![]() As a first test sample for their new algorithm, the researchers decided to re-analyze all 517 stars from K2 that were already known to host at least one transiting planet. After a technical defect, the telescope had to be used in an alternative observing mode, called the K2 mission, but it nevertheless monitored more than another 100,000 stars by the end of the mission in 2018. In the first mission phase from 2009 to 2013, Kepler recorded the light curves of more than 100,000 stars, resulting in the discovery of over 2300 planets. The researchers used data from NASA’s Kepler space telescope as a test bed for their new algorithm. "This method constitutes a significant step forward, especially in the search for Earth-like planets." ![]() "Our new algorithm helps to draw a more realistic picture of the exoplanet population in space," summarizes Michael Hippke of Sonneberg Observatory. René Heller's team has now been able to show that the sensitivity of the transit method can be significantly improved, if a more realistic light curve is assumed in the search algorithm. Their effect on the stellar brightness is so small that it is extremely hard to distinguish from the natural brightness fluctuations of the star and from the noise that necessarily comes with any kind of observation. Small planets, however, present scientists with immense challenges. Large planets tend to produce deep and clear brightness variations of their host stars so that the subtle center-to-limb brightness variation on the star hardly plays a role in their discovery. The maximum dimming of the star occurs in the center of the transit just before the star becomes gradually brighter again," he explains. When a planet moves in front of a star, it therefore initially blocks less starlight than at the mid-time of the transit. "In reality, however, a stellar disk appears slightly darker at the edge than in the center. René Heller from MPS, first author of the current publications. "Standard search algorithms attempt to identify sudden drops in brightness," explains Dr. If a star happens to have a planet whose orbital plane is aligned with the line of sight from Earth, the planet occults a small fraction of the stellar light as it passes in front of the star once per orbit. In their search for distant worlds, scientists often use the so-called transit method to look for stars with periodically recurring drops in brightness. Common search algorithms were not sensitive enough. And they have another thing in common: all 18 planets could not be detected in the data from the Kepler Space Telescope so far. The smallest of them is only 69 percent of the size of the Earth the largest is barely more than twice the Earth's radius. The 18 newly discovered worlds fall into the category of Earth-sized planets. Moreover, small worlds are fascinating targets in the search for Earth-like, potentially habitable planets outside the solar system. This percentage likely does not reflect the real conditions in space, however, since small planets are much harder to track down than big ones. Of these so-called exoplanets, about 96 percent are significantly larger than our Earth, most of them more comparable with the dimensions of the gas giants Neptune or Jupiter. Somewhat more than 4000 planets orbiting stars outside our solar system are known so far. The scientists describe their results in the journal Astronomy & Astrophysics. The team estimates that their new method has the potential of finding more than 100 additional exoplanets in the Kepler mission’s entire data set. The researchers re-analyzed a part of the data from NASA's Kepler Space Telescope with a new and more sensitive method that they developed. One of them is one of the smallest known so far another one could offer conditions friendly to life. The worlds are so small that previous surveys had overlooked them. Scientists at the Max Planck Institute for Solar System Research (MPS), the Georg August University of Göttingen, and the Sonneberg Observatory have discovered 18 Earth-sized planets beyond the solar system.
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