Earlier this month, astronomers spotted a bizarre interstellar object hurtling through the solar system.
Dubbed 3I/ATLAS, this 12 miles (20km) long visitor has travelled to our sun from another star on a journey that could have taken billions of years.
But now, a leading physicist says he has spotted the key piece of evidence that shows 3I/ATLAS could be an alien spacecraft.
Professor Avi Loeb, a theoretical physicist and cosmologist from Harvard University, told MailOnline that this interstellar object is simply too big to be natural.
Experts suggest that it must either be an exceptionally large solid mass or a smaller comet with a bright envelope of gas and dust.
If it is not a comet, Professor Loeb says 3I/ATLAS is so impossibly large that the chances of it naturally reaching our sun are incredibly low.
Professor Loeb says: 'It is difficult to imagine a natural process that would favour a plunge towards the inner solar system at 60 kilometres per second.
'An alternative is that the object targets the inner solar system by some technological design.'
To read more, click here.