Artistic representation of the Trojan system showing the large dual-shape Hektor and its moon.
H. Marchis & F. Marchis

What Gave an Asteroid Its Own Moon?

After 8 years of observing Hektor—the only known asteroid with its own moon—astronomers believe they’ve finally figured out more about its geology and orbit. In a study published online today in The Astrophysical Journal Letters, the team suggests that the asteroid is 250 kilometers wide and made of a mixture of rocks and ice, while the moon is 12 kilometers wide and orbits the asteroid every 3 days at 200 kilometers per hour. The team believes the unique pair may have formed after a collision between two icy asteroids.

See more Signal/Noise.

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