|Over 60 billion habitable planets probably present in our Milky Way (Credit: mickare/deviantart)|
Scientists have estimated that there could be over 60 billion habitable planets in our Milky Way alone. This estimate is about twice the previous estimates of at least one Earth-sized planet in the habitable zone of each red dwarf star.
Astrophysical Journal Letters
Previous estimate was made by the researchers from Harvard University and this new thinking has been reported by the researchers from the University of Chicago and Northwestern University.
This new estimate has been made by considering “cloud cover”. Cloud cover is the concept given to the dayside of the exoplanets that are tidally locked i.e. one hemisphere of the planet continually faces the star (dayside), while the other faces away (darkside). It was thought that dayside would have high level of stellar flux but recent computer simulations showed otherwise due to the presence of clouds.
Cloud cover could be the reason that “tidally locked planets have low enough surface temperatures to be habitable,” explained Jang in his recently published paper.
Red dwarfs “represent about ¾ of the stars in the galaxy, so it applies to a huge number of planets,” Dr. Abbot, co-author on the paper, told Universe Today.
Future observations will approve or disprove this finding by measuring the cloud temperatures and James Webb Space Telescope would be one of the better options to study.
Jun Yang, Nicolas B. Cowan, & Dorian S. Abbot (2013). Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets ApJ Letters, 771, L 45, 2013 arXiv: 1307.0515v