The solar constant is measured at. The solar constant tells, with which intensity the Sun on average shines vertically on an area on Earth. The specific value at Earth of 1,361 W/m2 is called the "solar constant". Since the values for the solar constant (K S), Earth's albedo, and the Stefan-Boltzmann constant (σ) are all known, it is possible to solve this equation for temperature (T). [48] Short-term overexposure is the cause of sunburn, snow blindness, and solar retinopathy. During the Neolithic Revolution, the domestication of plants and animals further increased human access to solar energy. [20], The solar constant is a measure of flux density, is the amount of incoming solar electromagnetic radiation per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit (AU) (roughly the mean distance from the Sun to Earth). In practice, the unit area is 1 m squared (m 2).Its value is about 1.98 calories per minute incident on each square centimeter (approximately 127.7 calories incident per minute on each square inch) of the upper atmosphere. The Sun may be said to illuminate, which is a measure of the light within a specific sensitivity range. The amount that actually reaches the ground can vary enormously and depends on: (a) the angle of the Sun's rays (b) the transparency of the atmosphere. Water vapour in the lower atmosphere produces further scattering and ozone, dust and water particles will also absorb particular wavelengths.[35][36]. Because of the elliptical orbit the solar “constant” varies from 1,415 W/m^2 at perihelion to 1,323 W/m^2 at aphelion, a swing of 92 W/m^2. It also formed the basis for religion in Ancient Egypt. ‘The solar constant is 1.37 kW m - 2, but the 24-hour average at the top of the atmosphere is of course much lower, and varies widely by geographic latitude and time of year.’ ‘The solar constant isn't constant.’ ‘Solar sails can be used to adjust the earth's solar constant (in … Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. These measurements show that the solar constant is not constant. It is most accurately measured from satellites where atmospheric effects are absent. For many people with light skin, one purpose for sunbathing is to darken one's skin color (get a sun tan), as this is considered in some cultures to be attractive, associated with outdoor activity, vacations/holidays, and health. RELATED ASSESSMENTS. Meaning of solar constant. 1,367 w/m^2. Vitamin D has a wide range of positive health effects, which include strengthening bones[44] and possibly inhibiting the growth of some cancers. The illumination of a horizontal surface will be considerably less than this if the Sun is not very high in the sky. solar constant in American English noun the average rate at which radiant energy is received from the sun by the earth, equal to 1.94 small calories per minute per square centimeter of area perpendicular to the sun's rays , measured at a point outside the earth's atmosphere when the … Information and translations of solar constant in the most comprehensive dictionary definitions resource on the web. The short-wavelength radiation reaching on the Earth is (A) 0.03 to 0.30 μm (B) 3 to 30 μm (C) 0.3 to 3 μm (D) None of these. solar constant in British English. The solar constant. In order to calculate the total amount of energy arriving at Earth, we need to know how much area is being lit. A The "solar constant" includes all types of solar radiation, not just the visible light. The direct normal illuminance (Edn), corrected for the attenuating effects of the atmosphere is given by: where c is the atmospheric extinction and m is the relative optical airmass. Aside from effects that arise at sunset and sunrise, the spectral composition changes primarily in respect to how directly sunlight is able to illuminate. To calculate the amount of sunlight reaching the ground, both the eccentricity of Earth's elliptic orbit and the attenuation by Earth's atmosphere have to be taken into account. [21][23][24][25] TSI observations continue with the ACRIMSAT/ACRIM3, SOHO/VIRGO and SORCE/TIM satellite experiments. ", "9,400 years of cosmic radiation and solar activity from ice cores and tree rings", "Dietary Supplement Fact Sheet: Vitamin D", "Effectiveness and safety of vitamin D in relation to bone health", "Sun Exposure, Vitamin D Receptor Gene Polymorphisms, and Risk of Advanced Prostate Cancer", "Sunlight and Reduced Risk of Cancer: Is The Real Story Vitamin D? These sugars are then used as building-blocks and in other synthetic pathways that allow the organism to grow. Appendix 3 259 The Greenhouse Effect, And Iii. (b) Assume the earth radiates an equal amount back into space ( that is , the earth is in equilibrium ) . The solar constant (as defined for the planet Earth) is the power collected at the top of the atmosphere by a unit area perpendicular to the light path. The warming of the ground (and other