Astronomers Record First Observation of an Interstellar Object

By Nathaniel Scharping | October 27, 2017 12:26 pm
Animation showing the path of A/2017 U1 through the solar system. (Credit: NASA/JPL)

Animation showing the path of A/2017 U1 through the solar system. (Credit: NASA/JPL)

Astronomers have spotted an interstellar visitor for the first time.

It’s either a comet or an asteroid, and came speeding right through the heart of our solar system; after a hairpin turn around the sun, it’s now on its way back out of our cosmic backyard. Scientists at the University of Hawaii’s Pan-STARRS 1 telescope at Haleakala first spotted the quarter-mile-wide object on Oct. 19, and knew immediately that it was something different.

“Its motion could not be explained using either a normal solar system asteroid or comet orbit,” says Rob Weryk, a postdoctoral researcher at the University of Hawaii. “This object came from outside our solar system.”

The object, named A/2017 U1 for now, is moving in a path much too eccentric to be a comet or asteroid from inside the solar system. It shot into our home system from above, at a far higher angle than any other objects orbiting the sun. It’s going fast, too, around 15.8 miles per second, another clue that it comes from far away. It’s the first time astronomers have managed to confirm an interstellar object in our solar system, although they’ve long suspected that comets and asteroids must be flying free throughout the universe.

The path A/2017 U1 took as it crossed through our solar system. (Credit: Brooks Bays / SOEST Publication Services / UH Institute for Astronomy)

The path A/2017 U1 took as it crossed through our solar system. (Credit: Brooks Bays/SOEST Publication Services/UH Institute for Astronomy)

The object dove inside of Mercury’s orbit before being spun around by the Sun’s gravitational pull and whipped outward again. It came closest to the Sun on September 9, and passed about 14 million miles from Earth on October 14. At the moment, its trajectory is taking it toward the constellation of Pegasus.

Before it goes, the astronomers hope to gather some information about its composition. Other solar systems may look a little different than ours, and pinning those differences down would help scientists understand how solar systems form and behave. Normally, they need to observe such systems from far away. Now, for a little bit at least, we’ve got part of another solar system right at hand.

CATEGORIZED UNDER: Space & Physics, top posts
  • Uncle Al

    Nice hyperbolic orbit. Solar-bound orbits impacting Earth can be above 40 miles/second geocentric,


    • Erik Bosma

      I suppose it may have something to do with its position and location in the Solar System?

    • Robin Walker

      Most of the conversation about the possibility of asteroids hitting Earth have focussed on known solar system objects in elliptical orbits. Objects from outside the solar system will necessarily follow hyperbolic orbits, and have much higher velocities, and will be essentially unpredictable. Very interesting (and perhaps a bit scary?) that this passed so close to us.

  • Erik Bosma

    So far I have only “seen” an animation. When do we get to see any images? Or didn’t we actually ‘see’ it?

  • JR

    Probably one of those hollowed-out asteroids the aliens use, coming in to the Sun to refuel.

  • Giovanni Caproni

    Wow, given the vastness of the universe, even of our galaxy, the odds of an object even approaching within a few light years of our solar system seems remote– for it to enter the solar system and “graze” the sun and earth seems almost fantastically improbable. Could there be other explanations for its speed and trajectory? Gravitational assists from one of the giant planets, perhaps?

    • Giovanni Caproni

      … although its trajectory would seem to rule out a planetary gravitational assist. Wow, just wow.

  • Don Haywood

    It may be more crowded out there than we currently think. Uranus was almost nailed by something big a long time ago. Still relatively very empty, though.

  • kapnlogos

    I wonder if we got a radar image of it?


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar