A planet in the goldilocks zone of its planet, a mere 20 light years from Earth was ‘proven’ not to exist in 2014. Now, according to new research, it’s back.

Gliese 581d is a super-Earth, orbiting a red dwarf star about 20 light years from Earth. It was the first exoplanet found in its sun’s “Goldilocks zone”. Although it is considered “Earth-like”, it is 1.5 times the size of the Earth with 1.6 times the gravity. It’s temperature ranges between 32 and 104 degrees Fahrenheit and is tidally locked, meaning the same side is always facing the Earth. It orbits its star fairly quickly, about every 67 days or maybe none of this is true.

The planet was discovered in 2007 when its ‘wobble’, a change in the wavelength of its star, picked up by a spectrometer, was detected.

Then, in 2014 it was, sort of, undiscovered. Researchers at Penn State said that the planet did not actually exist and that the change in wavelength of its star was due to normal stellar activity.

“We also have proven that some of the other controversial signals are not coming from two additional proposed Goldilocks planets in the star’s habitable zone, but instead are coming from activity within the star itself,” said Suvrath Mahadevan, an assistant professor of astronomy and astrophysics at Penn State in a statement at the time.

Now, just a year later, Gliese 581d appears to be back. A new study, published in the journal Science calls into question the methods used to remove 581d from the exoplanet. Researchers at Queen Mary University of London (QMUL) and University of Hertfordshire are strongly recommending that the planet be put back on the maps.

The researcher are also calling into question the methods used in the 2014 Penn State research, claiming that the technique is inadequate for identifying small planets.

The researchers claim that the method works for detecting large planets because their impact on the local star is so significant that it negates errors. Small planets, on the other hand are almost impossible to detect using those same methods.

Using what they believe is a more accurate model on existing data, the researchers claim that Gliese 581d is a real, Earth-like, potentially even habitable planet.

“The existence, or not, of GJ 581d is significant because it was the first Earth-like planet discovered in the ‘Goldilocks’-zone around another star and it is a benchmark case for the Doppler technique. 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 Dr Guillem Anglada-Escudé, lead author of the paper in a statement.

Hopefully, by the time human technology has advanced to the point where we might visit the planet, scientists will know for sure whether or not it’s there.