An object from outside the solar system has been spotted hurtling towards the sun, the European Space Agency (ESA) has said.
If confirmed, it would be the third visitor from the stars ever detected.
The object, which is currently being referred to as 'A11pl3Z', poses no threat to Earth, the ESA's planetary defence head Richard Moissl said.
"It will fly deep through the solar system, passing just inside the orbit of Mars," but not threatening to hit our neighbouring planet," he said.
Astronomers are still refining their calculations, but the object appears to be zooming at a speed up to 60km per second, which would mean it is not bound by the sun's orbit, unlike comets, which all originate from within the solar system.
Its trajectory also "means it's not orbiting our star, but coming from interstellar space and flying off to there again", Mr Moissl said.
"We are not 100% certain at the moment, but anything else would be a surprise," he added.
Official confirmation is expected to come from the International Astronomical Union's Minor Planet Center, which has recorded more than 100 observations of the object so far.
After the object was discovered, astronomers across the world then searched through past data, tracing its trajectory back to at least 14 June.
The object is currently estimated to be roughly 10-20km wide, though it could be smaller, Mr Moissl said.
He also said it will get brighter and closer to the sun until late October and then will still be observable by telescope until next year.
Third visitor from outside our solar system
It would be the third time humanity has detected something coming from the stars.
The first, 'Oumuamua', was discovered in 2017.
It was so strange that at least one prominent scientist became convinced it was an alien vessel - though this has since been dismissed by further research.
The second interstellar visitor to the solar system, '2I/Borisov', was spotted in 2019.
'Not feasible' to intercept new object
Mr Moissl said it is "not feasible" to send a mission into space to intercept the new object.
It appears to be "moving considerably faster than the other two extra-solar objects that we previously discovered" said Mark Norris, an astronomer at the UK's University of Central Lancashire.
Mr Norris pointed out that modelling estimates there could be as many 10,000 interstellar objects drifting through the solar system at any given time.
If true, this suggests that the newly online Vera C. Rubin Observatory in Chile could soon be finding these dim objects every month, he added.
These visitors offer a rare chance to study something outside of our solar system, Mr Norris said.
He added that if we detected precursors of life such as amino acids on such an object, it would give us "a lot more confidence that the conditions for life exist in other star systems".
