The Best Baby Picture Ever of a Planetary System


Protoplanetary disc surrounding the young star HL Tau.

Protoplanetary disc surrounding the young star HL Tau. ALMA (ESO/NAOJ/NRAO)



Astronomers have taken the best picture yet of a planetary system being born. The image, taken by the Atacama Large Millimeter/submillimeter Array (ALMA) in the high-altitude desert in Chile, reveals a planet-forming disk of gas around a young, sun-like star, in great detail.


“The first time I saw this image, I thought it was actually probably a simulation—it was way too good,” said Tony Beasley, director of the National Radio Astronomy Observatory, in a video accompanying a press release. The NRAO helps operate ALMA.


The disk has gaps and rings that are carved out by nascent planets—features that have only been modeled in computer simulations. The star, named HL Tau, is 450 light-years away in the constellation Taurus. It’s only about a million years old—remarkably young to be already giving birth to planets.


A star forms when a cloud of gas and dust collapses under its own weight. As the embryonic star comes together, it spins, and the excess gas and dust flatten out into a surrounding disk like a pizza. All that stuff in the disk starts to form particles that then clump together, accumulating until they eventually form asteroids, comets, and planets. As those budding bodies grow, they plow through the remaining material in the disk, creating the gaps and rings seen in the new ALMA image.


HL Tau's surroundings, as seen by Hubble.

HL Tau’s surroundings, as seen by Hubble. ALMA (ESO/NAOJ/NRAO), ESA/Hubble and NASA




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