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Encyclopedia > Sunspot
Sunspots imaged by the MDI instrument on NASA’s Solar and Heliospheric Observatory (SOHO) on 30 March 2001. It was the source of numerous flares and coronal mass ejections, including one of the largest flares recorded in 25 years on 2 April 2001.

A sunspot is a region on the Sun's surface (photosphere) that is marked by a lower temperature than its surroundings and has intense magnetic activity, which inhibits convection, forming areas of low surface temperature. You can only see them if you use sun-protective lenses. Although they are blindingly bright at temperatures of roughly 4000-4500 K, the contrast with the surrounding material at about 5800 K leaves them clearly visible as dark spots. If they were isolated from the surrounding photosphere they would be brighter than an electric arc. A minimum in the eleven-year sunspot cycle may have taken place in late 2007 [1] and while the observation of a reverse polarity sunspot [1] on 4 January 2008 officially began Cycle 24, no additional sunspots have yet been seen in this cycle. Sunspots are often related to intense magnetic activity such as coronal loops and reconnection. Most solar flares and coronal mass ejections originate in magnetically active regions around sunspot groupings. Similar phenomena observed on stars other than the Sun are commonly called starspots and both light (warm) and dark (cool) spots are seen.[2] A sunspot is a dark region that periodically appears on the surface of the Sun. ... Image File history File links Metadata Size of this preview: 800 × 225 pixelsFull resolution (1150 × 324 pixel, file size: 252 KB, MIME type: image/jpeg) Active region 9393 as seen by the MDI instrument on SOHO hosted the largest sunspot group observed so far during the current solar cycle. ... Image File history File links Metadata Size of this preview: 800 × 225 pixelsFull resolution (1150 × 324 pixel, file size: 252 KB, MIME type: image/jpeg) Active region 9393 as seen by the MDI instrument on SOHO hosted the largest sunspot group observed so far during the current solar cycle. ... For other uses, see NASA (disambiguation). ... The Solar and Heliospheric Observatory (SOHO) is a spacecraft that was launched on an Atlas IIAS launch vehicle on 2 December 1995 to study the Sun, and began normal operations in May 1996. ... is the 89th day of the year (90th in leap years) in the Gregorian calendar. ... This article is about the year. ... A composite image showing two CMEs (at 2 oclock and 8 oclock), with the sun at center. ... is the 92nd day of the year (93rd in leap years) in the Gregorian calendar. ... This article is about the year. ... Sol redirects here. ... Solar disk redirects here. ... For other senses of this word, see magnetism (disambiguation). ... Convection in the most general terms refers to the movement of currents within fluids (i. ... For other uses, see Kelvin (disambiguation). ... A 3000 volt electricity arc between two nails Electricity arcs between the power rail and electrical pickup shoe on a London Underground train An electric arc can melt calcium oxide An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current... 400 year history of sunspot numbers. ... is the 4th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... Typical coronal loops observed by TRACE Coronal loops form the basic structure of the lower corona and transition region of the Sun. ... Magnetic reconnection is the process whereby magnetic field lines from different magnetic domains are spliced to one another, changing the overall topology of a magnetic field. ... A solar flare is a violent explosion in the Suns atmosphere with an energy equivalent to tens of millions of hydrogen bombs. ... A solar coronal mass ejection blasts plasma throughout the Solar System. ... This article is about the astronomical object. ...

Contents

Sunspot variation

Main article: Solar variation
400 year sunspot history
400 year sunspot history
11,000 year sunspot reconstruction
11,000 year sunspot reconstruction
A drawing of a sunspot in the Chronicles of John of Worcester.
A drawing of a sunspot in the Chronicles of John of Worcester.

