New Study Finds at Least 45 Planets With Qualities Similar to Earth

Astronomers claim that at least 45 exoplanets are similar to Earth—from the composition of their atmosphere to the presence of liquid water that can possibly support life.

A team led by astronomers from Luleå University of Technology in Sweden has devised a novel method of testing the habitability, or their capability to support life as we know it, of these exoplanets through an analysis of their atmosphere.

It involves utilizing existing data on atmospheric species—or chemicals in their atmosphere—and how fast these chemicals exit into space. This data allows them to determine an exoplanet's similarity to our own Earth in terms of both chemical composition and average temperature.

Testing 55 Exoplanet Candidates

To test their newly-developed method, researchers tested it on 55 potentially habitable worlds whose data are available in the updated exoplanet catalog—focusing on exoplanets found in the so-called "Goldilocks zone" or the habitable zone of their respective galaxies as well as the star that hosts these planets.

According to their model, 17 out of the 55 planets from the catalog examined were able to meet the criteria set by the Luleå University of Technology team. It prompted the Swedish researchers to expand their initial search to other planets in the exoplanet catalog. So far, the team was able to identify as many as 45 Earth-like worlds.

With these findings, advanced search missions, both ground, and space-based, will be able to focus their efforts on these shortlisted exoplanets. This includes the European space telescope CHEOPS, or Characterizing Exoplanets Satellite, and NASA's upcoming James Webb Space Telescope.

The team also explained that detecting other habitable worlds is a difficult challenge because of their great distances, adding that probes can't be easily sent to find these planets. The nearest to us, Proxima Centauri b, which orbits within the Goldilocks zone of the red dwarf star Proxima Centauri. Proxima b, first discovered back in 2016 through Doppler spectroscopy, is located approximately 4.2 light-years away from Earth.

Changing The Search for Other Earths

In perspective, NASA's Juno Probe—tasked with understanding the gas giant Jupiter—reached a velocity of about 165,000 miles per hour as it approached its target. With the same velocity, Juno would need 17,157 years to reach Proxima b.

Currently, due to the apparent impossibility of conducting in situ exploration of these distant worlds, studies and hypotheses on whether these planets can sustain life are based on low-resolution spatial and spectral data from their atmosphere.

The team from the Luleå University of Technology proposed their new model based on the kinetic theory of gases, which determines how gasses escape their native atmospheres through thermal escape. However, the researchers establish that one of the limitations of this method concerns the possible phase changes of gas species that undergo thermal escape.

After testing their model, researchers suggest that the definition of the Habitable Zone around a star be revisited, adding that the capacity to host an atmosphere like our own and the ability to support liquid water—a widely accepted criterion for supporting life—be added.

Check out more news and information on Exoplanets in Science Times.