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The Sun's Atmosphere
Yohkoh Solar Observatory
Video: 126 kB, MPEG
This animation shows the multi-layered nature of the solar atmosphere. It was built from three images, a white-light image of the photosphere, a red-light image of the chromosphere, and an X-Ray image of the corona, the outermost layer. These images were captured on the same day by the telescope aboard the Yohkoh Solar Observatory satellite. The satellite was launched from Japan in August of 1991 and is used to investigate X-Rays and Gamma rays from the Sun. Yohkoh is Japanese for sunbeam.
Layers of the Solar Atmosphere
The Sun is a giant ball of gas; there is no hard surface on the Sun to stand on. However, there is a surface
through which we cannot see called the photosphere. The location of the photosphere is defined to be where the gas is so dense that it becomes opaque. The photosphere is about 330 kilometers thick and lies 696,000 kilometers from the center of the Sun. Above the photosphere is the chromosphere, about 2,000 kilometers thick, where the temperature rises from the 5,800-Kelvin-photosphere to tens of thousands of Kelvin. Beyond the chromosphere is the corona, where the density of the gas is very low and tenuous. The corona is difficult to observe and is only seen on Earth during a total solar eclipse.
Ellen Cohen
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Total Eclipse of the Sun
Fred Espenak (NASA/Goddard Space Flight Center)
Video: 2 MB, MPEG
The total solar eclipse featured here was recorded in Bolivia and took place November 3, 1994. The movie shows the entire eclipse cycle. First, the eclipse is partial, with just a sliver of the Sun remaining visible. As the Moon fully covers the solar disk, the eclipse becomes total. The totality phase is over when the Sun becomes visible on the opposite side. During totality, the corona of the Sun, the hot gas surrounding the Sun, is clearly visible.
About eclipses
A solar eclipse takes place when the Moon passes between an observer on Earth and the Sun. This occurs only during New Moon (New Moon occurs when the Moon is between the Sun and the Earth). Typically, the Sun and the Moon don't align properly to give us an eclipse more than a few times a year. On Earth, the Moon's shadow moves swiftly on the surface as the Moon moves in its orbit. In the narrow path of totality, daytime briefly turns to darkness and the halo of the Sun, the corona, comes into view. Minutes later (the maximum length of totality is about 7 minutes), daytime returns.
Ellen Cohen
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A Solar Flare
Big Bear Solar Observatory
This movie shows material erupting from a flare near the limb of the Sun on October 10, 1971. The ejected material is heated to many millions of degrees and produces an energy equivalent to as much as a million megatons of TNT. Flares are short bursts (5-10 minutes) of energy from the Sun. The origin of flares is not well understood, but it is thought that they are related to the liberation of energy stored in the solar corona.
Video: 4 MB, Quicktime MOV
Flare Monitoring
Flares are categorized by their brightness in X-Rays. The most energetic flares are X-Class flares followed by M-Class and C-Class. X-Class flares have a tenth the energy of M flares and C-Class flares have a tenth of the energy of an M flare. The National Oceanic and Atmospheric Administration monitors the X-Ray energy from the Sun using satellites. The radiation from flares disrupts the Earth's ionosphere, causing communication blackouts and power outages, and the Northern and Southern lights.
Ellen Cohen
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