Vaaju (Índia)

Astronomers identify asteroids of interstellar origin that live in our solar system

Publicado em 20 julho 2020

A study by researchers at São Paulo State University’s Institute of Geosciences and Exact Sciences (IGCE-UNESP) in Rio Claro, Brazil, has identified 19 asteroids of interstellar origin classified as Centaurs, external solar system objects orbiting the sun in the region between orbits to Jupiter and Neptune.

An article on the study entitled “An Interstellar Origin of High Slope Centaurs”; is published in Royal Astronomical Society monthly announcements. The study is supported by FAPESP.

“The solar system was formed 4.5 billion years ago in a star chamber with its planets and asteroids. The stars were close enough to each other to promote 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 could not distinguish between captured interstellar objects and objects formed around the sun. The first identification was made by us in 2018, ”said Maria Helena Moreira Morais, one of the two coauthors, Agência FAPESP.

The discovery of the Brazilian researcher reported in the Royal Astronomical Society’s Monthly Notices provides clues to understand the stellar chamber from which the sun came out. Credit: NASA

Morais graduated in physics and applied mathematics from the University of Porto (Portugal) and received a doctorate in solar system dynamics from the University of London (UK). She is currently a professor at IGCE-UNESP. The other co-author is Fathi Namouni, a researcher at the Côte d’Azur Observatory in Nice, France.

The first identification that Morais referred to was the asteroid 514107 Ka’epaoka’awela, reported by Agência FAPESP 2018.

The name Ka’epaoka’awela is Hawaiian and can roughly be translated as “evil opposite of Jupiter’s companion.” It has occupied the orbit corresponding to Jupiter’s orbit for at least 4.5 billion years but orbits the sun in the opposite direction to the planets, ie it is a retrograde co-orbital asteroid of Jupiter.

“When we identified it as an object coming outside the solar system, we did not know if it was an isolated case or part of a large population of immigrant asteroids,” Morais said. “In the latest study, we recognized 19 centaurs of interstellar origin.”

Composition made by the scientist of an artistic image from NASA was used to show what the original solar system would be like, with the addition of a Centaur in polar orbit in the outer region. Credit: Maria Helena Moreira Morais

Like Ka’epaoka’awela, the centaurs identified in the study have strongly inclined orbits with respect to the planet’s orbit. “To investigate the origin of these objects, we built a computer simulation that acts as a time machine and runs its orbits backwards by 4.5 billion years. The simulation made it possible for us to find out where these objects were at that time, Morais said.

The planets and asteroids that originated in the solar system came from a thin disk of gas and dust that once orbited the sun. For that reason, they all moved in the plane of the disk 4.5 billion years ago. If Centaurs originated in the solar system, they should also have moved in the plane of the disk at that time. “But our simulation showed that 4.5 billion years ago, these objects orbited the sun in orbits perpendicular to the plane of the disk. In addition, they did it in a region far removed from the gravitational effects of the original album, “said Morais.

These two findings showed that Centaurs did not originally belong to the solar system and must have been captured from nearby stars during the planet formation period.

Star nursery

The discovery in the solar system of a population of asteroids of interstellar origin is an important step in understanding the differences and similarities between objects formed in the solar system and objects in the solar system that were originally extrasolar. Future astronomical observations and possible space missions will deepen this understanding. “Studies of this population will show information about the stellar chamber from which the sun came out, the capture of interstellar objects in the primordial solar system and the importance of interstellar matter for the chemical enrichment of the solar system,” Morais said.

When it comes to chemical enrichment, it is worth remembering that the primordial universe consists mainly of hydrogen and helium. The lightest natural elements of the periodic table were created by nuclear fusion in the stars and then spread through space. The region where the solar system is located chemically was enriched by these elements, which contributed to the composition of the human body.

Reference: “An Interstellar Origin of Centaurs with High Slope” by F Namouni and MHM Morais, 23 April 2020, Royal Astronomical Society monthly announcements.

DOI: 10.1093 / mnras / staa712