Pan-STARRS-1 discovers interstellar object has entered our Solar System

Artist’s rendition of a Near Earth Object (NEO). Image Credit: NASA

An asteroid (or comet) recently discovered in an extreme orbit originated beyond the Solar System in interstellar space, astronomers noted in a recent report. Initially discovered with the Pan-STARRS 1 telescope at the University of Hawaii on October 19, the object is the first such detected by scientists.

Researchers at NASA’s Center for Near-Earth Object Studies (CNEOS), located at the Jet Propulsion Laboratory (JPL), confirmed the interstellar origin of the object, designated A/2017 U1 based on its highly unusual orbit.

“It’s long been theorized that such objects exist—asteroids or comets moving between the stars and occasionally passing through our Solar System—but this is the first such detection,” noted CNEOS Manager Paul Chodas via an agency-issued release. “So far, everything indicates this is likely an interstellar object, but more data would help to confirm it.”

University of Hawaii Institute for Astronomy (IfA) post-doctoral researcher Rob Weryk first spotted the object while conducting his nightly search for near-Earth Objects using Pan-STARRS 1.

Upon discovering the moving object, he reported it to the Minor Planet Center (MPC) in Cambridge, MA, which catalogs asteroids and comets, then looked at Pan-STARRS archives and found images of it captured on the previous night.

Pan-STARRS1 Observatory atop Haleakala Maui at sunset. Photo Credit: Rob Ratkowski

Recognizing it had an unusual orbit, Weryk contacted fellow IfA graduate Marco Micheli, who then imaged the object using the European Space Agency’s (ESA) Canary Islands telescope on Tenerife.

When they combined their data, both Weryk and Micheli agreed A/2017 U1 originated beyond the Solar System.

“Its motion could not be explained using either a normal Solar System asteroid or comet orbit,” Weryk said.

CNEOS scientists subsequently analyzed its past and future trajectories, discovering it came from the direction of the constellation Lyra at a speed of 15.8 miles (25.5 km) per second and is headed on a one-way journey out of the Solar System toward the constellation Pegasus, now traveling at 27 miles (44 km) per second.

“This is the most extreme orbit I have ever seen,” said CNEOS scientist David Farnocchia. “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.”

A/2017 U1 headed toward the Solar System from almost directly above the ecliptic or plane of Earth’s orbit. Since most planets and Solar System objects orbit near the ecliptic, it never came near any of them.

On September 2, then within the orbit of Mercury, the object crossed below the ecliptic, reaching its closest point to the Sun one week later.

With the Sun’s gravity pulling it, A/2017 U1 then made a quick U-turn, passing beneath Earth’s orbit at a distance of 15 million miles (24 million km) before speeding back above the ecliptic.

Long theorized to exist, such objects are likely material ejected from planetary systems during their planet formation processes, noted Karen Meech, an IfA astronomer who studies small objects and their connection to the formation of solar systems.

“What’s most surprising is that we’ve never seen interstellar objects pass through before,” she said.

Scientists worldwide are turning their telescopes toward the object, hoping to see observations of it as the object leaves the Solar System, which will shed light on its origin and composition.

Being the first of its kind, the object has a temporary designation as A/2017 U1 until the International Astronomical Union (IAU) comes up with a schematic for naming such objects.

“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,” MPC Director Matt Homan stated.

This animation shows the path of A/2017 U1, which is an asteroid – or perhaps a comet – as it passed through our inner Solar System in September and October 2017. From analysis of its motion, scientists calculate that it probably originated from outside of our Solar System. Animation & Caption Credit: NASA/JPL-Caltech

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Laurel Kornfeld

Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.