Sunspot numbers rise and fall with an irregular cycle with a length of approximately 11 years. In addition to this, there are variations over longer periods. The recent trend is upward from 1900 to the 1960s, then somewhat downward[3]. The Sun was last similarly active over 8,000 years ago. The number of sunspots has been found to correlate with the intensity of solar radiation over the period (since 1979) when satellite measurements of radiation are available. Since sunspots are dark it might be expected that more sunspots lead to less solar radiation and a decreased solar constant. However, the surrounding areas are brighter and the overall effect is that more sunspots means a brighter sun. The variation caused by the sunspot cycle to solar output is relatively small, on the order of 0.1% of the solar constant (a peak-to-trough range of 1.3 W m-2 compared to 1366 W m-2 for the average solar constant)[4][5]. This range is slightly smaller than the change in radiative forcing caused by the increase in atmospheric CO2 since the 18th century[6]. During the Maunder Minimum in the 17th Century there were hardly any sunspots at all. This coincides with a period of cooling known as the Little Ice Age. It has been speculated that there may be a resonant gravitational link between a photospheric tidal force from the planets, the dominant component by summing gravitational tidal force (75%) being Jupiter's with an 11 year cycle[7]. 400 year history of sunspot numbers. ... Image File history File links Download high-resolution version (1000x425, 41 KB) Description Changes in carbon-14 concentration in the Earths atmosphere, which serves as a long term proxy of solar activity. ... Image File history File links Download high-resolution version (1000x425, 41 KB) Description Changes in carbon-14 concentration in the Earths atmosphere, which serves as a long term proxy of solar activity. ... Image File history File links Sunspots_11000_years. ... Image File history File links Sunspots_11000_years. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... King Henry Is Dream in the Chronicle. ... Solar irradiance spectrum at top of atmosphere. ... Solar irradiance spectrum at top of atmosphere. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... Events and trends The Bonneville Slide blocks the Columbia River near the site of present-day Cascade Locks, Oregon with a land bridge 200 feet (60 m) high. ... The Maunder minimum in a 400 year history of sunspot numbers The Maunder Minimum is the name given to the period roughly from 1645 to 1715 A.D., when sunspots became exceedingly rare, as noted by solar observers of the time. ... Many inventions and institutions are created, including Hans Lippershey with the telescope (1608, used by Galileo the next year), the newspaper Avisa Relation oder Zeitung in Augsburg, and Cornelius Drebbel with the thermostat (1609). ... The Little Ice Age (LIA) was a period of cooling occurring after a warmer era known as the Medieval climate optimum. ...


History

Apparent references to sunspots were made by Chinese astronomers in 28 BC (Hanshu, 27), who probably could see the largest spot groups when the sun's glare was filtered by wind-borne dust from the various central Asian deserts. A large sunspot was also seen at the time of Charlemagne's death in 813 A.D. and sunspot activity in 1129 was described by John of Worcester. However, these observations were misinterpreted until Galileo gave the correct explanation in 1612. 2137 BC - Chinese book 书经 records the earliest known solar eclipse on October 22. ... The Book of Han (Ch: 漢書, Hanshu) is a classic Chinese historical writing covering the history of the Western Han Dynasty (206 BCE-9 CE). ... For the American band, see Charlemagne (band). ... King Henry Is Dream in the Chronicle. ... Galileo redirects here. ...


They were first observed telescopically in late 1610 by the English astronomer Thomas Harriot and Frisian astronomers Johannes and David Fabricius, who published a description in June 1611. At the latter time Galileo had been showing sunspots to astronomers in Rome, and Christoph Scheiner had probably been observing the spots for two or three months. The ensuing priority dispute between Galileo and Scheiner, neither of whom knew of the Fabricius' work, was thus as pointless as it was bitter. Thomas Harriot (ca. ... David and Johannes Fabricius were father and son astronomers from Frisia. ... David and Johannes Fabricius were father and son astronomers from Frisia. ... Christoph Scheiner (July 25, 1573 or 1575 – June 18, 1650) was a German astronomer and Jesuit. ...


Sunspots had some importance in the debate over the nature of the solar system. They showed that the Sun rotated, and their comings and goings showed that the Sun changed, contrary to the teaching of Aristotle. The details of their apparent motion could not be readily explained except in the heliocentric system of Copernicus. This article is about the Solar System. ... For other uses, see Aristotle (disambiguation). ... Heliocentric Solar System Heliocentrism (lower panel) in comparison to the geocentric model (upper panel) In astronomy, heliocentrism is the theory that the sun is at the center of the Universe and/or the Solar System. ... Copernicus redirects here. ...


