Scientists at Washington State University have discovered two dozen planets outside of the solar system that may be more suitable to host life than Earth. The researchers found that some of these planets orbit stars that may be better than even our sun.
The “superhabitable” planets that are being described are older, larger, a little warmer, and possibly wetter than Earth. The researchers also noted that life could thrive more easily on planets that orbit stars with longer lifespans than our sun, which change more slowly.
While these planets are all more than 100 light years away, study lead author Professor Dirk Schulze-Makuch said the findings could help direct future observation efforts.
“With the next space telescopes coming up, we will get more information, so it is important to select some targets,” said Professor Schulze-Makuch. “We have to focus on certain planets that have the most promising conditions for complex life. However, we have to be careful to not get stuck looking for a second Earth because there could be planets that might be more suitable for life than ours.”
Professor Schulze-Makuch collaborated with astronomers Rene Heller of the Max Planck Institute for Solar System Research and Edward Guinan of Villanova University to establish the criteria for superhabitable planets by analyzing the 4,500 known exoplanets.
The researchers used data from the Kepler Object of Interest Exoplanet Archive of transiting exoplanets to identify planets orbiting within the host star’s liquid water habitable zone.
A longer lifespan would allow a planet to exist long enough to support complex life just like that which evolved here on Earth. In order to be habitable, however, planets should not be so old that they have exhausted their geothermal heat and lack protective geomagnetic fields.
While Earth is around 4.5 billion years old, the researchers argue that the sweet spot for life falls between 5 billion to 8 billion years old.
Habitability also involves size, mass, and water. The researchers said that more water, especially in the form of moisture, clouds, and humidity would be most suitable.
In addition, a slightly overall warmer temperature, a mean surface temperature of about 5 degrees Celsius greater than Earth, combined with the additional moisture, would also be better for life. The benefits of additional warmth and moisture can be seen in tropical rainforest ecosystems that are biodiversity hotspots on Earth.
Among the 24 top candidates for superhabitability, only one planet had as many as four of the desired features. The experts said this planet is probably much more comfortable for life than Earth.
“It’s sometimes difficult to convey this principle of superhabitable planets because we think we have the best planet,” said Professor Schulze-Makuch. “We have a great number of complex and diverse lifeforms, and many that can survive in extreme environments. It is good to have adaptable life, but that doesn’t mean that we have the best of everything.”
The study is published in the journal Astrobiology.