In a paper published in the Astrophysical Magazine Letters, Harvard University astrophysicists Avi Loeb and Amir Siraj show that a similar mass star companion to the Sun in the solar birth cluster – the collection of stars that together with our star formed from the same dense cloud of molecular gas – at a separation of 1,000 AU would increase the chance of forming the observed population of objects in the outer Over Cloud and from establishing the Planet Nine hypothesis.
A conception of an artist of a potential solar companion, which theorists believe was developed in the natal cluster of the Sun and later lost. As evidenced, the theory of solar companionship would provide additional credibility to theories that shaped the Oort Cloud as we see it today, and that Planet Nine was taken prisoner instead of shaped in place. Image credit: M. Weiss.
Popular theory associates the formation of the Oort Cloud with pun left over from the formation of the solar system and its neighbors, where objects were scattered by large planets by large planets and some were exchanged between stars.
But a binary model could be the missing piece in the puzzle and should not come as a surprise to scientists.
“Previous models have had difficulty producing the expected ratio between scattered disk objects and outer Oort Cloud objects,” said Siraj, an undergraduate student in the astronomy department at Harvard University.
“The binary capture model offers significant improvement and refinement, which is evident in retrospect: most Sun-like stars are born with binary companions.”
If the Oort Cloud were indeed captured with the help of an early stellar companion, the implications for our understanding of the formation of the Solar System would be important.
“Binary systems are much more efficient at capturing objects than one-stars,” said Professor Loeb.
“If the Oort Cloud formed as observed, it would imply that the Sun actually had a companion of the same mass that was lost before the Sun left its birth cluster.”
More than just redefining the definition of our solar system, evidence of a captured Oort Cloud could answer questions about the origin of life on Earth.
‘Objects in the outer Oort cloud may have played important roles in the history of the earth, such as possibly supplying water to the earth and causing the extinction of the dinosaurs. Understanding their origins is important, ”said Siraj.
The model also has implications for the Planet Nine hypothesis, which is not the only team to consider.
“The puzzle is not only about the Oort clouds, but also extreme trans-Neptunian objects, such as the potential Planet Nine,” said Professor Loeb.
“It is unclear where they came from, and our new model predicts that there should be more objects with a similar orbital orientation than Planet Nine.”
If the sun had an early companion, which contributed to the formation of the outer solar system, its present absence raises the question: where did it go?
“Continuation of stars in the birth cluster would have removed the companion from her sun due to her gravitational influence,” said Professor Loeb.
“Before the loss of the binary, however, the solar system would have captured all of its outer envelope of objects, namely the Oort Cloud and the population of the Planet Nine,” Siraj added.
“The long-lost companion of the sun could now be anywhere in the Milky Way.”
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Amir Siraj and Abraham Loeb. 2020. The Case for an Early Solar Binary Companion. ApJL 899, L24; doi: 10.3847 / 2041-8213 / abac66
