The mysterious asteroid Oumuamua has been analysed by astronomers from the Harvard Smithsonian Centre for Astrophysics (CfA) after it was found to be unexpectedly speeding up.

NASA said earlier this year observations from their Hubble Space Telescope confirmed the object had an "unexpected boost in speed and shift in trajectory as it passes through the inner solar system."

Scientists have now concluded that the asteroid "might be a lightsail of artificial origin" using solar radiation to propel itself forward.

The study said: "Considering an artificial origin, one possibility is that Oumuamua is a lightsail, floating in interstellar space as a debris from an advanced technological equipment.

"Alternatively, a more exotic scenario is that Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilisation."

Professor Abraham Loeb, who carried out the study with Shmuel Bialy, told Universe Today: "Oumuamua could be an active piece of alien technology that came to explore our Solar System, the same way we hope to explore Alpha Centauri using Starshot and similar technologies.

"The alternative is to imagine that Oumuamua was on a reconnaissance mission."

Before he died, Professor Stephen Hawking said the most likely shape for an interstellar spacecraft would be a "cigar or needle" as this would "minimise friction and damage from interstellar gas and dust".