About 4.7 billion years ago, when the Solar System was formed, the Sun might not have been the only conductor. This is the hypothesis proposed by American astrophysicists who argue that initially, the Sun could have had a similar mass companion. This companion star would thus have played a role in the formation of the outer Solar System, in particular by capturing the objects making up the Oort cloud and the potential Nine Planet.
A new theory published today in the journal Astrophysical Journal Letters by physicists at Harvard University suggests that the Sun may have already had a similar mass binary companion. If confirmed, the presence of a first stellar companion increases the likelihood that the Oort Cloud has formed as currently observed and that Planet Nine has been captured rather than formed in the Solar System.
Avi Loeb, Frank B. Baird Jr. and Amir Siraj postulate that the existence of a long-lost stellar binary companion in the Sun’s birth star cluster – the collection of stars that formed with the Sun at starting from the same dense cloud of molecular gas – could explain the formation of the Oort cloud as we observe it today.
Oort cloud: it could have been born from the capture of objects by a binary system
Popular theory associates the formation of the Oort Cloud with debris left behind by the formation of the Solar System and its neighbors, where objects were scattered by planets at great distances and some were swapped between stars. But a binary model could be the missing piece of the puzzle and, according to Siraj, should come as no surprise to scientists.
« Previous models struggled to produce the expected ratio of scattered disk objects to outer Oort cloud objects. The binary capture model offers a significant improvement, which is apparently evident in retrospect: most Sun-like stars are born with binary companions. ».
The existence of a stellar companion at the beginning of the formation of the Solar System could explain the formation of the Oort cloud. Credit: NASA
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If the Oort cloud had indeed been captured with the help of an early stellar companion, the implications for our understanding of the formation of the solar system would be significant. ” Binary systems are much more efficient at capturing objects than single stars. If the Oort cloud formed as observed, this would imply that the Sun actually had a similar mass companion that was lost before the Sun left its initial cluster. Loeb explains.
More than a simple redefinition of the formation of our Solar System, evidence of a captured Oort cloud could answer questions about the origins of life on Earth. Objects in the Outer Oort Cloud may have played an important role in Earth’s history, such as bringing water to Earth and causing the dinosaurs to become extinct. Understanding their origins is therefore important.
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A plausible explanation for the existence of the potential Nine Planet
The model also has implications for the Planet Nine hypothesis, which Loeb and Siraj say is not the only planet in this area of the Solar System. ” The puzzle is not only about the Oort clouds, but also extreme transneptunian objects, like the potential Planet Nine. It is not known where they came from, and our new model predicts that there should be more objects with an orbital orientation similar to Planet Nine. Loeb says.
The Oort cloud and the proposed location for Planet Nine are so far from the Sun that direct observation and evaluation is a challenge for researchers today. But the Vera C. Rubin observatory, which will be launched in early 2021, will confirm or deny the existence of Planet Nine and its origins. Siraj is optimistic: “ If the VRO confirms the existence of Planet Nine, and also finds a population of similarly captured dwarf planets, then the binary pattern will be favored over the lone stellar story that has long been assumed. ».
If the sun had an early companion who helped form the Outer Solar System, its current absence begs the question: where has it gone? ” The passage of stars in the birth cluster would have moved the companion away from the sun thanks to their gravitational influence. Before the loss of the binary, however, the Solar System would already have captured its outer shell of objects, namely the Oort Cloud and the population of Planet Nine. The Sun’s long-lost companion could now be anywhere in the Milky Way », Concludes Loeb.
Sources : arXiv
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