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HL Tau hides real planets


The shot was taken in October 2014 when the Atacama Large Millimeter / submillimeter Array in Chile showed excellent and never before seen details in the protoplanetary disk of this young system. An animated debate has always been encountered between astronomers because around the concentric circles dark, it would hide planets in formation.
A group of astrophysicists from the University of Toronto have revisited a famous image of the cosmos, finding that the gaps in the disk of dust and gas around the young star HL Tau are actually planets in formation. The expert team is led by Daniel Tamayo. “This image of HL Tau is probably the first taken to study the early stages of planet formation,” said Tamayo. “This could be a huge step forward in our ability to understand how planets form.”

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Credit: ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY (ALMA)

This famous image was taken in October 2014 (Click HERE to read the article on Media INAF) by ALMA (Atacama Large Millimeter / submillimeter Array), which showed excellent detail never before seen in the protoplanetary disk. What you see is one of the first observations made by ALMA in its almost final configuration and one of the sharpest images ever made to sub-millimeter wavelengths.
Its publication has created a heated debate in the scientific community. Initially it was already assumed that the gaps could indicate the presence of planets in the making, but many were skeptical. For some, these concentric circles darker (i.e. “empty”) could not contain planets because they are too close to each other. The planets – according to this hypothesis – would be expelled due to the force of gravity. The study conducted by the Canadian team argued, however, the theory of planetary formation, because these blanks would be kept separate from what Tamayo calls “a special configuration of resonance”. For billion years, something similar happened between Pluto and Neptune, because their orbits intersect but the two planets never touched each other.
The HL Tau has less than a million years, to a radius of about 17.9 billion kilometers and is located 450 light years from Earth in the constellation Taurus. Already in 2014 the researchers had claimed that the disc of HL Tauri was much more developed than was expected given the age of the system. Thus, the image of ALMA had already suggested that the process of planet formation was faster than expected. Since young systems as HL Tau are enveloped by a dense cloud of gas and dust, and therefore cannot be seen with visible light, it comes to the rescue just ALMA using a series of radio telescopes are located 15 kilometers away using wave lengths much longer. “We found thousands of planets around other stars and it is surprising that many of the orbits are much more elliptical than those found in our Solar System,” said Tamayo. And in the future it will find out much more about exoplanets thanks to ALMA.

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Dan­iel Ta­ma­yo – Uni­vers­ity of To­ron­to

For now, because young, the system HL Tau remains relatively stable, but Tamayo believes that over billions of years, it will become a kind of “time bomb”: eventually the planets will disperse and many will be expelled violently leaving other bodies in elliptical orbits similar to those found around older stars. This “explosive” process does not seem to have occurred in our solar system, and in future the experts will be able to understand whether it is typical of other systems or not.

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