by Three is certainly not a crowd for the planets around a distant infant star.
Astronomers had already found two planets forming in the disk of gas and dust, or protoplanetary disk, around the infant star PDS 70. Now, using the James Webb Space Telescope (JWST), astronomers with the MIRI Survey The mid-infrared disk (MINDS) project has seen hints of a third world forming around the new star located about 400 light years from Earth.
Additionally, using JWST’s Near Infrared Camera (NIRCam), the MINDS team observed a large spiral stream of material fueling the growth of one of the previously discovered planets, PDS 70C. This giant planet is already surrounded by its own disk of matter, which is also being fed by this stream and is expected to become a moon.
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“We found new evidence for the presence of a third planet in the system, which was suggested based on VLT observations,” Valentin Christiaens, MINDS team member and postdoctoral researcher in astrophysics at KU Leuven and University of Liège told Space.com. (The VLT is the Very Large Telescope, operated by the European Southern Observatory in Chile.)
“Furthermore, the new infrared measurements we obtained for the two known prototypes indicate the presence of heated material around them – which could be the building blocks for moons forming around them,” said Christiaens.
The PDS 70 system has already been well studied by a multitude of telescopes, including the ground-based Advanced Millimeter/submillimeter Array (ALMA) and the VLT.
It remains a system of great interest to astronomers because the protostar and its protoplanetary disk are estimated to be no more than 5.5 million years old – a cosmic infant compared to our 4.5 billion year old solar system.
“PDS 70 is special, because it is the only protoplanetary disk so far in which all astronomers agree that we have been caught in the act of forming planets,” said Christiaens. “Detailed study of this system has allowed us to learn a lot about planet formation.”
The researcher said that not much is known about the properties of the potential third planet around PDS 70 so far. The planet – which would be confirmed as PDS 70D – appears to be shrouded in an enormous amount of dust, and orbits its infant star at about 13 times the distance between Earth and the sun.
“What is interesting is that this separation puts the planets PDS 70B and PDS 70C close to a 1:2:4 mean resonance. This means that their orbits would be almost twice as short as B and four times longer shorter than the planet C, respectively. ,” said Christiansens. “This is the case we know in the solar system with the three innermost Galilean moons of Jupiter: Io, Europa, and Ganymede.”
Spiral accretion streams similar to what the team had previously predicted theoretically in the protoplanetary disks around young stars. Signs of these currents are visible even in other young systems. But this new discovery stands out, the team members said.
“This is the first time that we can link this feature directly to a forming planet,” said Christiaens. “This may suggest that some of the spirals observed in other protoplanetary disks may be involved in the formation of planets. Therefore, these results have increased suspicion that there may be a direct involvement by spirals observed in other disks directly with planets embedded in their disks.”
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The PDS 70D detector is not set in stone; Christiaens said that this system will need more observations before full certification. That’s not bad, considering the researcher wasn’t sure the planet existed to begin with!
“Certainly the aspect that surprised me the most was finding this sign consistent with a third planet, as I was very skeptical at first about the original claim made in the first work – I thought that maybe the signal tracing the top of the inner disk,” he said.
When the researchers applied their best image processing algorithms, they saw an additional signal in their images, which did not seem to correspond to the disc or the other known planets. This sign also happens to be where they would expect the candidate suggested earlier to be now, if that sign tracks a planet moving in its orbit.
“The third planet was first detected in ground-based observations. We did not expect it to be detected again,” said Christiaens. “The original goal of all this observation was not to confirm it!”
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And the team has more JWST observations of the PDS 70 system to analyze.
“In the mid-term future, it will be a very interesting system to follow up with the Large Telescope (ELT), in particular, to confirm and characterize the third planet candidate,” said Christiaens concluded. “This could help us understand better. the composition of the forming planets and the properties of the material around the planets, the building blocks for potential moons.”
The MINDS team’s research was recently posted on the online paper repository arXiv.
