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3,000 years of distance from us, astronomers might have found what had for so long looking for: a planet “twin” of the Earth. And is that, among the more than 4,000 exoplanets discovered up to now, KOI-456.04 stands out among all the others . The reason? Orbit around a star that is like our Sun. And does so, moreover, at a distance that would allow that on the surface of that distant world temperatures compatible with life. The finding, which must still be confirmed through new observations, has just been published in Astronomy & Astrophysics.

The hopeful candidate planet was discovered by a team of astronomers led by researchers from the Max Planck Institute for Solar System Research in Göttingen, Germany. is Their star, called Kepler 160, emits visible light, such as our , and not infrared radiation, as is the case with the red dwarfs, weaker and smaller than the Sun, that light to most of the other exoplanets discovered up to now.

space telescopes such as CoRot, Kepler or TESS have enabled the discovery, for the past 14 years, more than 4,000 extra-solar planets different. Most of them, however, are gaseous worlds and giants, comparable in size to that of Neptune, and orbits relatively close around their star host.

But scientists also have discovered some planets, although not too many, rocky, and with sizes similar to that of the Earth. And a handful of them are also found at the right distance from its star so that its surface temperature is allow the existence of liquid water, an ingredient, as far as we know, essential to life . “However -explains René Heller, first author of the article , the full image of the habitability also involves a look at the qualities of the star”. And until now, nearly all the exoplanets from less than twice the size than ours and which have a potential of surface temperatures compatible with life are in orbit of red dwarfs.

The riddle of the red dwarfs

The red dwarfs have an extremely long life, and that’s why they have to favor the fact that the planets that orbit have had double the amount of time that the Earth to form and evolve life. But the greater part of the radiation that they emit those little star is infrared, and not visible light as we know it. Many of them, in addition, emit violent flares of power, which, as has been proven on several occasions now, they can “fry”, literally, to their planets and destroy, therefore, the life that might be on them.

finally, so that the heat received is sufficient for life, these worlds have to be so close to their stars (much fainter than the Sun), the gravity star lllega even deformarlos, abombándolos, and it is thought that the tidal forces could be sufficiently strong to cause in them violent episodes of global volcanism, which would also be fatal to the life.

In other words, these unfavorable conditions make the habitability of planets around red dwarfs it is a question much debated among the scientific community.

A star like the Sun

But in KOI-456.04 everything could be different. In their article, the team of scientists from the Max Planck institute, together with researchers of the Observatory of Sonnenberg, University of Göttingen, the University of California at Santa Cruz and the NASA report on the potential discovery of a planet whose size is less than twice that of the Earth, and that you receive a “light to moderate” a star very similar to the Sun .

about 3,000 light-years away, the star Kepler 160 was already widely estuduada by the probe Kepler, which followed between 2009 and 2013. Its radius is just a little larger than the Sun, its surface temperature is 5,200 degrees (300 degrees minus the Sun) and its luminosity is, also, almost the same, which makes it a true “double” of the star that illuminates the Earth.

six years ago, in addition, it is known that Kepler 160 is the host of two planets, called Kepler 160b and the Kepler 160c. Both are substantially greater than the Earth and continue to orbit very close to the star, so that the temperature make their surfaces in authentic ovens, incompatible with life . But a series of small variations in the orbital period of the planet Kepler 160c provided the scientists with the “signature” of a third planet, which, however, had not yet been confirmed.

Now, Heller and his colleagues have gone back to review those old data in search of another planet additional “hidden” in them. The team of researchers had already succeeded before in similar tasks, to find up to 18 exoplanets “lost” in the old data of Kepler.

A novel technique

When searching for exoplanets, generally astronomers are set in small variations in the brightness of stars that is repeated periodically. These slight attenuations, often less than 1% of the total stellar glare can be caused by planets that go “ahead” of their stars (that is to say, the passing) when observed from the Earth. Heller and his co-workers have perfected the technique of analysis of these subtle changes in brightness up to the point of allowing them to find in the data planets that had gone unnoticed the scrutiny of conventional astronomers. “Our improvement,” explains Heller- is particularly important in the search for small planets, the size of the Earth . The signal is planetary (in these cases) is so weak that it is almost completely hidden in the noise of the data. Our new mask search is something better at the time of separating a true signal exoplanetaria of the noise in the most critical cases”.

The new search algorithm was crucial for the discovery of KOI-456.04. “Our analysis,” continues Heller- suggests that Kepler 160 is not in orbit by two, but by four planets “. One of the two new worlds is Kepler 160d, the head of the orbit distorted Kepler 160c. And the other would be KOI-456.04, which has become formally a candidate for planet, an obligatory step for all the worlds discovered can be passed to the category of “confirmed” after new observations.

According to the researchers, KOI-456.04 has a radius of 1.9 earth radii and an orbital period of 378 days, just 13 more than the Earth. Given the similarity of their host star with the Sun and the orbital period of the planet, almost identical to our own, astronomers believe that both the light and the heat that KOI-456.04 receives from Kepler 160 are practically the same that the Earth receives from the Sun. The light emitted by Kepler 160, in effect, is visible light very similar to sunlight, and KOI-456.04 is located in the habitable zone of their star , the distance range around a star that allows the existence of surface water liquid. In all these senses, therefore, KOI-456.04 can be considered as a “twin” of the Earth.

“KOI-456.01 is relatively large in comparison with many other planets that are considered potentially habitable,” explains Heller-. But it’s the combination of that size from less than twice the Earth and its host star similar to the Sun what makes it so special and the family”.

A greenhouse effect similar to our

As a result of the above, the surface conditions in KOI-456.04 could be, if confirmed in order to their existence, very similar to those of the Earth. The amount of light that it receives from its host star is approximately 93 per cent of the sunlight received on the Earth. If KOI-456.04 had, in addition, an atmosphere mostly inert with a mild greenhouse effect similar to that of our own planet, then its surface temperature would be 5 degrees Celsius on average, about ten degrees lower than the average global temperature of the Earth.

however, currently cannot be ruled out completely that KOI-456.04 is, in reality, a simple coincidence, statistics, or an error of measurement in place of a planet is genuine. Until you perform the final verification, the team estimated that the chances of that are effectively treated of a planet are around 85%. But to obtain the formal status of planet requires the 99%.

Something that must be done with new observations both from the future ground and space applications. Between them, the space mission PLATE , of the European Space Agency, whose launch is scheduled for 2026, and whose aim is precisely that of discovering planets the size of Earth around stars similar to the Sun, has instrumentation sensitive enough to get it. Unfortunately, the precision required for that check is at the limit of the capacity of the instruments currently in service.