Related topics: sun

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The sun is the brightest object in the sky, and probably the most studied celestial object. Surprisingly, it still hosts mysteries that scientists have been trying to unravel for decades, for example, the origin of coronal ...

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Queen Mary University of London has led a study which describes the first direct measurement of how energy is transferred from the chaotic electromagnetic fields in space to the particles that make up the solar wind, leading ...

Nanoparticle breakthrough in the fight against cancer

A recent study, affiliated with South Korea's Ulsan National Institute of Science and Technology (UNIST) has introduced a novel targeted drug delivery system in the fight against cancer.

Mystery of coronae around supermassive black holes deepens

Researchers from RIKEN and JAXA have used observations from the ALMA radio observatory located in northern Chile and managed by an international consortium including the National Astronomical Observatory of Japan (NAOJ) to ...

Getting a grip on space weather

An international group of scientists has developed a new method for analyzing the sun's energy outbursts, which can help better understand and predict extreme space weather phenomena that directly affect the operation of ...

Image: Hubble spots a lonely blue dwarf

This captivating image from the NASA/ESA Hubble Space Telescope's Wide Field Camera 3 shows a lonely dwarf galaxy 100 million light-years away from Earth. This image depicts the blue compact dwarf galaxy ESO 338-4, which ...

NASA's Parker Solar Probe is about to lift off

At 3:33 a.m. EDT on Aug. 11, while most of the U.S. is asleep, NASA's Kennedy Space Center in Florida will be abuzz with excitement. At that moment, NASA's Parker Solar Probe, the agency's historic mission to touch the Sun, ...

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A corona is a type of plasma "atmosphere" of the Sun or other celestial body, extending millions of kilometers into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. The Latin root of the word corona means crown.

The high temperature of the corona gives it unusual spectral features, which led some to suggest, in the 19th century, that it contained a previously unknown element, "coronium". These spectral features have since been traced to highly ionized iron (Fe-XIV) which indicates a plasma temperature in excess of 106 kelvin. The fact that the Sun has a million degree corona was first discovered by Gotrian in 1939 and Bengt Edlén in 1941 by identifying the coronal lines (observed since 1869) as transitions from low lying metastable levels of the ground configuration of highly ionized metals (the green FeXIV line at 5303 Å, but also the red line FeX at 6374 Å).

Light from the corona comes from three primary sources, which are called by different names although all of them share the same volume of space. The K-corona (K for kontinuierlich, "continuous" in German) is created by sunlight scattering off free electrons; Doppler broadening of the reflected photospheric absorption lines completely obscures them, giving the spectral appearance of a continuum with no absorption lines. The F-corona (F for Fraunhofer) is created by sunlight bouncing off dust particles, and is observable because its light contains the Fraunhofer absorption lines that are seen in raw sunlight; the F-corona extends to very high elongation angles from the Sun, where it is called the Zodiacal light. The E-corona (E for emission) is due to spectral emission lines produced by ions that are present in the coronal plasma; it may be observed in broad or forbidden or hot spectral emission lines and is the main source of information about the corona's composition.

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