Astronomers have found at least 45 planets orbiting distant stars that possess Earth-like qualities including a similar atmosphere and life sustaining liquid water.
Experts from Luleå University of Technology, Sweden, created a new way to determine the habitability of these distant worlds by studying their atmosphere.
The team found a way to use information on 'atmospheric species', that is chemicals in the atmosphere, and how fast they escape into space to determine how close an exoplanet is in terms of temperature and composition to the Earth.
They then used their new model on the 55 potentially habitable worlds listed in the existing exoplanet catalogue - which focuses on habitable zone and the host star.
Only 17 of the 55 planets in the catalogue met the criteria defined by the Swedish researchers for being 'Earth-like' but the team found another 28 planets on the wider exoplanet list that also met the criteria - bringing the total of Earth-like worlds to 45.
The TRAPPIST-1 system contains one planet on the new list of 45 potentially Earth-like worlds - in this system it is known as TRAPPIST-1 d - the fourth from the star
This graphic shows the list of all potentially Earth-like worlds as determined by the Swedish team. The planets in blue were already on the Exoplanet Catalogue list of habitable worlds
Advanced ground and space based missions including the current CHEOPS and future James Webb telescope can now use this research to focus their searches.
Detecting habitable exoplanets is a difficult challenge as we can't just 'send a probe' the vast distances between stars, the team explained.
The nearest exoplanet with a potentially habitable atmosphere is Proxima b around the star Proxima Centauri 4.22 light-years - or 25 trillion miles away.
NASA's Juno probe reached speeds of 165,000 miles per hour as it approached Jupiter - at those speeds it would take 17,157 years to reach Proxima b.
This is an artists impression of Kepler-1649 c orbiting its host star. It is a planet on the list of potential Earth-like worlds that wasn't already in the exoplanet catalogue habitability list
Currently, determining an exoplanet's capability to host life relies on the restricted low-resolution spatial and spectral information of their atmospheres.
To create a 'short list' of habitable worlds, the team used the 'kinetic theory of gases' - how the gases move about the atmosphere - and a list of possible chemical retained in the atmospheres of currently known exoplanets.
'We conclude that, based on our current knowledge of the detected exoplanets, 45 of them are good candidates for habitability studies,' the authors wrote.
'These exoplanets could have Earth-like atmospheres and should be able to maintain stable liquid water.'
As part of the study the team used the atmosphere of planets in our own solar system - where we know the true makeup - as a base of reference.
They then listed the exoplanets with hydrogen, oxygen, dinitrogen and carbon dioxide atmospheres in their list of Earth-like candidates.
'We also propose a conservative list of 45 exoplanets with favourable conditions such as temperature and ability to retain the essential life-related gases in their atmospheres for further habitability studies,' the team wrote.
The team also recommend that the current definition of a habitable zone around a star should be revisited when considering whether a