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SEEING DOUBLEby Jeff Hecht

34 FEBRUARY 2020 • SKY & TELESCOPE

Binary

Worlds

PRIMITIVE WORLDThe Kuiper

Belt object 2014 MU 69 (now offi cially

named Arrokoth) is a contact binary,

each lobe a hodgepodge of smaller

regions. Scientists think this is the

most unchanged object from the

solar system’s formation that a

spacecraft has so far encountered.

Mercury Venus Earth Mars Asteroid belt Jupiter

127

near-Earth asteroids

(55 are contact

binaries)

28

Mars

crossing

asteroids

180

main-belt

asteroids

(1 co-classified

as a comet,

11 are contact

binaries)

3

Jupiter Trojan

asteroids (at L 4 )

(1 is a contact binary)

4

Jupiter Trojan

asteroids (at L 5 )

(1 is a contact binary)

1

contact binary

inside Earth’s orbit

6

contact binary

comets

NOT TO SCALE