Astronomers have today confirmed the existence of a planet orbiting the sun’s nearest neighbour, Proxima Centauri, which has the potential to host liquid water, and therefore life.

The exoplanet in question, Proxima b, is thought to be the Earth’s closest potentially habitable neighbour, making this discovery a major landmark in humanity’s exploration of the universe.

“We’ve found an exoplanet orbiting Proxima Centauri. It’s the nearest exoplanet we will ever find, because it’s the nearest star to the Sun, and we are very excited about it,” explained a delighted Dr Guillem Anglada-Escudé, from the School of Physics and Astronomy, Queen Mary, University of London, who participated in the epic research project.

The confirmation, which has been made by astronomers working with the European Southern Observatory (ESO), has finally resolved rumours about potential existence of such a planet, which have surrounded the astronomy world since the first hints were detected back in 2013.

“The first hints of a possible planet were spotted back in 2013, but the detection was not convincing. Since then we have worked hard to get further observations off the ground with help from ESO and others,” added Anglada-Escudé. This was achieved through the Pale Red Dot campaign, which charted systematic efforts around the world to confirm the signal, and was concluded in April of this year.

Proxima Centauri is just 4.243 light years away from Earth, and although this means a trip there is highly unlikely to occur within our lifetime, it does make it considerably closer than last year’s big planetary announcement, Kepler 452-b, which is 1,400 light years away.

However, while Kepler 452-b is a relatively close match to our home planet, Proxima b differs from Earth in a number of ways. It is slightly larger – at least 1.3 times Earth’s size – but has a dramatically smaller orbit, of just 11.2 days. This is because Proxima b orbits its sun at a distance of just 7 million km, which is only 5% of the distance between the Earth and our own Sun.

This is possible because Proxima Centauri is a red dwarf star, making it much smaller than our own Sun – it’s actually much closer in size to Jupiter – and giving it an effective temperature of just 3,050K, compared to the Sun’s 5,777K, making it considerably cooler.

However, with no images to refer to, there is only so much the scientists can say with absolute certainty about Proxima b. Nevertheless, they can speculate with relative confidence, particularly around the conditions that would determine whether it was capable of hosting life.

They are reasonably confident that the planet is terrestrial, meaning it has physical ground rather than being a gas ball, however the matter of an atmosphere is more complex.

“The bottom line is we have no clue whether this planet has an atmosphere or not, or whether it has water or not, but the existence of it is actually plausible,” said Dr Ansgar Reiners, from the Institut für Astrophysik, Georg-August-Universität Göttingen.

While some have suggested that the level of solar flare activity from Proxima Centauri means an atmosphere could not survive, the scientists do not believe this to be the case.

“It is a general misconception that these red dwarfs are flaring like hell and nothing can survive in the vicinity because it is so active,” said Reiners. “If it does have an atmosphere it would not get blown away or whatever by today’s activity of the star.”

If there is an atmosphere, however, it would mean the planet had a similar ground-based temperature to the Earth.

“The temperature they would have on the surface of this planet if there was no atmosphere would actually be -40°C, but if it has an atmosphere, it is actually pushing up the temperature through the greenhouse effect, meaning it would actually be above 0°C,” he added.

There is reasonable confidence, however, that the planet is tidally locked, meaning it takes as long to rotate on its own axis as it does to orbit its star. This would not only mean that a day on Proxima b would be as long as a year, but would also always have one side facing the sun, eliminating the conventional day-night cycle.

This has also been suggested by some as a reason why the planet could not have an atmosphere, however the scientists again rejected this as a misconception about the requirements to host life.

As the nearest exoplanet to Earth, Proxima B will no doubt in the future become a valuable focus of research.

“Proxima b is actually the next one outside the solar system, and that provides unmatched observation opportunities,” said Reiners. “It will be possible in the future to take pictures of this system with technology that is not too far away.”

While currently active telescopes do not provide a great enough resolution to make out Proxima b, there are several in the works with the potential, including the European Extremely Large Telescope, which is set to begin operations in 2024.

And when that happens, we could get our first images of our nearest neighbour, and if we’re really lucky, the first evidence of life beyond our planet.