A group of astronomers discovered what they thought was a super-Earth exoplanet orbiting the habitable zone of a star, and called it GJ 581d. They used a spectrometer to measure the slight fluctuations in the wavelength of the parent star due to the gravitational pull of the planet to determine its existence, writes Andrew McDonald of The Space Reporter.

Scientists Say Super-Earth Exoplanet Does Exist After All

A definitive conclusion?

Later on the existence of the exoplanet was called into question by a separate study, which claimed that what scientists believed was an exoplanet was in fact statistical noise in the collected data. The latest twist in the tale comes in the form of a new study led by Dr. Guillem Anglada-Escudé of Queen Mary University of London,

He has refuted the conclusions of the 2014 study, claiming that the statistical method used by those scientists was not appropriate for the detection of smaller exoplanets. His paper acknowledges that the method has proved to work well for the detection of more massive exoplanets, but in that case there were too many errors in the data due to the smaller size of GJ 581d.

A more accurate method was used by Anglada-Escudé and his team to pick out GJ 581d from the data noise. The paper could have profound consequences in the study of exoplanets, because GJ 581d was the first Earth-like planet discovered in the habitable zone of its parent star’s orbit, and it is believed that it could harbor life.

Impact on future study of exoplanets

The paper also validates the use of the Doppler technique in discovering new exoplanets.

“There are always discussions among scientists about the ways we interpret data but I’m confident that GJ 581d has been in orbit around Gliese 581 all along. In any case, the strength of their statement was way too strong. If they way to treat the data had been right, then some planet search projects at several ground-based observatories would need to be significantly revised as they are all aiming to detect even smaller planets. One needs to be more careful with these kind of claims,” said Anglada-Escudé in reference to the 2014 study.

The latest paper was published in the journal Science.