Awkward Visitor


by Brian Koberlein | 27 May 2018 | Astronomy

This is a companion discussion topic for the original entry at


Asteroids that are co orbital may face a lesser probability of colliding with other asteroids. But retrograde asteroids may have more chances of colliding with another asteroid. In this context, that it survived billion years is perhaps extraordinary.

That something is retrograde because it came from outside the solar system can be understood however improbable such an external event may be. But how can that retrograde motion also be coorbital with one of the planets? I thought ‘coorbital’ means it rotates in the same direction around the sun as other bodies, and retrograde means it rotates in the opposite direction to all other planets with respect to the sun.


This article includes a video simulation of the orbit: Science Alert: An Interstellar Object Has Been Hiding in Our Solar System This Whole Time.


Thank you Barthel. I think I had not understood the term co-orbital correctly when I asked the question. Your link helped me to reach out to more links and all of them collectively gave me an intuition about this.