All the asteroids and comets astronomers have ever spotted in our celestial neighborhood appear to come from somewhere else in the solar system and orbit the sun, just like Earth.
That is, until the University of Hawaii’s Pan-STARRS 1 telescope last week discovered what appears to be the first ever seen “interstellar object” – an asteroid (or maybe a comet) that escaped from the gravitational grasp of another star and fell through the roof of our solar system.
That makes the object currently designated A/2017 U1 an alien of sorts around our corner of the cosmos.
The foreign space-something is less than a quarter-mile (400 meters) across, but is moving super fast at 15.8 miles (25.5 kilometers) per second. That’s over three times faster than Asteroid 2012 TC4, the rock that gave Earth a close shave earlier this month.
“This is the most extreme orbit I have ever seen,” said Davide Farnocchia, at
NASA’s Center for Near-Earth Object Studies (CNEOS). “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 dropped into our neighborhood from “above” the relatively flat ecliptic plane in space where the planets and other asteroids orbit the sun. So, if you imagine our solar system as being more or less flat, it’s as if the object dropped in out of the sky. But rather than impacting anything in our solar system, the object passed closer to the sun than the orbit of Mercury on Sept. 2 before making a hairpin turn under our solar system and getting flung back out o