Life on Earth may not always be perfect, but most of us have always assumed that our planet is the best place for life.
But that might not be the case - as astronomers have pinpointed two dozen “superhabitable” planets which might actually be better than Earth.
The “superhabitable” planets include those that are older, a little larger, slightly warmer and possibly wetter than Earth.
Older planets in particular may have offered life more time to evolve, said the researchers from Washington State University.
Lead author Dirk Schulze-Makuch said, “With the next space telescopes coming up, we will get more information, so it is important to select some targets.”
“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.”
The 24 top contenders for superhabitable planets are all more than 100 light years away, but Schulze-Makuch said the study could help focus future observation effort.
The researchers searched among the 4,500 known exoplanets outside our solar system for candidates which could be even more habitable than Earth.
Schulze-Makuch said, “It’s sometimes difficult to convey this principle of superhabitable planets because we think we have the best planet.”
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.”
Habitability does not mean these planets definitely have life, merely the conditions that would be conducive to life.
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The researchers selected planet-star systems with probable terrestrial planets orbiting within the host star’s liquid water habitable zone from the Kepler Object of Interest Exoplanet Archive of transiting exoplanets.
While the sun is the center of our solar system, it has a relatively short lifespan of less than 10 billion years.
Since it took nearly 4 billion years before any form of complex life appeared on Earth, many similar stars to our sun, called G stars, might run out of fuel before complex life can develop.
In addition to looking at systems with cooler G stars, the researchers also looked at systems with K dwarf stars, which are somewhat cooler, less massive and less luminous than our sun.
K stars have the advantage of long lifespans of 20 billion to 70 billion years.
This would allow orbiting planets to be older as well as giving life more time to advance to the complexity currently found on Earth.
Size and mass also matter.
A planet that is 10% larger than the Earth should have more habitable land. One that is about 1.5 times Earth’s mass would be expected to retain its interior heating through radioactive decay longer and would also have a stronger gravity to retain an atmosphere over a longer time period.
Among the 24 top planet candidates none of them meet all the criteria for superhabitable planets, but one has four of the critical characteristics, making it possibly much more comfortable for life than our home planet.
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