objects) depends on the absorption of the electromagnetic radiation in the form of heat. A solar constant is a measurement of the solar electromagnetic radiation available in a meter squared at Earth's distance from the sun. The amount of radiation intercepted by a planetary body varies inversely with the square of the distance between the star and the planet. It is measured on a surface perpendicular to the rays, one astronomical unit (AU) from the Sun (roughly the distance from the Sun to the Earth). (However, the radiance at the center of the sun's disk is somewhat higher than the average over the whole disk due to limb darkening.) The solar constant S c = 1365 W/m 2 ± 0.3 % (Li et al., 2011) denes the amount of incoming radiation at a distance of one astronomical unit from the sun. To compensate for the brightness of sunlight, many people wear sunglasses. solar constant synonyms, solar constant pronunciation, solar constant translation, English dictionary definition of solar constant. Data indicate that SSI at UV (ultraviolet) wavelength corresponds in a less clear, and probably more complicated fashion, with Earth's climate responses than earlier assumed, fueling broad avenues of new research in "the connection of the Sun and stratosphere, troposphere, biosphere, ocean, and Earth's climate".[29]. Some common places for sunbathing include beaches, open air swimming pools, parks, gardens, and sidewalk cafes. Irradiance is sometimes referred to as flux and is a measurement of electromagnetic energy from the sun. Solar Constant > FAQ. Most of this radiation is in the visible and infrared part of the electromagnetic spectrum, with less the 1% emitted in the radio, UV and X-ray spectral bands. Nya_Pettway. See diffuse sky radiation for more details. Compute the solar constant, which is calculated using the intensity formula $I = \frac{P}{4\pi r^2}$. (slightly) variable star. noun. Problem. This is a composite graph produced by the World Radiation Centre and shows that our Sun is really a Sunlight is a key factor in photosynthesis, the process used by plants and other autotrophic organisms to convert light energy, normally from the Sun, into chemical energy that can be used to synthesize carbohydrates and to fuel the organisms' activities. n (Units) the rate at which the sun's energy is received per unit area at the top of the earth's atmosphere when the sun is at its mean distance from the earth and atmospheric absorption has been corrected for. solar constant synonyms, solar constant pronunciation, solar constant translation, English dictionary definition of solar constant. Hereby, Earth's atmosphere isn't taken into account, the practical value of the incoming radiation changes with weather and other atmospheric conditions. In this context, the solar constant provides a total measurement of the sun's radiant energy as it is absorbed at a given point. The solar constant is a measure of flux density, is the amount of incoming solar electromagnetic radiation per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit (AU) (roughly the mean distance from the Sun to Earth). The amount of variability is still a subject of debate, but is certainly very small apart from the long-term development in the history of the Sun. Since 1978 a series of overlapping NASA and ESA satellite experiments have measured total solar irradiance (TSI) – the amount of solar radiation received at the top of Earth's atmosphere – as 1.365 kilo⁠watts per square meter (kW/m²). The solar constant includes all types of solar radiation, not just the visible light. Elevated solar UV-B doses increase the frequency of DNA recombination in Arabidopsis thaliana and tobacco (Nicotiana tabacum) plants. [42] A dietary supplement can supply vitamin D without this mutagenic effect,[43] but bypasses natural mechanisms that would prevent overdoses of vitamin D generated internally from sunlight. The Sun is generally considered to produce a constant amount of power (although there are small variances in the output energy depending on sunspot cycles) with a surface intensity of , expressed in units of power per unit area.As the Sun's rays spread into space this radiation becomes less and less intense as an inverse square law. People often sunbathe in comfortable places where there is ample sunlight. Solar constant, the total radiation energy received from the Sun per unit of time per unit of area on a theoretical surface perpendicular to the Sun’s rays and at Earth’s mean distance from the Sun. [37] The effect of Sun angle on climate results in the change in solar energy in summer and winter. (D) in the terrestrial region. The actual illumination of the surface is about 14,000 lux, comparable to that on Earth "in the daytime with overcast clouds".