Reveals the secrets of the rocky planet at the cosmic ends

Astronomers find a group of molecules that are among the building blocks of rocky planets.

Space is a harsh environment, but some areas are harsher than others. The star-forming region, known as the Crayfish Nebula, hosts some of the most massive stars in our galaxy. Massive stars are hotter and therefore emit a greater amount of ultraviolet radiation. This ultraviolet light bathes the planet-forming disks around nearby stars. Astronomers expect ultraviolet radiation to break down many chemical molecules. However, James Webb Space Telescope Discover a variety of molecules in one of these discs, including water, carbon monoxide, carbon dioxide, hydrogen cyanide, and acetylene. Such molecules are among the building blocks of rocky planets.

This is an artist’s impression of a young star surrounded by a protoplanetary disk in which planets form. Credit: Esso

The Webb Space Telescope reveals that rocky planets can form in extreme environments

An international team of astronomers has used NASA’s James Webb Space Telescope to provide the first observations of water and other molecules in the rocky, highly radiated interior of planets in one of the most extreme environments in our galaxy. These results suggest that formation conditions for rocky planets can occur in a wider range of possible environments than previously thought.

The first results from the XUE program

These are the first results from the James Webb Extreme Ultraviolet (XUE) space telescope, which is focused on characterizing planet-forming disks (huge, rotating clouds of gas, dust, and bits of rock where planets form and evolve) in massive star-forming regions. These regions likely represent the environment in which most planetary systems formed. Understanding the influence of the environment on planet formation is important for scientists to gain insight into the diversity of different types of exoplanets.

Study of the Crayfish Nebula

The XUE program targets a total of 15 disks in three regions of the Crayfish Nebula (also known as NGC 6357), a large emission nebula about 5,500 light-years from Earth in the constellation Scorpius. The Crayfish Nebula is one of the newest and closest massive star-forming complexes, hosting some of the most massive stars in our galaxy. Massive stars are hotter and therefore emit more ultraviolet radiation. This can disperse the gas, making the disk’s expected lifespan as short as a million years. Thanks to Webb, astronomers can now study the effect of ultraviolet radiation on the inner terrestrial planet-forming regions of protoplanetary disks around stars like our Sun.

Unique web capabilities

“Webb is the only telescope with the spatial resolution and sensitivity to study planet-forming disks in regions of massive star formation,” said team leader Maria Claudia Ramírez Tanos of the Max Planck Institute for Astronomy in Germany.

Astronomers aim to characterize the physical properties and chemical composition of regions of planet-forming rocky disks in the Crayfish Nebula using medium-resolution spectrometers on Webb’s mid-infrared (MIRI) instrument. This first result focuses on a protoplanetary disk called XUE 1, which is located in the star cluster Pismis 24.

“Only the MIRI wavelength range and spectral resolution allow us to examine the molecular inventory and physical conditions of the warm gas and dust where rocky planets form,” added team member Arjan Beck from Stockholm University in Sweden.

Given its location near several massive stars in NGC 6357, scientists expect that XUE 1 was constantly exposed to high amounts of ultraviolet radiation throughout its life. However, in this extreme environment, the team still discovered a group of molecules that form the building blocks of terrestrial planets.

“We found that the inner disk around XUE 1 is remarkably similar to those found in nearby star-forming regions,” said team member Reins Waters of Radboud University in the Netherlands. “We detected water and other molecules such as carbon monoxide, carbon dioxide, hydrogen cyanide, and acetylene. However, the emissions found were weaker than some models predicted. This may mean a small outer radius of the disk.”

Lars Kuijpers from Radboud University added: “We were surprised and excited because this is the first time these molecules have been detected under such extreme conditions.” The team also found small, partially crystallized silicate dust on the surface of the disc. These are considered the building blocks for rocky planets.

Implications for rocky planet formation

These results are good news for rocky planet formation, as the science team found that conditions in the inner disk are similar to those in well-studied disks found in nearby star-forming regions, where only low-mass stars form. This suggests that rocky planets can form in a much wider range of environments than previously thought.

The team points out that the remaining observations from the XUE program are crucial to identifying commonalities between these conditions.

“XUE 1 shows us that the conditions necessary for rocky planets to form exist, so the next step is to check how common this is,” Ramirez-Taños says. “We will monitor other disks in the same area to determine the frequency at which these conditions can be observed.”

These results have been published in the Astrophysical Journal.

Reference: “XUE: Molecular inventory in the inner region of a highly irradiated protoplanetary disk” by María Claudia Ramírez-Taños, Arjan Beck, Lars Kuijpers, Reins Waters, Christian Goebel, Thomas Henning, Inga Kamp, Thomas Prebisch, Konstantin F. Getman, Germán Chaparro, Pablo Cuartas-Restrepo, Alex D. Cotter, Eric D. Vigilson, Sierra L. Grant, Thomas J. Elena Sabbi, Benoit Taboni, Andrew J. Winter, Anna F. McLeod, Roy van Bokel and Circus E. Van Terwisja, November 30, 2023, the Astrophysical Journal Letters.
doi: 10.3847/2041-8213/ad03f8

The James Webb Space Telescope is the world’s leading space science observatory. Webb solves the mysteries of our solar system, looks beyond the distant worlds around other stars, and explores the mysterious structures and origins of our universe and our place in it. WEB is an international led programme NASA With its partners the European Space Agency (ESA)European Space Agency) and the Canadian Space Agency.