Earth is not the most comfortable planet in the Universe. Scientists have discovered two dozen planets outside the solar system, where we could settle down with greater comfort: they are slightly larger, more massive or rotate around stars of another spectral class.
Scientists from the University of Washington State have published in Astrobiology magazine detailed characteristics of potentially “super habitable” planets. Some are older, others slightly larger, warmer or wetter than the Earth. All 24 candidates are over 100 light-years away, and the future generation of space observatories will help gather more information about them. However, suitability does not mean that these worlds have some kind of extraterrestrial life – only that they have suitable conditions for life, writes EurekAlert.
Our sun has a relatively short life span – less than 10 billion years, and it took about four billion years for a complex life to emerge. Many stars in the same spectral class run out of fuel earlier, scientists say. Another matter is class K stars. Their life expectancy can reach 70 billion years.
This means that the planets in their systems can develop longer. However, too old planets are also unsuitable for life – they are running out of geothermal energy and protective geomagnetic shields. Therefore, researchers have focused on worlds that are 5 to 8 billion years old.
Size and mass also matter. The planet 10% larger than Earth will have, on average, more land to live on. And if its mass is one and a half times greater than the earth’s, then the heat of radioactive decay and the atmosphere held by gravity will be preserved longer.
The key element for life is water, and scientists believe that there may be more, especially in the form of clouds and moisture. Life would also benefit if the surface temperature were 5 degrees Celsius higher. This would increase the planet’s biodiversity.
Of all 24 candidates, no planet meets all the essential criteria simultaneously, but one has four. It would probably be more comfortable to live on it than on Earth.