Researchers have found at least 24 planets outside of our solar system may be better for life than Earth. Each a little older, wetter, warmer, and larger than Earth, astronomers say that they may be the best places to search for other life in the Universe.
While astronomers have discovered over 4,000 exoplanets (planets outside our solar system) to date, most are not particularly conducive to life. However, some nevertheless fall into the star's habitable zone- distances between a planet and star that allow surface temperatures neither to be too hot nor cold for life to evolve.
In their research, astrobiologist Drik Schulze-Makuch and his team aimed to find 'superhabitable' planets- planets that are not just in the habitable zone, but boast the right features to enable life to blossom.
These features include a star of the right size and life span- given it took 3.5 billion years for complex life to evolve on Earth, and 4 billion years for humans to appear.
Planetary size also matters- a larger size equalling more space for landmass and habitats, as well as more gravity resulting in a thicker atmosphere- necessary for organisms to travel by flight within.
Being slightly warmer than Earth would mean more landmasses are habitable, given the Earth's large swathes of barren polar regions. Meanwhile, being wetter than Earth would ensure that the warmer regions would not become barren desserts.
The researchers also highlighted that the presence of a slightly larger moon, or one a little closer to the planet, would also be beneficial to stabilize the planet's orbit.
With these criteria in mind, the researchers managed to find 24 potential matches with the Kepler telescope. While two of the 24 have been confirmed as exoplanets (Kepler 126b and Kepler-69c), they say that until further investigation, the others may be false positives.
Nevertheless, of the 24 objects discovered, nine were orbiting around an 'ideal star' (identified as a K dwarf star slightly cooler than our sun and at around 5-8 billion years old). Only one candidate, however, known as KOI 5715.15 met all the criteria, although the planet's true surface temperature depends on the greenhouse effect in its atmosphere.
While exciting findings, the researches say that all the objects are over 100 light-years away, and as such, it will be difficult to examine them for signs of life anytime too soon. Nevertheless, Schulze-Makuch and his colleagues wrote that would a 'superhabitable' planet be discovered within 100 light-years from Earth, it should be the first place we look to for other signs of life in the Universe.