José Manuel NievesSEGUIR Updated: Save Send news by mail electrónicoTu name *
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When it comes to the Universe, the numbers can be dizzying. We live in a galaxy that contains about 400,000 million stars , most of them with one or more planets, and “out there”, beyond the borders of our Milky Way , the galaxies are counted by the billions.
Now, a team of astronomers led by Michelle Kunimoto , the University of British Columbia , has just carried out an estimate of the number of planets in our galaxy similar to Earth. And the result is 6,000 million , a giant amount but which represents just a small percentage of the total number of worlds that contains the Milky Way. The study was just published in The Astronomical Journal.
To be considered similar to the Earth , a planet must be rocky, about the same size as ours and to be, in addition to, in orbit around a star type G , similar to the Sun. It also has to orbit in the “zone of habitability” of that star, the correct distance so that the surface temperature of the planet allows the existence of liquid water, one of the fundamental ingredients for life.
Of the close to 400,000 million stars of the Milky Way, near the 7% are of type G . And that means that in our galaxy there are about six thousand million stars with the ability to have planets similar to Earth.
“My calculations -explained Kunimoto – set an upper limit of 0,18 Earth-like planets for every star type G . To estimate how common they are, the different types of planets around different classes of stars can provide important information about the formation of planets and their evolution, and thus help to improve future missions dedicated to discovering”.
Due to its small size, the planets, as the Earth tend to be overlooked by instruments such as the probe Kepler, dedicated to the systematic search of new worlds. And that means that their number is very small in comparison to other larger types of planets discovered by astronomers. To overcome this difficulty, Kunimoto used a technique known as ” modeling forward “.
“I Started by simulating the full population of exoplanets around the stars studied by the Kepler mission -explains the researcher-. After I marked each planet as ‘ detected ‘ or ‘ lost ‘, depending on the likelihood that my search algorithm would have found. Then, I compared the planets detected with my actual catalog of planets . If the simulation resulted in a close match, then the initial population probably represented correctly-the actual population of planets orbiting around those stars”.
The work of Kunimoto and colleagues also threw more light on one of the most controversial questions about exoplanets: the so-called ” gap radio “. The gap of the radio shows that it is rare for planets with periods orbitals of less than 100 days to have a size between 1.5 and two times that of the Earth . Kunimoto was found that, in reality, the gap of radio exists in a much more narrow range of periods orbital of what is believed. Their results of observation, in fact, provide important constraints on models of planetary evolution that explain the characteristics of the gap of the radio.