Scientists for the first time have calculated the approximate number of large "rogue planets" in the Galaxy that do not have their own star. It turned out that there are about ten times less of them than previously thought, according to an article published in the journal Nature Astronomy.
“We found that 'rogue planets' with a mass of Jupiter are at least ten times more common than we previously thought. On the other hand, this discovery did not come as a surprise - it is in good agreement with the observations of potential planets in the "stellar nursery" and corresponds to theoretical predictions about the frequency of appearance of large "rogue", - says Przemyslaw Mroz from the University of Warsaw (Poland), quoted by Space.com.
Over the past ten years, astronomers have discovered several extremely dim and cold celestial bodies in the nearby regions of the Galaxy, which they called "rogue planets." Their nature remains the subject of controversy among planetary scientists.
In particular, some researchers consider the "rogue planets" to be unusually large doubles of Jupiter, thrown out of the systems that gave birth to them as a result of gravitational interactions between the nascent celestial bodies. Other astronomers believe, referring to their size and temperature, that they are actually unborn stars, the so-called brown dwarfs, whose mass is too small for the start of thermonuclear reactions in their bowels.
Mroz and his colleagues carried out the first census of such objects in the history of science based on data collected by Polish astronomers as part of the OGLE project while observing how the gravity of various inhabitants of the solar system, including "rogue planets", bends the light of distant stars into paths to Earth.
How long and how much an object distorts light is directly related to its mass and size. This allows scientists to fairly accurately calculate the values of both parameters, observing the formation of the so-called "Einstein's lens" - a ring of light that occurs as a result of the gravitational bending of the rays of stars.
In total, Polish scientists and their colleagues have traced about 2,600 curvatures of light from stars generated by other luminaries, brown dwarfs and planets. This number of events was enough to understand how common "rogue planets" are and what their typical sizes are.
In total, astronomers managed to find six events, presumably generated by the "rogue planets". None of them were large - they all looked like Earth or its large rocky counterparts in other stars. All this indicates that in the Galaxy there are not hundreds of billions of large "rogue planets", but much less - for every four stars of the Milky Way, according to the calculations of Mroz and his colleagues, there is only one, not ten such planets.
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Such census results, according to scientists, indicate that large planets "catapult" from newborn star systems much less frequently than relatively small celestial bodies. Whether this is true or not, it is still quite difficult to verify, since to observe the "outcasts" one needs powerful space infrared telescopes like the American orbital observatory WFIRST and its European "brother" Euclid, which will be put into orbit no earlier than the beginning and mid-2020s. …
