We think of both comets and asteroids as belonging to our own solar system, our family of planets orbiting the sun, but NASA reported on October 26, 2017 that astronomers have been watching a small body – perhaps an asteroid, perhaps a comet – apparently from beyond our solar system, from somewhere in interstellar space. If so, it would be the first interstellar asteroid (or comet) to be observed and confirmed. The object is currently designated A/2017 U1, and it’s less than a quarter-mile (400 meters) in diameter. NASA said it is moving remarkably fast, some 15.8 miles (25.5 km) per second (similar to Earth’s own speed in orbit around the sun). Astronomers around the world are aiming earthly telescopes, and telescopes in space, in this unusual object’s direction. They’re trying to find out as much as they can about A/2017 U1, perhaps to determine its composition, and hopefully to confirm if indeed it is visiting us from somewhere else in our Milky Way galaxy, before it shoots away again … forever.
According to NASA explained, "The object approached our solar system from almost directly above the ecliptic, the approximate plane in space 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. On September 2, the small body crossed under the ecliptic plane just inside of Mercury’s orbit and then made its closest approach to the sun on September 9. Pulled by the sun’s gravity, the object made a hairpin turn under our solar system, passing under Earth’s orbit on October 14 at a distance of about 15 million miles (24 million km) — about 60 times the distance to the moon. It has now shot back up above the plane of the planets and, travelling at 27 miles per second (44 km per second) with respect to the sun, the object is speeding toward the constellation Pegasus."
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