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	Frequently Asked Questions Send to a friend  Printable version  En Español Keywords Sun  Sunspots and Solar Flares  Magnetism and Magnetic Fields  Star Colors and Temperatures  Resources FAQs about Earth, Moon, and the Sun Astronomy Gift Shop 2009 Sky Almanac McDonald Observatory logo cap What are sunspots?  Bright "granules" of hot gas that look like Rice Krispies, and dark magnetic sunspots highlight this false-color image of the Sun. Sunspots are regions on the Sun's visible surface, or "photosphere," where gases have been trapped by magnetic fields. The hotter material bubbling up from the Sun's interior cannot penetrate the strong magnetic fields (about 10,000 times stronger than Earth's), and thus are prevented from reaching the surface. These magnetic areas cool down (from about 9,800 to 6,700 degrees Fahrenheit (5,500 to 3,750 C)), so they don't glow as brightly as the rest of the photosphere. Sunspots are actually quite bright, but appear as dark spots against their much brighter surroundings. Sunspots have complex structures, which are caused by the geometry of the magnetic fields. The darkest area in the center, the "umbra," is where the magnetic field is strongest. Around the edge of the sunspot, the field weakens, so this "penumbra" is a little brighter and shows radial streaks. Sometimes "light bridges" cross the umbra, like sparks jumping the gap in a spark plug. The number of sunspots visible on the Sun's surface varies from maximum to minimum and back again over an average period of 11 years, called the "sunspot cycle." The current cycle peaked in 2001. Other FAQs Select FAQ category Earth, Moon, and the Sun The Solar System Space Probes and Human Exploration Stars and Nebulae Astronomers and Observatories Galaxies and Cosmology Stargazing and Star Lore » FAQs about StarDate Online Earth, Moon, and the Sun Links NASA Eclipse Home Page Exploring the Moon Earth Observatory Earth Science Picture of the Day Solar Dynamics Observatory Near-Earth Asteroid Tracking Home Page SpaceWatch Lincoln Near Earth Asteroid Research (LINEAR) Lowell Observatory Near-Earth-Object Search (LONEOS) Common Holidays in Relation to Equinoxes, Solstices & Cross-Quarter Days Earth and Moon Viewer Fireball Data Center Meteorite Central NASA Solar Data Analysis Center (SOHO) North American Meteor Network The Aurora Page Virtual Reality Moon Phase Pictures
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