Our Milky Way has a lot of potential The planet is like the earth, a new study found.
On average, each star is like the clear sun Galaxy Researchers have found that likely to contain rocky planets between 0.4 and 0.9 in its “habitable zone”, moderate orbital distances where liquid water could stabilize. on the world surface.
About 7% Among the 200 billion stars of the Milky Way are “G dwarfs” like SunSo that’s a lot of real estate that might look like Earth.
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“This is the first time all the pieces have come together to provide a reliable measurement of the number of habitable planets in the galaxy,”; study co-author Jeff Coughlin, researcher Exoplanets at SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, California, said in a statement.
“This is a key term of The Drake equation, used to estimate the number of contagious civilizations, “said Coughlin, who also directs the Kepler Science Office, which analyzes data gathered from NASA’s planet hunting operations. Kepler space telescope. “We go one step further along the long path to find out if we are alone in the universe.”
In the new study, a large team led by Steve Bryson of NASA’s Ames Research Center in California studied Kepler’s observations, which operated from 2009 to 2018. The spacecraft is extremely prolific. more than 2,800 exoplanets to date – Nearly two thirds of all known alien worlds. And Kepler’s data continued to grow as researchers continued to sift through its huge data set; thousands of Kepler’s “candidates” are waiting to be examined by further analysis and observations.
Bryson and his colleagues also examined data on stellar properties from the European Space Agency Gaia spaceship, accurately mapping for a billion stars in the Milky Way.
The team used this information to estimate the incidence of rocky planets in the habitable zone of sun-like stars. Scientists have defined “rocky planets” as worlds 0.5 to 1.5 times the diameter of Earth, and sun-like stars with surface temperatures between 8,180 and 10,880 degrees. F (4,527 to 6,027 degrees C). Most stars that meet that criterion are G dwarfs and “K dwarfs”, which are slightly smaller than G dwarfs and more than twice as large.
Habitable Area (HZ) is a confusing concept; Whether a planet resides in it or not depends on the thickness and composition of its atmosphere and the degree of activity of its host star, among other factors. (Other notes are also worth mentioning: The habitable zone is designed for life just like the Earth is dependent on water and it is not considered sub-surface liquid water, possibly existing on worlds. very cold, no air, like some moons of Jupiter and the Plan of Saturn.)
Related: How habitable zones for planets and alien stars work (infographic)
So Bryson and his team calculated the occurrence rates for both “conservative” and “optimistic” habitats – 0.37 to 0.60 planets per star for planets before and 0, 58 to 0.88 planets per star for the latter.
Both of these ranges have great uncertainty. But abundance however implies that potentially Earth-like worlds are all around us – including in the backyard of our solar system.
“We estimate with 95% confidence that, on average, the closest HZ planets around dwarfs G and K are ∼6 pc. [parsecs] The researchers wrote in the new study were accepted for publication in the Astronomical Journal. You can read its preprints for free at arXiv.org. (A parsec is about 3.26 light years.)
The new study was not considered red dwarf, also known as the M dwarf, makes up about three-quarters of the Milky Way’s star population. A 2013 study based on Kepler data estimated that approx 6% red dwarf system boasts an Earth-like planet in the habitable zone and such a world is the closest alien world to our solar system, at a distance of just 4.2 light-years – Proxima b, orbiting the red dwarf Proxima Centauri.
But the true viability of planets in the red dwarf system is a matter of debate. Because these stars are so faint, their habitable zones are very close together, meaning planets in this region are likely to be neatly locked, always displaying the same face as their host star, like like the moon to the Earth. Red dwarfs are also much more active than sun-like stars, especially at a young age. So intense outbursts can quickly remove the atmosphere The worlds revolve in the habitable zones of red dwarfs, scientists say.
Mike Wall is the author of “Out there“(Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.