The image above is not an illustration. If your eyes could detect the long wavelengths between radio and infrared, and were sharp enough to resolve structures around a star 450 light-years away, you might see something like that.
The psychedelic swirl is actually a dusty disk of debris surrounding the young, sunlike star HL Tau. Only about 1 million years old, this star — and that disk — have been captured in the process of birthing planets. It’s the most detailed image of planetary genesis shot so far, and was made with a cluster of telescopes in the southern hemisphere called the Atacama Large Millimeter/submillimeter Array.
Normally, planets grow from the swirling mass of gas and dust surrounding a young star; as clumps of that material begin sticking together, they form larger and larger bodies whose gravity attracts more and more material. Put simply, scientists think the outcome of this clumping differs depending on where the process is happening in the disk, which is why you sometimes end up with a rocky Earth, other times with a gassy Jupiter, and other times with an icy Neptune.
So where are the planets in this image?
Sometimes, the answers lie in what you don’t see. When planets grow big enough, they carve gaps in their disks (cc: Pluto). The new worlds sweep up or push away all those particles in their orbits, leaving a telltale void that suggests the presence of a young, mighty planet.
Scientists think that is what’s happening in the image above: Some of those dark, concentric stripes and splotches are the gaps produced by growing planets. The observation is a little surprising because HL Tau is still incredibly young, and it takes planets a while to grow big enough to produce those rings and splotches.
“These features are almost certainly the result of young planet-like bodies that are being formed in the disc. 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,” Stuartt Corder, ALMA Deputy Director, said in a statement.
To capture HL Tau and its curious disk, astronomers arranged the array’s 66 telescopes in a new configuration that allowed higher-resolution imaging. The result is an image even the Hubble Space Telescope would have a tough time generating. In the wavelengths Hubble sees, HL Tau and its disk are obscured by the surrounding gas and dust. But ALMA’s eyes can pierce that shroud and see the structures it hides.