Essential ingredient in the "recipe of life" found in exoplanet formation

A yellow haze of sulfur dioxide, a surprising discovery in the atmosphere of the exoplanet GJ 3470 b, has captivated astronomers and may hold crucial clues to how planets are formed.

This gas dwarf exoplanet, half the size of Neptune and ten times the mass of Earth, orbits a star 96 light-years away in the constellation Cancer.

GJ 3470 b is a peculiar world. According to the researchers, the planet’s orbit around its star takes it nearly over the star’s poles. In other words, GJ 3470 b is orbiting at a 90-degree angle to the expected path of planets in the system. 

Furthermore, it’s unusually close to its star, leading to the loss of a significant portion of its atmosphere – approximately 40% since its formation.

This unique orbit and substantial atmospheric loss suggest a turbulent past, potentially involving gravitational interactions with another planet.

How planets are made

Exoplanets, which are planets located beyond our solar system, provide astronomers with invaluable opportunities to investigate the diverse mechanisms through which planets form and evolve.

By studying the light emitted from a star as it passes through an exoplanet’s atmosphere during transit events, scientists can obtain a spectrum – a unique fingerprint of the light’s intensity at different wavelengths.

The spectrum contains absorption or emission lines corresponding to specific elements and molecules present in the exoplanet’s atmosphere.

Through careful analysis of these spectral features, astronomers can identify the chemical composition of the atmosphere, including the presence of gases like water vapor, methane, carbon dioxide, and even exotic compounds like sulfur dioxide.

These analyses offer crucial insights into the physical and chemical processes that govern planetary formation and atmospheric evolution, ultimately contributing to our understanding of the diversity of worlds that exist beyond our solar system.

Sulfur dioxide on a small exoplanet

GJ 3470 b is the lightest and coldest exoplanet found to harbor sulfur dioxide. The presence of this compound suggests active chemical reactions in the planet’s atmosphere, likely triggered by radiation from its nearby star.

“We didn’t think we’d see sulfur dioxide on planets this small, and it’s exciting to see this new molecule in a place we didn’t expect, since it gives us a new way to figure out how these planets formed,” said Professor Thomas Beatty of the University of Wisconsin–Madison.

“Discovering sulfur dioxide in a planet as small as GJ 3470 b gives us one more important item on the planet formation ingredient list.”

New window into planet formation

Professor Beatty compared the process of understanding planet formation to unraveling a cake recipe. “Laid out on our table, we have all the ingredients that go into a cake, and we have a finished cake. Now, can we figure out the recipe – the steps that turned the raw materials into the end product – by measuring what’s in the cake?”

GJ 3470 b’s unusual orbit and atmospheric loss offer clues to the “recipe” for its formation.

The planet’s migration history and mass loss are significant factors that astronomers don’t typically know about other exoplanets.

These unique characteristics provide a new window into the complex processes involved in planet formation.

Future of exoplanet research

The study of GJ 3470 b is just one piece of the puzzle in understanding how planets are formed.

With further analysis of its atmospheric composition and collaboration with experts in proto-planetary disks and migration dynamics, astronomers hope to gain a deeper understanding of how planets like GJ 3470 b came to be.

The James Webb Space Telescope and other advanced telescopes will continue to play a crucial role in this research, allowing astronomers to probe the atmospheres of exoplanets in unprecedented detail.

The discovery of sulfur dioxide on GJ 3470 b has opened a new chapter in the study of planet formation. This surprising finding, coupled with the planet’s unique characteristics, provides valuable clues to the complex processes that give rise to planets.

As we learn more about the diverse range of exoplanets, we will gain a clearer picture of the intricate processes and ingredients like sulfur dioxide that shape worlds throughout the universe.

The research was presented at the 244th meeting of the American Astronomical Society and will soon be published in Astrophysical Journal Letters.

Image Credit: University of Wisconsin–Madison

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