Possible Interstellar Object Spotted by Haleakalā Pan-STARRS Telescope

A possible asteroid or comet appears to have entered the solar system, and if confirmed by astronomers, would be the first interstellar object observed, originating from somewhere else in our galaxy.

The unusual object was discovered Oct. 19, 2017 by the University of Hawaiʻi’s Pan-STARRS 1 telescope on Haleakalā during the course of its nightly search for Near-Earth Objects for NASA.

This object designated by the name A/2017 U1, is less than a quarter-mile in diameter and astronomers say it is moving “remarkably fast.”

Astronomers are urgently working to point telescopes around the world and in space at the object to obtain additional data to be analyzed so that more can be known about its origin and composition.

Rob Weryk, a postdoctoral researcher at the University of Hawaiʻi Institute for Astronomy, was first to identify the moving object and submit it to the Minor Planet Center.  Weryk subsequently searched the Pan-STARRS image archive and found it was present in images taken the previous night, but was not initially identified by the moving object processing.

Weryk realized it was an unusual object saying, “Its motion could not be explained using either a normal solar system asteroid or comet orbit.”  Weryk contacted IfA graduate Marco Micheli, who had the same realization using his own follow-up images taken at the European Space Agency’s telescope on Tenerife in the Canary Islands. But with the combined data, Weryk said everything made sense. “This object came from outside our solar system,” said Weryk.

“This is the most extreme orbit I have ever seen,” said Davide Farnocchia, a scientist at NASA’s Center for Near-Earth Object Studies at the agency’s Jet Propulsion Laboratory in Pasadena, California. “It is going extremely fast and on such a trajectory that we can say with confidence that this object is on its way out of the solar system and not coming back.”

The CNEOS team plotted the object’s current trajectory and looked into its future. A/2017 U1 came from the direction of the constellation Lyra, cruising through interstellar space at a brisk clip of 15.8 miles (25.5 kilometers) per second, according to the IfA.

Astronomers say “The object approached our solar system from almost directly “above” the ecliptic, the plane in space near where the planets and most asteroids orbit the Sun, so it did not have any close encounters with the eight major planets during its plunge toward the Sun.”

According to the IfA, the small body crossed under the ecliptic just inside of Mercury’s orbit on Sept. 2, and then made its closest approach to the Sun on Sept. 9.  Pulled by the Sun’s gravity, the object made a hairpin turn under our solar system, passing below Earth’s orbit on Oct. 14 at a distance of about 15 million miles — about 60 times the distance to the Moon, according to the IfA.

Astronomers say it has now “shot back up” above the plane of the planets and, travelling at 27 miles per second with respect to the Sun, the object is speeding toward the constellation Pegasus.

“We have long suspected that these objects should exist, because during the process of planet formation a lot of material should be ejected from planetary systems. What’s most surprising is that we’ve never seen interstellar objects pass through before,” said Karen Meech, an astronomer at the IfA specializing in small bodies and their connection to solar system formation.

The small body has been assigned the temporary designation A/2017 U1 by the Minor Planet Center in Cambridge, Massachusetts, where all observations on small bodies in our solar system — and now those just passing through — are collected. MPC Director Matt Holman commented saying, “This kind of discovery demonstrates the great scientific value of continual wide-field surveys of the sky, coupled with intensive follow-up observations, to find things we wouldn’t otherwise know are there.”

“We have been waiting for this day for decades,” said CNEOS Manager Paul Chodas. “It’s long been theorized that such objects exist – asteroids or comets moving around between the stars and occasionally passing through our solar system – but this is the first such detection. So far, everything indicates this is likely an interstellar object, but more data would help to confirm it.”

Courtesy image: Photo of the Pan-STARRS 1 telescope atop Haleakala, Maui by Rob Ratkowski. Photomontage by Karen Teramura using an image of the Trifid Nebula taken with this telescope.

This schematic diagram of our solar system shows the dramatic path of A/2017 U1 (dashed line) as it crossed the plane of the planets (known as the ecliptic), and then turned and headed back out. The inset shows the object’s path through the inner solar system, with the short solid segment showing the small two-week-long portion of the path during which the object can be observed by large telescopes. For comparison, the highly elongated orbit of a comet, which is part of our solar system, is also depicted.
Credit: Brooks Bays / SOEST Publication Services / UH Institute for Astronomy

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