A pair of astronomers have found and categorised half a million new asteroids lurking in old data. Figuring out exactly where these objects came from could be crucial to understanding the early solar system.
and at C么te d鈥橝zur University in France found the objects by sifting through images from the (SDSS). This survey, which uses a telescope at the Apache Point Observatory in New Mexico, took images of a huge swathe of the sky from 1998 to 2009. It also measured the colours of the objects it spotted.
Sergeyev and Carry examined the images looking for fast-moving objects, which could be asteroids or comets. They found more than 1 million observations of objects that we already knew about, along with 506,200 observations of objects not linked with anything we have observed before, most of them asteroids.
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The number of asteroids that hadn鈥檛 yet been catalogued was surprising, says Carry. 鈥淲e were expecting maybe 30,000 or 40,000 more asteroids, and suddenly we had this monster catalogue,鈥� he says. 鈥淚t was supposed to be a few weeks鈥� work, and it turned out to be one year.鈥�
The researchers used the colour and brightness measurements from SDSS to categorise the asteroids, as these properties reveal what their surfaces are made of. Now that they are categorised, the next step is to figure out their origins.
鈥淯nderstanding the distribution of these asteroids, not only their orbits but also their compositions, gives you the key to understanding what happened in the solar system in the past, such as the planetary migrations that pushed them into the asteroid belt,鈥� says Carry.
Continuing observations with other telescopes will allow researchers to find millions more asteroids, he says. In the meantime, these ones will have to be monitored to find out their trajectories, with the goal of both determining whether they really are new or have been observed before, and figuring out if any of them might be hazardous to Earth.
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