Using the advanced GRAVITY+ instrument at ESO’s Very Large Telescope Interferometer (VLTI), astronomers have measured the carbon isotope ratio in the atmosphere of the young exoplanet Beta Pictoris b, offering groundbreaking insights into the formation of giant planets.
Artist’s impression of a gas giant exoplanet within the disk of Pictoris Beta. Image credit: L. Calçada / ESO.
Beta Pictoris b, discovered in November 2008 via ESO’s Very Large Telescope, is a gas giant resembling Jupiter but with a mass between 9 and 13 times greater.
This exoplanet orbits its host star Pictoris Beta at a distance eight times greater than that between the Earth and the Sun.
The host star is also accompanied by at least two planets and a circumstellar disk filled with gas and dust, which could ultimately evolve into an icy body torus similar to the Kuiper belt in our solar system.
In this recent research, Antonia von Stauffenberg, a Ph.D. student at the Max Planck Institute for Astronomy, and her team sought to explore the origins and possible atmospheric variability of Beta Pictoris b.
They employed the cutting-edge GRAVITY+ instrument for their observations.
“We utilized a method developed years ago to determine the planetary formation location within its disk,” the researchers detailed.
“By analyzing the relative abundance of two carbon isotopes (C) trapped in carbon monoxide (CO) gas of Beta Pictoris b’s atmosphere, we can deduce whether the planet formed inside or outside the disk’s icy regions.”
“As radiation from the host star heats the disk from its center, it directly correlates to how far from the star the planet formed.”
The temperature boundary at which gas condenses into ice is commonly referred to as the snow line.
“Isotopes contain the same number of positively charged protons but differ in neutrons, such as carbon-12 (12C) and carbon-13 (13C).
“Despite their differing masses, their chemical properties are similar.”
“In cosmic contexts, carbon often exists in combinations with oxygen, appearing as 12CO and 13CO molecules.”
“Interestingly, past assessments of the 12CO/13CO diagnostic yield were conducted using the original GRAVITY setup, resulting in relatively low ratios.”
“We suspected that the original GRAVITY instrumentation was insufficient for resolving key signals in this dataset and advised caution in interpreting the results.”
“Following the rationale above, preliminary findings suggest Beta Pictoris b likely formed in the outer disk, beyond the snowline, by accumulating CO ice instead of gaseous CO.”
“Yet, positioned approximately 10 astronomical units from its star, Beta Pictoris b orbits within the disk’s transition zone between the host star and the snowline, where gas predominately comprises CO.”
“If these results hold true, they imply that Beta Pictoris b may have migrated across the disk during its formation.”
Astronomers also detected subtle variations in magnetic flux from the planet over time.
“While statistically insignificant, the primary variation closely corresponds to the planet’s rotation period of approximately 8.7 hours,” the researchers noted.
“If confirmed, this could indicate the presence of clouds or chemical processes in Beta Pictoris b’s atmosphere, but further sensitive observations are essential.”
“The proposed restoration plan for the gas giant’s birthplace necessitates new, precise measurements of the 12CO/13CO abundance, clearly indicating a position in the warmer inner zones of its natal planet-forming disk.”
“Moreover, this ratio aligns well with values typically found in the interstellar medium extending across our solar system and the Milky Way.”
“The majority of the 12 young gas giant planets assessed for CO ratios displayed comparable values.”
“This consistency may actually signal challenges, as carbon isotope abundances appear to provide minimal diagnostic value when determining a planet’s location relative to its host star.”
“The probable explanation is that fluctuations during planet formation are too subtle to be captured effectively by our proposed methodology.”
“This suggests that 12CO/13CO ratios may not provide specific insights into individual planet-forming environments.”
“Consequently, we are likely overlooking essential physical factors influencing the chemistry of CO ice in planet-forming disks.”
“Hence, the 12CO/13CO ratio may not shed substantial light on the distinction between gaseous environments and regions abundant in CO ice.”
“At this moment, this wide-orbiting gas giant remains reluctant to disclose its origins.”
“We require innovative tools capable of differentiating between planet formation scenarios, and GRAVITY+ could significantly contribute to identifying and evaluating these scenarios.”
The findings are published in today’s issue of Astronomy and Astrophysics.
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A. von Stauffenberg et al. 2026. 13CO and potential variations in β Pictoris b using GRAVITY+. A&A 711, L2; doi: 10.1051/0004-6361/202660275
Source: www.sci.news
