Before astronomers first knew their telescopes in the early 17th century, the star had existed for about 4.5 billion years. We have only seen a brief glimpse of the long and extensive life cycle of our Sun.
According to a new study, we miss a spectacular view: Long ago, the sun differed in brightness and activity. It may have had twins as well.
The study, published this week in The Astrophysical Journal Letters, proposes a model whereby the sun was part of a binary system. The authors theorize that the Sun’s companion was expelled by another star that came too close.
The model has implications for the mysterious Planet Nine, and increases its chances of being once captured by the stellar duo.
The idea may seem wild to most, but Amir Siraj, the paper’s lead author and a student at Harvard University, finds it rather surprising.
“A large portion of Sun-like stars are born with binary companions,” Siraj explains Inverse. “And so in hindsight, it is quite surprising that it was never seriously considered that the Sun had an early binary companion that was lost. “
The connection between the sun and Planet 9
The idea of this study arose while Siraji was looking for answers to the formation of the Oort Cloud and the mystery behind a proven Planet Nine.
The Oort Cloud is a theoretical cloud of small icy objects that surround the sun at a distance of up to 3.2 light-years away. Meanwhile, Planet Nine is a hypothetically gigantic ninth planet orbiting the Sun in a very elongated orbit that lies far beyond Pluto.
This potential planet, also called “Planet X”, may have a mass about 10 times that of Earth and orbits about 20 times farther from the sun than Neptune, the eighth and farthest known planet from the sun. . However, it has never been directly observed.
“I was interested in two independent issues, the first was the formation of the Oort Cloud,” says Siraj.
Although extensive modeling of this cloud has been done, none of the models add up with the ratio of objects that exist in the Oort Cloud.
“Separately, there’s Planet Nine that fascinates me personally,” Siraj adds.
Astronomers at the California Institute of Technology (CALTECH) announced the discovery of Planet Nine in 2015 based on mathematical evidence. Although its existence is still theoretical to this day, immediate discovery of a ninth planet would be the first discovery of a new planet orbiting the solar system in two centuries.
However, astronomers have not been able to come up with a model to explain how Planet Nine could have originated in the first place and travel so far away from the sun. The three leading theories are either:
- It was taken prisoner and dragged
- It formed at a distant location
- It formed under the giant planets of the solar system, then dispersed
“What surprised me was that all of these formation scenarios had low odds,” Siraj says. “I had these two kinds of puzzles in the solar system that I thought about for a while.”
Through his research into binary galaxies, Siraj knew that these systems were much more efficient at capturing objects than solitary stars. Based on this, he created a model of the Sun as part of a binary system, together with a guiding star.
“This greatly increases the chance that Planet Nine exists.”
The stars are said to have been about 1,500 astronomical units apart and orbited their center of mass until a transient star sort of split the binary duo and the companion protruded, according to the study.
As a binary system, the two stars could capture the number of objects in the Oort cloud, as well as a ninth, distant planet. By itself, a lone sun would not be able to do the same.
The model increases the chances that Planet Nine was captured by a factor of 20, according to the researchers.
“This is significant because none of the origin scenarios for Planet Nine have a very high chance,” says Siraj. “This greatly increases the chance that Planet Nine exists.”
Siraj and his colleagues will be able to verify their model through observations of Planet Nine by the upcoming Ruby Observatory’s Large Synoptic Survey Telescope, which is expected to launch in the year 2021.
“It’s kind of poetic that we might have once been part of a binary system itself, which may have formed the Oort Cloud,” says Siraj.
Abstract: We show that an equal mass, temporary binary companion for the Sun in the solar birth cluster at a separation of ~ 103 au would increase the chance of forming the observed population of outer Oort Cloud objects and capturing Planet Nine. In particular, the discovery of a captive origin for Planet Nine would favor our binary model by an order of magnitude relative to a solitary stellar history. Our model predicts an abundance of dwarf planets, discovered by Legacy Survey of Space and Time, with similar orbits as Planet Nine, which would result in capture by the stellar binary.
