The outer solar system is littered with big chunks of rock and ice, but rarely do their orbits bring them close enough to Earth for us to get a good look. And then there’s 2014 UN271, an approaching object that astronomers believe to be a huge comet on a million-year orbit around the sun. In a few years, UN271 might get close enough to put on a neat fireworks display, reports Gizmodo.
UN271 most likely originated in the Oort Cloud, a theorized cluster of icy chunks of rock hovering at the solar system’s edge. This material is believed to be left over from the solar system’s formation, but it’s too far away to see clearly. Every now and then, an object from the Oort Cloud is perturbed out of its orbit and falls in toward the sun. And we would then (probably) call that object a comet.
The mystery object is currently about 22 AU from Earth. One AU (or astronomical unit) is the average distance between Earth and the sun. The edge of the solar system is about 123 AU distant, and the Oort Cloud begins around 2000 AU beyond that. It’s extremely difficult to spot comets before they get toward the inner solar system and form a coma or tail. UN271 is somewhere between 62 and 230 miles across — it could therefore be one of the largest comets ever seen. Even being so large, it took years of observation and analysis to nail down its orbit and position.
Some people asked why it was only announced now: finding TNOs with DES is a massive computational problem (my PhD was solving this problem). The search itself took 15~20 million CPU-hours, and the catalog production from our 80,000 exposures probably took more than that!
— Dr. Pedro Bernardinelli (@phbernardinelli) June 20, 2021
Algorithms used to process data in the Dark Energy Survey (DES) spotted UN271 in 2014. Astronomers made several dozen observations of the object that year and then watched it intermittently through 2018. According to project scientist Pedro Bernardinelli, detecting trans-Neptunian objects like 2014 UN271 with DES is a computationally complex process. In all, the DES collected 80,000 exposures and it took 15-20 million CPU hours to process the data.
Depending on how large UN271 actually is, it may never be visible to the naked eye. At its closest approach, UN271 will be 10.9 AU away in 2031. That puts it inside the orbit of Saturn. Astronomers will be treated to quite a show even if you won’t be able to look up and see UN271 with the naked eye. It’s possible that this object could turn out to be a so-called “pristine comet,” meaning it has never approached the sun before. Observing how it forms a coma could shed light on the nature of this untouched cosmic material.