The cyclic variation of the number of sunspots was first observed by Heinrich Schwabe between 1826 and 1843 and led Rudolf Wolf to make systematic observations starting in 1848. The Wolf number is an expression of individual spots and spot groupings, which has demonstrated success in its correlation to a number of solar observables. Also in 1848, Joseph Henry projected an image of the Sun onto a screen and determined that sunspots were cooler than the surrounding surface.[8] Samuel Heinrich Schwabe (October 25, 1789–April 11, 1875) was a German astronomer. ... Johann Rudolf Wolf (7 July 1816, Fällanden - 6 December 1893, Zurich) was a Swiss astronomer and mathematician best known for his research on sunspots. ... Joseph Henry Joseph Henry (December 17, 1797 – May 13, 1878) was a Scottish-American scientist who served as the first Secretary of the Smithsonian Institution. ...


Wolf also studied the historical record in an attempt to establish a database on cyclic variations of the past. He established a cycle database to only 1700, although the technology and techniques for careful solar observations were first available in 1610. Gustav Spörer later suggested a 70-year period before 1716 in which sunspots were rarely observed as the reason for Wolf's inability to extend the cycles into the seventeenth century. The economist William Stanley Jevons suggested that there is a relationship between sunspots and crises in business cycles. He reasoned that sunspots affect earth's weather, which, in turn, influences crop yields and, therefore, the economy. Friederich Wilhelm Gustav Spörer (October 23, 1822 – July 7, 1895) was a German astronomer. ... [William Stanley Jevons] William Stanley Jevons (September 1, 1835 - August 13, 1882), English economist and logician, was born in Liverpool. ...


Edward Maunder would later suggest a period over which the Sun had changed modality from a period in which sunspots all but disappeared from the solar surface, followed by the appearance of sunspot cycles starting in 1700. Careful studies revealed the problem not to be a lack of observational data but included references to negative observations. Adding to this understanding of the absence of solar activity cycles were observations of aurorae, which were also absent at the same time. Even the lack of a solar corona during solar eclipses was noted prior to 1715. Edward Walter Maunder (April 12, 1851 – March 21, 1928) was an English astronomer best remembered for his study of sunspots and the solar magnetic cycle that led to his identification of the period from 1645 to 1715 that is now known as the Maunder Minimum. ... Aurora borealis Polar aurorae are optical phenomena characterized by colorful displays of light in the night sky. ... This article is about the astronomical term. ... Photo taken during the 1999 eclipse. ...


Sunspot research was dormant for much of the 17th and early 18th centuries because of the Maunder Minimum, during which no sunspots were visible for some years; but after the resumption of sunspot activity, Heinrich Schwabe in 1843 reported a periodic change in the number of sunspots. Since 1981, the Royal Observatory of Belgium keeps track of sunspots as the World data center for the Sunspot Index. The Maunder minimum in a 400 year history of sunspot numbers The Maunder Minimum is the name given to the period roughly from 1645 to 1715 A.D., when sunspots became exceedingly rare, as noted by solar observers of the time. ...


Radio communications interference

Solar flares also create a wide spectrum of radio noise; at VHF (and under unusual conditions at HF) this noise may interfere directly with a wanted signal. The frequency with which a radio operator experiences solar flare effects will vary with the approximately 11-year sunspot cycle; more effects occur during solar maximum (when flare occurrence is high) than during solar minimum (when flare occurrence is very low). A radio operator can experience great difficulty in transmitting or receiving signals during solar flares due to more noise and different propagation patterns.


Significant events

An extremely powerful flare was emitted toward Earth on 1 September 1859. It interrupted electrical telegraph service and caused visible Aurora Borealis as far south as Havana, Hawaii, and Rome with similar activity in the southern hemisphere. A solar flare observed by Hinode in the G-band. ... is the 244th day of the year (245th in leap years) in the Gregorian calendar. ... Year 1859 (MDCCCLIX) was a common year starting on Saturday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Thursday of the 12-day slower Julian calendar). ... The Aurora Borealis, or Northern Lights, shines above Bear Lake Aurora Borealis as seen over Canada at 11,000m (36,000 feet) Red and green Aurora in Fairbanks, Alaska Aurora Borealis redirects here. ... Aurora borealis Polar aurorae are optical phenomena characterized by colorful displays of light in the night sky. ...


