'Revolutionary' New View of Baby Planets Forming Around a Star

Welcome to HL Tauri — a star system that is just being born and the target of one of the most mind-blowing astronomical observations ever made.

Observed by the powerful Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, this is the most detailed view of the proto-planetary disk surrounding a young star 450 light-years away. And those concentric rings cutting through the glowing gas and dust? Those, my friends, are tracks etched out by planets being spawned inside the disk.

In short, this is the mother of all embryonic star system ultrasounds. But this dazzling new observation is so much more — it’s a portal into our solar system’s past, showing us what our system of planets around a young sun may have looked like over 4 billion years ago. And this is awesome, because it proves that our theoretical understanding about the evolution of planetary systems is correct.

However, there are some surprises.

“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,” said Stuartt Corder, ALMA Deputy Director.

“When we first saw this image we were astounded at the spectacular level of detail,” said Catherine Vlahakis, ALMA Deputy Program Scientist. “HL Tauri is no more than a million years old, yet already its disc appears to be full of forming planets. This one image alone will revolutionize theories of planet formation.”

After a star sparks to life from the gravitational collapse of a star-forming nebula, the leftover gas and dust will collect around the star, creating a disk. Conventional theory suggests that, over time, the disk cools and small particles begin to accrete, forming small pebbles, then asteroids, then planetesimals and, eventually, planets.

As these embryonic planetary bodies orbit the star, they clear a track in the remaining disk of dust, ‘vacuuming’ up the remaining debris with their increasing gravitational dominance, continuing to bulk up their mass.

And this is exactly what we are seeing here. HL Tauri has a protoplanetary disk that is being populated with planets carving out their individual orbital paths. Eventually, the majority of the dust in HL Tauri will be consumed by the growing population of asteroids and planets, maturing into a stable star system like ours. However, the star system seems to be growing up fast, a puzzle that astronomers will no doubt be trying to understand for some time to come.

ALMA is nearing completion and this is the first precision observation in it’s near-fully commissioned configuration. Using the technique of long-baseline interferometry, ALMA is composed of many individual antennae spread over a large area. The distance between the antennae mimics one large antenna spread over a huge area. ALMA can therefore beat the precision of any other observatory on Earth or even in space, including Hubble.

Read more at Discovery News