Scientists utilizing NASA’s James Webb Space Telescope have achieved a groundbreaking revelation in unraveling the mysteries of planet formation. The key lies in the observation of water vapor within protoplanetary disks, confirming a physical process involving the migration of ice-coated solids from the outer reaches of the disk into the rocky-planet zone.
Long-standing theories propose that the icy pebbles, akin to those forming in the outer regions of protoplanetary disks where comets originate in our solar system, serve as the fundamental building blocks of planets. Central to these theories is the notion that these pebbles should drift inward toward the star, propelled by friction in the gaseous disk, delivering both solids and water to nascent planets.
A pivotal prediction of these theories asserts that as icy pebbles traverse the warmer region within the “snowline,” where ice transitions to vapor, they should release substantial amounts of cold water vapor. This prediction aligns precisely with the observations made by the Webb telescope.
Principal investigator Andrea Banzatti of Texas State University, San Marcos, Texas, expressed the significance of Webb’s findings, stating, “Webb finally revealed the connection between water vapor in the inner disk and the drift of icy pebbles from the outer disk. This finding opens up exciting prospects for studying rocky planet formation with Webb!”
Team member Colette Salyk of Vassar College in Poughkeepsie, New York, elaborated on the paradigm shift these findings bring, stating, “In the past, we had this very static picture of planet formation, almost like there were these isolated zones that planets formed out of. Now we actually have evidence that these zones can interact with each other. It’s also something that is proposed to have happened in our solar system.” The discovery challenges the previously static view of planet formation, revealing an intricate interplay between different zones and offering new avenues for exploration with the James Webb Space Telescope.
Compares two types of distinct, planet-forming disks around stars.
Two different types of planet-forming disks, one compact and one extended with gaps, surrounding newborn stars. Researchers using the Webb telescope recently observed four protoplanetary disks, two of each type, to determine if compact disks contain more water in their inner regions compared to extended disks. This could be due to the efficient drift of ice-covered pebbles towards the inner regions of the star, delivering large amounts of solids and water to the rocky, inner planets that are in the process of forming.
Recent studies suggest that the presence of large planets in these disks can create rings of increased pressure, where pebbles tend to collect as they drift. While this does not completely stop the drift of pebbles, it does slow it down. This phenomenon may also explain the scarcity of water on our own small, inner rocky planets in our solar system, with Jupiter potentially inhibiting the delivery of pebbles and water to these planets. Overall, this artist’s concept provides a visual representation of ongoing research on planet formation and offers insight into the potential role of large planets like Jupiter in shaping our own solar system.
Researchers were able to study four disks around Sun-like stars. These disks, estimated to be between 2 and 3 million years old, are just newborns in the cosmic timeline. The team used Webb’s MIRI instrument, specifically the Medium-Resolution Spectrometer, to gather data on two compact and two extended disks. The results of the observations revealed that the compact disks experience efficient pebble drift, delivering pebbles to the inner regions of the disks.
In contrast, the extended disks retain their pebbles in multiple rings further out. The observations also confirmed the expectation that compact disks have a higher water abundance in their inner regions, due to the efficient pebble drift delivering solid mass and water to inner planets. This highlights the potential of harnessing Webb’s power, specifically the MIRI instrument, to gain valuable insights into the formation of planetary systems and the delivery of water to potential habitable worlds.
Emission Spectrum – Water Abundance:
Used a powerful instrument called MIRI’s Medium-Resolution Spectrometer to study the water content in two different types of disks around stars (GK Tau and CI Tau). The top graph shows the spectra of warm and cool water in both disks, revealing more cool water in the compact GK Tau disk. The bottom graph subtracts the cool water data of the extended CI Tau disk from the compact GK Tau disk, showing the excess cool water in purple, closely matching a model spectrum of cool water.
Imagine pebbles drifting in a cosmic stream. When they hit areas of increased pressure called pressure bumps, they gather there. These pressure traps don’t stop the pebble movement but slow it down. In disks with rings and gaps, like those around large planets, these pressure traps could explain why pebbles collect in specific areas. The idea is that even in our solar system, Jupiter might have played a role in limiting the delivery of pebbles and water to our inner rocky planets by creating pressure zones.
The research team was puzzled by results showing compact disks had colder water and large disks had hotter water, despite selecting stars with similar temperatures. The breakthrough came when they overlaid the data from both types of disks, revealing that compact disks have extra cool water just inside the snowline, much closer than Neptune’s orbit.
Interpreting Data from Webb’s MIRI, Mid-Infrared Instrument.
This graphic illustrates data from Webb’s Mid-Infrared Instrument, highlighting the difference between pebble drift and water content in compact versus extended disks with rings and gaps. In the compact disk on the left, ice-covered pebbles drift inward unhindered, releasing water vapor beyond the snow line, enriching inner planets. On the right, the extended disk’s rings and gaps impede pebble movement, trapping many before they can contribute water across the snow line, limiting water delivery to the inner disk region.
The team’s findings were published in the November 8 edition of the Astrophysical Journal Letters. The James Webb Space Telescope, a collaboration between NASA, ESA (European Space Agency), and the Canadian Space Agency, is a leading space science observatory, unraveling mysteries within our solar system, exploring distant exoplanets, and del