A frozen ‘super-Earth’ has been discovered orbiting Barnard’s Star, the closest single star to the sun.
Despite surface temperatures of around -150°C (-238°F), scientists believe pockets of liquid water could lie beneath the ice capable of harbouring life.
The newly detected planet, Barnard’s Star b, is thought to be rocky and at least 3.2 times larger than the Earth.
Its host, Barnard’s Star, is six light years from Earth – hardly any distance on astronomical scales – with a luminosity 0.0035 times that of the sun.
The only closer star system is Alpha Centauri, which consists of three stars bound together by gravity, around four light years away.
At 3,170 Kelvin (2,896°C / 5,246°F), this dim dwarf gives off most its light in the infrared end of the spectrum, bathing Barnard’s Star b in a strange orange hue.
A frozen ‘super-Earth’ has been discovered orbiting Barnard’s Star, the closest single star to the sun. Despite surface temperatures of around -150°C (-238°F), scientists believe pockets of liquid water could lie beneath the ice capable of harbouring life (artist’s impression)
Barnard’s Star b circles a cool red-dwarf star, smaller and older than the sun, completing one orbit every 233 days, an international team of researchers – including the Institut de Ciències de l’Espai in Spain – has found.
Because of the lack of heat the planet remains deep frozen despite being much closer to its parent star than the Earth is to the sun.
But astronomers have not ruled out the chances of life evolving on the icy world.
Unlike many other red dwarfs, Barnard’s Star is relatively inactive and not so likely to blast nearby planets with radiation that would not give life a chance.
‘While the starlight from Barnard’s Star is too feeble for Barnard’s Star b to have liquid water on its surface, Barnard’s Star b probably has a similar temperature to Jupiter’s moon Europa,’ said Professor Carole Haswell, head of astronomy at the Open University and a member of the international team that announced the discovery.
‘Famously, Europa has a sub-surface ocean which has been considered as a potential habitat for life. It is possible Barnard’s Star b may offer similar niches for life.
‘Tantalisingly, super-Earths like Barnard’s Star b probably sustain geothermal activity for longer than their lower mass counterparts.
‘This could be helpful to life by providing sustained heat and the chemicals needed to build complex organic molecules.
‘This new discovery offers exciting prospects to learn more about the galaxy’s diversity of planetary systems, starting with our own solar system’s near neighbours.’
The newly detected planet, Barnard’s Star b (artist’s impression), is thought to be rocky and at least 3.2 times more massive than the Earth. It circles a cool red-dwarf star, smaller and older than the sun, completing one orbit every 233 days
WHAT IS BARNARD’S STAR?
Barnard’s Star is named after Yerkes Observatory’s E.E. Barnard (1857-1923), who discovered it in 1916.
It is close to not being visible to the naked eye, even though at a distance of just six light years it is the second closest star to the Earth – if you consider the three stars of Alpha Centauri system, including Proxima, as a unit.
That is just what you would expect from a dim, low mass, class M (M4) dwarf.
At 3,170 Kelvin (2,896°C / 5,246°F), this dim dwarf has a luminosity 0.0035 times that of the sun, most of the most of it in the infrared end of the spectrum.
These emissions show it has a diameter only 20 per cent that of the sun and a mass 17 per cent of our nearest star.
#Far from rare, the great majority of stars fall into the M dwarf category, they are just so faint – like Proxima Centauri – that they are not visible to the naked eye.
Barnard’s Star is old, born before exploding stars had enhanced the amount of interstellar metals to that seen today, with a metal content only 10 per cent that of the Sun.
Its age is also attested to by its long rotation period of 130 days – stars slow down as they age – which is five times longer than the sun’s.
Barnard’s Star still has some magnetic activity, occasionally popping a flare caused by the release of magnetic-field energy, has an active X-ray corona heated magnetically to two million Kelvin – as does the Sun – and starspots, from which the rotation period is inferred.
Barnard’s low internal temperature and resulting feeble energy-generation rate give it an incredibly long life.
Indeed, no class M dwarf ever born in all the history of the Galaxy has ever died.
The planet’s existence was confirmed after two decades of observations using several different ground-based telescopes and instruments.
One of them was the new state-of-the-art planet-hunting instrument Carmenes at the Calar Alto Observatory in Spain.
Even the most powerful telescopes in use today would not be able to image Barnard’s Star b directly.
Instead, astronomers used the tried and trusted ‘radial velocity’ technique of looking for light frequency variations that betray the ‘wobble’ an orbiting planet imparts on a star.
