A study conducted by scientists from the Institute of Geosciences and Exact Sciences of the State University of Sao Paulo (IGCE-UNESP) in Rio Claro, Brazil, identified 19 asteroids of interstellar origin classified as Centauri, objects of the external Solar System that revolve around the Sun in the region between the orbits of Jupiter is Neptune.
An article on the study entitled “An interstellar origin for high-inclined centaurs”; is published in Monthly notices from the Royal Astronomical Society. The study was supported by FAPESP.
“The Solar System was formed 4.5 billion years ago in a stellar nursery, with its systems of planets and asteroids. The stars were close enough to each other to favor strong gravitational interactions that led to an exchange of material between the systems. Some objects now in the Solar System must therefore have formed around other stars. Until recently, however, we have not been able to distinguish between captured interstellar objects and objects that formed around the Sun. The first identification was made by us in 2018, “Maria Helena Moreira Morais told FAPESP of the two co-authors.
Morais graduated in physics and applied mathematics from the University of Porto (Portugal) and holds a PhD in solar system dynamics from the University of London (United Kingdom). He is currently a professor at IGCE-UNESP. The other coauthor is Fathi Namouni, researcher at the French Riviera Observatory in Nice, France.
The first identification Morais referred to was the asteroid 514107 Ka’epaoka’awela, as reported by Agência FAPESP in 2018.
The name Ka’epaoka’awela is Hawaiian and can be roughly translated into “mischievous opposite companion of Jupiter”. It has occupied the path corresponding to Jupiter’s orbit for at least 4.5 billion years, but rotates around the Sun in the opposite direction to that of the planets, that is, it is a retrograde co-orbital asteroid of Jupiter.
“When we identified it as an object from outside the Solar System, we didn’t know if it was an isolated case or part of a large population of immigrant asteroids,” said Morais. “In this latest study, we recognized 19 centaurs of interstellar origin.”
Similar to Ka’epaoka’awela, the Centaurs identified in the study have orbits very inclined with respect to the orbital plane of the planets. “To investigate the origin of these objects, we created a computer simulation that works like a time machine, performing their backward trajectories of 4.5 billion years. The simulation allowed us to find out where these objects were at the time, “said Morais.
The planets and asteroids originating from the Solar System emerged from a thin disk of gas and dust that once orbited the Sun. For this reason, they all moved on the disk plane 4.5 billion years ago. If the Centaurs originated in the Solar System, at that time they would have had to move also on the plane of the disk. “However, our simulation showed that 4.5 billion years ago, these objects rotated around the Sun in orbits perpendicular to the plane of the disk. In addition, they did so in a region distant from the gravitational effects of the original disk,” he said. Morais.
These two results showed that the Centaurs did not originally belong to the Solar System and that they must have been captured by nearby stars during the planet’s formation period.
The discovery in the Solar System of an interstellar population of asteroids is an important step in understanding the differences and similarities between objects that formed in the Solar System and objects in the Solar System that were originally extrasolar. Future astronomical observations and possibly space missions will deepen this understanding. “Studies of this population will bring to light information on the stellar nursery from which the Sun emerged, on the capture of interstellar objects in the primordial Solar System and on the importance of interstellar matter for the chemical enrichment of the Solar System,” said Morais.
As for chemical enrichment, it is worth remembering that the primordial universe is mainly composed of hydrogen and helium. The lightest natural elements on the periodic table were created by nuclear fusion within the stars and then spread to space. The region in which the Solar System is located has been chemically enriched by these elements, which have contributed to the composition of the human body.
Reference: “An interstellar origin for high-inclined centaurs” by F Namouni and M H M Morais, 23 April 2020, Monthly notices from the Royal Astronomical Society.
DOI: 10.1093 / mnras / staa712