The bizarre cigar-shaped space rock is believed to have been wandering among the stars for hundreds of millions of years and it is the first foreign object in our solar system to be spotted.
The asteroid has been dubbed Oumuamua and is about 400 metres long and is a dark red colour, according to a study published in the journal Nature.
It was spotted by the Pan-STARRS1 telescope in Hawaii on October 19 and travelling at about 95,000 kilometres per hour.
Scientists had originally thought that the asteroid originated from the star Vega, which is 25 light years away, but by analysing the trajectory of the rock, they have determined that Vega would have been no where near its current positing 300,000 years ago when Oumuamua’s journey started.
This has led scientists to believe that it has been wandering the Milky Way aimlessly for hundreds of millions of years.
Dr Karen Meech, from the Institute for Astronomy in Hawaii, said: “Oumuamua may well have been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with the solar system.
“This unusually large variation in brightness means that the object is highly elongated.
“We also found that it has a dark red colour, similar to objects in the outer solar system, and confirmed that it is completely inert, without the faintest hint of dust around it.”
Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at the agency’s headquarters in Washington, DC, said: “For decades we’ve theorised that such interstellar objects are out there, and now — for the first time — we have direct evidence they exist.
“This history-making discovery is opening a new window to study formation of solar systems beyond our own.”
Scientists believe that interstellar objects enter our solar system about once a year, but they are difficult to spot because they are so faint.
Analysis of the rock suggests that it has a high metal content, but is lacking in water and ice.