[Music throughout] Last summer, an amateur astronomer discovered 
 the first interstellar comet zipping through our solar system – 2I/Borisov. 
It was clear from its path that the comet would dim from view within months, 
so scientists were quick to turn their telescopes towards the alien comet for a view. 
Among them was an international team led by NASA Goddard. 
They used the ALMA telescope array in northern Chile to probe 2I/Borisov while it was close by. 
Inside the halo of gas around the comet, they detected something peculiar.  
2I/Borisov was releasing a higher concentration of carbon monoxide
than any comet observed at a similar distance from the Sun.
NASA’s Hubble Space Telescope later confirmed this, too.
Scientists wondered – Could this be our first glimpse of the chemistry of another planetary system?
Or are we learning that there’s more chemical diversity among comets than we knew of?
Carbon monoxide is one of the most abundant molecules in space. 
Scientists expect to see it inside all comets; yet, there’s a huge variation – which is puzzling
Regardless, 2I/Borisov is off the charts.
To preserve its carbon monoxide, the comet likely formed 
very far away from its star in one of the coldest environments known. 
In our solar system, this would have been in the vicinity of Neptune. 
When comets were forming, temperatures there could’ve reached -420 degrees Fahrenheit. 
Scientists think that gravitational disturbances from young, jostling planets may have thrown 
2I/Borisov out of its home star system and onto a cold, lonely voyage. 
Our solar system is tiny compared to the distances between star systems.
It’s incredibly rare for an interstellar comet to pass within observable range. 
However, big, sophisticated telescopes are coming online, 
so scientists expect to see more alien comets like 2I/Borisov. 
Will they all be similarly exotic? 