From these measurements they are able to estimate a planet’s mass and orbital period.
Two years ago the same astronomical team detected a planet orbiting the sun’s closest neighbour, Proxima Centauri, part of the Alpha Centauri system.
The planet, Proxima Centauri b, is just 4.2 light years from Earth. Although Proxima Centauri b has a surface possibly warm enough for liquid water, the chances of finding life there are reduced by hostile X-rays and ultraviolet radiation pouring out of its star.
Barnard’s Star is six light years from Earth – hardly any distance on astronomical scales – a dim dwarf with a luminosity 0.0035 times that of the sun. The only closer star system is Alpha Centauri 4.4 light years away
Professor Haswell added: ‘Thirty years ago, as far as we knew, our solar system could be utterly unique, with planets formed by a freak event in the sun’s early history.
‘Technological developments over the last 20 years have shown that planets are common, and we are now pretty sure – based on statistics – that the majority of stars have planets.
‘This means we can begin to put our own solar system in context, and draw informed conclusions about just how special the Earth is.
‘This discovery of Barnard’s Star b, orbiting the nearest single star to the sun, shows that the statistical conclusions are correct: most stars seem to have planets.
‘At a distance of only six light years, Barnard’s Star b could conceivably be visited by people from Earth. Certainly, even with our current technology, we could launch unmanned probes to send back pictures of this planet.’
Lead astronomer Dr Ignasi Ribas, from the Institute of Space Studies of Catalonia in Spain, said the team had studied 771 measurements.
She added: ‘After very careful analysis we are over 99 per cent confident that the planet is there.
‘However we must remain cautious and collect more data to nail the case in the future.’
The full findings of the study were published in the journal Nature.
WHAT ARE THE KEY DISCOVERIES HUMANITY HAS MADE IN ITS SEARCH FOR ALIEN LIFE?
Discovery of pulsars
British astronomer Dame Jocelyn Bell Burnell was the first person to discover a pulsar in 1967 when she spotted a radio pulsar.
Since then other types of pulsars that emit x-rays and gamma rays have also been spotted.
Pulsars are essentially rotating, highly magnatised neutron stars but when they were first discovered it was believed they could come from aliens.
‘Wow!’ radio signal
In 1977, an astronomer looking for alien life in the nigh sky above Ohio spotted a powerful radio signal so strong that he excitedly wrote ‘Wow!’ next to his data.
In 1977, an astronomer looking for alien life in the nigh sky above Ohio spotted a powerful radio signal so strong that he excitedly wrote ‘Wow!’ next to his data
The 72-second blast, spotted by Dr Jerry Ehman through a radio telescope, came from Sagittarius but matched no known celestial object.
Conspiracy theorists have since claimed that the ‘Wow! signal’, which was 30 times stronger than background radiation, was a message from intelligent extraterrestrials.
Fossilised martian microbes
In 1996 Nasa and the White House made the explosive announcement that the rock contained traces of Martian bugs.
The meteorite, catalogued as Allen Hills (ALH) 84001, crashed onto the frozen wastes of Antarctica 13,000 years ago and was recovered in 1984.
Photographs were released showing elongated segmented objects that appeared strikingly lifelike.
Photographs were released showing elongated segmented objects that appeared strikingly lifelike (pictured)
However, the excitement did not last long. Other scientists questioned whether the meteorite samples were contaminated.
They also argued that heat generated when the rock was blasted into space may have created mineral structures that could be mistaken for microfossils.
Behaviour of Tabby’s Star in 2005
The star, otherwise known as KIC 8462852, is located 1,400 light years away and has baffled astonomers since being discovered in 2015.
It dims at a much faster rate than other stars, which some experts have suggested is a sign of aliens harnessing the energy of a star.
The star, otherwise known as KIC 8462852, is located 1,400 light years away and has baffled astonomers since being discovered in 2015 (artist’s impression)
Recent studies have ‘eliminated the possibility of an alien megastructure’, and instead, suggests that a ring of dust could be causing the strange signals.
Exoplanets in the Goldilocks zone in 2015
In February this year astronomers announced they had spotted a star system with planets that could support life just 39 light years away.
Seven Earth-like planets were discovered orbiting nearby dwarf star ‘Trappist-1’, and all of them could have water at their surface, one of the key components of life.
Three of the planets have such good conditions, that scientists say life may have already evolved on them.
Researchers claim that they will know whether or not there is life on any of the planets within a decade, and said ‘this is just the beginning.’