An ‘interstellar object’ was observed arriving in our solar system

By Ben Thompson Globe Correspondent 

A quarter-mile-wide object appears to have entered our solar system, inspiring scientists around the world to turn their telescopes in its direction.

“This is the first time that people have confidence they’re seeing an object that’s from another solar system,” said Matt Holman, director of the Minor Planet Center at the Harvard-Smithsonian Center for Astrophysics.


The “interstellar object,” the first ever observed intruding in the orbits of our planets, was picked up by telescopes earlier this month at the University of Hawaii’s Haleakalā Observatory, the National Aeronautics and Space Administration said in a statement.

Designated “A/2017 U1” by the Minor Planet Center, the object, which scientists think might be an asteroid, is “moving remarkably fast” through space, NASA said.

The object was first seen Oct. 19 by the Hawaiian observatory’s Pan-STARRS 1 telescope, and was identified and reported to the Harvard center by University of Hawaii postdoctoral researcher Rob Weryk.

While the center tracks thousands of comets and minor planets each year, the object has the distinction of being the first visitor to the solar system to be observed from Earth. However, Holman noted similar objects might have flown by in the past, undetected.

“In the process of forming planets, a lot of material is ejected from those budding solar systems,” he said. “A lot of that material goes into interstellar space, and you’d expect that, eventually, some of that material would go our way.”


“The surprise is really that we haven’t seen this before,” Holman said.

In addition to its interstellar origins, NASA said, the object’s movement is also unique.

A NASA Center for Near-Earth Object Studies team was able to determine that the object came from the direction of the Lyra constellation, traveling “at a brisk clip” of around 15.8 miles per second.

It plunged into the solar system from above the ecliptic — the approximate plane on which planets and asteroids tend to orbit the sun.

After passing near the sun, the object “made a hairpin turn” under the solar system and passed around 15 million miles under Earth’s orbit on Oct. 14. NASA said the object has now “shot back up above” the ecliptic outside the inner solar system and is racing toward the Pegasus constellation at 27 miles per second.

The object is currently around 1.4 astronomical units from the sun, Holman said. One AU is the distance from the sun to the Earth. As the object continues on its path, it should reach around 2 AUs away from the center of the solar system by November, nearly two months after it was closest to the sun.


“It just looks like it’s passing through,” Holman said.

Holman said some objects from the spherical Oort cloud, which surrounds the solar system, can also take trans-ecliptical paths, but even among those the direction of A/2017 U1 stands alone.

“It came in on a very inclined orbit not on the plane of the solar system,” he said.

And while that path could be “similar to a long-period comet” from the Oort cloud, Holman said, “It’s hard to find an explanation for its orbit that would come in connection to our solar system.”

What is the object made of?

Holman said University of Belfast researchers who have done closer imaging on the object believe it might have similar characteristics to the minor planets with no atmospheres that orbit the sun beyond Neptune.

“It looks red; it looks like a trans-Neptunian object,” he said.

Holman said the discovery opens a new door to grasping how such objects move through space.

“It also starts the process of trying to understand ‘What does it mean?’ and how common this is,” Holman said. “There’s a category of object that really needs some more observational attention.”

“What we don’t really know yet is: Is this the only one of these things that has come through and been detected, or have many come through and we’re not really good at detecting them?’” he said.

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