[31]. Sidebar: 'Solar Constant' is an Oxymoron. The extraterrestrial solar illuminance (Eext), corrected for the elliptic orbit by using the day number of the year (dn), is given to a good approximation by[3]. where dn=1 on January 1; dn=32 on February 1; dn=59 on March 1 (except on leap years, where dn=60), etc. C 1367 W/m2. D 1377 W/m2. 36. Solar Constant and Solar Intensity on Earth. Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun. Its value is 1367 watts per square metre. These fossil fuels are the remnants of ancient plant and animal matter, formed using energy from sunlight and then trapped within Earth for millions of years. These solar constant is varying over 1 Wm2 by periodic disturbances and explosions in the solar surface basically related to sun spot. Surface temperature of the Sun: $5772 K$ Earth-Sun distance: $1.5 \times {10}^{11} m$ Radius of the Earth: $6.4 \times 10^6 m$ Radius of the Sun: $7.0 \times 10^8 m$ Temperature of outer space: $2.7 K$ FOS … These effects are apparent in natural light photography where the principal source of illumination is sunlight as mediated by the atmosphere. The solar constant is calculated by multiplying the sun's surface irradiance by the square of the radius of the sun over the average distance between the Earth and the sun. Solar constant, the total radiation energy received from the Sun per unit of time per unit of area on a theoretical surface perpendicular to the Sun’s rays and at Earth’s mean distance from the Sun. absorption of the electromagnetic radiation, Learn how and when to remove this template message, "The 8-minute travel time to Earth by sunlight hides a thousand-year journey that actually began in the core", "Reference Solar Spectral Irradiance: Air Mass 1.5", NASA Solar System Exploration – Sun: Facts & Figures, "Fermi Detects Solar Flare's Highest-Energy Light", "The Multispectral Sun, from the National Earth Science Teachers Association", "Sunlight and Vitamin D: A global perspective for health", https://www.who.int/uv/faq/whatisuv/en/index2.html, "Ultraviolet Radiation Exposure and Its Impact on Skin Cancer Risk", "Visible Light | Science Mission Directorate", "Direct Solar Radiation On Various Slopes From 0 To 60 Degrees North Latitude", "Satellite observations of total solar irradiance", "Secular total solar irradiance trend during solar cycles 21–23", "Construction of a Composite Total Solar Irradiance (TSI) Time Series from 1978 to present", "Comparison: ACRIMSAT/ACRIM3, SOHO/VIRGO and SORCE/TIM results", "NASA Goddard Space Flight Center: Solar Radiation", "Graph of variation of seasonal and latitudinal distribution of solar radiation", "Modeling the Sun's Magnetic Field and Irradiance since 1713", "Total solar irradiance since 1996: is there a long-term variation unrelated to solar surface magnetic phenomena? The solar constant is a flux density measuring mean solar electromagnetic radiation (solar irradiance) per unit area. As the amount of fossil fuel is large but finite, this cannot continue indefinitely, and various theories exist as to what will follow this stage of human civilization (e.g., alternative fuels, Malthusian catastrophe, new urbanism, peak oil). This changes dramatically, however, at the surface of the Earth, as sunlight has to pass through varying layers of atmosphere depending on latitude and sea … Multiplying this by π gives an upper limit to the irradiance which can be focused on a surface using mirrors: 48.5 MW/m2.[8]. Such changes associated with the redistribution of solar energy are considered a likely cause for the coming and going of recent ice ages (see: Milankovitch cycles). Thus the level of terrestrial solar UV-B radiation likely affects genome stability in plants. The luminosity of the Sun is about 3.86 x 1026 watts. THE SOLAR CONSTANT & SOLAR VARIABILITY. Most autotrophs, such as plants, use the energy of sunlight, combined with carbon dioxide and water, to produce simple sugars—a process known as photosynthesis. The Habitable Zone Of A Planetary System. C 42. As mentioned above, if the host star is variable, it is good to define these values for average and maximum (for flare stars). It varies on many time scales, including the 11-year sunspot solar cycle. Sunbathers typically wear limited amounts of clothing or some simply go nude. It is measured on a surface perpendicular to the rays, one astronomical unit (AU) from the Sun (roughly the distance from the Sun to the Earth). The spectrum on the surface is slightly redder than that on Earth, due to scattering by reddish dust in the Martian atmosphere. 3. GEO 102 Midterm 1 Chapter 2 30 Terms. (a) Estimate , using the solar constant , the rate at which the whole earth receives energy from the sun . This process is known as cellular respiration. When the direct radiation is not blocked by clouds, it is experienced as sunshine. This is the total power radiated out into space by the Sun. (b) The Time-averaged Value Of The Solar Constant Is 1368 W M−2. Animals that had previously provided humans with only meat and tools once they were killed were now used for labour throughout their lives, fueled by grasses inedible to humans. What is the number value for The Solar Constant? It is probably fortunate for us that our star does not show such a typical variability, as we might then well see temperature variations not to our liking. The Solar Constant, Ii. This energy is also radiated isotropically, that is, uniformly into space, independent of direction. 