Scientists have revealed the age of the mysterious interstellar comet, 3I/ATLAS, for the first time.    

The strange object sparked fears of an alien invasion when it whizzed through our solar system at the end of the last year. 

Thankfully, NASA soon confirmed that it was simply a comet. 

'We want very much to find signs of life in the universe... but 3I/ATLAS is a comet,' Amit Kshatriya, a senior NASA official, said at the time. 

While 3I/ATLAS is definitely a comet, its composition and age have remained unclear.

Now, astronomers have used the European Southern Observatory's Very Large Telescope (VLT) to solve these mysteries. 

According to their observations, 3I/ATLAS likely originated in the outskirts of an old star system, and is around three times older than Earth. 

'The field of interstellar objects is still very new, and we do not really know what to expect. Every time a new one is discovered, we have new surprises,' said Cyrielle Opitom, a researcher at the University of Edinburgh.

3I/ATLAS is only the third interstellar object ever discovered, after 1I/ʻOumuamua and 2I/Borisov, which were spotted in 2017 and 2019, respectively. 

The composition of the first two interstellar objects was difficult to determine, as they were too faint. 

However, thanks to 3I/ATLAS' unprecedented brightness, scientists were able to determine its composition – and therefore age.

The team measured the ratios of carbon and nitrogen isotopes in cyanide molecules present in the gas around the comet, which are known to be good indicators of a comet's origin. 

'Unlike comets from our Solar System, this interstellar visitor carries unusually high carbon and nitrogen isotopic ratios,' explained Aravind Krishnakumar, a researcher at the University of Liège and co–author on the new study. 

According to the analysis, the comet likely formed in the outer regions of an old, 'low–metallicity' star.

As the name suggests, this is a type of star with few elements heavier than helium, that is thought to have formed when the universe was much younger – and less chemically rich – than it is now. 

For this reason, the team suggests that 3I/ATLAS originated around a star much older than the sun. 

'3I/ATLAS is a really exciting opportunity to probe the composition of another planetary system, one that formed long before our Sun and Solar System even existed,' said co–author Rosemary Dorsey, a researcher at the University of Helsinki, Finland. 

3I/ATLAS is now moving away from the sun, meaning it is getting progressively fainter. 

Unfortunately, this means that opportunities to view the comet with the VLT are also nearing their end. 

However, the European Southern Observatory is currently working on an even bigger telescope, appropriately named the Extremely Large Telescope (ELT), which could provide further viewing opportunities in the future.