An international collaboration including U-M researchers have used JWST to provide an unprecedented window into the formation of planets around young star systems
Study: The James Webb Interferometer: Space-based interferometric detections of PDS 70 b and c at 4.8 μm (DOI: 10.3847/1538-3881/ad9b94)
University of Michigan researchers contributed to an international collaboration that's providing an unparalleled view into how planets are born using the JWST-the most powerful space telescope ever launched.
In particular, the team studied PDS 70, a young star with two growing planets in its orbit. Located 370 lightyears away, this system gives scientists a rare chance to see how planets form and evolve during their earliest stages of development.
This new study, led by University of Victoria doctoral candidate Dori Blakely and an international team of researchers, used a creative approach with JWST's unique tools to uncover details about the planets and the swirling disk of gas and dust they're forming within.
"What we're trying to do with JWST is confirm ideas about these protoplanets that have been speculated upon by other observatories," said Michael Meyer, a co-author of the study and chair of the U-M Department of Astronomy. "These observations separate light from the protoplanet and light from the circumstellar disk in which it is embedded with this unique capability."
The findings, published in The Astronomical Journal, offer a fresh perspective on how planets grow over time, competing with their host stars for material.
A young star and its planetary nursery
PDS 70 is a young star, only about 5 million years old-practically a newborn compared to our 4.6-billion-year-old sun. Surrounding the young star is a disk of gas and dust, flattened out like a pancake, with a big gap in the middle where two planets, PDS 70 b and PDS 70 c, are taking shape.
This gap is a planetary construction zone, where brand new worlds are scooping up material to grow larger.
"We're seeing snapshots of the early stages of planetary growth, showing us what happens as worlds compete for survival in their cosmic nursery," Blakely said. "What's remarkable is that we can see not just the planets themselves, but the very process of their formation-they're competing with their star and each other for the gas and dust they need to grow."
To get such a clear view of the planets and disk, the team used JWST's Near-Infrared Imager and Slitless Spectrograph, or NIRISS, in its aperture masking interferometry mode-a clever trick with the telescope. They placed a special mask with several tiny holes over the telescope, which allowed only a small amount-about 15%-of the light to pass through and interfere, creating overlapping patterns, similar to the way ripples from two pebbles interact on the surface of water.
By analyzing these patterns, they could 'see' the hidden details of the system with extraordinary precision.
"This innovative technique is like turning down the young star's blinding spotlight so you can see the details of what's around it-in this case, planets," said René Doyon, director of the Trottier Institute for Research on Exoplanets, or IREx. Doyon is also the principal investigator for JWST's NIRISS instrument.
This approach allowed the team to uncover features that traditional telescope imaging can't detect, making this study a groundbreaking proof of concept for such observations with the powerful space-based telescope. With its ability to see details at a level never achieved before, JWST is revolutionizing the way we study planets and their origins.
"This work shows how JWST can do something completely new," said IREx's Loïc Albert, JWST NIRISS instrument scientist. "We're using innovative techniques to look at planets in ways we've never done before."
U-M's Meyer, who has been involved with the development of JWST instruments for decades, is excited that astronomers are getting a demonstration of the new possibilities afforded by NIRISS.
"This is the start of a longer story," Meyer said. "This is not the standard way of taking data that most scientists are used to, but it is very powerful. We hope to apply it to other systems and we want other people to use it."
Former U-M graduate student Matthew De Furio along with former U-M postdoctoral researchers Gabriele Cugno and Alexander Greenbaum are also co-authors of the study.
Growing planets still under construction
The JWST observations confirmed the presence of two giant planets still in the process of forming. These planets are pulling in material from the disk, much like children grabbing building blocks to construct a tower.
The researchers measured the planets' light in the mid-infrared using JWST's NIRISS instrument and determined that both planets appear to be accumulating gas-a critical phase in their development. The strong detection signatures of PDS 70 b and PDS 70 c allowed for precise measurements of their brightness and location.
These findings provide direct evidence that the planets are still growing and competing with their host star for material in the disk, supporting the idea that planets form through a process of 'accretion,' gradually pulling in mass from the gas and dust around them.
This rare snapshot of planets during their growth phase may help scientists understand how worlds like Jupiter and Saturn may have formed in our own solar system.
"These observations give us an incredible opportunity to witness planet formation as it happens," said Doug Johnstone, principal research officer at the National Research Council of Canada's Herzberg Astronomy and Astrophysics Research Center.
"Seeing planets in the act of accreting material helps us answer long-standing questions about how planetary systems form and evolve. It's like watching a solar system being built before our very eyes."
The data also suggests that the planets might have rings of material around them called circumplanetary disks. These disks could be where moons are forming-like those that orbit Jupiter and Saturn today.
A Step Forward for Planetary Science
The discoveries in PDS 70 give astronomers a clearer picture of how planets and stars form and evolve together. By watching these planets grow and interact with their environment, scientists are learning how planetary systems-like our own-come to be.
"This is like seeing a family photo of our solar system when it was just a toddler," said Blakely. "It's incredible to think about how much we can learn from one system."
Perhaps the most intriguing discovery was the detection of a faint, unresolved source of light within the gap of the protoplanetary disk. While the nature of this emission is unclear, it could represent a structure like a spiral arm of gas and dust, or even a third planet also forming in the system.
Follow-up observations with JWST's other instruments will be critical to confirm whether the glow is a new planet, a disk feature, or something entirely unexpected.
This research is part of the NIRISS Guaranteed Time Observations program, led by Johnstone.
