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Plutons in the dust


ALMA has identified around the young star HD 107146 – a sort of “Sole teenager” – a swarm of planetesimals large as Pluto and an abnormal rut in dust disk.
Shines at 90 light-years away in the constellation Coma Berenices, and is a star poised between childhood and maturity. Like any teenager, HD 107146 (its name) knows how to surprise those who – like the 66 antennas of ALMA, the Atacama Large Millimeter / submillimeter Array – are able to penetrate the impenetrable armor. Armor formed by a disk of dust. And it is the distribution of the dust of the protoplanetary disk to surprise: contrary to what common sense would suggest, and what actually happens in the stars even younger, around HD 107146 dust thickens much more in extreme periphery than in the center.

Artist impression of the debris disk around HD 107146

Source: NRAO/AUI/NSF

To find out, a team of astrophysicists led by Luca Ricci- is appointed to do research at the famous Smithsonian Center for Astrophysics Harvard after he passed, in order through the State University of Milan (for graduation), in Monaco (for the PhD, carried out at ESO) and, for the postdoc at Caltech, California.
Ricci and colleagues will publish these results in The Astrophysical Journal and they are more than a surprise, actually they represent the confirmation of a suspect they already had. According to the latest models, a higher density of dust in the outer regions of the disk, as has been found in the course of this observation can be explained only by the presence of newly formed celestial bodies with size comparable to that of Pluto. Their severity perturbs the orbits of planetesimals (planetesimals are solid objects thought to exist in protoplanetary disks and in debris disks.) minor fact, increasing the frequency of their collisions and, consequently, an increase of the powder, as detected by ALMA.
“The debris disk observed by us,” says Luca Ricci, referring to the belt of debris around HD 107146, “around a star that has the same mass as the Sun, but with” only “100 million years of life, So about 50 times younger. These observations allow us then to study a planetary system like our solar system could be in his teens. In particular, the range of objects beyond Neptune (the Kuiper Belt) was, in the past, much more massive than it is now, and has played a key role on the current architecture of the planets. Our observations thus, allow investigate fundamental processes for the dynamics and evolution of these systems. ”
But that’s counter-intuitive distribution of dust is not the only surprise emerged from observations of HD 107146. Around the young star has been indeed discovered a sort of gigantic “groove” – more than a billion kilometers wide – where the own debris seem to be missing. The region is located at a distance from the star of approximately two and a half times that separating Neptune from the Sun, so much closer to the center of the system than the area we were talking about earlier, one where crowding dust and planets are similar to Pluto. And to trace the abnormal groove sweeping away the debris, the scientists suggest that they may have been forming a planet with a mass similar to that of the Earth.
Two discoveries, this one and the previous one, made possible only thanks to the capabilities of interferometric antennas the Atacama Large Millimeter / submillimeter Array. “ALMA was crucial for this study due to its unprecedented sensitivity we were able to study in great detail the distribution of the dust from which we can draw information on the physical mechanisms that govern the evolution of planetesimals or current asteroids and comets. In the past, similar instruments had observed HD 107146, but no one had been able to study the spatial distribution of the dust, “says Ricci,” and therefore to obtain information relevant to the dynamics of this system. “

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