Earth-sized planet just 40 light-years away could have an atmosphere capable of sustaining life, astronomers reveal
An Earth-sized planet just 40 light-years away could be a viable home for alien life, scientists have discovered.
The planet TRAPPIST-1e orbits its star in the so-called Goldilocks Zone, where life-supporting liquid water can exist at the surface in the form of a global ocean.
However, this is only possible if the planet has an atmosphere to keep its temperature stable.
Now, using the new measurements from the James Webb Space Telescope (JWST), astronomers have shown that this might be the case.
The researchers aimed the JWST’s NIRSpec (Near-Infrared Spectrograph) instrument at the planet just as it passed in front of its star.
As the starlight shines through the atmosphere, if there is one, the gases absorb certain wavelengths of light depending on their chemical makeup.
Study co-author Dr Ryan MacDonald, of the University of St Andrews, says: ‘We are seeing two possible explanations.
‘The most exciting possibility is that TRAPPIST-1e could have a so-called secondary atmosphere containing heavy gases like nitrogen.’
TRAPPIST-1 is an extremely small and cool red dwarf star, known as an M dwarf, with a diameter of just 52,300 miles (84,180 kilometres) and a surface temperature less than half that of the sun’s.
Of the three planets within the habitable zone, the fourth planet from the star, TRAPPIST-1e, is the most promising candidate to be a liveable world.
With a mass of 0.692 Earths, TRAPPIST-1e is a bit smaller than our own planet.
It also sits extremely close to its star, at around three per cent of the distance between the Earth and the Sun, completing a full orbit once every 6.1 Earth days.
However, due to TRAPPIST-1’s extremely cool surface temperature, astronomers think the planet might hold large surface oceans of liquid water as well as frozen expanses of ice.
Scientists have been trying to see whether TRAPPIST-1e has an atmosphere for years, but this task has proven to be exceptionally tricky.
Co-author Professor Hannah Wakeford, of the University of Bristol, told The Daily Mail: ‘The amount of light that would shine through an atmosphere like our own is incredibly small, so measuring that takes a lot of precise observations.
‘We are looking for “part per million” changes, that is around a 0.001 per cent change in the light we measure from the star during the planet’s crossing.’
To make things even more difficult, TRAPPIST-1 itself is extremely active and produces lots of solar flares and star spots, cool regions created by powerful magnetic fields.
The researchers have spent the last year carefully gathering data from transitions and correcting for this solar activity to get as close as possible to a measurement of the atmosphere.
Their data shows that there is a good chance that TRAPPIST-1e does have an atmosphere very similar to Earth’s, and so could be home to liquid water.
This comes just weeks after scientists used the JWST to show that another planet in the TRAPPIST-1 system does not have an Earth-like atmosphere.
Using the same transit method, scientists found that TRAPPIST-1d, the third planet from the star, did not host any molecules that are common in Earth’s atmosphere.
Interestingly, if the TRAPPIST-1e does have an atmosphere, then it’s almost certainly not its original one.
When planets form, they collect the hydrogen and helium gas from the clouds surrounding their home star to make a ‘primordial’ atmosphere.
However, lots of activity from the nearby star means that this first atmosphere is often stripped away relatively quickly.
Professor Wakeford says: ‘For small planets like TRAPPIST-1e, the planet will not be able to hold onto this hydrogen and helium as well, because the small gravity and light particles mean they are more likely to escape back into space.’
Instead, the researchers believe that TRAPPIST-1e could have a ‘secondary atmosphere’ made up of heavy gases like nitrogen.
‘The same thing happened to the Early Earth,’ says Professor Wakeford.
‘A secondary atmosphere, like our own, is then made via outgassing from the rocks that make up the planet itself.
‘In our case, through volcanic activity and asteroid bombardment events, which lead to the release of vast amounts of nitrogen, which makes up the bulk of our atmosphere.’
This is important because a nitrogen-rich atmosphere would produce a greenhouse effect that should keep the planet warm and stable.
Since TRAPPIST-1e is tidally locked, meaning one side always faces the sun, this means it could have an ocean on the sunward side and ice in the darker regions.
The new data also ruled out the possibility that TRAPPIST-1e could have a thin CO2-rich atmosphere like Mars or Venus in our own solar system.
‘These new observations have definitively ruled out the presence of a primordial atmosphere, but we cannot yet tell between secondary atmosphere scenarios and the possibility that no secondary atmosphere formed,’ says Professor Wakeford.
Likewise, Professor Wakeford also says that we cannot tell from these measurements alone whether TRAPPIST-1e could harbour alien life or whether it could be a viable home for humans in the future.
However, in the future, the researchers hope to gather more data, which should reveal a clearer picture.
This data was based on just four JWST observations of TRAPPIST-1e, and soon the researchers will have 20 observations to work from.
That data should allow the researchers to distinguish between the no atmosphere and secondary atmosphere scenarios, revealing whether the planet really is habitable.
Dr MacDonald concludes: ‘We finally have the telescope and tools to search for habitable conditions in other star systems, which makes today one of the most exciting times for astronomy.’
Source: daily mail
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Earth-sized planet just 40 light-years away could have an atmosphere capable of sustaining life, astronomers reveal