The planet, dubbed Gliese 581 g was discovered by by Steven Vogt of the University of California, Santa Cruz, Paul Butler of the Carnegie Institution of Washington in DC, and their colleagues.
According to them, Gliese 581 g sits in the middle of its host star's habitable zone, where temperatures are in the right range for liquid water to exist.
Now, however, a second team of astronomers have looked for signals of Gliese 581 g in their own data and failed to find it.
"We easily recover the four previously announced planets, "b", "c", "d", and "e". However, we do not see any evidence for a fifth planet in an orbit of 37 days," New Scientist quoted Francesco Pepe of the Geneva Observatory in Switzerland, as saying.
The two groups arrived at their disparate results using some of the same data, which was collected by HARPS, an instrument mounted on a 3.6-metre telescope at the European Southern Observatory in Chile. HARPS, which measures the spectrum of starlight, is used to look for wobbles in the motion of stars that could result from the gravitational tugs of orbiting planets.
Although the Geneva team cannot find evidence for the new planet, they cannot exclude the possibility that Gleise 581 g exists.
"We are not trying to prove the nonexistence of a planet. It's really difficult to prove that something does not exist. We are just saying we do not see a significant signal that is really different from noise," said Pepe.
Surprisingly, Vogt, who didn't wish to comment on the Geneva team's find, said the negative result is not entirely unexpected.
"I am not overly surprised by this as these are very weak signals, and adding 60 points onto 119 does not necessarily translate to big gains in sensitivity," Vogt said.
"I feel confident that we have accurately and honestly reported our uncertainties and done a thorough and responsible job extracting what information this data set has to offer," Vogt added.
"In 15 years of exoplanet hunting, with over hundreds of planets detected by our team, we have yet to publish a single false claim, retraction, or erratum."