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The Milky Way contains at least 100 billion planets. And scientists are hell-bent on finding which ones could support life.
Our galactic neighborhood may be full of other worlds, but a new study estimates that only 300 million of those 100 billion planets may have the right ingredients for life.
And some of them may be closer than we think.
The study, published on the ArXiv prepress server and accepted for publication on The astronomical diary, provides perhaps the most reliable estimate of habitability in our galaxy to date
Previous assumptions about how much of the Milky Way can be habitable have ranged from 40 billion to six billion planets.
But using data from exoplanet hunting missions such as Kepler and Gaia, the researchers behind the new study say their estimate is much more accurate.
“This is the first time that all the pieces have been put together to provide a reliable measure of the number of potentially habitable planets in the galaxy,” Jeff Coughlin, exoplanet researcher at the SETI Institute and Director of the Kepler Office of Science, and co-author of the new study, he said in a statement.
The astronomers focused on three main determinants of habitability. First, they estimated the number of Earth-sized exoplanets in the Milky Way; they are more likely to be rocky planets. Then, they looked at how many stars are similar in age and temperature to our Sun. Finally, they considered whether the planets have the necessary conditions to support liquid water, a critical ingredient for life.
Older studies only looked at a planet’s distance from its host star to calculate habitability, a crude measure, the new study suggests. Instead, this research also takes into account how much light a planet would receive from its star based on more than just distance. NASA’s Kepler mission zoomed in on the stars to see if there are planets orbiting within their habitable zone. Meanwhile, the Gaia mission of the European Space Agency measured the positions, distances and movements of the stars to obtain a more definitive estimate of the amount of light, and therefore heat, that they give to their planets.
The study found that there could be 300 million habitable planets in the Milky Way. Some are only 30 light years from the Sun, the data suggests.
Scientists have confirmed the existence of more than 4,000 exoplanets, although another 3,000 suspected exoplanets are awaiting confirmation. Some of these planets have shown signs of potential habitability, but it will be extremely difficult to determine if they harbor life.
“Knowing how common different types of planets are is extremely valuable in designing upcoming exoplanet search missions,” said Michelle Kunimoto, a member of the Transiting Exoplanet Exploration Satellites Team at the Massachusetts Institute of Technology and a co-author. of the new study. in a sentence. “Surveys targeting small, potentially habitable planets around Sun-like stars will rely on results like these to maximize their chances of success.”
Summary: We present the occurrence rates of rocky planets in the habitable zones (HZ) of main sequence dwarf stars according to the Kepler DR25 planet candidate catalog and Gaia-based stellar properties. We provide the first analysis in terms of star-dependent installation flux, which allows us to track HZ planets. We define η⊕ as the occurrence of HZ of planets with radius between 0.5 and 1.5 R⊕ orbiting stars with effective temperatures between 4800 K and 6300 K. We find that η⊕ for conservative HZ is between 0.37 + 0.48-0.21 (errors reflect 68 % credible intervals) and 0.60 + 0.90−0.36 planets per star, while the optimistic occurrence of HZ is between 0.58 + 0.73−0.33 and 0.88 + 1.28−0.51 planets per star. These limits reflect two extreme assumptions about extrapolating the completeness beyond the orbital periods where completeness data from DR25 are available. The large uncertainties are due to the small number of small HZ planets detected. We found similar occurrence rates using a Bayesian Poisson probability analysis and an approximate Bayesian calculation. Our results are corrected so that the catalog is complete and reliable. Both the integrity and the rate of occurrence of the planet depend on the effective stellar temperature. We also present rates of occurrence for various stellar populations and planet size ranges. We estimate with 95% confidence that on average the closest planet HZ around the G and K dwarfs is about 6 pc away, and there are about 4 rocky planets HZ around the G and K dwarfs at 10 pc of the sun.
