Rating for extraterrestrial life

An international team of scientists made a rating of planets on which life can exist, according to BBC News. Among the heavenly bodies with the greatest chance of being the Saturn moon Titan and the exoplanet Gliese 581g, located at a distance 20.5 light years away in the constellation Libra. In an article published in the journalAstrobiology, The researchers offer 2 rating: index of similarity with the Earth (Earth Similarity Index, ESI) and the index of the population of the planet (Planetary Habitability Index, PHI).

As to the first index, as the name implies, there are a planet in the degree of similarity with the Earth in size, density, or distance from the star. "The first question before us - whether there are planets like our own, in other worlds, because we know that in such circumstances may be life," - says Dirk Schulze-cake (Dirk Schulze-Makuch) from Washington State University (Washington State University), USA .

The second rating is based on several factors: whether the planet is solid or icy surface, whether it has an atmosphere or magnetic field. Also, when calculating this ranking scientists calculated whether there is enough energy for the existence of organisms. They also drew attention to the presence of organic compounds and formulations needed for chemical reactions.

Not surprisingly, the first index, the highest rating (1.00) got Earth. And the second took place in the list of Gliese 581g with a rating of 0.89 and exoplanet Gliese 581d, orbiting the same star (0.74). Results of the second rankings are slightly different: the first position is occupied by Titan with a rating of 0.64. Then comes Mars (0.59), and Europe, the moon of Jupiter (0.47).

There are currently more than 500 known extrasolar planets , ie planets beyond the limits of our solar system. Dozens of years ago, when no such planet was not discovered, Carl Sagan, astronomer and popularizer of science, imagined the existence of such worlds and life, which may exist on them.