Using a new method of analyzing the data of the NASA’s Kepler telescope that completed its scientific career, astronomers discovered 18 previously unnoticed exoplanets, one of which is the smallest among all known, and the other is located in the habitable zone of its star.
The worlds are so small that previously we simply did not notice them. However, thanks to the new method, we were able to identify them, and, according to our estimates, it will allow us to find more than 100 similar exoplanets in the complete data set of the Kepler mission, the authors of the study write.
Today, more than 4 thousand planets orbiting far stars are known. 96 percent of them are much larger than the Earth and comparable in size to the giants Neptune or Jupiter. However, this percentage most likely does not reflect reality, since tracking down small planets is much more difficult than large ones. In addition, small worlds are interesting targets in search of Earth-like potentially inhabiting planets outside the solar system.
When hunting for exoplanets, scientists mainly rely on the transit method, which is to identify the failure of the luminosity of target stars as they pass through their object disk.
Standard search algorithms attempt to identify sudden drops in brightness. However, in reality, the star’s disk looks slightly darker at the edge than at the center. Therefore, when the planet moves between it and the observer, at the beginning of the transit, it blocks less light than in the middle.
-Rene Heller, lead author of the research from the Institute of Solar System Studies. Max Planck (Germany)
Large planets, as a rule, produce deep and clear changes in the brightness of their stars, but comparable in size to the Earth only slightly distort the light curves, so it is difficult to distinguish them from the natural fluctuations of the star’s brightness and noise, which necessarily accompanies any observation. To solve this problem, the Rene Heller team developed a new analysis algorithm and showed that the sensitivity of the transit method can be significantly improved.
Our new algorithm will help to draw a more realistic picture of the population of exoplanets in space. This method represents a significant step forward, especially in the search for worlds like Earth.
-Michael Hippke, co-author of the study from the Zonneberg Observatory (Germany)
To test their algorithm, astronomers chose 517 stars in the K2 campaign data of the Kepler telescope, in which at least one transit planet is already known. And, having conducted a repeated analysis, they were able to reveal 18 more previously out-of-mind extrasolar worlds. They all fall into the category of exoplanets the size of Earth. The smallest of them is one third smaller than our planet, and the largest is more than twice as large as the Earth.
In most of the planetary systems that we studied, the newly discovered planets are the smallest among the neighbors. Moreover, most of them rotate closer to their stars than their previously known companions. This means that their surfaces are hotter than 100 degrees Celsius, and some are heated to 1000 degrees Celsius. The only exception is one new world, it is probably located in the habitable zone of its red dwarf, that is, it can have rivers, seas and oceans.
-Kai Rodenbek, co-author of the study from the University of Göttingen (Germany)
Astronomers point out that even their more accurate method may be blind to other planets in the systems that they investigated, in particular, to small worlds in distant orbits.
In the future, scientists plan to double-check the complete data set of the Kepler mission, including the light curves of hundreds of thousands of stars. They believe that their method will allow to find more than 100 other worlds the size of Earth.
18 previously unnoticed exoplanets discovered
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