New Study Reveals How Solar System Formed Gas Giants

Astronomers use JWST to determine gas giants in HR 8799 system formed through core-accretion process like Jupiter

Published on Feb. 9, 2026

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A research team including astronomers from the University of Michigan used data from the James Webb Space Telescope to determine that the three innermost gas giants in the HR 8799 system, located over 130 light-years away, formed through the same core-accretion process that created Jupiter in our solar system. The findings provide new insights into how large planets can form and challenge some previous models that favored a different formation pathway.

Why it matters

Understanding how gas giants like Jupiter and the planets in the HR 8799 system form is a longstanding question in astronomy. The new study provides empirical evidence that a 'bottom-up' core-accretion process, rather than a 'top-down' gravitational collapse, is responsible for creating these massive planets, even when they are much larger and farther from their host star than Jupiter.

The details

The research team, led by Jean-Baptiste Ruffio of UC San Diego and Jerry Xuan of Caltech, used the Near-Infrared Spectrograph (NIRSpec) instrument on the JWST to analyze the atmospheric composition of the three innermost gas giants in the HR 8799 system. They found that, like Jupiter, these planets are enriched in elements heavier than hydrogen and helium, indicating they formed through core-accretion. The team also detected the presence of sulfur in the atmosphere of one of the planets, HR 8799 c, suggesting a similar formation process across the three worlds.

  • The JWST observations of the HR 8799 system were made in July 2023.
  • The study was published in the journal Nature Astronomy in February 2026.

The players

Jean-Baptiste Ruffio

A research scientist at the University of California San Diego and lead author of the study.

Jerry Xuan

A 51 Pegasi b Fellow at the University of California, Los Angeles, who developed the atmospheric models used in the study.

Michael Meyer

A professor of astronomy at the University of Michigan and co-author of the study, who has been involved with the JWST for over two decades.

HR 8799

A star system located over 130 light-years from Earth, which hosts three innermost gas giant planets that were the focus of this study.

JWST

The James Webb Space Telescope, the world's most powerful space observatory, which was used to make the observations and atmospheric analyses in this study.

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What they’re saying

“The empirical answer is in. These gas giants are formed through core-accretion. It's a bottom-up process.”

— Michael Meyer, Professor of Astronomy, University of Michigan (Mirage News)

“With the detection of sulfur, we are able to infer that the HR 8799 planets likely formed in a similar way to Jupiter despite being five to ten times more massive, which was unexpected.”

— Jean-Baptiste Ruffio, Research Scientist, University of California San Diego (Mirage News)

“The quality of the JWST data is truly revolutionary and existing atmospheric model grids were simply not adequate. To fully capture what the data were telling us, I iteratively refined the chemistry and physics in the models.”

— Jerry Xuan, 51 Pegasi b Fellow, University of California, Los Angeles (Mirage News)

What’s next

Researchers plan to examine more exoplanet systems beyond HR 8799 to further investigate the limits of planet formation and the transition between planet and brown dwarf formation.

The takeaway

This study provides new empirical evidence that the core-accretion process that formed Jupiter can also create much larger gas giants in distant planetary systems, challenging previous models and opening new questions about the upper limits of planet size and formation efficiency.