While taking the Atacama Large Millimeter/submillimeter Array’s new high-resolution mode for a test run, astronomers managed to snap a phenomenal photograph that far exceeded their expectations. The image shows a young star, named HL Tauri, and its planet-forming disk in astonishing detail.
HL Tauri, which is less than a million years old, is located some 450 light-years from Earth in the constellation Taurus. Cloudy, concentric rings of dust and gas surround the Sun-like star, which are the remnants from its birth. Amidst these rings, dark gaps can clearly be seen, which suggest that planet formation is already taking place.
Compositite image of HL Tauri and its surroundings. ALMA (ESO/NAOJ/NRAO), ESA/Hubble and NASA, Judy Schmidt.
“These features are almost certainly the result of young planet-like bodies that are being formed in the disc,” said ALMA Deputy Director Stuartt Corder in a news release. “This is surprising since such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image.”
Astronomers believe that stars and planets are forged inside a collapsing cloud of dust and gas located within a much bigger cloud called a nebula. As gravity draws the material inside the cloud closer together, it becomes compressed and starts to rotate. Eventually, the spinning cloud flattens into thin a disk, called a protoplanetary disk, where asteroids, comets and planets eventually form.
As the disk continues to spin, material within it collides and sticks together in clumps, forming the beginnings of planets. When these bodies acquire enough mass, they start to remodel their surroundings, carving rings and gaps into the disk as they hungrily pull in more and more material. And that’s what ALMA’s latest image is showcasing in more detail than ever seen before. But the spectacular sharpness of the image isn’t the only reason that it’s titillating astronomers; HL Tauri was thought to be far too young to be churning out planets, so the fact that this process is already well underway suggests that planet formation could be much faster than originally believed.
“HL Tauri is no more than a million years old, yet already its disc appears to be full of forming planets,” ALMA Deputy Program Scientist Catherine Vlahakis said in a news release. “This one image alone will revolutionize theories of planet formation.”
HL Tauri can’t be seen in visible light because it’s masked by a shield of dust and gas. But ALMA is able to peer through this cloudy veil because it observes at much longer wavelengths. Its outstanding resolution capabilities were made possible by comparing the signal from numerous antennas that were spaced up to 15 km apart.
Hopefully, ALMA will keep up the good work because images like this are key to understanding how our own planet likely formed within the Milky Way billions of years ago. While physicists have a good idea of how planets form, this is largely based on theories rather than observational data, but it seems that ALMA is set to change that.
Artist's impression of a young star and its protoplanetary disk. ESO/L. Calçada