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. However, to be habitable, planets should not be so old that they have exhausted their geothermal heat and lack protective geomagnetic fields.
Earth is around 4. Size and mass also matter. One that is about 1. Water is key to life, and the authors argue that a little more of it would help, especially in the form of moisture, clouds and humidity. Different types of planets may drive processes that help or hinder habitability in different ways.
For example, planets orbiting low-mass stars in the habitable zone may be tidally locked, with only one hemisphere facing the star at all times. Some planets may be limited to only periodic or local habitable regions on the surface if, e. In order to understand the full range of planetary environments that could support life and generate detectable biosignatures, we require more detailed and complete models of diverse planetary conditions.
In particular, understanding the processes that can maintain or lead to the loss of habitability on a planet requires the use of multiple coupled models that can examine these processes in detail, especially at the boundaries where these processes intersect each other.
The size and mass of a planet can also influence how well it can support life. One that is about 1. A heavier planet would also have stronger gravity to help retain its atmosphere over a longer span of time. Worlds that are slightly warmer than Earth by about 8 degrees Fahrenheit 5 degrees Celsius might be super-habitable, since they could have larger tropical zones that could be more benign for more biodiversity.
However, warmer planets might also need more moisture, since greater heat could expand deserts. In addition, planets with the same amount of land area as Earth but broken up into smaller continents might be more habitable. When it comes to continents that are too large such as Earth's past continent Gondwana about million years ago , their centers are far from oceans, often rendering the interiors of large continents vast, inhospitable deserts. All in all, the scientists identified 24 potentially super-habitable planets.
None of them met all the criteria the researchers drew up for super-habitable planets, but one did meet at least two — KOI It might have an average surface temperature about 4.
Schulze-Makuch's favorite potentially super-habitable world from these 24 was KOI All 24 of these potentially super-habitable planets are more than light-years from Earth. The scientists detailed their findings online Sept. Follow Charles Q. Choi on Twitter cqchoi. Follow us on Twitter Spacedotcom and on Facebook.
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