James Webb spots surprise organic PAHs by huge black holes

Data from the James Webb Space Telescope (JWST) has revealed the presence of carbon-based molecules near black holes at the centres of distant galaxies – right where astronomers assumed they weren’t.

Polycyclic aromatic hydrocarbons (PAHs) are small organic molecules very common in the universe (organic in the chemical sense: containing carbon and hydrogen).

But until this new data, from JWST’s MIRI, it was thought that they couldn’t exist close to black holes: they’d be pulled apart instead.

“The JWST MIRI provides us with a fantastic opportunity to observe galaxies in a way that just hasn’t been possible up until now,” says Dr Ismael García-Bernete, a researcher at Oxford University and lead author on a paper describing the research, published in Astronomy & Astrophysics.

“We were excited to find that these organic molecules can actually survive in extremely harsh conditions.”

PAHs produce bright infra-red light, which makes them prime candidates for investigating with JWST.

The researchers investigated the centres of three different galaxies, showing there were PAHs in each, in the vicinity of the galaxies’ central supermassive black holes.

But the black holes did have an effect on the PAHs. There were more large, and neutral, PAHs near the black holes – meaning smaller, charged molecules still got destroyed.

“This research is of great interest to the wider astronomy community, particularly those focused on the formation of planets and stars in the most distant and faint galaxies,” says García-Bernete.

“It is incredible to think that we can observe PAH molecules in the nuclear region of a galaxy, and the next step is to analyse a larger sample of active galaxies with different properties.

“This will enable us to better understand how PAH molecules survive and which are their specific properties in the nuclear region.

“Such knowledge is key to using PAHs as an accurate tool for characterising the amount of star formation in galaxies, and thus, how galaxies evolve over time.”

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