A recent discovery could shake up our ideas about the formation of planets. While studying the forming exoplanet PDS 70b, located about 400 light years from Earth, a team of researchers observed an unexpected anomaly in its chemical composition. This planet, almost three times more massive than Jupiter, has an atmosphere whose carbon and oxygen content does not correspond to expectations.
PDS 70b: an exoplanet in formation
The planet PDS 70b is part of a unique star system located in the constellation Centaurus. This contains two planets currently forming. It is also one of the rare known systems where planets are still forming, which makes it a valuable object of study for astronomers. PDS 70b orbits its star at a distance similar to that of Uranus’ orbit around the Sun. Scientists believe that this planet is at the end of training process after about 5 million years of growth. This makes it an ideal candidate for understanding the link between nascent planets and their native disks of gas and dust.
Astronomers used the Keck II telescopelocated in Hawaii, to observe the atmosphere of PDS 70b. By analyzing the chemical composition of the planet’s atmosphere, they were particularly interested in the amount of carbon monoxide and water, two key elements in the formation of planets. These observations allowed the researchers to deduce the carbon and oxygen concentrations in the atmosphere of PDS 70b, essential elements for understanding the chemical processes involved in the formation of planets.
An unexpected chemical composition
The results of the analyzes were surprising. According to classical models, the forming planets should have a chemical composition similar to that of the protoplanetary disk, that is to say rich in carbon and oxygen. However, the atmosphere of PDS 70b contained much less carbon and oxygen than astronomers had anticipated.
This discrepancy has led researchers to question standard models of planet formation, suggesting that they are too simplistic to explain the chemical diversity observed in some planetary systems.
To explain this discrepancy, astronomers propose two main scenarios. The first suggests that PDS 70b would have mainly incorporated its carbon and oxygen from solid materialslike ice and dust, rather than directly from the gas of the protoplanetary disk. This hypothesis is supported by recent observations from the space telescope James Webb which show that some nascent planetary systems have solid compounds, such as ice, that can influence the chemical composition of the planets.
The second scenario proposes that the protoplanetary disk around the star PDS 70 has recently been enriched in carbon. This hypothesis is based on the idea that chemical processes within the disk can change over time, influencing the composition of the forming planets. However, current data do not allow a decision between these two hypotheses. Astronomers await future observations, including those of the second planet in the system, PDS 70cto determine with more certainty which scenario is most likely.