The most powerful flare observed by satellite instrumentation began on 4 November 2003 at 19:29 UTC, and saturated instruments for 11 minutes. Region 486 has been estimated to have produced an X-ray flux of X28. Holographic and visual observations indicate significant activity continued on the far side of the Sun. is the 308th day of the year (309th in leap years) in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ...


Physics

A sunspot viewed close-up in ultraviolet light, taken by the TRACE spacecraft.
A sunspot viewed close-up in ultraviolet light, taken by the TRACE spacecraft.
Main article: Solar cycle

Although the details of sunspot generation are still somewhat a matter of research, it is quite clear that sunspots are the visible counterparts of magnetic flux tubes in the convective zone of the sun that get "wound up" by differential rotation. If the stress on the flux tubes reaches a certain limit, they curl up quite like a rubber band and puncture the sun's surface. At the puncture points convection is inhibited, the energy flux from the sun's interior decreases, and with it the surface temperature. Image File history File links Sunspot_TRACE.jpeg‎ Original NASA description: It was a quiet day on the Sun in September of 2000. ... Image File history File links Sunspot_TRACE.jpeg‎ Original NASA description: It was a quiet day on the Sun in September of 2000. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... Look up Trace in Wiktionary, the free dictionary. ... It has been suggested that this article or section be merged with Schwabe-Wolf cycle. ... ... The convection zone is a region of a stars interior where energy is transferred toward the surface by convection currents, rather than energetic photons. ... Differential rotation is seen if parts of a rotating object move with different angular velocity. ...


The Wilson effect tells us that sunspots are actually depressions on the sun's surface. This model is supported by observations using the Zeeman effect that show that prototypical sunspots come in pairs with opposite magnetic polarity. From cycle to cycle, the polarities of leading and trailing (with respect to the solar rotation) sunspots change from north/south to south/north and back. Sunspots usually appear in groups. In 1769 a Scottish astronomer named Alexander Wilson noticed that the shape of sunspots noticeably flattened as they approached the Suns limb as the Sun rotated. ... The Zeeman effect (IPA ) is the splitting of a spectral line into several components in the presence of a magnetic field. ...


The sunspot itself can be divided into two parts:

  • The central umbra, which is the darkest part, where the magnetic field is approximately vertical
  • The surrounding penumbra, which is lighter, where the magnetic field lines are more inclined.

Magnetic field lines would ordinarily repel each other, causing sunspots to disperse rapidly, but sunspot lifetime is about two weeks. Recent observations from the Solar and Heliospheric Observatory (SOHO) using sound waves traveling through the Sun's photosphere to develop a detailed image of the internal structure below sunspots show that there is a powerful downdraft underneath each sunspot, forming a rotating vortex that concentrates magnetic field lines. Sunspots are self-perpetuating storms, similar in some ways to terrestrial hurricanes. For the indie-pop band, see The Magnetic Fields. ... The Solar and Heliospheric Observatory (SOHO) is a spacecraft that was launched on an Atlas IIAS launch vehicle on 2 December 1995 to study the Sun, and began normal operations in May 1996. ... Vortex created by the passage of an aircraft wing, revealed by coloured smoke A vortex (pl. ... This article is about weather phenomena. ...

Butterfly diagram showing paired Spörer's law behavior.

Sunspot activity cycles about every eleven years. The point of highest sunspot activity during this cycle is known as Solar Maximum, and the point of lowest activity is Solar Minimum. At the start of a cycle, sunspots tend to appear in the higher latitudes and then move towards the equator as the cycle approaches maximum: this is called Spörer's law. Image File history File links Size of this preview: 800 × 500 pixelsFull resolution (2048 × 1280 pixel, file size: 132 KB, MIME type: image/gif) (All user names refer to en. ... Image File history File links Size of this preview: 800 × 500 pixelsFull resolution (2048 × 1280 pixel, file size: 132 KB, MIME type: image/gif) (All user names refer to en. ... Spörers law predicts the variation of sunspot latitudes during a solar cycle. ... Spörers law predicts the variation of sunspot latitudes during a solar cycle. ...


