In an astronomical first, we may have directly observed a star forming at the same time as a world that orbits it, proving a long-held theory about planet formation.
Planets are thought to form in a disc of dust and gas, also known as a protoplanetary disc, surrounding a host star. Theoretical models suggest planets should begin to take shape while the host star is still growing 鈥� but until now, we have only seen active evidence of planet formation after the star itself had formed.
Looking at a system about 532 light years away, Felipe De Oliveira Alves at the Max Planck Institute for Extraterrestrial Physics in Germany and his colleagues may have directly observed star and planet growth happening at the same time.
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鈥淭heory predicts star and planet formation happening simultaneously, but we just did not have the technology to see it and to better understand it,鈥� says De Oliveira Alves.
Using the ALMA observatory in Chile, the researchers first discovered what may be a growing planet around a star with a mass about twice that of our sun. The researchers were able to do this by observing a gap created as the planetary body accrued matter in the star鈥檚 protoplanetary disc.
They estimate that the planet is between four and 70 times the mass of Jupiter.
The researchers then discovered two streams of gas feeding into the protoplanetary disc. Some of this gas is believed to replenish the materials required for planet growth within the disc, while some of it feeds the still-growing star, which suggests planets form while their star itself is also still forming.
There is more work to do to confirm the observation. De Oliveira Alves and his colleagues note that the planetary body they discovered could actually be what is known as a brown dwarf substar 鈥� an object with more mass than a gas giant planet, but less mass than a star. More analysis should help establish the object鈥檚 true identity, they say.
Seeing star formation occur simultaneously with planet formation will be important, De Oliveira Alves says, because it would suggest ways to refine our models of planet formation.
鈥淣ormally when discussing planet formation, most [researchers] have isolated the problem and focused just on the formation of the planet,鈥� says Zoe Leinhardt at the University of Bristol, UK. 鈥淚 think that is now changing; it is becoming clear that planets 鈥� especially giant planets 鈥� don鈥檛 evolve in isolation. The entire system is dynamic and evolving.鈥�
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