1. In colder countries, many people prefer sunnier days and often avoid the shade. The solar constant (as defined for the planet Earth) is the power collected at the top of the atmosphere by a unit area perpendicular to the light path. It has a value of about 1368 W m −2.The solar constant is a fundamental quantity in atmospheric physics since it represents the amount of solar energy arriving at the top of the atmosphere. As a result, the Sun does not emit gamma rays from this process, but it does emit gamma rays from solar flares. The solar constant, a measure of flux density, is the conventional name for the mean solar electromagnetic radiation (the solar irradiance) per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit (AU) from the Sun (roughly the mean distance from the Sun to the Earth). These skills allowed humans to harvest more of the sunlight than was possible through glycolysis alone, and human population began to grow. Scientist refer to the amount of incoming energy from sunlight as "insolation". The local solar (or stellar) constant is the energy output at a specified distance. [34] The useful range for color vision in humans, for example, is approximately 450–650 nm. Thus, the tan gradually disappears with time, when one is no longer exposed to these sources. (C) in the extraterrestrial region. It has a value of about 1368 W m −2.The solar constant is a fundamental quantity in atmospheric physics since it represents the amount of solar energy arriving at the top of the atmosphere. The solar constant is the energy output of the Sun or another celestial body as received on the orbit of Earth or another planet, moon or asteroid. For example, Venus's thick atmosphere reflects more than 60% of the solar light it receives. The solar constant is a measure of the power of a square meter of sunlight directly impacting on a perpendicular plane of space above the atmosphere of the Earth, and is considered to be a uniform value of 1,370 watts per square meter. La constante solar es la cantidad de energía que el Sol deposita por unidad de tiempo y superficie y que es directamente expuesta como luz solar. Epidemiological data shows that people who have more exposure to sunlight have less high blood pressure and cardiovascular-related mortality. Fields devoted to crops were enriched by inedible plant matter, providing sugars and nutrients for future harvests. Although the solar corona is a source of extreme ultraviolet and X-ray radiation, these rays make up only a very small amount of the power output of the Sun (see spectrum at right). Geology 1710 30 Terms. While the color of the sky is usually determined by Rayleigh scattering, an exception occurs at sunset and twilight. solar constant. The solar constant is measured (A) near the Sun. In practice, the unit area is 1 m squared (m 2).Its value is about 1.98 calories per minute incident on each square centimeter (approximately 127.7 calories incident per minute on each square inch) of the upper atmosphere. It has also been suggested that this variation might explain some of the terrestrial temperature variations. In practice, the unit area is 1 m squared (m 2). Many animals (including humans) have a sensitivity range of approximately 400–700 nm,[33] and given optimal conditions the absorption and scattering by Earth's atmosphere produces illumination that approximates an equal-energy illuminant for most of this range. The solar constant is used to quantify the rate at which energy is received upon a unit surface such as a solar panel . The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a principal source of vitamin D3 and a mutagen. But the seasonal and latitudinal distribution and intensity of solar radiation received at Earth's surface does vary. The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a requisite for vitamin D3 synthesis and a mutagen. Irradiance is sometimes referred to as flux and is a measurement of electromagnetic energy from the sun. the rate at which the sun's energy is received per unit area at the top of the earth's atmosphere when the sun is at its mean distance from the earth and atmospheric absorption has been corrected for. [4] In terms of energy, sunlight at Earth's surface is around 52 to 55 percent infrared (above 700 nm), 42 to 43 percent visible (400 to 700 nm), and 3 to 5 percent ultraviolet (below 400 nm). Define solar constant. The spectrum of the Sun's solar radiation is close to that of a black body[9][10] with a temperature of about 5,800 K.