Today it is known that there are various periods in the Wolf number sunspot index, the most prominent of which is at about 11 years in the mean. This period is also observed in most other expressions of solar activity and is deeply linked to a variation in the solar magnetic field that changes polarity with this period, too. The Wolf number (also known as the International sunspot number, relative sunspot number, or Zürich number) is a quantity which measures the number of sunspots and groups of sunspots present on the surface of the sun. ... 20 years of solar irradiance data from satellites Solar variation refers to fluctuation in the amount of energy emitted by the Sun. ...


A modern understanding of sunspots starts with George Ellery Hale, in which magnetic fields and sunspots are linked. Hale suggested that the sunspot cycle period is 22 years, covering two polar reversals of the solar magnetic dipole field. Horace W. Babcock later proposed a qualitative model for the dynamics of the solar outer layers. The Babcock Model explains the behavior described by Spörer's law, as well as other effects, as being due to magnetic fields which are twisted by the Sun's rotation. George Ellery Hale, Sc. ... The Babcock Model describes a mechanism which can explain magnetic and sunspot patterns observed on the Sun. ...


Sunspot observation

Sunspots are observed with land-based solar telescopes as well as ones on Earth-orbiting satellites. These telescopes use filtration and projection techniques for direct observation, in additional to filtered cameras of various types. Specialized tools such as spectroscopes and spectrohelioscopes are used to examine sunspots and areas of sunspots. Artificial eclipses allow viewing of the circumference of the sun as sunspots rotate through the horizon. Image File history File links Metadata Size of this preview: 399 × 599 pixelsFull resolution‎ (682 × 1,024 pixels, file size: 96 KB, MIME type: image/jpeg) Made and released into the public domain by Tim van Werkhoven. ... Image File history File links Metadata Size of this preview: 399 × 599 pixelsFull resolution‎ (682 × 1,024 pixels, file size: 96 KB, MIME type: image/jpeg) Made and released into the public domain by Tim van Werkhoven. ... The Swedish Solar Telescope (or SST) is a 1m telescope on La Palma in the Canary Islands. ... The seeing statistics for Roque de los Muchachos Observatory make it the third best location for optical and infrared astronomy after Dome C, Antarctica and Mauna Kea Observatory, Hawaii. ... This article is about one of the Canary Islands. ... Anthem: Arrorró Capital Las Palmas de Gran Canaria and Santa Cruz de Tenerife Official language(s) Spanish Area  â€“ Total  â€“ % of Spain Ranked 13th  7,447 km²  1. ... The 1 m Swedish Solar Telescope at Roque de los Muchachos Observatory, La Palma in the Canary Islands. ... This article is about artificial satellites. ... A spectroscope is a device which measures the spectrum of light. ... A spectrohelioscope is a telescope designed to show the Sun in a particular wavelenght of light. ...


Since looking directly at the Sun with the naked eye, through binoculars or a telescope is extremely dangerous, amateur observation of sunspots with the unaided eye is generally done by projection or via using proper filtration. Small sections of very dark filter glass, such as a #14 welder's glass is sometimes employed. The eyepiece of a telescope is also used in the role of a "projector" to project the image, without filtration, on to a white screen where it can be viewed indirectly, and even traced, so sunspot evolution can be followed. Special purpose hydrogen-alpha narrow bandpass filters as well as aluminum coated glass attenuation filters (which have the appearance of mirrors due to their extremely high optical density) are also used on the front of a telescope to provide safe direct observation through the eyepiece. An optical filter is a device which selectively transmits light having certain properties (often, a particular range of wavelengths, i. ... In physics and astronomy, H-alpha, also written Hα, is a particular emission line created by hydrogen. ... Vacuum deposition is a process used to create a thin layer of a substance (a coating) on a solid object (the substrate). ... Optical density is the absorbance of an optical element for a given wavelength λ per unit distance: Where: Although absorbance does not have true units, it is quite often reported in Absorbance Units or AU. Accordingly, optical density is measured in ODU, which are equivalent to AU cm−1. ...


