"a much stronger toroidal field. However, recent radio observations of cooler stars and brown dwarfs, which do not have a radiative core and only have a convection zone, have demonstrated that they maintain large-scale, solar-strength magnetic fields and display solar-like activity despite the absence of tachoclines. This suggests that the convection zone alone may be responsible for the function of the solar dynamo. The most prominent time variation of the solar magnetic field is related to the quasi-periodic 11-year solar cycle, characterized by an increasing and decreasing number and size of sunspots.<ref name=""doi10.1146/annurev-astro-081913-040012""></ref> Sunspots are visible as dark patches on"
"visible as dark spots. This is because the luminance (which is essentially ""brightness"" in visible light) of a heated black body (closely approximated by the photosphere) at these temperatures varies extremely with temperature—considerably more so than the (temperature to the fourth power) variation in the total black-body radiation at all wavelengths (see Stefan–Boltzmann law). Isolated from the surrounding photosphere a sunspot would be brighter than the Moon. Sunspots have two parts: the central umbra, which is the darkest part, where the magnetic field is approximately vertical (normal to the Sun's surface) and the surrounding penumbra, which is lighter, where the"
"on Earth. During a total solar eclipse, when the disk of the Sun is covered by that of the Moon, parts of the Sun's surrounding atmosphere can be seen. It is composed of four distinct parts: the chromosphere, the transition region, the corona and the heliosphere. The coolest layer of the Sun is a temperature minimum region extending to about above the photosphere, and has a temperature of about . This part of the Sun is cool enough to allow the existence of simple molecules such as carbon monoxide and water, which can be detected via their absorption spectra. The"
"series of dark patches in the Milky Way, is more visible and striking in the southern hemisphere than in the northern. It vividly stands out when conditions are otherwise so dark that the Milky Way's central region casts shadows on the ground. Some cultures have discerned shapes in these patches and have given names to these ""dark cloud constellations"". Members of the Inca civilization identified various dark areas or dark nebulae in the Milky Way as animals and associated their appearance with the seasonal rains. Australian Aboriginal astronomy also describes dark cloud constellations, the most famous being the ""emu in"
"He assumed that dark areas might be low flat ""seas"", as they are on the Moon, while ""land"" would be lighter. In particular he noted several light patches that he took to be islands; he named the most striking circular one Hellas (for Greece), and two others Chryse and Argyre. It was only with the observations made from Martian orbit by Mariner 9 in 1972 that it became clear that these light areas were not islands at all, but depressions carpeted with light windblown dust. Chryse is really a low flat plain, but the name has been kept, and it"
"Sunspots are relatively dark areas on the Sun's radiating 'surface' (photosphere) where intense magnetic activity inhibits convection and cools the Photosphere. Faculae are slightly brighter areas that form around sunspot groups as the flow of energy to the photosphere is re-established and both the normal flow and the sunspot-blocked energy elevate the radiating 'surface' temperature. Scientists began speculating on possible relationships between sunspots and solar luminosity in the 17th century. Luminosity decreases caused by sunspots (generally < - 0.3%) are correlated with increases (generally < + 0.05%) caused both by faculae that are associated with active regions as well as"
"Sunspot Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection. Sunspots usually appear in pairs of opposite magnetic polarity. Their number varies according to the approximately 11-year solar cycle. Individual sunspots or groups of sunspots may last anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun, with diameters ranging from to . The larger variety are visible from Earth"
"a temperature of , together with a warm spot of . Sunspot Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection. Sunspots usually appear in pairs of opposite magnetic polarity. Their number varies according to the approximately 11-year solar cycle. Individual sunspots or groups of sunspots may last anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun, with diameters"
"has steadily increased in luminosity by 40% since it first became a main-sequence star. The Sun has also undergone periodic changes in luminosity that can have a significant impact on the Earth. The Maunder minimum, for example, is believed to have caused the Little Ice Age phenomenon during the Middle Ages. The visible outer surface of the Sun is called the photosphere. Above this layer is a thin region known as the chromosphere. This is surrounded by a transition region of rapidly increasing temperatures, and finally by the super-heated corona. At the center of the Sun is the core region,"
