“The solar system did not grow up in isolation,” Fathi Namouni of the Observatoire de la Côte d’Azur told the Guardian.
It makes sense—the universe doesn’t have compartments or closed doors. But now we have direct evidence that bodies from beyond our solar system might have played a role in bringing organic material and water to planet Earth. Scientists have discovered a permanent visitor from interstellar space cruising through our solar system.
This marks the first time we’ve identified a permanent local asteroid that didn’t originally come from our own solar system. ‘Oumuamua, a different asteroid detected earlier this year, was only a temporary visitor. Named 2015 BZ509, this permanent asteroid was first spotted in late 2014 by the Pan-Starrs project at the Haleakala Observatory in Hawaii. Astronomers then noticed that the asteroid has a retrograde orbit (or, an orbit in the opposite direction of the planets).
Here’s Nicola Davis, reporting for the Guardian:
Asteroids that orbit the sun on paths that take them between the giant planets—Jupiter, Saturn, Uranus and Neptune—are known as centaurs, and it is thought that many might come from distant bands of material within the solar system such as the scattered disk or the Oort cloud. Several, like BZ509, are known to have retrograde paths, although how they ended up on such orbits is unclear.
What’s more, centaurs’ orbits are difficult to pin down precisely and are thought to be unstable.
But there was a clue there was something unusual about BZ509: while previous studies suggested retrograde centaurs stay gravitationally “tied” to planets for 10,000 years at most, recent work had suggested this asteroid’s orbit had been linked to Jupiter for far longer, probably as a result of the planet’s mass and the way both take the same time to orbit the sun.
Researchers writing in the journal of the Royal Astronomical Society this week concluded, after further analyzing the asteroid’s orbit, that the asteroid’s orbit seems to have been linked to Jupiter’s for 4.5 billion years—or, the end of planet formation. The team also inferred—through computer modeling—that asteroids captured in such a way by Jupiter but that had since broken free (unlike BZ509) from its gravitational pull would now be orbiting the Sun on a path that is perpendicular to the plane of the solar system.
The finding isn’t just a cool anomaly. It suggests that cross-contamination between solar systems can happen, thus increasing our odds of finding life elsewhere beyond our solar system.