Ice's crucial role in planet and comet formation mapped by Webb

Ice's crucial role in planet and comet formation mapped by Webb
by Robert Schreiber
Berlin, Germany (SPX) Dec 07, 2023

In a significant breakthrough, a Dutch-led international team of astronomers has harnessed the power of the James Webb Space Telescope to create the first comprehensive two-dimensional inventory of ice within a planet-forming disk surrounding a young star. The findings, published in the journal Astronomy and Astrophysics on December 6, open a new window into the crucial role of ice in the formation of planets and comets.

Ice is a fundamental component in the process of planetary and cometary formation. It acts as a binding agent for solid dust particles, facilitating their aggregation into larger structures from which planets and comets ultimately emerge. Moreover, the impact of ice-bearing comets likely played a pivotal role in the Earth's water composition, contributing to the formation of its vast oceans. The ice within these disks also contains key elements-carbon, hydrogen, oxygen, and nitrogen-essential for the development of life's molecular building blocks. However, until now, the precise mapping of ice within planet-forming disks remained an elusive endeavor, hindered by the Earth's atmospheric interference and the limitations of previous space telescopes.

The James Webb Space Telescope has now transcended these constraints, offering a revolutionary glimpse into the realm of ice within these celestial disks. The research team focused their study on the young star HH 48 NE, located approximately 600 light years from Earth in the southern constellation Chameleon. The planet-forming disk, seen edge-on, resembles a hamburger with a central dark lane flanked by two bright "buns." As starlight traverses this disk on its way to the telescope, it interacts with countless molecules within the disk, producing absorption spectra with distinctive peaks corresponding to individual molecules.

Despite the challenges posed by the disk's density and the limited light reaching the telescope, the James Webb Space Telescope's extraordinary sensitivity allowed the researchers to identify several types of ice within the disk. Notable discoveries include water ice (H2O), carbon dioxide ice (CO2), carbon monoxide ice (CO), as well as traces of ammonia (NH3), cyanate (OCN-), carbonyl sulfide (OCS), and heavy carbon dioxide (13CO2). The presence of regular and heavy carbon dioxide enabled the calculation of carbon dioxide quantities within the disk, with a surprising revelation that CO ice may coexist with less volatile CO2 and water ice closer to the star than previously assumed.

Lead author of the study, Ardjan Sturm of Leiden University in the Netherlands, explains the significance of this achievement: "The direct mapping of ice in a planet-forming disk provides important input for modeling studies that help to better understand the formation of our Earth, other planets in our Solar System and around other stars. With those observations, we can now begin to make firmer statements about the physics and chemistry of star and planet formation."

Co-author Melissa McClure of Leiden University, who leads the research program, adds, "In 2016, we created one of the first JWST research programs, Ice Age. We wished to study how the icy building blocks of life evolve on the journey from their origins in cold interstellar clouds to the comet-forming regions of young planetary systems. Now the results are starting to arrive. It's a really exciting time."

The Ice Age research team is committed to expanding their observations, with plans to study more extensive spectra of the same planet-forming disk in the near future. Additionally, they will broaden their observations to other planet-forming disks. If the findings regarding CO ice mixtures hold true, it could reshape our current understanding of planetary compositions, potentially leading to the discovery of more carbon-rich planets located closer to their host stars. Ultimately, these revelations aim to enhance our comprehension of the formation pathways and resulting compositions of planets, asteroids, and comets.

This groundbreaking research underscores the James Webb Space Telescope's transformative impact on our understanding of the cosmos and the critical role of ice in shaping the celestial bodies that populate it.

Research Report:A JWST inventory of protoplanetary disk ices: The edge-on protoplanetary disk HH 48 NE, seen with the Ice Age ERS program