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How many Earth-like planets are there around Sun-like stars?



  How many Earth-like planets are there around Sun-like stars?
Artistic representation of NASA's Kepler Space Telescope, which has discovered thousands of new planets. New research using Kepler data provides the most accurate estimate of how often we should expect to find Earth-like planets near sun-like stars. Picture credits: NASA / Ames Research Center / W. Stenzel / D. Rutter

A recent study provides the most accurate estimate of the abundance of earth-like planets in their size and distance from their host star around sun-like stars. Knowing the speed at which these potentially habitable planets appear is important in designing future astronomical missions that can characterize nearby rocky planets around sun-like stars that could support life. An article describing the model will be published on August 1

4, 2019 in the Astronomical Journal .

Thousands of planets were discovered by NASA's Kepler Space Telescope. Kepler, launched in 2009 and suspended by NASA in 2018 when its fuel supply was depleted, observed hundreds of thousands of stars and identified planets outside our solar system – exoplanets – by documenting transit events. Transit events occur when the orbit of a planet passes between its star and the telescope and blocks some of the star's light, causing it to darken. By measuring the amount of dimming and the duration between passes and using information about the properties of the star, astronomers characterize the size of the planet and the distance between the planet and its host star.

"Kepler discovered planets with a variety of sizes, compositions and orbits," said Eric B. Ford, a professor of astronomy and astrophysics at Penn State and one of the heads of the research team. "We intend to use these discoveries to improve our understanding of planet formation and to plan future missions to search for planets that may be habitable, but it is misleading to count only exoplanets of a certain size or orbit distance, as it is much more difficult is to find small planets far away from their star planets to find as large planets near their star. "

To overcome this hurdle, researchers developed a new method to increase the abundance of planets over derive a wide range of sizes and orbits. The new model simulates "universes" of stars and planets and then "observes" these simulated universes to determine how many of Kepler's planets would have been discovered in each "universe".

"We used Kepler's final catalog of identified planets and enhanced star properties of the European Space Agency's Gaia spacecraft to create our simulations," said Danley Hsu, Ph.D. student at Penn State and first author of the paper. "By comparing the results with the planets cataloged by Kepler, we characterized the planetary rate per star and the dependence on the size of the planet and the orbit distance, and our novel approach enabled the team to consider several effects that were not considered in earlier studies. " , "

The results of this study are particularly relevant to the planning of future space missions to characterize potentially Earth – like planets: while the Kepler mission discovered thousands of small planets, most of them are so remote that it is difficult for astronomers to get details

"Scientists are particularly interested in finding biomarkers – molecules that point to life – in the Earth's atmosphere of roughly planet-sized planets orbiting in the" habitable zone "of sun-like stars." said Ford. "The habitable zone is a series of orbits where the planets can hold liquid water on their surfaces. The search for evidence of life on Earth-sized planets in the habitable zone of Sun-like stars requires a great new space mission. "

The size of this mission depends on the abundance of Earth-sized planets. NASA and the National Academies of Science investigate presently, missionary concepts that vary greatly in size and performance.When Earth-sized planets are rare, the closest Earth-like planets are farther away, and a large, ambitious mission will be required to search for evidence of life on possibly Earth-like planets on the other hand, when earth-sized planets are common, there are earth-sized exoplanets orbiting stars near the Sun, and a relatively small observatory may be able to study their atmospheres.

"While most stars, the Kepler observed, typically thousands of light-years from In the absence of sun, Kepler observed a sufficiently large sample of stars to make a rigorous statistical analysis to estimate the rate of planets of the Earth's size in the habitable zone of the nearby sun-like stars. [Hsu] said

Based on their simulations, the researchers estimate that planets whose size is very close to Earth are about three quarters to one and a half times those of Earth, and orbital periods between 237 and 500 days are about one It is important that their model quantifies the uncertainty in this estimate, suggesting that future planetary detection missions will schedule a true rate that ranges from one planet per 33 stars to nearly one planet per two stars.

"Knowledge How often we should expect to find planets Optimizing surveys for exoplanets and planning upcoming space missions of a specific size and orbit is extremely helpful in maximizing their chances of success, "said Ford." Penn State is a leading provider of state-of-the-art statistical and computer-aided methods for analyzing astronomical observations to this Ar t to answer questions. Our Institute for CyberScience (ICS) and the Center for Astrostatistics (CASt) provide infrastructure and support that makes this kind of project possible.

Penn State's Exoplanet and Habitable World Center includes faculties and students studying the full spectrum of extrasolar planetary science, and a Penn State team rebuilt the Habitable Zone Planet Finder, an instrument for finding low-mass planets Cool Stars, which recently began its scientific work on the Hobby Eberly telescope, whose founding partner is Penn State A second Penn State-built spectrograph will be tested before a complementary study to discover and measure the masses of low-mass planets around solar-like Starts This Study Provides Predictions on What Such Planetary Investigations Will Find and Provides a Context for Interpreting Their Findings.

Along with Ford and Hsu, Darin Ragozzine and Keir Ashby of Brigham Young University are also part of the research team supported by NASA; the US National Scienc e Foundation (NSF); and the Eberly College of Science, the Department of Astronomy and Astrophysics, the Center for Exoplanets and Habitable Worlds, and the Penn State Center for Astrostatistics. The Penn State Institute for CyberScience, including the NSF-funded CyberLAMP cluster, provided advanced computing resources and services.


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Further information:
Danley C. Hsu et al. Occurrence Rates of Planets Orbiting FGK Stars: Combination of Kepler DR25, Gaia DR2 and Bayesian Inference, The Astronomical Journal (2019). DOI: 10.3847 / 1538-3881 / ab31ab

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Pennsylvania State University




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How many earth-like planets are there around sun-like stars? (2019, 14th of August)
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