A space rock whose strange cigar-shape led to speculations it could be an alien spacecraft is simply an asteroid, British scientists have concluded.
The object, known as "Oumuamua" was spotted on October 19 by the University of Hawaii's Pan-STARRS1 telescope and astronomers across the world have been tracking its progress ever since, according to the Daily Telegraph UK.
It is thought to be the first asteroid to have come from outside the Solar System, and last week Stephen Hawking's Breakthrough Listen project, which is searching for evidence of civilisations beyond Earth, announced it was studying the object for signs of alien technology.
Researchers working on long-distance space transportation have previously suggested that a cigar or needle shape is the most likely architecture for an interstellar spacecraft, since this would minimise friction and damage from interstellar gas and dust.
However, today scientists at Queen's University in Belfast confirmed that the object is an asteroid which is the same size and shape of London's Gherkin skyscraper.
The team, which also featured scientists from the US, Canada, Taiwan and Chile, said they had made "key observations" about the chemical make up of the rock.
Dr Michele Bannister, whose research is published in Astrophysical Journal Letters this week, said the greyish-red object was covered in dust and grit and the surface looked similar to asteroids in our own solar system.
"None of the astronomers have ever talked about it being anything alien, except that it comes from outside the solar system," she said.
"The surface composition is consistent of a layer of insulating material, so something along the lines of dust and grit, maybe organic compounds.
"We don't know that the interior does contain ice but if it did contain ice it would have been insulated by the layer on the surface."
Professor Alan Fitzsimmons, who is also based at Queen's and whose separate research paper is published in Nature Astronomy, said the "half-metre thick coating of organic-rich material could have protected a water-ice-rich comet-like interior from vaporising when the object was heated by the sun, even though it was heated to over 300C".
The research is the latest in a flurry of papers published about the rock, the first object discovered in the solar system that appears to have originated from another part of the galaxy.
The discovery is an "exciting" one, Bannister said, describing it as like a piece of space driftwood which provides clues to what is happening outside our solar system.
She said: "The nice thing about driftwood is that it tells you that there's trees that grow on distant shores, so this is a little tangible piece of evidence that the way planets formed and grew in our own solar system, it's happening the same way in other solar systems far away."
"Oumuamua" - is named after the Hawaiian term for "scout" or "messenger" - and passed Earth at about 85 times the distance to the Moon in October.
Future research on the rock, which is expected to take years to leave the Solar System, is likely to be focused on tracking its exact origin.
"For decades we've theorised that such interstellar objects are out there, and now, for the first time, we have direct evidence they exist," said Thomas Zurbuchen, associate administrator for Nasa's Science Mission Directorate in Washington.
"This history-making discovery is opening a new window to study formation of solar systems beyond our own."