Meet BZ509 - Jupiter's hipster asteroid that goes around the solar system the wrong way

It's been stable for around a million years though.

Almost all planets and asteroids in our solar system orbit around the sun in the same direction – apart from one of Jupiter’s hipster companions.

Asteroid 2015 BZ509 (catchy, right?) has been found to orbit in reverse – known as orbiting in retrograde – while managing to stay stable and not crash, which is pretty impressive.

The study, published in the journal Nature, found that while all the planets in the solar system orbit in a prograde motion, along with 99.99% of currently known asteroids, BZ509, or BZ for short, acts a little differently.

In the animation below, BZ is the green dot, orbiting the sun alongside Jupiter and its thousands of other asteroids.

Not only does BZ orbit in reverse, its movements are known as “retrograde co-orbital motion”, which is even more rare.

Most asteroids which orbit in reverse are far away from planets, to reduce the risk of collision.

The study’s corresponding author, Paul Wiegert, wrote on his blog: “This makes sense: if a clown car is going to survive going the wrong way around the track, best to stay away from the big trucks.”

However, BZ is too cool for that rule – it shares the orbital space of Jupiter, the largest planet in our solar system.

Stars in the Milky Way pictured in clear skies at the Kielder observatory, Northumberland (Owen Humphreys/PA)
(Owen Humphreys/PA)

There should be a collision risk – BZ travels backwards, sharing the same space as Jupiter’s more than 6,000 Trojan asteroids that all go the right way.

But BZ is stable, and has been for around a million years – it passes Jupiter twice per obit, but a small gravitational tug keeps it from colliding with the gas giant.

Astronomers predict that BZ will stay this stable for the next million years at least- which is more than any of us can say.


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