Forming planets observed by the ALMA telescope

Picture of the HL Tauri system with its forming planets taken by the ALMA telescope (Image ALMA (ESO/NAOJ/NRAO))
Picture of the HL Tauri system with its forming planets taken by the ALMA telescope (Image ALMA (ESO/NAOJ/NRAO))

In September 2014, ESO’s ALMA (Atacama Large Millimeter/submillimeter Array) telescope began the long baseline campaign, the one with the antennas separated by the maximum length achieved so far, which is 15 km away (a little more than 9 miles). In this mode, more powerful than before, ALMA observed with great results HL Tauri, a young star about 450 light years from Earth. It’s surrounded by a disk of dust that is slowly coalescing in certain areas to form planets.

HL Tauri is a star of T Tauri type, meaning a star that is very young and in the early stages of its life. Its estimated age is in fact under a million years and hasn’t yet entered the main sequence, which is the stable phase and the longest of its life. The considerable amount of dust and gas which now surrounds this star hides it to visible light but ALMA can observe it in different wavelengths.

HL Tauri’s proto-planetary disk of dust and gas has been known for a long time and is one of the elements that made it an ideal candidate for the new observations with ALMA. The results were sensational, with the sharpest pictures ever made at the wavelengths observed by this telescope. Those studies are helping to understand the development of solar systems.

ALMA allowed to see that the disk of dust and gas is divided into concentric rings separated by gaps in which matter is coalescing to form planets. The resolution achieved in the images is five times the distance between Earth and the Sun. To understand the quality, just think that it’s better than what can be obtained using the Hubble Space Telescope.

The details of the images are really extraordinary and very interesting from a scientific point of view. Astronomers didn’t think that a star that’s almost newborn could already have forming planets. According to Catherine Vlahakis, ALMA’s deputy scientific director and scientific director for the long baselines campaign, these images are enough to revolutionize the theories of planet formation.

ESO Director General Tim de Zeeuw pointed out that our understanding of planet formation was based on theories that were used to build computer simulations or artistic representations. Now, thanks to an amazing instrument such as ALMA we can directly observe solar systems in the early stages of their lives.

Observing HL Tauri is like going back in time by more than four billion years to observe the early stages of life of the solar system and the formation of the Earth and the other planets. Watching other very young solar systems will allow to get real data on those events. We can expect more images that will be breathtaking and at the same time outstanding from the scientific point of view.

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