Sun may have had a sibling in the past, both may have trapped the mysterious Oort cloud and Planet Nine: Study
The Sun is a lone-star now. But during its infancy, it might have had a sibling. Together, these giants acted as "fishing nets", trapping objects that crossed their paths, according to a new theory. It also raises hopes of finding Planet Nine, whose existence is a matter of debate.
As time rolled by, our Sun's companion was driven out. "But before doing that, the solar system would have already captured its outer envelope of objects, namely the Oort cloud and the Planet Nine population," Dr Avi Loeb from Harvard University, who was a part of the study, told MEA WorldWide (MEAWW).
The Oort cloud, which occupies the far reaches of the solar system, is a strange place. Unlike most objects that have a disc-like orbit, this one looks like a spherical bubble wrapping the Sun, planets, and their moons, along with other asteroids. The occupants of the Oort cloud do not have a set orbit as they move aimlessly across the sphere. In fact, the icy comets, which occasionally visit the inner solar system, are thought to inhabit this unsual place.
Previous theories have suggested that the Oort cloud contains debris left behind by the solar system during its formation stage. But something about it did not sit right with Dr Loeb and his undergraduate student Amir Siraj, a Harvard undergraduate student. "This model has difficulty reproducing the observed ratio between the scattered disk population of objects and the more spherical Oort cloud," Dr Loeb said. But the existence of a second sun could account for that.
Stars are formed in nurseries
Stars are born in clusters or nurseries. "It resembles a family in which many children are born and then get dispersed," Dr Loeb explained. With time, the stars drift apart either due to stellar winds or due to the tidal gravitational force of the Milky Way galaxy, he added.
It is estimated that more than half of sun-like stars have a companion --and are called binary stars. "The situation is similar to having a twin brother at birth and losing that person from your orbit once you leave home," Dr Loeb added.
According to their theory, when the Sun was still in its birth cluster, its companion resided at a distance of 1,000 times between the Earth and the Sun. The team showed that this assumption reproduces the known properties of the Oort cloud and Planet Nine. What is more, the binary system increases the odds of the existence of Planet nine by a factor of roughly 20.
The theory will need testing. Vera Rubin Observatory, a telescope that is still under construction, could provide answers. The observatory is sensitive enough to look for Planet Nine and additional objects. "The binary model predicts that the orbital planes of these objects will be roughly aligned (and different from the plane of the Solar System planets) if they were all trapped by the same "fishing net" of the Sun and its companion," Dr Leob explained.
The study is published in Astrophysical Journal Letters.