For the first time in recorded history, astronomers have observed an object from outside the solar system.

The small, fast-moving object, likely an asteroid or a comet, is less than a quarter-mile wide, according to NASA, which reported the observations last week. Scientists are scrambling to study it for as long as possible before its orbit takes it back out of the system and into the far reaches of the Milky Way.

David Trilling, an astronomy professor at Northern Arizona University, studies near-Earth objects that are large enough to do some damage if they collide with the planet, focusing on the size, temperature and ability of the objects to reflect sunlight. He called this space rock, identified as A/2017 U1, a completely new class of object. 

“We know from spectroscopic observations that its surface has a reddish color similar to objects from the outer regions of our solar system,” he said. “But that's it—we don't know where it came from or precisely where it is headed, and we don't know what it's made of.” 

Trilling earned his undergraduate degree from Harvard and his doctorate in planetary science from the University of Arizona. In September he authored a study examining the likely number of near-Earth asteroids, and earlier this year he oversaw a team of the students who created an infrared camera the size of a deck of cards, called TIPSI, that can determine the size of asteroids based on the amount of heat it emits.

Contact: David Trilling, associate professor of physics and astronomy, [email protected] or (928) 523-5505

Talking points

  • Astronomers measured the object’s orbit and determined it is “unbound”—an interloper that is not part of the solar system.
  • The presence of A/2017 U1 implies planet formation must be commonly occurring elsewhere in the galaxy.
  • The existence of orbs like A/2017 U1 has been proposed for years, and more are likely to be discovered in the future as telescope technology continues to improve.
  • Read more of Trilling's observations.