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Io in Eclipse
NASA/JPL/University of Arizona
Video: 936 kB, MPEG
In this movie, the inner-most satellite of Jupiter, Io, is in the eclipse shadow of Jupiter (Jupiter is blocking the Sun for Io). This allowed NASA's spacecraft Cassini to image the active moon in darkness. These images were taken over a two-hour period and nearly capture the entire eclipse which took place on January 1, 2001. The spacecraft was over 10 million kilometers (6.3 million miles) away, yielding a resolution of 61 kilometers (40 miles) per pixel on these images.
Glows on Io
While Io is enshrouded in darkness, several glows are revealed to us. The bright points of light are hot lava from the active volcanoes on Io. The brightest of these is the volcano Pele which appears to be erupting constantly. To the right and slightly above Pele is a pair of bright spots from the volcano Pillan, the source of a major eruption in 1997. A second source of glow on Io is the faint, diffuse emission of atmospheric aurorae. Similar to the aurora borealis (northern lights) on Earth, the aurorae on Io result from collisions of charged particles (from the electrical currents that flow between Jupiter and Io) with gases in Io's tenuous atmosphere. The aurorae are seen here as a faint glow around Io's equator.
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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