Astronomers discover potentially habitable planet

An Earth-like planet with the potential to support human life has been discovered just 40 light-years away.

Named Gliese 12 b, the planet orbits its host star every 12.8 days, and is comparable in size to Venus – so slightly smaller than Earth.

It has an estimated surface temperature of 42C, which is lower than most of the 5,000-odd exoplanets (planets outside of the solar system) confirmed so far.

Astronomers suggest Gliese 12 b is one of the few known planets where humans could theoretically survive, but they are still unsure what its atmosphere looks like, if it has one at all.

Getting an answer to what the atmosphere looks like is vital because it would reveal if the planet can maintain temperatures suitable for liquid water – and possibly life – to exist on its surface.

Masayuki Kuzuhara, a project assistant professor at the Astrobiology Centre in Tokyo, who co-led one research team with Akihiko Fukui, said: “We’ve found the nearest, transiting, temperate, Earth-size world located to date.

“Although we don’t yet know whether it possesses an atmosphere, we’ve been thinking of it as an exo-Venus, with similar size and energy received from its star as our planetary neighbour in the solar system.”

The University of Warwick’s Professor Thomas Wilson, a physicist, was involved in the discovery, using data from Nasa’s satellites to confirm the planet’s existence and characteristics such as its size, temperature, and distance away from Earth.

He said: “This is a really exciting discovery and will help our research into planets similar to Earth.

“Sadly, this planet is a little far away for us to experience it more closely. The light we are seeing now is from 40 years ago – that’s how long it has taken to reach us here on Earth.

“Planets like Gliese 12 b are few and far between, so for us to be able to examine one this closely and learn about its atmosphere and temperature is very rare.”

The two teams, including one in Tokyo, used observations by Nasa’s TESS (Transiting Exoplanet Survey Satellite) to help make their discovery.

The planet’s equivalent of the Sun, called Gliese 12, is a cool red dwarf located in constellation Pisces.

The star is only about 27% of the Sun’s size, with about 60% of the Sun’s surface temperature.

Gliese 12 b is not the first Earth-like exoplanet to have been discovered, but Nasa said there are only a handful of worlds like it that warrant a closer look.

It has been billed as a potential target for further investigation by the US space agency’s £7.5 billion James Webb Space Telescope.

The newly discovered planet could also be significant because it may help reveal whether the majority of stars in the Milky Way galaxy are capable of hosting temperate planets that have atmospheres and are therefore habitable.

The distance separating the planet and its star is just 7% of the distance between Earth and the Sun, and the planet receives 1.6 times more energy from its star than Earth does from the Sun.

One important factor in retaining an atmosphere is the storminess of its star.

Red dwarfs tend to be magnetically active, resulting in frequent, powerful X-ray flares.

However, analyses by scientists conclude that Gliese 12 shows no signs of extreme behaviour.

“Gliese 12 b represents one of the best targets to study whether Earth-size planets orbiting cool stars can retain their atmospheres, a crucial step to advance our understanding of habitability on planets across our galaxy,” said Shishir Dholakia, a doctoral student at the Centre for Astrophysics at the University of Southern Queensland in Australia.

He co-led a research team with Larissa Palethorpe, a doctoral student at the University of Edinburgh and University College London (UCL).

Co-author Dr Vincent Van Eylen, also from UCL, said: “GJ12b is an incredibly exciting planet because its size is identical to that of Earth.

“Even though GJ12b is about 15 times closer to its star than Earth is to our Sun, because it orbits such a small star the temperature on the planet may be quite similar to that on Earth.

“That doesn’t necessarily guarantee that the planet is habitable, but it does make it a great place to start looking.

“Fortunately it’s also a very nearby star, so we will learn much more about the planet and its atmosphere with telescopes like JWST in the next years.”

A paper led by researchers in Tokyo is published in The Astrophysical Journal Letters, and the Dholakia and Palethorpe findings are published in Monthly Notices of the Royal Astronomical Society.