"haze, observed through variation in brightness, still present today, thought to be due to sublimating ice. Ice would not last long in such warm conditions exposed to the vacuum of space, so that would suggest it is being brought to the surface to this day. The brightest cluster of spots (""Spot 5"") is located in an crater called Occator, which is located at 19.86° N latitude; 238.85 E longitude. The spot in the center of the crater is named ""Cerealia Facula"", and the group of spots to the east - ""Vinalia Faculae"". These names were approved by International Astronomical Union"
"Coalsack Nebula The Coalsack Nebula (Southern Coalsack, or simply the Coalsack) is the most prominent dark nebula in the skies, being easily visible to the naked eye as a dark patch silhouetted against the southern Milky Way. It is located at a distance of approximately 600 light-years away from Earth, in the constellation Crux. The Coalsack Nebula covers nearly 7° by 5° and overlaps somewhat into the neighbor constellations Centaurus and Musca. The first observation was reported by Vicente Yáñez Pinzón in 1499. It was named """"il Canopo fosco"""" (the dark Canopus) by Amerigo Vespucci and was also called """"Macula"
"sunspots and faculae, occur in the photosphere, spicules, Hα filaments and plages in the chromosphere, prominences in the chromosphere and transition region, and flares and coronal mass ejections happen in the corona and chromosphere. If flares are very violent, they can also perturb the photosphere and generate a Moreton wave. On the contrary, quiescent prominences are large, cool dense structures which are observed as dark, ""snake-like"" Hα ribbons (appearing like filaments) on the solar disc. Their temperature is about 5000–8000 K, and so they are usually considered as chromospheric features. In 2013, images from the High Resolution Coronal Imager revealed"
"temperature decreases with respect to the surrounding regions or when the zone of intense magnetic field empties. The same physical effect renders sunspots apparently dark in the photosphere. Bright points are small active regions found on the solar disk. X-ray bright points were first detected on April 8, 1969 during a rocket flight. The fraction of the solar surface covered by bright points varies with the solar cycle. They are associated with small bipolar regions of the magnetic field. Their average temperature ranges from 1.1x10 K to 3.4x10 K. The variations in temperature are often correlated with changes in the"
"darker than the north. The north polar region is dominated by a very large dark area informally dubbed ""Mordor"" by the ""New Horizons"" team. The Mordor Macula is distinctly red. Aside from Mordor, however, ""New Horizons"" imaged unexpectedly few other impact craters on Charon and found a youthful surface, indicating that Charon is probably geologically active. In particular, the southern hemisphere has fewer craters than the northern and is considerably less rugged, suggesting that a massive resurfacing event—perhaps prompted by the partial or complete freezing of an internal ocean—occurred at some point in the past and removed many of the"
"see is produced as electrons react with hydrogen atoms to produce H ions. The photosphere is tens to hundreds of kilometers thick, and is slightly less opaque than air on Earth. Because the upper part of the photosphere is cooler than the lower part, an image of the Sun appears brighter in the center than on the edge or ""limb"" of the solar disk, in a phenomenon known as limb darkening. The spectrum of sunlight has approximately the spectrum of a black-body radiating at 5,777 K, interspersed with atomic absorption lines from the tenuous layers above the photosphere. The photosphere"
"Facula A facula (plural: faculae ), Latin for ""little torch"", is literally a ""bright spot"". The term has several common technical uses. It is used in planetary nomenclature for naming certain surface features of planets and moons, and is also a type of surface phenomenon on the Sun. In addition, a bright region in the projected field of a light source is sometimes referred to as a facula, and photographers often use the term to describe bright, typically circular features in photographs that correspond to light sources or bright reflections in a defocused image. Solar faculae are bright spots that"
"Coronal hole Coronal holes are areas where the Sun's corona is colder, hence darker, and has lower-density plasma than average because there is lower energy and gas levels. Coronal holes are part of the Sun's corona and are constantly changing and reshaping because the corona is not uniform. The Sun contains magnetic fields that arch away from areas in the corona that are very thin due to the lower levels of energy and gas, which cause coronal holes to appear when they do not fall back. Thus, solar particles escape at a rate great enough to create a lower density"
