Spacewatch: Watching the skies for hazardous objects

The exhortation to "keep watching the sky!" Dates science fiction film 1951 "The Thing From Another World", but it is a task that astronomers have taken seriously . Instead of UFOs, however, his career was NEOs, or near-Earth objects, and more particularly the subset of NEOs are Phos, or potentially dangerous objects, because of the serious consequences if we were to strike our planet.

comet may include strange, but the vast majority of NEOs are asteroids and phosphates for the NEA and PHA terms are often used instead. For NEO orbit of the object must be within 45 million miles of Earth's orbit, but for this potential to be a miss-PHO distance must be less than 7.5 million miles and should appear to be greater than 150 meters in diameter.

of 9500 known NEOs are Phos 1360 and 154 of them can be greater than 1 km wide and is close to the size of the body alleged that wiped out the dinosaurs 65 million years. None of these should be on a collision course, and there may be only 25 or so left uncovered.

remarks earlier this month have effectively excluded any danger that the asteroid Apophis over 250 km could hit Earth in 2036. Meanwhile, the body of 45 meters DA14 2012 is due to the skim milk to 28,000 km from the Earth's surface and in the geostationary orbital distance, the 15th of the following month.

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