The First Interstellar Object to Be Seen May Have Just Visited Our Solar System
The object zoomed into our solar system from an extreme angle above the path in which most planets and asteroids orbit the sun.
Astronomers may have spotted the first comet or asteroid to visit from beyond the solar system. They’re now scurrying to aim telescopes at the object, provisionally called A/2017 U1, to learn more about its mysterious origins.
Here’s what is known so far: It’s roughly 1300 feet in diameter and is moving in a weird orbit, highly inclined to the plane of the solar system. It appears to have come from the constellation Lyra and was moving really quickly in interstellar space, at a speed of about 15.8 miles a second.
The object zoomed into our solar system from above the path in which most planets and asteroids orbit the sun, called the ecliptic. Comets can be more inclined to the ecliptic, but they’re not this extreme in inclination. They also tend to come from two zones: the Kuiper Belt beyond Neptune, or the Oort Cloud closer to the edge of the solar system.
“We have been waiting for this day for decades,” said Paul Chodas, who manages NASA’s Center for Near-Earth Object Studies (CNEOS) at the agency’s Jet Propulsion Laboratory, in a joint statement from NASA and the University of Hawaii. “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.”
Although the new object was identified on Oct. 19 by University of Hawaii postdoctoral researcher Rob Weryk, astronomers can calculate where the object was even before its discovery. Its closest approach to the sun came about a month before, on Sept. 9, as the object flew “under” our solar system. The sun’s gravity caused the object to make a steep turn, and it passed safely under the Earth’s orbit on Oct. 14 at about 15 million miles, which is roughly 60 times the distance between Earth and the moon.
The object is now cruising above the ecliptic at roughly 27 miles (44 kilometers) per second and making a beeline for the constellation Pegasus.
“This is the most extreme orbit I have ever seen,” stated CNEOS scientist Davide 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.”
“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,” said Karen Meech, an astronomer at the IfA specializing in small bodies and their connection to solar system formation. “What’s most surprising is that we’ve never seen interstellar objects pass through before.”
A/2017 U1 was identified by the University of Hawaii’s Pan-STARRS 1 automated telescope, whose goal is to find near-Earth objects for NASA through surveys of the sky. Weryk was the first to spot the object and to submit it to the Minor Planet Center. He also found the object in images taken on Oct. 18, the day before its discovery.
Weryk, who works at the university’s Institute for Astronomy, suspected that the object was interstellar. He contacted IfA graduate Marco Micheli, who confirmed his suspicion using images he took using the European Space Agency’s Tenerife telescope, which is located in the Canary Islands.
If confirmed, the introduction of an interstellar object will present an interesting discussion for the International Astronomical Union, which is the official arbiter of names and designations in astronomy. The union will need to decide on a naming convention for A/2017 U1 and any future interstellar cruisers.
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