Astronomers have discovered strong evidence for a giant gas planet in a nearby solar system – with moons that could be habitable.
The planet was first detected by the James Webb Space Telescope (JWST) in the star system Alpha Centauri, around 4.5 light years away.
The Saturn–sized planet orbits a star similar to our Sun but is likely enveloped in a thick gas cloud meaning it could not support life itself.
However, it could have icy moons which may provide the right conditions for life to form.
‘This is an incredibly exciting find,’ Dr Carly Howett, associate professor of space instrumentation at the University of Oxford, told the BBC.
‘Four light years is a long way for us, but in the context of our galaxy, it’s very close – it’s practically in our cosmic backyard.
‘The fact that this planet orbits a star so similar to our Sun, with comparable temperature and brightness, makes it an important target when we think about habitable worlds.’
While it was first detected last year, the planet seemed to have disappeared in follow–up observations. Astronomers are now looking for it again to prove it definitely exists.
This artist’s concept depicts the gas giant planet that NASA’s Webb telescope found strong evidence for in the star system Alpha Centauri
The image on the left represents what can be seen in Alpha Centauri during a digitised sky survey. The image on the right shows what the JWST was able to reveal, with the gas giant visible once starlight had been subtracted
The closest star system to the Earth is the famous Alpha Centauri group. Located in the constellation of Centaurus (The Centaur), at a distance of 4.3 light–years, this system is made up of the binary formed by the stars Alpha Centauri A and Alpha Centauri B, plus the faint red dwarf Alpha Centauri C, also known as Proxima Centauri
Dr Howett explained that the planet may have ‘disappeared’ in recent observations because it is currently too close to its star, which is blocking the view with the amount of bright light being emitted.
Experts now hope to use the Grace Roman Space Telescope – a new NASA instrument which is due to start operating in 2027 – to look for more signs of the planet.
Further observations by JWST may be able to provide more detail on what the planet is made up of and what it looks like.
This could also provide crucial evidence on how habitable any orbiting moons may be.
Some of the gas giants in our own solar system – Saturn and Jupiter – have icy moons, and missions have been launched to explore whether they could support life.
These planets, however, are relatively far away from our Sun. In comparison, this potential ‘new’ planet is close to its star.
‘With this system being so close to us, any exoplanets found would offer our best opportunity to collect data on planetary systems other than our own,’ Charles Beichman, from NASA’s Jet Propulsion Laboratory, said.
‘Yet, these are incredibly challenging observations to make, even with the world’s most powerful space telescope, because these stars are so bright, close, and move across the sky quickly.’
Pictured, Jupiter’s moon Europa, where an ocean hidden under kilometers of ice is considered a prime candidate for extraterrestrial life. Scientists have found carbon dioxide (CO2) on Europa’s surface and the next step is determining where it came from
Moons – also referred to as ‘natural satellites’ – are defined as such when they orbit a planet. There are hundreds that we know about in our solar system, but the best candidates for life include Europa, Enceladus and Callisto
‘If confirmed, the potential planet seen in the Webb image of Alpha Centauri A would mark a new milestone for exoplanet imaging efforts,’ co–first author Aniket Sanghi, from the California Institute of Technology, said.
‘Of all the directly imaged planets, this would be the closest to its star seen so far. It’s also the most similar in temperature and age to the giant planets in our solar system, and nearest to our home, Earth.
‘Its very existence in a system of two closely separated stars would challenge our understanding of how planets form, survive, and evolve in chaotic environments.’
The new findings have been published in The Astrophysical Journal Letters.
