Related topics: sun

Team creates high-fidelity images of Sun's atmosphere

In 1610, Galileo redesigned the telescope and discovered Jupiter's four largest moons. Nearly 400 years later, NASA's Hubble Space Telescope used its powerful optics to look deep into space—enabling scientists to pin down ...

NuSTAR sees rare blurring of black hole light

NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) has captured an extreme and rare event in the regions immediately surrounding a supermassive black hole. A compact source of X-rays that sits near the black hole, called ...

Researchers explain magnetic field misbehavior in solar flares

When a solar flare filled with charged particles erupts from the sun, its magnetic fields sometime break a widely accepted rule of physics. The flux-freezing theorem dictates that the magnetic lines of force should flow away ...

Retired star found with planets and debris disc

(Phys.org) —ESA's Herschel space observatory has provided the first images of a dust belt – produced by colliding comets or asteroids – orbiting a subgiant star known to host a planetary system. The team of scientists ...

X-ray laser takes aim at cosmic mystery

Scientists have used powerful X-rays from the Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory, to study and measure, in atomic detail, a key process at work in extreme plasmas like those found ...

What's down with the Sun? Major drop in solar activity predicted

(PhysOrg.com) -- A missing jet stream, fading spots, and slower activity near the poles say that our Sun is heading for a rest period even as it is acting up for the first time in years, according to scientists at the National ...

Scientists find giant solar twists

(PhysOrg.com) -- Scientists have, for the first time, detected giant twisting waves in the lower atmosphere of the Sun, shedding light on the mystery of the Sun's corona (the region around the Sun, extending more than one ...

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Corona

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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