[11] The Sun emits EM radiation across most of the electromagnetic spectrum. In prehistory, humans began to further extend this process by putting plant and animal materials to other uses. For some, an alternative to sunbathing is the use of a sunbed that generates ultraviolet light and can be used indoors regardless of weather conditions. Sunbathing is a popular leisure activity in which a person sits or lies in direct sunshine. It is interesting to note that the average G-type star (which is the class of star that the Sun falls into) typically shows a variation of about 4%. When illumination is indirect, Rayleigh scattering in the upper atmosphere will lead blue wavelengths to dominate. For the purposes of solar energy capture, we normally talk about the amount of power in sunlight passing through one square metre at the Earth's distance from the Sun (and that one square metre is assumed to be at normal incidence, or 'face on' to the direction from which the sunlight is coming). ", "Benefits of sunlight: a bright spot for human health", "Is the current public health message on UV exposure correct? In many world religions, such as Hinduism, the Sun is considered to be a god, as it is the source of life and energy on Earth. Some researchers have tried to reconstruct this variation (by correlating it to sunspot numbers) back over the last 400 years, and have suggested that the Sun may have varied in its power output by up to one percent. The luminosity of the Sun is about 3.86 x 10 26 watts. The solar constant (as defined for the planet Earth) is the power collected at the top of the atmosphere by a unit area perpendicular to the light path. Which of the following is true relative to insolation at the thermopause relative to latitude? When direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. Most of this radiation is in the visible and infrared part of the electromagnetic spectrum, with less the 1% emitted in the radio, UV and X-ray spectral bands. Its value is about 1.98 calories per minute incident on each square centimeter (approximately 127.7 calories incident per minute on each square inch) of the upper atmosphere. Measuring the Solar Constant Purpose With this activity, we will let solar radiation raise the temperature of a measured quantity of water. It is about 3.3% higher than average in January and 3.3% lower in July (see below). Skin tanning is achieved by an increase in the dark pigment inside skin cells called melanocytes, and is an automatic response mechanism of the body to sufficient exposure to ultraviolet radiation from the Sun or from artificial sunlamps. where The solar constant is the amount of power that the Sun deposits per unit area that is directly exposed to sunlight. There is the origin of the seasons. Solar constant definition is - the quantity of radiant solar energy received at the outer layer of the earth's atmosphere that has a mean value of 1370 watts per square meter. The solar constant is the amount of solar irradiance at the outer edge of Earth’s atmosphere. before penetrating the Earth's atmosphere) at the average distance of the Earth from the Sun.The intensity is not strictly constant for all the wavelengths of radiation involved. ", "13th Report on Carcinogens: Ultraviolet-Radiation-Related Exposures", 20.500.11820/8f7d93d4-db22-418d-a1cc-3dbf9ddad8c3, Total Solar Irradiance (TSI) Daily mean data, Construction of a Composite Total Solar Irradiance (TSI) Time Series from 1978 to present, A Comparison of Methods for Providing Solar Radiation Data to Crop Models and Decision Support Systems, Evaluation of three model estimations of solar radiation at 24 UK stations, High resolution spectrum of solar radiation, https://en.wikipedia.org/w/index.php?title=Sunlight&oldid=994256768, Short description is different from Wikidata, Articles with unsourced statements from March 2017, All articles with vague or ambiguous time, Vague or ambiguous time from December 2016, Articles needing additional references from February 2011, All articles needing additional references, Articles needing additional references from January 2015, Creative Commons Attribution-ShareAlike License, This page was last edited on 14 December 2020, at 20:38. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. The value of the constant is approximately 1.366 kilowatts per square metre. The spectrum of surface illumination depends upon solar elevation due to atmospheric effects, with the blue spectral component dominating during twilight before and after sunrise and sunset, respectively, and red dominating during sunrise and sunset. The solar constant is the amount of power that the Sun deposits per unit area that is directly exposed to sunlight. Popular Questions. The solar constant is calculated by multiplying the sun's surface irradiance by the square of the radius of the sun over the average distance between the Earth and the sun. The smoothed variation (black line) in the solar constant can be seen (from the graph) to be about 0.1% over a period of 34 years. Geometry & algebra. "Preferential absorption of sunlight by ozone over long horizon paths gives the zenith sky its blueness when the sun is near the horizon".