Last updated May 22, 2018 at 9:44 pm
Astronomers have discovered an object orbiting Jupiter which they say is not from our solar system.
These are images of 2015 BZ509 obtained at the Large Binocular Telescope Observatory (LBTO) that established its retrograde co-orbital nature. The bright stars and the asteroid (circled in yellow) appear black and the sky white in this negative image. Credit: C. Veillet / Large Binocular Telescope Observatory
When the interstellar asteroid ‘Oumuamua passed us by last year, astronomers peered intently hoping to find the secrets of rocks and asteroids from other solar systems.
Now, scientists have discovered an asteroid currently nestling in Jupiter’s orbit which they say started life in another solar system.
The difference between it and ‘Oumuamua, however, is that while ‘Oumuamua was just passing through our solar system, the newly discovered asteroid has moved in permanently.
Interstellar immigrant
The asteroid, with the catchy name (514107) 2015 BZ509, started life in a different solar system – which one, we’re not sure of yet.
The giveaway that it doesn’t belong to us comes from its orbit itself.
All of the planets in our Solar System, and the vast majority of other objects as well, travel around the Sun in the same direction. However 2015 BZ509 is different – it moves in the opposite direction in what is known as a ‘retrograde’ orbit.
“How the asteroid came to move in this way while sharing Jupiter’s orbit has until now been a mystery,” said lead author Dr Fathi Namouni, from France’s Observatoire de la Côte d’Azur.
“If 2015 BZ509 were a native of our system, it should have had the same original direction as all of the other planets and asteroids, inherited from the cloud of gas and dust that formed them.”
The researchers ran simulations to trace the location of 2015 BZ509 back to the birth of our Solar System, 4.5 billion years ago. At this time, the planets had just formed and the solar system was more closely like what we see today.
In their simulation, they plotted millions of 2015 BZ509 clones with slight changes in their orbit in order to trace how their orbits evolved over time. Most of the alternates collided with the Sun, or were ejected from the solar system completely. Only a handful survived the entire life of the solar system – those which closely followed the orbit of 2015 BZ509.
This, they suggest, mean that it is likely that it had been in that orbit for nearly the entire life of the solar system, anything else and it would have disappeared long ago. And for that entire time, 2015 BZ509 would have been moving in the opposite direction, according to the simulation.
The authors claim this retrograde orbit means that it could not have been there originally and must have been captured from another system – had it come from the process of formation of the solar system it should have been rotating the same direction as the other components.
However, the simulations did not reveal where else the asteroid could have come from, leaving a massive hole in the story. And that hole has some researchers worried with the conclusion drawn.
Instead, some told the National Geographic, it could be an inactive comet from the outer regions of our solar system. After being pushed retrograde far from the Sun, it could have then subsequently been pushed and pulled into its orbit in the last few million years.
This is an image of stellar nursery NGC 604 (NASA/HST), where star systems are closely packed and asteroid exchange is thought to be possible. Asteroid (514107) 2015 BZ 509 emigrated from its parent star and settled around the Sun in a similar environment. Credit: NASA / Hubble Heritage Team (AURA/STScI)
Picking up a passenger from another solar system
Namouni and his colleagues’ model suggest that at some point probably quite early in the life of our solar system, the asteroid was essentially exchanged from another solar system and got trapped in orbit with Jupiter.
“Asteroid immigration from other star systems occurs because the Sun initially formed in a tightly-packed star cluster, where every star had its own system of planets and asteroids,” said Dr Helena Morais, who was also part of the team which made the discovery.
“The close proximity of the stars, aided by the gravitational forces of the planets, help these systems attract, remove and capture asteroids from one another.”
The researchers think that 2015 BZ509’s settlement in our Solar System could one day provide clues about the Sun’s original star nursery, and about the potential enrichment of our early environment with components necessary for the appearance of life on Earth.
The big advantage that researchers have when it comes to tackling those questions, however, is its stable life in our solar system.
Unlike a visitor such as ‘Oumuamua, future missions to Jupiter could include a study of 2015 BZ509 during flyby, or even landing a probe.
“Direct sampling of the asteroid is a fossil into the distant past of one of our Sun’s possible siblings. We can learn about the conditions of that alien star system and begin to understand what ways our Solar System was unique such life arose here,” said astronomer Alan Duffy, who was not involved with the current research.
“We can relatively easily send explorers to Jupiter and its surrounding moons. It’s not impossible that we could send a spacecraft to land on this asteroid, and even return a sample to Earth in just a few years.”
And a probe would probably answer the question of its origin. Whatever answer came out, the results would be a boon for researchers.
Duffy agrees, saying that this is a unique opportunity offering information that would otherwise be beyond our reach.
“It’s beyond humanity’s ability to directly explore another star system.”
“To think of actually returning a sample from around another star is pure science fiction and yet with this asteroid a potential alien star system has come to us!”
The research has been published in Monthly Notices of the Royal Astronomical Society: Letters
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