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Sun

The Sun is the closest star to Earth, at a mean distance from our planet of 149.60 million kilometers (92.96 million miles). This distance is known as an astronomical unit (abbreviated AU), and sets the scale for measuring distances all across the solar system. The Sun, a huge sphere of mostly ionized gas, supports life on Earth. It powers photosynthesis in green plants, and is ultimately the source of all food and fossil fuel. The connection and interactions between the Sun and Earth drive the seasons, ocean currents, weather, and climate. The Sun is 332,900 times more massive than Earth and contains 99.86 percent of the mass of the entire solar system. It is held together by gravitational attraction, producing immense pressure and temperature at its core. The Sun has six regions - the core, the radiative zone, and the convective zone in the interior; the visible surface, known as the photosphere; the chromosphere; and the outermost region, the corona.

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  • Sun - Detail Featured Article Sun - Detail Sun - Detail

    The Sun is the star around which the Earth revolves and the gravitational center of the Solar System; it lies about 270,000 times closer to us than the next nearest star. The Sun... More »

  • Sun - Detail, Expanded Featured Article Sun - Detail, Expanded Sun - Detail, Expanded

    The Sun is a huge, glowing ball at the center of our solar system. The sun provides light, heat, and other energy to Earth. The sun is made up entirely of gas. Most of it is a... More »

  • Sun - Overview Featured Article Sun - Overview Sun - Overview

    The Sun, our solar system's star, has inspired mythological stories in cultures around the world, including those of the ancient Egyptians, the Aztecs of Mexico, Native American... More »

  • ACRIMSat Featured Article ACRIMSat ACRIMSat

    ACRIMSAT measured Total Solar Irradiance (TSI) during its primary five-year mission. The instrument, third in a series of long-term solar-monitoring tools built for NASA by the... More »

  • Hinode Featured Article Hinode Hinode

    Hinode is an international mission to study our nearest star, the sun. To accomplish this, the Hinode mission includes a suite of three science instruments -- the Solar Optical... More »

  • SUNRISE telescope delivers spectacular... Featured News Article SUNRISE telescope delivers spectacular... SUNRISE telescope delivers spectacular...

    KATLENBURG-LINDAU, GERMANY (Nov. 11, 2009) – The Sun is a bubbling mass. Packages of gas rise and sink, lending the sun its grainy surface structure, its granulation. Dark... More »

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Solar radiation Last Updated on 2010-01-24 19:11:07   Almost all of the energy that drives the various systems (climate systems, ecosystems, hydrologic systems, etc.) found on the Earth originates from the sun (Figure 1). Solar energy is created at the core of the sun when hydrogen atoms are fused into helium by nuclear fusion (Figure 2). The core occupies an area from the sun’s center to about a quarter of the star’s radius. At the core, gravity pulls all of the mass of the sun inward and creates intense pressure. This pressure is high enough to force the fusion of atomic masses. For each second of the solar nuclear fusion process, 700 million tons of hydrogen is converted into the heavier atom helium. Since its formation 4.5 billion years ago, the sun has used up about half of the hydrogen found in its core. The solar nuclear process also creates immense heat that causes atoms to discharge photons.... More »
Sun: Magnetic Fields Last Updated on 2009-11-11 17:05:08 Solar flares, prominences, and so-called coronal mass ejections are three different manifestations of stored magnetic energy near the sun's surface being released in sudden eruptions. The energy for these dramatic events comes ultimately from the motions of the charged particles in the hot gas. There is considerable interest in understanding these events because of their potentially disruptive effects on earth via the solar wind. In the traditional explanation, called the "storage model," the stressed magnetic field is suddenly realigned, something like a rubber band snapping, but remains in tact. The problem with this explanation is that it predicts that the magnetic field strength following eruptive events should (to a substantial degree) remain unchanged, while a recent series of observations implies a much more complex picture with magnetic field changes that have... More »
SUNRISE telescope delivers spectacular pictures of the Sun's surface Last Updated on 2009-11-11 00:00:00 KATLENBURG-LINDAU, GERMANY (Nov. 11, 2009) – The Sun is a bubbling mass. Packages of gas rise and sink, lending the sun its grainy surface structure, its granulation. Dark spots appear and disappear, clouds of matter dart up - and behind the whole thing are the magnetic fields, the engines of it all. The SUNRISE balloon-borne telescope, a collaborative project between the Max Planck Institute for Solar System Research in Katlenburg-Lindau and partners in Germany, Spain and the USA, has now delivered images that show the complex interplay on the solar surface to a level of detail never before achieved. FIGURE CAPTION – The IMaX instrument not only depicts the solar surface, it also makes magnetic fields visible; these appear as black or white structures in the polarised light. SUNRISE enables tiny magnetic fields on the surface of the Sun to be measured at a level of... More »
Hinode Last Updated on 2009-09-29 00:00:00 Hinode is an international mission to study our nearest star, the sun. To accomplish this, the Hinode mission includes a suite of three science instruments -- the Solar Optical Telescope, X-ray Telescope and Extreme Ultraviolet Imaging Spectrometer. Together, these instruments will study the generation, transport, and dissipation of magnetic energy from the photosphere to the corona and will record how energy stored in the sun's magnetic field is released, either gradually or violently, as the field rises into the sun's outer atmosphere. By studying the sun's magnetic field, scientists hope to shed new light on explosive solar activity that can interfere with satellite communications and electric power transmission grids on Earth and threaten astronauts on the way to or working on the surface of the moon. In particular they want to learn if they can identify the magnetic field... More »
ACRIMSat Last Updated on 2009-09-24 11:18:47 ACRIMSAT measured Total Solar Irradiance (TSI) during its primary five-year mission. The instrument, third in a series of long-term solar-monitoring tools built for NASA by the Jet Propulsion Laboratory, will continue to extend the database first created by ACRIM I, which was launched in 1980 on the Solar Maximum Mission (SMM) spacecraft. ACRIM II followed on the Upper Atmosphere Research Satellite (UARS) in 1991. The Active Cavity Radiometer Irradiance Monitor (ACRIM) I instrument was the first to clearly demonstrate that the total radiant energy from the sun was not a constant. However, the solar variability was so slight (0.1% of full scale) that continuous monitoring by state-of-the-art instrumentation was necessary. It is theorized that as much as 25% of the anticipated global warming of the earth may be solar in origin. In addition, seemingly small (0.5%) changes in the TSI... More »