[32]. We should note that relative variations of the measured flux are thus more accurate than is the absolute value. THE SOLAR CONSTANT & SOLAR VARIABILITY. The total amount of energy received at ground level from the Sun at the zenith depends on the distance to the Sun and thus on the time of year. For other uses, see, For natural lighting of interior spaces by admitting sunlight, see, Total solar irradiance (TSI) and spectral solar irradiance (SSI) upon Earth, Spectral composition of sunlight at Earth's surface. The solar constant, a measure of flux density, is the conventional name for the mean solar electromagnetic radiation (the solar irradiance) per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit (AU) from the Sun (roughly the mean distance from the Sun to the Earth). This power is termed the solar constant, and is approximately 1370 watts per square metre (W m-2). Because of the tilted axis any particular point on ToA sees a 700 W/m^2 swing from solstice to solstice. Long-term sunlight exposure is known to be associated with the development of skin cancer, skin aging, immune suppression, and eye diseases such as cataracts and macular degeneration. Sunshine exposure is needed biologically for the creation of Vitamin D in the skin, a vital compound needed to make strong bone and muscle in the body. UV radiation. ingrithaa PLUS. Start studying Solar Constant. The solar constant is the amount of solar radiation incidence that is received at a distance of 1 astronomical unit (AU) from the Sun. Since 2003 the SORCE Spectral Irradiance Monitor (SIM) has monitored Spectral solar irradiance (SSI) – the spectral distribution of the TSI. It is presently calculated as being 1,366 W/m2. Although there are accurate solar radiometers at many locations on the Earth's surface, the absolute determination of the solar constant is a difficult problem, because the Earth's atmosphere is essentially opaque to most of the ultraviolet spectrum and parts of the infrared spectrum. Solar constant definition is - the quantity of radiant solar energy received at the outer layer of the earth's atmosphere that has a mean value of 1370 watts per square meter. The value of the solar constant indicated by 30 years of observation by the Smithsonian Institution is revised in the light of the scale correction announced in 1952 and new solar spectral-irradiance data for outside the earth's atmosphere obtained by the Naval Research Laboratory. Using a little more algebra, we can write the expression above as: Earth's overall, average albedo is about 0.31 (or 31%). The solar illuminance constant (Esc), is equal to 128×103 lux. A table comparing the amount of solar radiation received by each planet in the Solar System at the top of its atmosphere:[30], The actual brightness of sunlight that would be observed at the surface also depends on the presence and composition of an atmosphere. The value of the constant is approximately 1.366 kilowatts per square metre. The solar constant is defined as the total irradiance of the sun at the mean orbital distance of the Earth. The Habitable Zone Of A Planetary System. This variation has been measured by radiometers aboard several satellites since the late 1970's and is shown in the graph below. The solar constant is the amount of solar radiation incidence that It is presently calculated … Although the Sun produces gamma rays as a result of the nuclear-fusion process, internal absorption and thermalization convert these super-high-energy photons to lower-energy photons before they reach the Sun's surface and are emitted out into space. The uneven distribution of insolation by latitude is primarily a result of. This is the total power radiated out into space by the Sun. Even when we correct for the changing Earth-Sun distance we still find that there is a small variation in the solar constant, and this is due to a variation in the intrinsic luminosity of the Sun itself. 4\Pi r^2 } $, if the star has a different spectra then Sol, it would give and... As sunshine still amounts to a massive 1.75 x 1017 watts solar System receive light of an intensity proportional! It would give perceptions and  feel '' very much like Earth daylight some the... To a massive 1.75 x 1017 watts when blocked by clouds or off. Amounts to a massive 1.75 x 1017 watts also, if the Sun at the intensity... Per watt of radiant flux even on Pluto, the unit area variation has been measured by radiometers aboard satellites. Linear scale and plotted against wavenumber, visible, and so on it receives that... 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