The Webb Telescope rewrites the rules of the game for planet formation

The Webb Telescope rewrites the rules of the game for planet formation

Planet formation neon web signs

NASA’s Spitzer telescope’s 2008 discovery of a unique protoplanetary disk around SZ Cha, with unusual ultraviolet radiation, contradicted later findings by the James Webb Telescope of typical radiation levels. These conflicting observations, especially the different neon signatures, indicate a large and previously unnoticed change in disc radiation exposure. This challenges current models of planetary formation and requires further research.

The contradiction between James Webb Space TelescopeSpitzer Space Telescope observations, just 15 years ago, indicate changing conditions around a Sun-like star.

In 2008 NASASpitzer Space Telescope has found a protoplanetary disk like no other. The disk of dusty gas surrounding the young, sun-like star SZ Chamaeleontis (SZ Cha) was being hit hard by ultraviolet radiation — something that had only previously been seen in computer models, and never happened in the real universe. Planets in this system would have a longer time to form than a disk that is vaporized by X-rays, which is normal. However, when the James Webb Space Telescope followed SZ Cha, it found nothing out of the ordinary – no abundance of ultraviolet radiation. In a short period of cosmic time, conditions in the SZ Cha disk changed, leaving astronomers to make sense of the mismatched data and its implications for the formation of other solar systems.

SZ Chamaleontis

In this artist’s concept, the young star SZ Chamaeleontis (SZ Cha) is surrounded by a disk of dust and gas with the potential to form a planetary system. Our solar system only looked like this, before planets, moons, and asteroids formed. The raw ingredients, including those needed for life on Earth, were present in the protoplanetary disk of the sun. Image credit: NASA, ESA, CSA, Ralph Crawford (STScI)

The Webb Space Telescope follows neon signs toward new thinking about planet formation

Scientists track neon signs for clues to the future of one planetary system and the past of another, our solar system. In a bizarre follow-up to NASA’s former flagship infrared observatory, the now-retired Spitzer Space Telescope, the agency’s James Webb Space Telescope has discovered distinct traces of neon in the dust disk surrounding the young, sun-like star SZ Chamaeleontis (SZ Cha). ).

The differences in neon readings between Spitzer and Webb indicate a never-before-observed change in the high-energy radiation reaching the disk, eventually causing it to evaporate, limiting the time during which planets must form.

“How did we get here? It really comes down to this big question, and SZ Cha is the same type of young star, a T-Tauri star, as our Sun was 4.5 billion years ago at the dawn of the solar system,” said astronomer Katherine Espaillat of Boston University. ., in Massachusetts, who led the 2008 Spitzer observations and the new Webb findings just published in the Astrophysical Journal Letters.

“The raw materials for Earth, and ultimately life, were in the disk of matter that surrounded the Sun after it formed, so studying these other young systems is the closest we can get to going back in time to see how our planet might have evolved. The story begins.”

SZ Cha protoplanetary disk (Webb MIRI spectrum)

Contrasting data from NASA’s James Webb and Spitzer space telescopes show a change in the disk surrounding the star SZ Chamaeleontis (SZ Cha) in just 15 years. In 2008, Spitzer’s discovery of a significant neon III made SZ Cha exceptional among similar protoplanetary disks. However, when Webb followed SZ Cha in 2023, the Neon II to III ratio was within typical levels. Image credit: NASA, ESA, CSA, Ralph Crawford (STScI)

Neon as an indicator of radiation and the puzzling behavior of SZ Cha

Scientists use neon as an indicator of the amount and type of radiation hitting the disk surrounding the star and eroding it. When Spitzer observed SZ Cha in 2008, he saw an anomalous presence, with neon readings unlike any other young T-Tauri disc. The difference was the discovery of neon III, which is normally rare in protoplanetary disks exposed to high-energy X-rays. This means that the high-energy radiation in the SZ Cha disk was coming from ultraviolet radiation rather than X-rays. Besides being the only strange result in a sample of 50 to 60 young stellar disks, the difference between ultraviolet and X-ray radiation is important for the age of the disk and potential planets.

“The planets are basically in a race against time to form in the disk before it evaporates,” explained Boston University’s Thanawath Thanathipudi, another astronomer on the research team. “In computer models of developing systems, extreme ultraviolet radiation allows planetary formation for a million more years than if evaporation were mostly caused by X-rays.”

So, SZ Cha was already a big mystery when Espaillat’s team returned to study it with Webb, only to find a new surprise: the unusual neon III signature had almost disappeared, indicating the typical dominance of X-ray radiation.

The research team believes that the differences in neon signatures in the SZ Cha system are the result of shifting winds that, when present, absorb ultraviolet light and leave X-rays to hit the disk. The team says winds are common in a system containing an active, newly forming star, but it is possible to capture the system during a quiet, wind-free period, which is what happened to Spitzer.

“The Spitzer and Webb data are excellent, so we knew this had to be something new we were observing in the SZ Cha system – a significant change in conditions in just 15 years,” added co-author Ardjan Sturm from Leiden University. , Holland.

Continuing research and complexity of the universe

The Espaillat team is already planning more observations of SZ Cha with Webb, as well as other telescopes, to solve its mysteries. “It will be important to study SZ Cha, and other young systems, in multiple wavelengths of light, such as X-rays and visible light, to discover the true nature of this anisotropy we found,” said co-author Kelly Pittman of the University of California. Boston University. “It is possible that short, quiet periods dominated by extreme ultraviolet radiation are common in many young planetary systems, but we have not been able to capture them.”

“Once again, the universe is showing us that none of its methods are as simple as we would like to make it out. We need to rethink, re-observe and collect more information. We will follow the neon signs,” Espaillat said.

This research was published on November 15 in Astrophysical Journal Letters.

Reference: “JWST detects neon line fluctuations in protoplanetary disk” by C. C. Espaillat, T. Thanathibodee, C. V. Pittman, J. A. Sturm, M. K. McClure, N. Calvet, F. M. Walter, R. Franco-Hernández and J. Muzerolle Page, 15 November 2023, Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ad023d

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 program led by NASA with its partners the European Space Agency (ESA).European Space Agency) and the Canadian Space Agency.

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