How 'wrong-way' asteroid avoids collision with Jupiter decoded

Scientists have found how an asteroid orbiting the wrong way around the Sun has been avoiding slamming into Jupiter, despite being on an apparent collision course with the giant planet and about 6,000 other asteroids.

The asteroid, nicknamed Bee-Zed, is the only one in this solar system that is known both to have an opposite, retrograde orbit around the Sun while at the same time sharing a planet's orbital space, said Paul Wiegert from Western University in the US.

All but 82 of the million or so known asteroids in our solar system travel around the Sun in what is called a prograde motion: that is, counter-clockwise when visualised from above.

However, asteroid 2015 BZ509 ("Bee-Zed" for short) circles clockwise, in a retrograde motion - moving against the flow of all other asteroids in the giant planet's orbital entourage.

"It is as if Jupiter is a monster truck on a track circling the sun, and the asteroids in Jupiter's orbit are sub-compact cars all whizzing along in the same direction," researchers said.

"Bee-Zed is the rogue - driving around the track in the wrong direction - steering between the 6,000 other cars and swerving around the monster truck," they said.

It has been doing this in every single lap for thousands of laps for a million years or more.
Western University asteroid expert Paul Wiegert explains how recently discovered asteroid Bee-Zed has managed to avoid slamming into Jupiter, despite its being on an apparent collision course with the giant planet.

Jupiter's gravity actually deflects the asteroid's path at each pass so as to allow both to continue safely on their way, Wiegert said.

Little is known about the asteroid, which was discovered in January, 2015. It has a diameter of about three kilometers and it may have originated from the same place as Halley's comet, which also has a retrograde orbit.

The team has not been able to determine yet if Bee-Zed is an icy comet or a rocky asteroid.
However, their analysis - based on complex calculations and on observations through the Large Binocular Camera on the Large Binocular Telescope in Mt Graham, Arizona, during a span of 300 days - show Bee-Zed is somehow able to maintain a stable orbit even as an outlier.

The calculations conducted by the team show the orbit has been stable for at least a million years and will be stable for at least a million more.

Learning more about the asteroid provides another intriguing glimpse into previously unknown and unmapped features of our solar system.