Asteroid 2010 TD54 - an earth-crossing asteroid 5-10 meters in diameter missed the Earth by about 48,000 km (about 28,000 mi) early today - October 12 at 11:25 UT. Phil Plait
has the story at the Bad Astronomy blog along with a video from an amateur astronomer.
According to Phil:
Images like this one can actually be pretty important: they can be used to nail down the orbit of the asteroid. The orbit is calculated mathematically using images of the asteroid over time. Uncertainty in the measurements, the exact position of the asteroid, the user’s location, and more can all add up to the orbit being imprecisely known. That means that we might be able to predict where it is in the near future, but as time goes on the prediction gets fuzzier. The more observations we get, the more we can smooth out those issues.
And when they pass as close as TD54 did — just 46,000 km (28,000) above the Earth! — its orbit can change a lot due to Earth’s gravity. Observations like this one can really be important to be to know where TD54 will be heading in its future travels.
… and one more thing. This is good practice. In April 2029, the 250-meter wide asteroid Apophis will be passing the Earth at about the same distance as TD54 did. We know Apophis won’t hit us, but if it passes at just the right distance, Earth’s gravity will bend its orbit enough to bring it back on an impact trajectory 7 years later! We’re pretty sure there’s literally only a one in a million chance of that happening, but if we get hundreds of observations of the asteroid when it passes, we’ll have its orbit nailed down enough to predict the path of Apophis well into the future. While even Apophis isn’t a huge threat (in that we don’t think it’ll hit any time soon), there are hundreds and thousands of other rocks out there on orbits that cross ours.
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