This story is one that is just beginning, really. In an article first reported in New Scientist and rapidly being picked up everywhere else, a trans-Neptunian object has been found and confirmed using data from the Dark Energy Survey. The object, called 2014 UN271, was captured in data from 2014, 2016 and 2018, and is either a minor planet or a large comet, somewhere between 100 and 370 kilometers in diameter. [Ed. note: This body is now officially a comet named C/2014 UN271 (Bernardinelli-Bernstein).] Its orbit is about 600,000 years, with the furthest distance at 0.6 light-years, and incredibly eccentric or elliptical. And at the end of this decade, it will make its way almost to Saturn’s orbit.

One of the hopes for UN271 is that it will be a comet, and as it approaches closer and closer to the Sun, even at its great distance, it will show the characteristic signs of a coma, outgassing and glowing in the night sky. But before anyone gets too excited that this might be a big, showy comet, it won’t be. Citizen astronomer Sam Deen calculates that UN271 will only get as bright as Pluto or maybe Charon. This means it won’t be visible to the unaided eye, but observatories and telescopes should still be able to acquire some good images.

And there is even talk already of a potential mission to UN271. Mark McCaughrean at the European Space Agency has noted that any mission would have to launch in the next six or seven years to reach the object, and that timeline is doable. I suspect we’ll be hearing more and more about UN271 in the years to come. As Samantha Lawler at the University of Regina noted: We haven’t really seen any 100-kilometer [outer solar system] objects close up. Maybe it’ll be some totally bizarre shape. 

She’s really hoping it has rings, and she’s made a bet on Twitter that it will.

While researching for this story, I got a lot of information from the scientists here at the Planetary Science Institute. One scientist noted that with all the orbital elements I mentioned earlier, UN271 is likely to be coming directly at Earth, appearance-wise, which means a lot of observations had to be taken to get those orbital elements and confirm them. Another scientist cautioned that making any calculations from this distance is unreliable.

At this point, though, UN271 has already crossed Neptune’s orbit. It’s already in the main part of our solar system, y’all. And astronomers are making observations. A team used the SkyGems Remote Telescope in Namibia to image UN271 and reported that there is clear evidence for cometary activity, capturing images of an elongated tail. The magnitude is down between 18 and 20, and we’ll have links for finding UN271 at our website, DailySpace.org.

I am pretty excited about UN271. There’s a lot we don’t know about trans-Neptunian objects and outer solar system comets, so no matter what this object actually is, we will learn a lot from observing it. And if someone can get a spacecraft out there, even better.

More Information

An enormous ‘mega comet’ is flying into our solar system (New Scientist)

Extremely eccentric minor planet to visit inner solar system this decade (New Atlas)

2014 UN271: A possible dwarf planet from the Oort Cloud on a tour through the Solar System (MPLM Forum)

Minor Planet Electronic Circular 2021-M53: 2014 UN271 (Minor Planet Center)