Anish Vij
An expert has explained why he thinks that an interstellar object travelling through space could be an 'alien aircraft'.
3I/ATLAS is the third interstellar object, that we know of, to enter our solar system following 'Oumuamua in 2017 and comet Borisov in 2019.
It was only discovered last month (1 July) by the ATLAS survey telescope in Chile and NASA was quick to confirm that the comet wasn't from our solar system.
Observations showed that it wasn't an asteroid and instead revealed a coma (a cloud of gas and dust), possibly between 20km and 24km across.
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And given that it's travelling at 60 km/s, it’s moving too fast to be gravitationally bound by the Sun, confirming it to be interstellar.
Thankfully, ATLAS poses no threat to us as it's expected to pass between the orbits of Earth and Mars without striking anything.
Its closest point to the Sun will be on 30 October, 130 million miles away.
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Professor Avi Loeb, of Harvard University, told MailOnline that if ATLAS turns out not to be a comet, it could suggest something out of the novel Rendezvous with Rama by Arthur C. Clarke.
It's the story of an object from beyond our solar system which turns out to be a spacecraft from an alien civilisation.
The theoretical physicist says the latest calculations show 3I/ATLAS to be up to 200 times larger than the 100-metre-long 'Oumuamua.
Professor Loeb said: "Now you ask, 'how many objects on the scale of 'Oumuamua are there for each object that is 24 kilometres in size?'
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"The answer is about a million. But we haven't seen a million 'Oumuamua-sized interstellar objects before seeing this one, it's very strange."
Expressing how weird it is for something so large to be flying around, he added: "It's not like these objects are floating around in all directions, this object was aiming to get to the inner solar system.
"The question is: 'Why was it sent in the direction of the inner solar system?'"
Professor Loeb said its size 'makes zero sense' and 'ends up being a quarter of the mass of the stars in the Milky Way'.
"But because only two percent of the mass in stars is in heavy elements that make rocks, you don't have the mass to make enough rocks of this size," the expert added.
NASA said astronomers don't know exactly how big 3I/ATLAS is, but from their observations, they can see that it’s active.
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Its 'icy nucleus and coma (a bright cloud of gas and dust as it approaches the Sun)' is why 3I/ATLAS is categorised as a comet and not an asteroid.