A paper published in the Astrophysical Journal this week presents the first direct observations of small asteroids in the outer solar system. This story began in June, when two amateur astronomers, on different continents, happened to be pointing their telescopes at Jupiter when they both simultaneously observed a two-second flash, apparently in Jupiter's atmosphere. Since then, astronomers have been working to explain what was seen.

It's likely that what was seen was a small meteor burning up in Jupiter's upper atmosphere, and research published this week produces a fairly precise estimate of the size of the object: probably around 10 metres across.

That's fascinating because it's the first time that we have been able to directly observe such a small object at such a large distance from the Earth. We've always suspected that there must be a large number of small rocks in the Solar System, but have never been able to see them or get much idea of how many there might be in the Solar System's outer reaches.

This story was given another twist in August when a second similar flash was observed by another pair of amateur astronomers, apparently also caused by a meteor entering Jupiter's atmosphere. Two events having occured in such quick succession, it seems highly likely that they have always been occuring at a rate of a few per year, but that they've gone unrecorded, probably because they've generally been thought impossible to observe. If so, we may well expect to see a flurry of more similar discoveries in coming months.

If we do indeed see such a flurry, that will be really exciting because we will begin to get an idea of exactly how many asteroid there are around Jupiter, and what the distribution of their sizes looks like. That will really help us to understand how material is distributed in the asteroid belt, and perhaps help us to understand where it came from.

The sky on 28 Apr 2024

Source

Hueso et al., ApJ, 721, L129 (2010)

Transcript of a news story presented on the Naked Scientists, 12th September 2010.

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