Application

Due to their link to other kinds of solar activity, sunspots can be used to predict the space weather and with it the state of the ionosphere. Thus, sunspots can help predict conditions of short-wave radio propagation or satellite communications. Aurora australis observed by Discovery, May 1991. ... Relationship of the atmosphere and ionosphere The ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. ... Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly in use at that time. ... Radio propagation is a term used to explain how radio waves behave when they are transmitted, or are propagated from one point on the Earth to another. ... U.S. military MILSTAR communications satellite A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications using radio at microwave frequencies. ...

A large group of sunspots in year 2004. The grey area around the spots can be seen very clearly, as well as the granulation of the sun's surface.
A large group of sunspots in year 2004. The grey area around the spots can be seen very clearly, as well as the granulation of the sun's surface.

Image File history File links Description: A large sunspot group in 2004 photographed at the 2. ... Image File history File links Description: A large sunspot group in 2004 photographed at the 2. ...

Starspots on other stars

Periodic changes in brightness had been first seen on red dwarfs and in 1947 G. E. Kron proposed that spots were the cause.[2] Since the mid 1990s observations of starspots have been made using increasingly powerful techniques yielding more and more detail: photometry determined starspot regions grew and decayed and showed cyclic behaviour similar to the Sun's; spectroscopy examined the structure of starspot regions; Doppler imaging showed differential rotation of spots for several stars and distributions different from the Sun's; spectral line analysis measured the temperature range of spots and the stellar surfaces. For example, in 1999, Strassmeier reported the largest cool starspot ever seen rotating the giant K0 star XX Triangulum (HD 12545) with a temperature of 3500 kelvin, together with a warm spot of 4800 kelvin.[2][9] This article describes the British science fiction comedy television series. ... Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical objects electromagnetic radiation. ... Animation of the dispersion of light as it travels through a triangular prism. ... For other uses, see Kelvin (disambiguation). ...

Image File history File links This is a lossless scalable vector image. ...

See also

Here is the list of Solar cycles (or sunspot cycles), tracked since 1755: March 1755 - June 1766 June 1766 - June 1775 June 1775 - September 1784 September 1784 - May 1798 May 1798 - December 1810 December 1810 - May 1823 May 1823 - November 1833 November 1833 - July 1843 July 1843 - December 1855 December... Since the sun is composed of a gaseous plasma, it does not have a fixed rotation rate. ... Aurora australis observed by Discovery, May 1991. ... Radio propagation is a term used to explain how radio waves behave when they are transmitted, or are propagated from one point on the Earth to another. ...

References

  1. ^ First sunspot of new solar cycle glimpsed, NewScientist (retrieved 8 January 2008)
  2. ^ a b c press release 990610, K. G. Strassmeier, 1999-06-10, University of Vienna, "starspots vary on the same (short) time scales as Sunspots do", "HD 12545 had a warm spot (350 K above photospheric temperature; the white area in the picture)"
  3. ^ Sunspot index graphics, Solar Influences Data Analysis Center (retrieved 27 September 2007).
  4. ^ Solar Forcing of Climate. Climate Change 2001: Working Group I: The Scientific Basis. Retrieved on March 10, 2005.
  5. ^ Weart, Spencer (2006), "Changing Sun, Changing Climate?", in Weart, Spencer, The Discovery of Global Warming, American Institute of Physics, <http://www.aip.org/history/climate/solar.htm>. Retrieved on 14 April 2007 
  6. ^ Recent Greenhouse Gas Concentrations, CDIAC (retrieved 27 September 2007).
  7. ^ Wainwright, G. (2004). Jupiter's influence. New Scientist 2439, 30 (retrieved 27 September 2007).
  8. ^ Hellemans, Alexander; Bryan Bunch (1988). The Timetables of Science. New York, New York: Simon and Schuster, 317. ISBN 0671621300. 
  9. ^ derived images showing rotation of cool and warm starspots

Events of 2008: (EMILY) Me Lesley and MIley are going to China! This article is about the year. ... is the 161st day of the year (162nd in leap years) in the Gregorian calendar. ... The University of Vienna (German: ) is a public university located in Vienna, Austria. ... is the 270th day of the year (271st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 69th day of the year (70th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Director of the Center for History of Physics of the American Institute of Physics. ... Director of the Center for History of Physics of the American Institute of Physics. ... The American Institute of Physics (AIP) is a professional body representing American physicists and publishing physics related journals. ... The Carbon Dioxide Information Analysis Center (CDIAC) is an organization within the United States Department of Energy that has the primary responsibility for providing the US government and research community with global warming data and analysis as it pertains to energy issues. ... is the 270th day of the year (271st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... New Scientist is a weekly international science magazine covering recent developments in science and technology for a general English-speaking audience. ... is the 270th day of the year (271st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ...

