A group of scientists says they “decisively” overturned the prevailing theory of how planets formed.
The most accepted notion was that the violent clash of objects formed increasingly large clusters until they became planets.
The new findings, however, suggest that the process was less catastrophic and that matter gradually accumulated without so many shocks.
The study appears in the journal Science and was presented at the meeting of the American Association for the Advancement of Science, in Seattle.
Alan Stern, principal investigator of the study, said the discovery was of «Great magnitude».
“Before there was the predominant theory of the late sixties of violent collisions and a more recent theory of smooth accumulation,” Stern told the BBC.
«Now the first became dust and the other is the only one still standing. This rarely happens in planetary science, but today we have solved the matter ».
Stern’s claims arise from the detailed study of an object in the confines of the solar system.
It is called Arrokoth, also known as Ultima Thule, and is located more than 6,000 million kilometers from the Sun, in a region called the Kuiper belt.
The scientists obtained images of high resolution from Arrokoth when NASA’s New Horizons spacecraft passed near it a little over a year ago.
The probe gave scientists their first chance to prove which of the two competing theories was correct: was it a shock or a delicate encounter?
The analysis performed by Stern and his team could not find evidence of a violent impact. They found no stress fractures, nor was there any flattening, indicating that the objects came together gently.
“This is completely decisive,” says Stern. “In one fell swoop, Arrokoth’s overflight could decide between the two theories.”
The scientist is optimistic because these Kuiper belt objects have remained largely the same since the formation of the solar system. They are, in effect, perfectly preserved fossils from this distant time.
The new theory of soft agglomeration was developed 15 years ago by Professor Anders Johansen at the Lund Observatory in Sweden. At that time I was a young PhD student. The idea came from computer simulations.
After talking with Stern, I gave Professor Johansen the phone first that his theory had been confirmed. There was a pause on the line before answering that “he felt great.”
«It is a special moment. I remember when I was a PhD student and I felt very nervous about these new results because they were very different from the previous ones, ”the professor added.
«I was worried that there was an error in my code or that I had made a miscalculation”.
«And then, when you see these results confirmed by real observations, it’s a true relief ».
Professor Johansen celebrated the occasion by eating pizza with his family.
Engineer Maggie Aderin-Pocock, who co-presents the BBC’s Sky at Night program, warned that care must be taken to bring down a whole theory based on the observation of an object, but said that Stern’s interpretation “makes a lot of sense.”
«It is good to have this evidence because crash theory was a good theory, but it had some questions. Why did the objects stick and not bounce? There were many things that did not add up ».