Corona like the chromosphere the corona was first

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Corona. Like the chromosphere, the corona was first observed only during total eclipses, but unlike the chromosphere, the existence of the corona has been known for many centuries. Many of the early investigators regarded the corona as an optical illusion. The corona extends for at least a million miles beyond the photosphere and emits half as much light as the full moon. Below is a photo from a solar eclipse in 1999 that shows the corona: A ____________ is a temporary cooler region in the solar photosphere that appears dark by contrast against the surrounding hotter photosphere of the sun. Explanation: Sunspot. Galileo first showed that sunspots are actually on the surface of the sun itself, rather than being opaque patches in the Earth's atmosphere or the silhouettes of planets between the sun and Earth as some believed. These "spots" are not actually depressions in the photosphere, but are regions where the gases are cooler than those of the surrounding regions. In 1892, the ___________________ was invented--an instrument for photographing the sun or part of the sun in monochromatic light. Explanation: Spectroheliograph. The spectroheliograph works in conjunction with a telescope to produce a photo of the sun's surface with a selected wavelength of the spectrum isolated. The wavelength is chosen to correspond to the spectral wavelength of a specific element contained in the sun--i.e. hydrogen or calcium.
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The sun is 99.9% hydrogen and helium, but it contains other elements such as iron, silicon, and carbon. The image below shows photos with various elements isolated: ____________ are often referred to as "clouds of calcium" or "clouds of hydrogen" and are seen through spectroheliograms. Explanation: Plages. Plages are regions where calcium and hydrogen happen to be emitting light at the wavelengths observed in the spectroheliograms. The plages then are not "clouds" of any particular element, but are regions where some of the atoms of the element observed are changing their states of ionization or excitation and are emitting light. When the chromosphere is viewed at the edges of the sun, ______________ can be seen rising vertically through it. Explanation: Spicules. The small jet-like spikes of gas rise vertically through the chromospheres and move upward with speeds near 20 km/sec and last for only a few minutes.
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Among the more spectacular of chromospheric and coronal phenomena are the _________________. Explanation: Prominences. Prominences are huge clouds of relatively cool dense plasma suspended in the Sun's hot, thin corona. They have been viewed telescopically during solar eclipses for centuries. They appear as red flame-like protuberances rising above the limb of the sun. Prominences can now be viewed at any time on spectroheliograms. Note that pictures such as the one above are taken in a specific wavelength of light, in this case the wavelength
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Corona Like the chromosphere the corona was first observed...

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