'Habitable exoplanet' may not exist, says Geneva team

Posted by Emma Woollacott

Oh, great. The moving men were booked, we'd said goodbye to the neighbors and we'd given away the cat - and now it seems that there may not be a habitable planet orbiting Gliese 581 after all.

At a meeting of astronomers this week, doubt has been cast on whether  data from the system really shows the existence of a fifth planet, or is just random background noise.

Just two weeks ago, astronomers at the University of California, Santa Cruz, and the Carnegie Institution of Washington said they had 'compelling evidence' for the existence of a roughly earth-like planet, Gliese 581g, orbiting a star in the constellation of Libra.

The evidence for this came from 11 years' worth of data from the HIRES spectrometer on ESO's 3.6-metre telescope at La Silla, Chile.

But at a meeting of the International Astronomical Union this week, Geneva Observatory astronomer said that he and his team had examined the data themselves, and found no evidence that the planet even exists.

"Simulations on the real data have shown that the probability that such a signal is just produced 'by chance' out of the noise is not negligible, of the order of several percent," he said.

“Under these conditions we cannot confirm the presence of the announced planet Gliese 581g."

Indeed, according to Astrobiology Magazine, they couldn't find any hard evidence of Gliese 581f either, although further data from HARPS appeared to confirm the existence of the four other previously announced planets b, c, d and e.

The dispute highlights the occasionally controversial process of peer review. It's usual for peer review papers to appear a month or more after the original research they are aiming to confirm or cast doubt upon. Inevitably, negative findings tend to receive far less publicity than the original announcement.