"in albedo, with a bright equatorial band and darker poles. The north polar region is dominated by a very large dark area informally dubbed ""Mordor"" by the ""New Horizons"" team. The favored explanation for this phenomenon is that they are formed by condensation of gases that escaped from Pluto's atmosphere. In winter, the temperature is −258 °C, and these gases, which include nitrogen, carbon monoxide, and methane, condense into their solid forms; when these ices are subjected to solar radiation, they chemically react to form various reddish tholins. Later, when the area is again heated by the Sun as Charon's"
"significantly farther in advance than for CME related disturbances. Coronal hole Coronal holes are areas where the Sun's corona is colder, hence darker, and has lower-density plasma than average because there is lower energy and gas levels. Coronal holes are part of the Sun's corona and are constantly changing and reshaping because the corona is not uniform. The Sun contains magnetic fields that arch away from areas in the corona that are very thin due to the lower levels of energy and gas, which cause coronal holes to appear when they do not fall back. Thus, solar particles escape at"
"Noctilucent cloud Noctilucent clouds, or night shining clouds, are tenuous cloud-like phenomena in the upper atmosphere of Earth. They consist of ice crystals and are only visible during astronomical twilight. ""Noctilucent"" roughly means ""night shining"" in Latin. They are most often observed during the summer months from latitudes between 50° and 70° north and south of the Equator. They are visible only during local summer months and when the Sun is below the observer's horizon, but while the clouds are still in sunlight. Recent studies suggests that increased atmospheric methane emissions produce additional water vapor once the methane molecules reach"
"sun the sunshade is usually called a heatshield. Notable spacecraft [designs] with heatshields include : Space sunshade A space sunshade or sunshield is a parasol that diverts or otherwise reduces some of a star's radiation, preventing them from hitting a spacecraft or planet and thereby reducing its insolation, which results in reduced heating. Light can be diverted by different methods. First proposed in 1989, the original space sunshade concept involves putting a large occulting disc, or technology of equivalent purpose at the L1 gravitation point (Lagrangian point) between the Earth and Sun. A sunshade is of particular interest as a"
"chromosphere, transition region, and corona are much hotter than the surface of the Sun. The reason is not well understood, but evidence suggests that Alfvén waves may have enough energy to heat the corona. Above the temperature minimum layer is a layer about thick, dominated by a spectrum of emission and absorption lines. It is called the ""chromosphere"" from the Greek root ""chroma"", meaning color, because the chromosphere is visible as a colored flash at the beginning and end of total solar eclipses. The temperature of the chromosphere increases gradually with altitude, ranging up to around near the top. In"
"that the Moon has cooled much more slowly than thought, possibly due to heat released from radioactive decay of radioisotopes in the Moon. Irregular mare patch An irregular mare patch also known as an IMP, is a smooth, rounded, slightly mounded area, generally about 500 meters wide, occurring in the lunar maria. Due to their small size, and corresponding difficulty of observational astronomy from Earth, the first irregular mare patch discovered, Ina, was only found in 1971 after analysis of photographs taken by Apollo 15. More were discovered by the Lunar Reconnaissance Orbiter, which was launched in 2009 and found"
"to a dark plain. Current understanding is that the hills (also referred to as highlands) are composed mainly of water ice. Dark organic compounds, created in the upper atmosphere by the ultraviolet radiation of the Sun, may rain from Titan's atmosphere. They are washed down the hills with the methane rain and are deposited on the plains over geological time scales. After landing, ""Huygens"" photographed a dark plain covered in small rocks and pebbles, which are composed of water ice. The two rocks just below the middle of the image on the right are smaller than they may appear: the"
"center of an crater called Occator. These bright features have an albedo of about 40%, four times brighter than the average of Ceres's surface. The spots appear to be mostly sodium carbonate (), implying that hydrothermal activity followed by evaporation of the water is probably what created the spots. source: http://www.solarviews.com/eng/sun.htm Facula A facula (plural: faculae ), Latin for ""little torch"", is literally a ""bright spot"". The term has several common technical uses. It is used in planetary nomenclature for naming certain surface features of planets and moons, and is also a type of surface phenomenon on the Sun. In"
