Yesterday, the European Southern Observatory released the first images taken with the upgraded version of its ALMA telescope. The images capture a disk of material orbiting the young star HL Tauri in exquisite detail, showing gaps in the disk that are likely to be created by the formation of larger, potentially planet-sized bodies.

ALMA stands for the Atacama Large Millimeter/submillimeter Array. As its name implies, it's located in the Atacama Desert, one of the driest regions on the planet. It's also placed at 5,000 meters above sea level; the combination limits the imaging complications posed by Earth's atmosphere. ALMA is an array of multiple individual telescopes, with the final image constructed by mathematically processing the input of each individual telescope.

The final resolution of these images depends on the distance among the telescopes, and ALMA has just received an upgrade that places them up to 15 kilometers apart. This is close to the planned final configuration (which will allow 16km separations) and much larger than previous telescopes that imaged at this wavelength, which were limited to separations of about 2km.

The millimeter range sits between infrared and radio wavelengths. It's produced by relatively cold objects, like clouds of gas and dust, and it's not absorbed by many of the materials that can shroud distant objects from view. As such, ALMA should provide a new window into the formation of stars and planets, which often start out in cool, dense clouds.

HL Tauri is a very young star that's about 450 light years from Earth and sits inside a molecular cloud, material that is cool enough to allow the formation of molecules (as opposed to an energetic, ionized gas). Molecular clouds are sometimes referred to as "stellar nurseries," and the Taurus molecular cloud appears to be no exception. HL Tauri is an extremely young star, one that has yet to initiate stable nuclear fusion, instead being powered largely by the energy released as it contracts under the pull of gravity.

There were signs that HL Tauri also played host to a disk of material of the type that is thought to give birth to planets. So, it made a good target to test out ALMA's newly built optical muscles. And ALMA definitely delivered, revealing not only the presence of the disk, but lots of details of its internal structure.

The gaps seen in the image are typically cleared out by the presence of larger bodies—potentially planet-sized—in the area or influenced by the presence of gravitational resonances among multiple planets in a single system. Either option suggests that planet formation is well under way in the HL Tauri exosolar system—before there's even a fully formed star present.

Existing models of planet formation suggest that the process shouldn't be able to produce bodies of sufficient size to create these gaps within the relatively short time that HL Tauri has existed. So, this will almost certainly not be the last time that ALMA directs its gaze to HL Tauri, and the full description of these observations may cause a rethink of our models of planetary formation.