Astronomers have long theorized that planetary systems, including our own, are formed by spinning discs of dust-and-gas that slowly coalesce. Now, by combining input from an array of radio telescopes located in the Chilean desert, they have sharp images showing what they believe to be just such planet formation.
EarthSky.org explains the theory like this: "As the clouds spin, they flatten out into these disks. Over time, the dust particles in the cloud begin to stick together by a process known as [accretion], and that process is what ultimately forms the planets like our Earth, and moons like our moon, plus the asteroids, all of which mostly still move (as they did in the original cloud) in this flat space – this disk-like space – encircling the parent star."
The image above of the mere 100,000-year-old HL Tauri, located about 450 light years away in the constellation Taurus, also appears to show a massive protoplanetary disc.
Although hints of HL Tauri's disc have been seen before, in visible light, it is largely obscured. By contrast, the Atacama Large Millimeter/submillimeter Array, or ALMA, "operates in such a way that it can see through the cloud and study the processes right at the center. This new ALMA image provides the clearest evidence to date that not only does this process occur, but also that it is faster than previously thought," the radio observatory notes.
The National Radio Astronomy Observatory adds that "features in this system, including multiple concentric rings separated by clearly defined gaps ... suggest that planet formation is already well underway around this remarkably young star."
ALMA Deputy Director Dr Stuartt Corder: "These features are almost certainly the result of young planet-like bodies that are being formed in the [disc]."