charged particle. As with gravity, magnetism has a long-range effect, and magnetic fields are associated with many astronomical objects. Continued 8

9 Glossary, continued Plasma A hot gas composed of ions, electrons, and other particles. Our Sun is made of plasma.. While the charge of a plasma is overall neutral, the many electrons enable the gas to conduct electricity. Plasma is regarded as an additional state of matter because its properties are different from those of solids, liquids, and normal gases. Proton A positively charged elementary particle that resides in the nucleus of every atom. Reflector (Reflecting telescope) A type of telescope, also known as a reflecting telescope, which uses one or more polished, curved mirrors to gather light and reflect it to a focal point. Refractor (Refracting telescope) A type of telescope, also known as a refracting telescope, that uses a transparent convex lens to gather the light and bend it to a focal point. Solar flare A violent explosion that occurs within the Sun s atmosphere. Most solar flares occur in or around sunspots and are the result of intense magnetic fields emerging from the Sun s surface. Spectroheliograph An instrument developed by George Ellery Hale in 1890 that images the visible surface of the Sun in a single wavelength of light. Sunspot A region on the Sun s surface (photosphere) that is marked by a higher magnetic field and lower temperature than its surroundings. Because the surface areas surrounding sunspots are much hotter, sunspots appear dark. Sunspots usually appear in pairs or groups with specific magnetic polarities that indicate electromagnetic origins. X-rays The part of the electromagnetic spectrum with energy between ultraviolet light and gamma rays. X-rays are used in medicine to detect broken bones and cavities in teeth. Astronomers can detect X-rays from exploding stars and black holes. 9

10 Related Educational Resources from NASA's Amazing Space Web site Amazing Space uses the Hubble Space Telescope s discoveries to inspire and educate about the wonders of our universe. The Amazing Space Web site includes curriculum support tools, a section for the general public, and a special section for educators and developers. The curriculum support tools are developed by a team of scientists, education specialists, and multimedia experts. They are aligned with national educational standards and are reviewed for scientific accuracy. Find teaching tools, graphic organizers, Online Explorations, and more. Online Explorations Online Explorations are fun, interactive activities for exploring various space science topics. Telescopes From the Ground Up Telescopes From the Ground Up traces the 400 years of telescope development from Galileo s refractor to NASA s Great Observatories. The overview for this activity can be found at: Specific sections of Telescopes From the Ground Up related to this exhibit panel include: Telescopes take on our closest star the Sun, which describes the development and design of solar telescopes. Snow Solar Telescope, which describes the development and design of the first telescope devoted to the study of the Sun. Biography: George Ellery Hale, which describes the American astronomer who studied the Sun. Solar System Trading Cards This Online Exploration involves identifying solar system objects. A card about the Sun is included. The overview for this activity can be found at: Fast Facts This is a collection of tables that provide vital statistics for the planets and other celestial objects. The Sun This table lists key facts about the Sun in an easy-to-read format. 10