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Arthur T Knackerbracket has found the following story:

All comets might share their place of birth, new research says. For the first time ever, astronomer Christian Eistrup applied chemical models to fourteen well-known comets, surprisingly finding a clear pattern. His publication has been accepted in the journal Astronomy & Astrophysics.

Comets travel through our solar system and are composed of ice, dust, and small rock-like particles. Their nuclei can be as large as tens of kilometers across. "Comets are everywhere, and sometimes with very funky orbits around the Sun. In the past, comets even have hit the Earth," Christian Eistrup says. "We know what comets consist of and which molecules are present in them. They vary in composition, but are normally seen as just one group of icy balls. Therefore, I wanted to know whether comets are indeed one group, or whether different subsets can be made."

"What if I apply our existing chemical models to comets?", Eistrup thought during his Ph.D. at Leiden University. In the research team at Leiden Observatory, which included Kavli Prize winner Ewine van Dishoeck, he developed models to predict the chemical composition of protoplanetary discs—flat discs of gas and dust encompassing young stars. Understanding these discs can give insight into how stars and planets form. Conveniently, these Leiden models turned out to be of help in learning about comets and their origins.

"I thought it would be interesting to compare our chemical models with published data on comets," says the astronomer. "Luckily, I had the help of Ewine. We did some statistics to pin down if there was a special time or place in our young solar system, where our chemical models meet the data on comets." This happened to be the case, and to a surprising extent. Where the researchers hoped for a number of comets sharing similarities, it turned out that all fourteen comets showed the same trend. "There was a single model that fitted each comet best, thereby indicating that they share their origin."

And that origin is somewhere close to our young Sun, when it was still encircled by a protoplanetary disc and our planets were still forming. The carbon monoxide becomes ice—relatively far away from the nucleus of the young Sun. "At these locations, the temperature varies from 21 to 28 Kelvin, which is around minus 250 degrees Celsius. That's very cold, so cold that almost all the molecules we know are ice.

Original Submission