Astronomers said on Monday that they had identified another invasive asteroid. The asteroid, known as 2015 BZ509 — “BZ” for short — was discovered in 2014 sharing orbital space with Jupiter, making a circuit of the sun about every 11.6 years. But it goes around the sun in the opposite direction of Jupiter and the other planets — in a so-called retrograde orbit. The only reason it can avoid banging into Jupiter is that its orbit is egg-shaped and so the rock slips inside and then outside of the giant planet’s orbit as it goes around. BZ had to have been an outsider from the start.

Source: New York Times May 21, 2018 12:17 UTC