Bizarre, backwards asteroid might be from another star, scientists say

2015 BZ509 is in Jupiter’s orbit, circling the sun in the opposite direction

For billions of years, without our knowing it, scientists say, our solar system has harbored a visitor from another star.

This interstellar immigrant — an asteroid dubbed 2015 BZ509 — lurks in the orbit of Jupiter, where it circles the sun in the opposite direction of the gas giant planet and nearly everything else in the solar system. The twin facts that it shares an orbit with a planet and flies against the flow of traffic make it like no other known object in our celestial neighborhood.

According to new research published Monday in the Monthly Notices of the Royal Astronomical Society, that’s because it doesn’t come from here. Careful analysis of the asteroid’s orbit and repeated simulations of every possible origin scenario found that it most likely migrated from another planetary system when the sun still inhabited the stellar nursery of its infancy, 4.5 billion years ago.

“We were not at all expecting to find out it came from another star,” said Fathi Namouni, an astronomer with the Observatory of Côte d’Azur in France, who coauthored the study alongside Sao Paolo State University researcher Helena Morais.

“But the general idea, which is very encouraging, is we now know the solar system did not form in isolation,” Namouni said.

It’s a provocative conclusion — reached without demonstrating how 2015 BZ509 could have been captured from another star, outside researchers noted.

“It’s feasible … but there are other possibilities,” said Elisa Quintana, an astrophysicist at NASA’s Goddard Space Flight Center who was not involved in the new study. “… it’s hard to rule out just pure chaos and collisions.”

Last year, Quintana was part of a team of NASA researchers that analyzed “Oumuamua” — the first interstellar solar system visitor scientists have ever seen. That cigar-shaped space rock is tumbling past us at such high speeds that it could only have originated elsewhere, researchers said, and it’s already on its way back out into space. It will pass Neptune’s orbit in 2022 and eventually leave the solar system en route to the constellation Pegasus, according to NASA.

By comparison, 2015 BZ509 — known as “Bee Zed” — appears to be here for the long haul.

SOURCE: NASA On Monday, scientists reported that an asteroid sharing Jupiter’s orbit, but in reverse, hails from a neighboring star system and has been in this peculiar orbit for about 4.5 billion years.