There's a popular theory about the comets that wiped out the dinosaurs and caused other cyclical mass extinctions on Earth: they might be under the gravitational control of a star called Nemesis. A new study shows that the entire idea may be a fantasy.

If there's ever an example designed to shows that PR works, it's the concept of Nemesis. Nemesis is an unknown star, or other large astronomical object, that is locked in an eccentric orbit of our sun. It plows through the Oort Cloud, a massive group of asteroids, every 27 million years, and its motion and gravity cause comets to race toward Earth, causing global extinctions. This is a theory, and a name, so cool that people were just a little bit disappointed that doubt was cast on it last year when the extinction patterns proved too regular for the eratic orbit that Nemesis would have to have. Better to risk mass death, sacrificing ourselves and everybody we ever loved, than to give up our own personal Nemesis.

Sadly it looks like there is now a new theory that deems the possibility of Nemesis lurking out there in space less likely. A new analysis of the meteor craters on Earth indicates that, not only is there no evil star causing these cyclical meteor hits, there are no cyclical meteor hits at all. The Max Planck Institute for Astronomy believes that the so-called patterns of meteor hits are a statistical flaw. A new study uses Bayesian Statistics to analyse the data. Bayesian Statistics uses different sets of data, each of which are given a probability of likelihood. The combination of the data sets, and the likelihood of each, leads to a conclusion. The conclusion to this analysis showed that there was probably no cycle of high and low comet activity, and therefore no Nemesis. The analysis showed that comet impacts were getting more frequent over the years, but that that was likely the result of fresher craters being easier to spot, while older ones being worn away by time.

Or maybe that's what Nemesis wants us to think.

Via Discovery, MPIA, and Duke University(pdf).

Image: NASA