Asteroids are common in our solar system, but astronomers have never seen one from outside the solar system, until now.

Last month astronomers using the Pan-STARRS1 telescope atop Haleakala noticed a weak image of an object moving remarkably fast. The object, now called A/2017 U1, is small. It is less than a quarter-mile in diameter and moving at 15.8 miles per second, or 56,880 mph.

By projecting the trajectory backward, astronomers were able to calculate that A/2017 U1 entered the solar system early in September, although Pan-STARRS1 did not observe it until Oct. 18.

Asteroids in our solar system orbit in a nearly flat plane along with the planets. A/2017 U1 entered the solar system from the direction of the constellation Lyra at nearly 90 degrees to the plane between the orbit of Mercury and the sun. It dipped below the plane, then flipped around the sun, slipped by Earth at a mere 15 million miles on Oct. 15, which is about 60 times the distance to the moon, then crossed the plane again and is now speeding out of the solar system toward the constellation Pegasus.

THE DISCOVERY did not occur until A/2017 U1 had already passed Earth and was on its way out of the solar system, so the amount of data astronomers could collect was limited.

Nevertheless, with the current state of telescopes, recording instruments and analytical tools, they were able to get quite a bit of preliminary information.

Davide Farnocchia, a scientist at NASA’s Center for Near-Earth Object Studies (CNEOS) at the agency’s Jet Propulsion Laboratory in Pasadena, Calif., said, “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.”

SINCE SIR Isaac Newton published his masterwork, “Principia,” we have been able to calculate the orbits of celestial objects under the influence of the sun’s gravity. Sir Edmund Halley applied this method soon thereafter to calculate the orbit and predict the return of the comet that now bears his name.

The trajectory of A/2017 U1 is clearly hyperbolic, whereas objects in solar orbit such as a typical asteroid have elliptical orbits.

For an object from our near interstellar neighborhood to approach from such an angle, it would have to have come from the Oort cloud, which surrounds the sun at a distance that extends to several light-years from the sun. Objects in the Oort cloud are icy remnants of the solar system’s origin. It is unlikely in our current theories of the solar system’s origin that a rocky object would have formed that far away.

Early results suggest that A/2017 U1 might be similar in makeup to many of those of the Kuiper belt, many of which, like ex-planet Pluto, are composed of both rock and ice. But it is traveling way too fast, and the Kuiper belt lies along the solar system plane.

EARLY SPECTRAL analysis of the fleeting image, although subject to a large margin of error, showed that the asteroid looks to be largely featureless and red like many objects from the Kuiper belt beyond Neptune.

Astronomers are surprised that such interstellar objects have not been discovered before, but they are delighted that this one appeared, brief though it was. We are now awaiting a formal classification and naming of A/2017 U1 as the first in a new category of heavenly objects.

Many have already suggested the name Rama, after Sir Arthur C. Clarke’s 1973 sci-fi novel “Rendezvous With Rama,” which described a similar trajectory of interstellar origin.

Richard Brill is a professor of science at Honolulu Community College. His column runs of the first and third Friday of the month. Email questions and comments to brill@hawaii.edu.