PSU: How Many Earth-like Planets Are Around Sun-like Stars?

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bystander
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PSU: How Many Earth-like Planets Are Around Sun-like Stars?

Post by bystander » Thu Aug 15, 2019 5:19 pm

How Many Earth-like Planets Are Around Sun-like Stars?
Penn State University | 2019 Aug 14
A new study provides the most accurate estimate of the frequency that planets that are similar to Earth in size and in distance from their host star occur around stars similar to our Sun. Knowing the rate that these potentially habitable planets occur will be important for designing future astronomical missions to characterize nearby rocky planets around sun-like stars that could support life. ...

Thousands of planets have been discovered by NASA’s Kepler space telescope. Kepler, which was launched in 2009 and retired by NASA in 2018 when it exhausted its fuel supply, observed hundreds of thousands of stars and identified planets outside of our solar system—exoplanets—by documenting transit events. Transits events occur when a planet’s orbit passes between its star and the telescope, blocking some of the star’s light so that it appears to dim. By measuring the amount of dimming and the duration between transits and using information about the star’s properties astronomers characterize the size of the planet and the distance between the planet and its host star.

“Kepler discovered planets with a wide variety of sizes, compositions and orbits,” said Eric B. Ford ... “We want to use those discoveries to improve our understanding of planet formation and to plan future missions to search for planets that might be habitable. However, simply counting exoplanets of a given size or orbital distance is misleading, since it’s much harder to find small planets far from their star than to find large planets close to their star.”

To overcome that hurdle, the researchers designed a new method to infer the occurrence rate of planets across a wide range of sizes and orbital distances. The new model simulates ‘universes’ of stars and planets and then ‘observes’ these simulated universes to determine how many of the planets would have been discovered by Kepler in each `universe.’ ...

Occurrence Rates of Planets Orbiting FGK Stars: Combining
Kepler DR25, Gaia DR2, and Bayesian Inference
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Re: PSU: How Many Earth-like Planets Are Around Sun-like Stars?

Post by BDanielMayfield » Fri Aug 16, 2019 4:29 am

And their answer to this important question is:
Based on their simulations, the researchers estimate that planets very close to Earth in size, from three-quarters to one-and-a-half times the size of earth, with orbital periods ranging from 237 to 500 days, occur around approximately one in six stars. Importantly, their model quantifies the uncertainty in that estimate. They recommend that future planet-finding missions plan for a true rate that ranges from as low about one planet for every 33 stars to as high as nearly one planet for every two stars.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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Re: PSU: How Many Earth-like Planets Are Around Sun-like Stars?

Post by rstevenson » Thu Aug 22, 2019 6:35 pm

BDanielMayfield wrote: Fri Aug 16, 2019 4:29 am And their answer to this important question is:
Based on their simulations, the researchers estimate that planets very close to Earth in size, from three-quarters to one-and-a-half times the size of earth, with orbital periods ranging from 237 to 500 days, occur around approximately one in six stars. Importantly, their model quantifies the uncertainty in that estimate. They recommend that future planet-finding missions plan for a true rate that ranges from as low about one planet for every 33 stars to as high as nearly one planet for every two stars.
One in six stars is a useful estimate -- perhaps the first scientifically determined one -- for plugging into at least one of the factors in the Drake Equation.

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