Move over, ‘Oumuamua, there’s a new interstellar asteroid in town, and this one is here to stay. In fact, it has been here all along, ever since our solar system was first shaped into existence.
A new study published yesterday in the journal, Monthly Notices of the Royal Astronomical Society: Letters, announced the discovery of a peculiar asteroid that has taken up residence in Jupiter’s orbital path.
The newfound space rock, dubbed (514107) 2015 BZ509, or “BZ” for short, is “alien” in every sense of the word: it originated in another solar system and tumbled into our own in its early beginnings, right after the planets had finished forming.
The Royal Astronomical Society is calling it an “interstellar immigrant” because, unlike ‘Oumuamua, our first confirmed interstellar interloper that only popped by for a short visit last year, BZ has been with us for a very long time.
Study lead author Fathi Namouni, an astronomer at the Observatoire de la Côte d’Azur in France, told Reuters that BZ has a permanent-resident status and that it won’t be going away any time soon.
“If the solar system had a consular service and could issue visas to incoming asteroids, then ‘Oumuamua had only a short-stay visa whereas BZ was issued a green card.”
According to Space.com, the alien asteroid, which only measures 2 miles (3 km) in diameter, was first discovered in November, 2014, by the Pan-STARRS telescope at the Haleakala Observatory, in Hawaii — the same ground-based telescope that spotted ‘Oumuamua on October 19, 2017.
The most striking thing about this asteroid, and the detail that ultimately gave away its alien origin, is that it orbits the sun backwards. Traveling on the same orbit as Jupiter, BZ is circling the sun in the opposite direction of nearly all the objects in the solar system, including all eight planets.
Its bizarre orbit, described in the video below, is also known as a retrograde orbit and it’s what tipped off astronomers that BZ formed in another star system and migrated here.
“How the asteroid came to move in this way while sharing Jupiter’s orbit has until now been a mystery,” says Namouni.
“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,” he explains.
To get to the bottom of this, Namouni and study co-author Helena Morais, from São Paulo State University in Brazil, used computer models that traced the asteroid’s movement backwards in time. Described in the study as the “one million clone simulation,” the experiment produced a million possibilities for BZ’s orbit and observed their evolution, notes The Guardian.
The results revealed that the alien asteroid made the jump into our solar system 4.5 billion ago and has remained linked to Jupiter’s orbit ever since our planets first emerged in the early days of our solar system.
This suggests that BZ could very well be the oldest object in our solar system, says Namouni, pointing out that the asteroid “is a strong candidate” for this title.
The theory of how our interstellar immigrant got here has to do with how our sun was formed, notes Morais. As she explains, the sun was born in a dense stellar cluster, just like the ones recently spotted in the Orion A molecular cloud, where massive stars emerged in close quarters, each with its own planets and asteroids.
“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,” says Morais.
The discovery of our first interstellar immigrant has prompted astronomers to believe there could be others just like BZ hiding away in our solar system. Aside from shining new light into the birthplace of our sun, the newfound asteroid, whose composition is still unknown, could hold important clues about how life sparked in the universe, Morais added.
“This discovery tells us that the solar system is likely to be home to more extra-solar asteroids and comets captured early in its history. Some of these objects may have collided with the Earth in the past possibly carrying water, biomolecules or even organic material.”