Posted on 12/27/2024 6:01:58 AM PST by Red Badger
The natal disk of PDS 70 with new planet PDS 70b (bright spot on the right). By studying this system, researchers uncovered a mismatched composition of gases in the planet’s atmosphere compared to gases within the disk. Credit: ESO, VLT, André B. Müller
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A new study challenges traditional views of planet formation by showing discrepancies in the composition of gases between a developing exoplanet and its surrounding disk.
The research, based on analysis of the PDS 70 system, suggests that planets might not simply accrete gas from their natal disks but may also significantly incorporate solid materials.
New Findings on Planet Formation
Many scientists have long believed that developing planets closely resemble the swirling disks of gas and dust from which they form, much like children often resemble their parents.
However, a new study led by astrophysicists from Northwestern University suggests this resemblance may not be as strong as previously thought. By examining a still-forming exoplanet and its surrounding natal disk, the researchers discovered a surprising mismatch in the composition of gases between the planet’s atmosphere and its birth disk.
A Simplified Picture of Planet Formation Challenged
This unexpected finding supports long-standing doubts about the accuracy of the simplified models traditionally used to explain planet formation.
The research, published on December 18 in Astrophysical Journal Letters, is the first to directly compare data from an exoplanet, its natal disk, and its host star.
“For observational astrophysicists, one widely accepted picture of planet formation was likely too simplified,” said Northwestern’s Chih-Chun “Dino” Hsu, who led the study. “According to that simplified picture, the ratio of carbon and oxygen gases in a planet’s atmosphere should match the ratio of carbon and oxygen gases in its natal disk — assuming the planet accretes materials through gases in its disk. Instead, we found a planet with a carbon and oxygen ratio that is much lower compared to its disk. Now, we can confirm suspicions that the picture of planet formation was too simplified.”
Hsu is a postdoctoral associate at the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). He is advised by Jason Wang, an assistant professor of physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences and member of CIERA.
Searching for Visible Birth Material
All planets are born from a natal disk, a rotating disk of gas and dust that surrounds a new star. Over millions of years, gravity pulls gas and dust together to form clumps, which eventually grow into planets. Until recently, it was impossible to obtain a direct view of a natal disk in order to track a planet’s birth. Most observable exoplanets are too old, so their natal disks have already disappeared.
The exception, however, is PDS 70, a natal disk that envelopes two fledgling gas-giant exoplanets — similar to Jupiter — called PDS 70b and PDS 70c. Located just 366 million lightyears from Earth within the constellation Centaurus, the planets are, at most, a youthful 5 million years old.
“This is a system where we see both planets still forming as well as the materials from which they formed,” Wang said. “Previous studies have analyzed this disk of gas to understand its composition. For the first time, we were able to measure the composition of the still-forming planet itself and see how similar the materials are in the planet compared to the materials in the disk.”
Examining Planetary Fingerprints
To measure the materials, Hsu, Wang and their team examined the light emitted from PDS 70b. This light, or spectra, is like a fingerprint, revealing an object’s composition, motion, temperature and other characteristics. Each molecule or element produces its own spectrum. So, by studying these spectra, researchers can pinpoint the specific molecules or elements within an object.
In previous work, Wang co-developed new photonics technologies that enable astronomers to capture the spectrum of targeted faint objects near much brighter stars. The researchers used this technique to zero in on the faint features of the young planetary system.
“These new tools make it possible to take a really detailed spectra of faint objects next to really bright objects,” Wang said. “Because the challenge here is there’s a really faint planet next to a really bright star. It’s hard to isolate the light of the planet in order to analyze its atmosphere.”
Unexpected Results: Carbon-Oxygen Ratio Mismatch
With the spectra, the researchers obtained information about carbon monoxide and water from PDS 70b. From that, they calculated the inferred ratio of carbon and oxygen within the planet’s atmosphere. Then, they compared that ratio to previously reported measurements of gases in the disk.
“We initially expected the carbon-to-oxygen ratio in the planet might be similar to the disk,” Hsu said. “But, instead, we found the carbon, relative to oxygen, in the planet was much lower than the ratio in the disk. That was a bit surprising, and it shows that our widely accepted picture of planet formation was too simplified.”
Solid Components and Planetary Formation
To explain this mismatch, Hsu and Wang think two different scenarios might be at play. One explanation is the planet might have formed before its disk became enriched in carbon. Another explanation is the planet might have grown mostly by absorbing large amounts of solid materials in addition to gases. While the spectra show only gases, some of the carbon and oxygen initially could be accreted from solid — trapped in ice and dust.
“If the planet preferentially absorbed ice and dust, then that ice and dust would have evaporated before going into the planet,” Wang said. “So, it might be telling us that we can’t just compare gas versus gas. The solid components might be making a big difference in the carbon-to-oxygen ratio.”
The Next Steps in Planetary Research
For this study, the team only studied PDS 70b. Next, they plan to observe the spectra from the other planet in the PDS 70 system.
“By studying these two planets together, we can understand the system’s formation history even better,” Hsu said. “But, also, this is just one system. Ideally, we need to identify more of them to better understand how planets form.”
Reference:
“PDS 70b Shows Stellar-like Carbon-to-oxygen Ratio”
by Chih-Chun Hsu, Jason J. Wang, Geoffrey A. Blake, Jerry W. Xuan, Yapeng Zhang, Jean-Baptiste Ruffio, Katelyn Horstman, Julianne Cronin, Ben Sappey, Yinzi Xin, Luke Finnerty, Daniel Echeverri, Dimitri Mawet, Nemanja Jovanovic, Clarissa R. Do Ó, Ashley Baker, Randall Bartos, Benjamin Calvin, Sylvain Cetre, Jacques-Robert Delorme, Gregory W. Doppmann, Michael P. Fitzgerald, Joshua Liberman, Ronald A. López, Evan Morris, Jacklyn Pezzato-Rovner, Tobias Schofield, Andrew Skemer, J. Kent Wallace and Ji Wang, 18 December 2024, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ad95e8
The study was supported by the Heising-Simons Foundation, the Simons Foundation and the National Science Foundation.
X-O Planet Ping!..................
Thanks Red Badger.
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Thanks for the heads up. Maybe we can send that deadly CO2 there to save us? 🤔🌠
The young Exoplanet did not break any formation rules because there are no rules, all there are are theories because no human has seen a planet form over millions of years , let alone made money themselves.
Planets and the universe make the rules, not people. Scientists need to admit that they don’t know all the rules.
How do you know the composition elements of the planet or “nearby” gases by studying the light that is reflected from it?
Yes. Spectrographic absorption lines tell all.............
Rules that are broken are not rules anymore.
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