Galactic winds of change captured by the Webb Space Telescope

Researchers have imaged for the first time a wind coming from an ancient planet-forming disk, dispersing its gas content.

the James Webb Space Telescope JWST helps scientists discover how planets form by enhancing understanding of their birthplaces and the circumstellar disks surrounding young stars. In a paper published in Astronomical magazine, a team of scientists led by Naman Bajaj of the University of Arizona and including Dr. Uma Gorti at the SETI Institute, imaged for the first time, winds from an ancient planet-forming disk (still very young relative to the Sun) actively dispersing its gas content. The disk had been imaged before, and the wind had not been imaged from older disks. Knowing when gas is spreading is important, because it limits the time remaining for emerging planets to consume gas from their surroundings.

Insights from the eroded disk of TCha

At the heart of this discovery is the observation of TCha, a young (relative to the Sun) star surrounded by an eroding disk characterized by a wide dust gap, with a radius of about 30 AU. For the first time, astronomers have imaged dispersed gas (also known as wind) using the four lines of the noble gases neon (Ne) and argon (Ar), one of which is the first detection in a planet-forming disc. photo [Ne II] It turns out that the wind comes from an extended region of the disk. The team, all members of the JWST program led by Ilaria Pascucci (University of Arizona), are also interested in learning how this process occurs so they can better understand the history and impact on our solar system.

“These winds could be driven either by high-energy stellar photons (starlight) or by the magnetic field weaving the disk that forms the planet,” Naman said.

Uma Gorti of the SETI Institute has been researching disk scattering for decades, and she and her colleague predicted the powerful argon emission now detected by the James Webb Space Telescope. She's “excited to finally be able to pull apart the physical conditions in the wind to understand how to launch them.”

The James Webb Space Telescope (JWST) is an advanced astronomical observatory designed to uncover the secrets of the universe, from the formation of galaxies, stars and planets to detecting potential signs of life on exoplanets. Launched in December 2021, it serves as the leading space science observatory for the next decade, building on the legacy of the Hubble Space Telescope with its more powerful instruments and broader observing capabilities. Credit: NASA

Evolution of planetary systems

Planetary systems like our solar system appear to contain more rocky bodies than gas-rich ones. These include the inner planets around our Sun, the asteroid belt, and the Kuiper Belt. But scientists have long known that planet-forming disks start out with a mass 100 times greater in gas than in solids, leading to a pressing question: When and how does most of the gas leave the disk/system?

During the very early stages of planetary system formation, planets assemble into a rotating disk of young gas and dust around the young star. These particles clump together, accumulating into larger and larger pieces called planetesimals. Over time, these planetesimals collide and stick together, eventually forming planets. The type, size and location of planets that form depends on the amount of matter available and how long it remains in the disk. Therefore, the outcome of planet formation depends on the evolution and propagation of the disk.

The same group, in another paper led by Dr. Andrew Sellick of the Leiden Observatory, performed simulations of the scattering caused by stellar photons to distinguish between the two. They compared these simulations with actual observations and found that scattering by high-energy stellar photons could explain the observations and therefore could not be ruled out as a possibility. Andrew described how “the simultaneous measurement of all four lines by the James Webb Space Telescope proved important in characterizing the winds and helped us prove that large amounts of gas are being dispersed.” To put the matter in context, researchers calculate that the mass dispersed each year is equivalent to the mass of the Moon! A companion paper, currently under review by Astronomical magazineI will detail these results.

Transformative discoveries and future prospects

the [Ne II] The line was first detected toward several planet-forming disks in 2007 using the Spitzer Space Telescope and was quickly identified as a wind tracer by project leader Professor Pascucci at the University of Arizona; These evolving research efforts have focused on understanding disk gas dispersion. Spatially resolved discovery [Ne II] The first detection [Ar III] Using the James Webb Space Telescope may be the next step toward changing our understanding of this process.

“We first used NEON to study planetary-forming disks more than a decade ago, and tested our computational simulations against data from Spitzer, and new observations we obtained using Eso “The VLT,” said Professor Richard Alexander of the University of Leicester's School of Physics and Astronomy. We've learned a lot, but those observations haven't allowed us to measure how much mass the disks lose. The new James Webb Space Telescope data is amazing, and being able to analyze the disc's motions in images is something I never thought possible. With more observations like these, the James Webb Space Telescope will enable us to understand emerging planetary systems like never before.

In addition, the group also discovered that T Cha's inner disk evolves on very short timescales of decades; They found that the JWST spectrum of T Cha differs from the previous Spitzer spectrum. According to Qingyan Xie of the University of Arizona, lead author of this ongoing work, this mismatch can be explained by a small, asymmetric inner disk that lost part of its mass in just 17 years. Combined with other studies, this also indicates that the T Cha disk is at the end of its development. Qingyan adds: “We may be able to see all the dust mass in T Cha's inner disk dissipate within our lifetime!”

The implications of these findings provide new insights into the complex interactions that lead to the dispersion of gas and dust essential for planet formation. By understanding the mechanisms behind disk dispersion, scientists can better predict the timelines and environments leading to planetary birth. The team's work demonstrates the power of the James Webb Space Telescope and defines a new way forward in exploring the dynamics of planetary formation and the evolution of circumstellar disks.

Reference: “JWST MIRI MRS observations of T Cha: discovery of a spatially resolved disc wind” by Naman S. Bajaj, Ilaria Pascucci, Uma Gorti, Richard Alexander, Andrew Sellek, Jane Morrison, Andras Gaspar, Cathie Clarke, Chengyan Xie, Giulia Palabio Wu Dingshan Ding, March 4, 2024, Astronomical magazine.
doi: 10.3847/1538-3881/ad22e1

The data used in this work were acquired using the JWST/MIRI instrument through the General Controllers Course 1 program PID 2260 (PI: I. Pascucci). The research team includes Naman Bajaj (graduate student), Professor Ilaria Pascucci, Dr Uma Gorti, Professor Richard Alexander, Dr Andrew Sellick, Dr Jane Morrison, Professor András Gaspar, Professor Cathy Clark, Qingyan Xie (graduate student), and Dr Julia Palabio. , Dingshan Ding (graduate student).