Based on Kepler Data, There’s a 95% Chance of an Earth-Like Planet Within 20 Light-Years


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In the past few decades, the study of exoplanets has grown by leaps and bounds, with 4296 confirmed discoveries in 3,188 systems and an additional 5,634 candidates awaiting confirmation. Because of this, scientists have been able to get a better idea about the number of potentially-habitable planets that could be out there. A popular target is stars like our own, which are known as G-type yellow dwarfs.

Recently, an international team of scientists (led by researchers from the NASA Ames Research Center) combined data from by the now-defunct Kepler Space Telescope and the European Space Agency’s (ESA) Gaia Observatory. What this revealed is that half of the Sun-like stars in our Universe could have rocky, potentially-habitable planets, the closest of which could be in our cosmic backyard!

The study that describes their findings, “The Occurrence of Rocky Habitable Zone Planets Around Solar-Like Stars from Kepler Data,” recently appeared online and will soon be published in The Astronomical Journal. The study was performed by NASA scientists who were joined by colleagues from universities, institutes, observatories, and laboratories from all around the world.

The Kepler mission, which was in operation from 2009 to 2018 (when it ran out of fuel) is responsible for the majority of exoplanet discoveries to date. Based on the number of planets it found, scientists now estimate that there could be more planets than stars in the Milky Way (the latest estimates say there are between 100 to 400 billion stars). As Steve Bryson, a researcher at NASA’s Ames Research Center and the lead author on the study, explained:

“Kepler already told us there were billions of planets, but now we know a good chunk of those planets might be rocky and habitable. Though this result is far from a final value, and water on a planet’s surface is only one of many factors to support life, it’s extremely exciting that we calculated these worlds are this common with such high confidence and precision.”

For the purposes of calculating how often potentially-habitable, Earth-like planets occur in our galaxy, the team focused on stars in Kepler‘s final data set that were similar to our Sun in terms of age (ca. 4.6 billion years) and temperature – plus or minus up to 815 °C (15,000 °F). They further looked at planets that were between 0.5 and 1.5 Earth radii, which are most likely to be rocky.

From this, the team found that there could be as many as 300 million potentially habitable planets in the Milky Way galaxy alone. What’s more, their results indicate that four of these exoplanets could be located within 30 light-years of the Solar System – the closest of which could be just 20 light-years from us. Overall, their analysis included a wide range of stars, each of which has its own particular properties that affect habitability.

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Keppler uses the transit method to find planets, and that relies on the orbital plane of the system being aligned correctly in order to produce a transit from our viewpoint. If this is not the case, a system could have planets without Keppler being able to detect them.
Yah, they'll have to corroborate with other methods, such as wobble detection.
Any other methods? other then the gravitational tug, and/or the transit method?
The gravitational tug [wobble] would be the most convincing I imagine?