Related topics: sun

Astronomers take 'heartbeat' of black hole

A black hole gets a large corona before it emits jets. This is revealed, among other things, by the heartbeat graph that an international team of astronomers has made of a black hole and a star orbiting around each other. ...

NASA rocket mission to study the origin of slow solar winds

The Sun's atmosphere, or corona, is beaming with activity. Solar flares and coronal mass injections send high-energy particles out into space and the corona constantly releases particles known as the solar wind.

Study: Scientists carry greater credibility than spiritual gurus

What influence does the source of information have on its credibility? Scientists have more authority than spiritual sources, both among religious and non-religious people. This is apparent from a large-scale experiment conducted ...

New evidence of geologically-recent Venusian volcanism

New data analysis techniques allow evidence of recent volcanism to be found in old Magellan spacecraft data. It is unclear if this activity is occurring today, or if it occurred within tens of million years, but geologically ...

'Campfires' offer clue to solar heating mystery

Computer simulations show that the miniature solar flares nicknamed 'campfires," discovered last year by ESA's Solar Orbiter, are likely driven by a process that may contribute significantly to the heating of the sun's outer ...

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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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