Is ‘Oumuamua an Interstellar Asteroid or Comet?

This artist’s illustration shows the wayward interstellar visitor ‘Oumuamua (pronounced oh-MOO-ah-MOO-ah) racing toward the outskirts of our solar system.
The object, heated by the Sun (lower right), is venting gaseous material from its surface, as a comet would.

Researchers suggest this “outgassing” is one possible cause for ‘Oumuamua’s slight acceleration, as detected by several telescopes. The irregularly shaped object is now traveling away at about 70,000 miles per hour. The orbits of the major planets are included for scale. The box-shaped constellation Corvus is in the background near image center, and the bright blue star Spica is at upper left of center, in the constellation Virgo. The stars at bottom left belong to the constellation Hydra.

As the complex rotation of the object makes it difficult to determine the exact shape, there are many models of what it could look like.

CREDIT: NASA, ESA, and J. Olmsted and F. Summers (STScI) Larger image