A new study estimates that our galaxy may contain 100 million planets that could support complex life forms.
A research team from the University of Texas, El Paso, studied more than 1,000 exoplanets regarding a number of characteristics that are considered important for sustaining multicellular life, such as density, chemical composition, temperature, age, and distance from the parent star, and formulated a “biological complexity index”, whose values range between 0 and 1.
The estimation showed that 1,6% of planets had a higher BCI than Jupiter’s moon Europa, which is considered to have good chances of hosting life. At the same time, five exoplanets (each of which is orbiting around a red dwarf star) got a higher score than Mars. Therefore, averaging one planet per star, it would mean that out of the 10 billion stars in the Milky Way there are at least 100 million planets better suited for life than Europa.
As Dr. Louis Irwin, the lead author of the study and professor at the University of Texas, claimed, “this is the first study that relies on observable data from actual planetary bodies beyond our solar system”. However, it still cannot be said for sure whether complex multicellular life exists on any of these planets, while the study only confirms the fact that they have the conditions that may be favorable for life. Dr. Irwin also emphasized that it is not assumed that any life form on these planets would be intelligent, but only that there could exist organisms larger and more complex than microorganisms.
“Planets with the highest BCI values tend to be larger, warmer, and older than Earth, so any search for complex or intelligent life that is restricted just to Earth-like planets, or to life as we know it on Earth, will probably be too restrictive,” said the researcher.
Another challenge is that most planets with a high probability of having complex life are far away. That is, if the 100 million planets were randomly distributed across the galaxy, their average distance from Earth would be equal to about 24 light years. An example of such planet is the Gliese 581, which is located at a distance of 20 light years from us.
On the one hand, it seems highly unlikely that we are alone. On the other hand, we are likely so far away from life at our level of complexity, that a meeting with such alien forms is extremely improbable for the foreseeable future,” concluded Dr. Irwin.
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Original study: http://www.mdpi.com/2078-1547/5/1/159