“ Failure of the star ” imitates a key sign of life, complicating our search for foreigners

For scientists, the urgent problem of phosphine – a molecule has presented a potential sign of life – is not so much where it comes from, but why this is not where we think it should be. After a decade of research, a long -awaited result confirmed that our astronomical models are not a total bust. At least, for the moment.

In a scientific article published today, astronomers report the very first detection of strong phosphine signatures on a brown dwarf – a type of planet -star hybrid more massive than planets like Jupiter but not large enough to maintain the fusion of hydrogen which feeds the stars. Important chemical models had long predicted that cosmic entities with gaseous atmospheres would be rich in phosphine, but years of research had revealed almost nothing. The results thus give the closure of a problem that tormented astronomers for at least a decade.

Just as important, the observation has important implications for astrobiology. Phosphine detected on this brown dwarf, named Wolf 1130c, is almost certainly formed by natural and abiotic processes. The challenge is now to determine how an object like this could generate as much lifeless. Until researchers can explain that any detection of phosphine – whether on a gas giant or a rocky planet like Venus – cannot be considered a reliable sign of biology.

“The community was waiting for this,” said Sara Seager, a MIT astrophysicist who is not involved in the new work. Seager co-wrote a founding paper of 2020 on the detection of phosphine in Venus. On earth, phosphine exists mainly as the by-product of anaerobic life, or creatures that thrive without oxygen. Because the chemical environment of Venus is not conducive to the natural formation of phosphine, article 2020 has left astronomers wondering if phosphine could come from a source of life – a biosignature.

“It’s very refreshing – finally!” Nathalie Cabrol, director of research at the Carl Sagan Center of the SETI Institute, added. Cabrol, also not involved in the new study, told Gizmodo in a video call that the document has “clear and simple” data from phosphine on the brown dwarf – just as the models predicted.

A pursuit of wild phosphine

If the results had been ten years old, that would not have been so important, Adam Burgasser, principal author of the study and astrophysicist at the University of California in San Diego, told Gizmodo. The chemical models had long supported the natural presence of phosphine on brown dwarfs or exoplanets with gaseous atmospheres. The fact that Jupiter and Saturn have atmospheres rich in phosphine also contributed to this hypothesis.

But after a decade of zero (or rather, several disputed signs) of phosphine where the models expected it to be, astronomers began to become a rather dark burgasse. In fact, astronomers had started to seriously consider the main models considerably to take into account the lack of phosphine.

“It was a real strange problem because it is just this molecule that seems to be a little deactivated,” said Burgasser. “So, it is actually a surprise that we finally detected it – in fact, detected it in abundance in this particular brown dwarf.”

Webb search

Wolf 1130c is located at around 54.1 light years from the earth. The team chose this object for its slightly unusual composition, its low metallicity and its relatively low surface temperature. The idea was to adopt a slightly different approach, because the previous surveys had already targeted brown dwarfs with the right temperature or the right composition, but astronomers had not “seen the level of phosphine that we expect,” explained Burgasser.

Their intuition has proven to be correct. While studying the spectral data of the James Webb telescope spectrograph, the team noticed a distinct check in their intrigue – a characteristic of phosphine signatures. But the researchers swallowed their enthusiasm to double and triple their work.

“We said to ourselves,” We must make sure that it is absolutely correct, “recalls Burgasser. Fortunately, the team included an IT modeling expert who directed one week’s simulations of the dwarf atmosphere, as well as a scientist whose career had revolved around phosphine.

“A combination of all these things – the more the analysis we have done to (describe) abundances – we realize that we have had a very obvious and solid detection,” said Burgasser.

No foreigners here

Again, the detection does not represent a biosignature, which Burgasser, Seager and Cabrol have all stressed. This has to do with an often brilliant appearance of the search for signs of extraterrestrial life, said Cabrol. No molecule in itself is necessarily a biosignature; We are rather looking for the “co-evolution of life and its environment,” she said. In other words, a compound is considered to be a biosignature that if the surrounding environment suggests that it could not have been formed by non -biological chemistry alone.

The verification of these environmental contexts would be easier for places like Venus, which is close enough for us to plan the missions, said Cabrol. “We do not have this luxury with exoplanets. When you do not know the environment … You cannot claim that something is a biosigenature unless something is reconstructed in a way that nature alone cannot explain. “

For brown dwarfs, phosphine is not a biosignature. These stellar bodies are hot and rich in hydrogen, which is conducive to the presence of phosphine, said Seager.

“Chemically, there is no life involved in there,” added Burgasser.

Duties of the universe

That said, the team is not completely certain how phosphine ended up on Wolf 1130c, although it explores certain options. This could be due to the low metallicity of the brown dwarf, where the local environment could have been conducive to the accumulation of phosphine on Wolf 1130c. Overall, researchers are not sure.

At the same time, “the inability of models to systematically explain all these sources indicates an incomplete understanding of phosphorus chemistry in low -temperature atmospheres”, noted the article.

It is as if nature had come and said: “Yes, here are more homework, a more difficult test question for you,” joked Burgasser. “We do not even understand the natural chemistry of phosphorus-until we get things, we cannot really count on phosphine as a viable biosignature,” he added.

The next obvious step would be to search for other objects with similar phosphine supplies, which could help fill the gaps that remain. Of course, it is quite possible that future discoveries can put models in an even more important confusion. Anyway, the results mark a new chapter in our understanding of the cosmos.

“But the process that will lead to this day is magnificent in itself,” said Cabrol, “because it is the progress of human knowledge.”