Three discs to watch live the birth of new extrasolar planets. With the SPHERE instrument, mounted on the VLT (Very Large Telescope) ESO, it was possible to "capture" a clear, detailed and the special structures in the planet-forming disks around young stars.
SPHERE, which saw first light in 2014, has allowed researchers to witness the complex dynamics of
the young planetary systems - including one that is literally changing before our eyes. The results recently published in three studies (see Lonk to bottom) in Astronomy & Astrophysics who also participated researchers National Institute for Astrophysics (INAF), highlight the considerable ability of the instrument to capture the forms that sculpt planets the disks from which they form, showing the complexity of the environment from which new worlds are born. SPHERE has been used by the team of astronomers to shed light on the evolution enigmatic infant planetary systems. The explosion in recent years in the number of known exoplanets has made their study one of the most active fields of modern astronomy.
HOW TO FORM THE PLANETS. We now know that planets form by large gas and dust disks around stars present newborn, known as protoplanetary disks, and that stretch for thousands of millions of kilometers. With the passage of time, the particles that form the protoplanetary disk collide, combine and eventually grow to global proportions. The most minute details of the evolution of these disks, however, are still unknown.
SPHERE, built by a European consortium that also includes the Naazionale Institute of Astrophysics, is a recent addition to the instrumental park of the VLT and, with its combination of innovative technologies, is very effective in getting direct and detailed images of the protoplanetary disks .
The instrument uses a particular combination of adaptive optics to remove the distortions induced by the atmosphere on the images, a coronagraph to block most of the light from the central star and a combination of differential images and polarimetry to isolate the light produced by the disc structures .
ENIGMA OPEN. The interaction between the protoplanetary disks, and the growing planets can shape the discs in different forms: large rings, spiral arms or voids in the shade. They are particularly interesting because it has not yet identified a clear link between the structures and the planets that form. It is a mystery that astronomers are trying to unravel. Fortunately, the direct observation of these amazing structures in the protoplanetary disks is within reach of SPHERE, with its ability to return packed pictures.
Elizabeth Rigliaco, post-doc researcher at the INAF Padova, explained: "The analysis and modeling of these complex structures allows us to obtain a lot of information on disk geometry, the dynamic processes that take place within it, and the presence any planets that work to carve the observed structures. "
"SATURN" NTH POWER. Take for example RXJ1615, a young star in the constellation Scorpius, about 600 light years from Earth. A team led by Jos de Boer (has nothing to do with the former Inter coach, works of Leiden Observatory in the Netherlands), has found a complex system of concentric rings surrounding the young star that looks like a titanic version of Saturn's rings. Pictures of an intricate sculpture of rings like this have so far been obtained only for a handful of stars. The disc shows signs of the effect produced by planets still in the process of formation.
"The whole system seems to have more than 1.8 million years," he stressed Silvano Wants researcher INAF Padova, which determined together with the age of the star connecting Sergio Messina (INAF Catania) and its other key features. "The age of the protoplanetary disk just revealed makes RXJ1615 an exceptional system, since most of the other disks so far found are relatively old or evolved."
The unexpected result of De Boer was immediately taken up by the findings of another team led by Christian Ginski, always on the strength of Leiden Observatory, who observed the young star HD97048 in the constellation Chamaeleon, about 500 light years from Land. By means of a detailed analysis we have been able to locate the concentric rings also in the still immature disk around this star.
The symmetry in these two systems is surprising, since most of protoplanetary systems contain asymmetric spiral arms, voids and vortices. These discoveries make grow the number of known systems in which rings are present multipi with high degree of symmetry.
DISCS ASYMMETRIC. A particularly spectacular example of asymmetric disk, the most common, was obtained by a group of astronomers, led by Tomas Stolker dell'Anton Pannekoek Institute for Astronomy, Netherlands. The disk surrounding the star HD135344B, about 450 light-years away. Despite this star has been well studied in the past, SPHERE has allowed to observe the protoplanetary disk with a detail never seen before. It is thought that the very large central cavity and the two structures that resemble the spiral arms have been created by one or more massive protoplanets, destined to become similar to Jupiter.
Also you can see four dark bands, apparently shadows cast by the moving material in HD135344B disk. It is interesting to note that one of these bands has changed considerably in the months between the various periods of observation: a rare example of planetary evolution observed in real time.
This suggests that changes in the inland areas of the discs can not be directly observed by SPHERE. In addition to producing very beautiful pictures, these wavering shadows provide a unique way to investigate the dynamics of the inner regions of the disk. As well as the concentric rings found by de Boer and Ginski, these observations of the team of Stolker show that the complex and changing environment of discs around young stars still reserving new surprises.
"SPHERE is providing an impressive amount of high quality data on protoplanetary disks. This brings us closer to understanding the interaction of with the disks from which planets are formed - and hence the same planet formation, "concludes Rigliaco.
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