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Stairway to the Stars
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Io, the innermost of Jupiter's Galilean sattellites, is covered with active volcanoe-like geysers. The presense of these geysers explains the lack of impact craters on the constantly changing surface. The energy needed for the eruptions is caused by tidal forces from Jupiter's magnetic pull on the moon. Temperatures can reach up to 1500 K but average at about 130 K. These hot spots are a primary source of lost heat. Io's compostion is believed to be mostly rock with little or no water being present.
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Eta Carinae may be about to explode. But no one knows when - maybe next year, maybe one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova. Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Now clearly visible are two distinct lobes, a hot central region, and strange radial streaks. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks remain unexplained.
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The Perseid Meteor Shower has reached its maximum. Grains of rocky ice streak across the sky as they evaporate during entry into Earth's atmosphere. These ice chips were shed from Comet Swift-Tuttle. The Perseids result from the annual crossing of the Earth through Comet Swift-Tuttle's orbit. The Perseids are typically the most active meteor shower of the year. In a clear dark sky, an observer might see a meteor a minute. The colors are representative but digitally enhanced. As the meteor streaked across the night sky, different excited atoms emitted different colors of light. The origin of the green tinge visible at the right is currently unknown, however, and might result from oxygen in Earth's atmosphere. Perseid meteors can best be seen from a relaxing position, away from lights.
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