External links

Aurora australis observed by Discovery, May 1991. ...

Sunspot data

Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Sol redirects here. ... The structure of the Sun The core of the Sun is considered to extend from the center to about 0. ... The radiation zone is the middle zone in the suns interior. ... The convection zone is a region of a stars interior where energy is transferred toward the surface by convection currents, rather than energetic photons. ... Image File history File links Sun920607. ... Photo taken during the French 1999 eclipse The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone. ... Solar disk redirects here. ... The chromosphere (literally, color sphere) is a thin layer of the Suns atmosphere just above the photosphere, roughly 10,000 kilometers deep (approximating to, if a little less than, the diameter of the Earth). ... TRACE 19. ... This article is about the astronomical term. ... The heliosphere is a bubble in space produced by the solar wind. ... Heliospheric current sheet The Heliospheric current sheet (HCS) is the surface within the Solar System where the polarity of the Suns magnetic field changes from north to south. ... The locations of Voyagers 1 and 2 as of 2005 In space physics, the termination shock is the boundary marking one of the outer limits of the suns influence. ... The locations of Voyagers 1 and 2 as of 2005 The heliosheath is the zone between the termination shock and the heliopause at the outer border of the solar system. ... The heliopause is the boundary between the heliosphere and the interstellar medium outside the solar system. ... In a planetary magnetosphere, the bow shock is the boundary at which the solar wind abruptly drops as a result of its approach to the magnetopause. ... Coronal holes are areas where the Suns corona is darker, colder, and has lower-density plasma than average. ... Typical coronal loops observed by TRACE Coronal loops form the basic structure of the lower corona and transition region of the Sun. ... A composite image showing two CMEs (at 2 oclock and 8 oclock), with the sun at center. ... Photo taken during the 1999 eclipse. ... The bright areas visible here on the Sun are facula. ... A solar flare observed by Hinode in the G-band. ... Solar photosphere Granules on the photosphere of the Sun are caused by convection currents of plasma within the Suns convective zone. ... Animation of a Moreton wave which occurred on December 6, 2006 A Moreton wave is a kind of shockwave on the Suns chromosphere. ... Filaments surrounding a solar flare, caused by the interaction of the plasma in the Suns atmosphere with its magnetic field. ... Solar irradiance spectrum at top of atmosphere. ... 400 year history of sunspot numbers. ... A spicule is a dynamic jet of about 500km diameter on the Sun. ... Supergranulation is one of the influences on the Sun. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... This article is about the Solar System. ... The solar dynamo is the physical process that generates the Suns magnetic field. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ...

Gallery

Please remember observing sunspots at sunsets without proper solar filters may permanently damage your eyes.


  Results from FactBites:
 
Sunspot - Wikipedia, the free encyclopedia (1616 words)
Apparent references to sunspots were made by Chinese astronomers in 28 BC, who probably could see the largest spot groups when the sun's glare was filtered by wind-borne dust from the various central Asian deserts.
Sunspot research was dormant for much of the 17th and early 18th centuries because of the Maunder Minimum, during which no sunspots were visible for some years; but after the resumption of sunspot activity, Heinrich Schwabe in 1843 reported a periodic change in the number of sunspots.
Sunspots are self-perpetuating storms, similar in some ways to terrestrial hurricanes.
Solar variation - Wikipedia, the free encyclopedia (4340 words)
Study was hampered during the 1600s and 1700s due to the low number of sunspots during what is now recognized as an extended period of low solar activity, this event named the Maunder Minimum.
Sunspots are relatively dark areas on the surface of the Sun and are thus cooler than its average surface.
An increase in solar activity (more sunspots) is accompanied by an increase in the "solar wind," which is an outflow of ionized particles, mostly protons and electrons, from the sun.
  More results at FactBites »

 
 

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