Scientists discover 18 new planets beyond the solar system, one of them could harbour alien life

Scientists have discovered 18 Earth-sized planets beyond solar system, including one of smallest kwn so far and ar that could offer conditions friendly to life.

exoplanets are so small that previous surveys h overlooked m, said researchers at Max Planck Institute for Solar System Research (MPS) in Germany.

study, published in journal Astromy & Astrophysics, re-analysed a part of data from NASA's Kepler Telescope with a new and more sensitive method that y developed.

team estimates that new method has potential of finding more than 100 ditional exoplanets in Kepler mission's entire data set.

Somewhat more than 4,000 planets orbiting stars outside our solar system are kwn so far.

Of se so-called exoplanets, about 96 per cent are significantly larger than our Earth, most of m more comparable with dimensions of gas giants Neptune or Jupiter.

This percent likely does t reflect real conditions in , however, since small planets are much harder to track down than big ones.

Moreover, small worlds are fascinating targets in search for Earth-like, potentially habitable planets outside solar system.

18 newly discovered worlds fall into category of Earth-sized planets.

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smallest of m is only 69 per cent of size of Earth; largest is barely more than twice Earth's rius.

Common search algorithms were t sensitive eugh, researchers said.

In ir search for distant worlds, scientists often use so-called transit method to look for stars with periodically recurring drops in brightness.

If a star happens to have a planet whose orbital plane is aligned with line of sight from Earth, planet occults a small fraction of stellar light as it passes in front of star once per orbit.

Small planets, however, present scientists with immense challenges.

ir effect on stellar brightness is so small that it is extremely hard to distinguish from natural brightness fluctuations of star and from ise that necessarily comes with any kind of observation.

team, including Rene Heller from MPS, has w been able to show that sensitivity of transit method can be significantly improved, if a more realistic light curve is assumed in search algorithm.

new algorithm does t search for abrupt drops in brightness like previous standard algorithms, but for characteristic, grual dimming and recovery.

This makes new transit search algorithm much more sensitive to small planets size of Earth.

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"Our new algorithm helps to draw a more realistic picture of exoplanet population in ," said Michael Hippke of Sonneberg Observatory.

"This method constitutes a significant step forward, especially in search for Earth-like planets," Hippke said.

"In most of planetary systems that we studied, new planets are smallest," said Kai Rodenbeck of University of Gottingen in Germany.

Most of new planets orbit ir star closer than ir previously kwn planetary companions.

surfaces of se new planets refore likely have temperatures well in excess of 100 degrees Celsius; some even have temperatures of up to 1,000 degrees Celsius.

Only one of bodies is an exception: it likely orbits its red dwarf star within so-called habitable zone.

At this favourable distance from its star, this planet may offer conditions under which liquid water could occur on its surface -- one of basic prerequisites for life as we kw it on Earth.