The gravitational effect in this case is minute, causing it to move back and forth by no more than 51 centimeters (20 inches) per second.
Alpha Centauri is a three-star system consisting of two stars similar to our sun and a faint red star called Proxima Centauri. The planet orbits Alpha Centauri B.
Astronomers have speculated about planets orbiting these suns since the 19th century but small planets like this are hard to find and instruments have only recently become sensitive enough to detect them.
“Our observations extended over more than four years using the HARPS instrument” said Dumusque.
The researchers said they will make their data available to other astronomers to test their findings but in the meantime some remain skeptical.
“Actually, I still have my doubts,” astronomer Artie Hatzes at Thuringian State Observatory in Tautenburg, Germany, told Reuters.
Hatzes said the wobble detected in the star could be caused by a series of other factors, including sun spots, so the data need to be tested by other researchers.
“These activity variations have to be filtered from the data before one can extract the signal due to the possible planet,” he said. “It could well be that someone else analyzing the same data may come up with a different conclusion. That is why I am not 100 percent certain.”
But Dumusque is confident. “We have considered in this analysis all the known possible explanations, including instrumental noise and stellar origin. In the end, the planetary solution is the most likely one.”