"Far side of the Moon The far side of the Moon (archaic dark side of the Moon -- with ""dark"" meaning ""hidden"" rather than unilluminated) is the hemisphere of the Moon that always faces away from Earth. The far side's terrain is rugged with a multitude of impact craters and relatively few flat lunar maria. It has one of the largest craters in the Solar System, the South Pole–Aitken basin. Both sides of the Moon experience two weeks of sunlight followed by two weeks of night; the far side is sometimes called the ""dark side of the Moon,"" meaning unseen"
"Sun is never directly overhead, and the climate is mild, generally ranging from warm to cool. The four annual seasons, spring, summer, autumn and winter, occur in these areas. The North Temperate Zone includes Europe, Northern Asia, and North and Central America. The South Temperate Zone includes Southern Australasia, southern South America, and Southern Africa. The two frigid zones, or polar regions, experience the midnight sun and the polar night for part of the year - at the edge of the zone there is one day at the winter solstice when the Sun is invisible, and one day at the"
"Thermal low Thermal lows, or heat lows, are non-frontal low-pressure areas that occur over the continents in the subtropics during the warm season, as the result of intense heating when compared to their surrounding environments. Thermal lows occur near the Sonoran Desert, on the Mexican plateau, in California's Great Central Valley, the Sahara, over north-west Argentina in South America, over the Kimberley region of north-west Australia, the Iberian peninsula, and the Tibetan plateau. Over land, intense, rapid solar heating of the land surface results in heating of the lowest layers of the atmosphere via reradiated energy in the infrared spectrum."
"and dark. For a person or object touching the surface where the shadow is projected (e.g. a person standing on the ground, or a pole in the ground) the shadows converge at the point of contact. A shadow shows, apart from distortion, the same image as the silhouette when looking at the object from the sun-side, hence the mirror image of the silhouette seen from the other side. The names umbra, penumbra and antumbra are often used for the shadows cast by astronomical objects, though they are sometimes used to describe levels of darkness, such as in sunspots. An astronomical"
"Solar transition region The solar transition region is a region of the Sun's atmosphere, between the chromosphere and corona. It is visible from space using telescopes that can sense ultraviolet. It is important because it is the site of several unrelated but important transitions in the physics of the solar atmosphere: Helium ionization is important because it is a critical part of the formation of the corona: when solar material is cool enough that the helium within it is only partially ionized (i.e. retains one of its two electrons), the material cools by radiation very effectively via both black body"
"scales. Turbulent convection in this outer part of the solar interior sustains ""small-scale"" dynamo action over the near-surface volume of the Sun. The Sun's thermal columns are Bénard cells and take the shape of hexagonal prisms. The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light. Above the photosphere visible sunlight is free to propagate into space, and almost all of its energy escapes the Sun entirely. The change in opacity is due to the decreasing amount of H ions, which absorb visible light easily. Conversely, the visible light we"
"Oort cloud The Oort cloud (), named after the Dutch astronomer Jan Oort, sometimes called the Öpik–Oort cloud, is a theoretical cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from 2,000 to 200,000 AU (0.03 to 3.2 light-years). It is divided into two regions: a disc-shaped inner Oort cloud (or Hills cloud) and a spherical outer Oort cloud. Both regions lie beyond the heliosphere and in interstellar space. The Kuiper belt and the scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth as far from the Sun as the Oort"
"structures. Often associated with dark spots are brighter, persistent methane clouds that form around the tropopause layer. The persistence of companion clouds shows that some former dark spots may continue to exist as cyclones even though they are no longer visible as a dark feature. Dark spots may dissipate when they migrate too close to the equator or possibly through some other unknown mechanism. Neptune's more varied weather when compared to Uranus is due in part to its higher internal heating. Although Neptune lies over 50% farther from the Sun than Uranus, and receives only 40% its amount of sunlight,"