For the first time that we know, an interstellar visitor has zoomed through our solar system. The small space rock, tentatively called A/2017 U1, is about a quarter of a mile long and astronomers across the world are racing to study it before it departs just as quickly as it arrived.

“We’ve never seen anything like this before,” said Rob Weryk, an astronomer at the University of Hawaii Institute for Astronomy.

On Oct. 19, Dr. Weryk was reviewing images captured by the university’s Pan-STARRS 1 telescope on the island of Maui when he came across the object. At first he thought it was a type of space rock known as a near earth object, but he realized its motion did not make sense. It was much faster than any asteroid or comet he had seen before. He quickly realized that it was not of this solar system.