A new series of observations suggests that planets might start forming before a star is fully formed. A team of European researchers discovered that around protostar TMC1A there is a distinct lack of carbon monoxide radiation and they suspect that millimeter-sized grains of dust have been absorbing it.

The growth of dust grains is the first step in the formation of planets, but this system appears to have started the process too early. The star hasn’t finished growing yet. As reported in Nature Astronomy, these findings suggest that some planets might form before their star reaches maturity. The team estimates that there are definitely enough dust grains in the stellar disk to form a planet the size of Jupiter.

"The results indicate that planets already start forming while the star is still developing. The star is only half to three-quarters of its final mass. This is new," said lead researcher Daniel Harsono, from Leiden University in the Netherlands, in a statement.

There are lots of uncertainties when it comes to the formation and early evolution of star systems. The material present, the type of star that is forming, and the subtle interactions between the protoplanets all play a role. Timings have also been suspected to come into play but so far, there was no evidence to support the early formation of giant planets.

"It can be an explanation for the formation of giant planets that are comparable to Jupiter and Saturn," added Per Bjerkeli from Chalmers University. "Only early protoplanetary discs contain sufficient mass to form giant planets." 

TMC1A is clearly a big piece of evidence for planetary formation, but it is not clear if it is just an exception to the rule. This particular system might simply be a bit too eager when it comes to planet formation. It's possible that there isn't one single model that applies to all stellar disks, while factors we are yet to consider might be important.

The team is planning observations of similar protostars to better understand the potential early formation of dust grains. This research was conducted with the Atacama Large Millimeter/submillimeter Array (ALMA), a collection of 66 radio telescopes that work as one. ALMA has already snapped some pretty incredible images of forming exoplanets (check out this one, for example) and is capable of studying stellar systems in their infancy.