Earth is home to the only life we know about, but there could be planets out there better suited for life than our planet, astronomers argue. These planets are considered “superhabitable” and while it is unknown if they have life, they have properties that could facilitate the evolution of living organisms. Researchers have now discussed these properties in the journal Astrobiology.
The scientists started with the stars. While we can’t complain too much about the Sun, there are stars out there that are more life-friendly. Smaller stars than the Sun in the G and K class tend to live between two and seven times longer. They are also cooler and less luminous, producing less harmful light such as ultraviolet.
K-type stars are also three to four times more common than G-stars like the Sun, a fact that makes it more likely to have planets with the right set of conditions. These superhabitable planets are also slightly bigger (a 10 percent increase in radius) and up to 1.5 times more massive. This allows these planets to keep internal heating and an atmosphere for longer. They would also have more habitable land.
The final key ingredient is water. A slightly warmer world rich in water would be better suited for life (like tropical rainforests compared to colder drier areas on Earth).
So how many of these worlds are out there? We don’t know yet but of the 4,500 confirmed exoplanets, 24 are fairly good fits. However, none meet all of the criteria for superhabitable planets. The top contender has four of the eight characteristics recognized in the study, which means it's possibly more hospitable than our own planet. All of the candidates are over 100 light-years from Earth but more of these could be discovered with current and upcoming telescopes.
“It’s sometimes difficult to convey this principle of superhabitable planets because we think we have the best planet,” lead author Professor Dirk Schulze-Makuch, from Washington State University, said in a statement. “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.”
NASA’s James Web Space Telescope, the LUVIOR space observatory, and the European Space Agency’s PLATO space telescope could help discover more “superhabitable” planets.