A new study claims that the Milky Way is home to one hundred million planets on which alien life could exist. And not a simple microbial life, but a complex alien life.
A research team consisting of Luis Irwin of the University of Texas at El Paso, Alberto Feiren of Cornell University, Abel Mendes of the University of Puerto Rico Planet Habitability Laboratory at Arecibo, and Dirk Schulze-Macuch of Washington State University analyzed an expanding list of confirmed exoplanets (currently there are 4461), then estimated the density, temperature, substrate, chemical composition, distance from the parent star, and the age of each planet.
The team used this information to calculate the Biological Complexity Index (BCI), rating these planets on a scale of 0 to 1.0, according to characteristics that are believed to be important in sustaining multicellular life.
Professor Schulze-Makuch explains:
"The BCI calculation showed that 1 to 2 percent of known exoplanets have a BCI rating higher than Jupiter's moon Europa, which has a subsurface global ocean that can be hospitable to life."
"Based on an estimate of 10 billion stars in the Milky Way and assuming that there is an average of one planet per star, the figure is 100 million. Some scientists believe that this number could be 10 times more."
Schulze-Makuch also tries to emphasize that the study does not claim that complex life finally exists on one hundred million planets. It only indicates that the necessary conditions for the maintenance of life can exist on so many planets.
The group's research was published in the journal Challenges in an article entitled "Assessing the Possibility of Biological Complexity on Other Worlds Evaluating the Emergence of Complex Life in the Milky Way Galaxy."