NASA Confirms Largest Comet Ever Seen Is Heading Towards Earth

NASA Just Confirmed The Largest Comet Ever Detected, And It's Truly Gargantuan

Sequence showing comet nucleus isolation. (NASA, ESA, Man-To Hui, David Jewitt, Alyssa Pagan)

The largest comet ever discovered has been orbiting the Sun for more than a million years, and its massive size sheds insight on the mystery objects that make up one of our Solar System's largest structures.

 

Astronomers confirmed that the solid centre of the big comet C/2014 UN271 (Bernardinelli-Bernstein) is the largest comet nucleus ever identified in New research using the Hubble Space Telescope. At about 140 kilometres in diameter, it is 50 times larger than most known comets (about 85 miles).

 

However, that bizarrely big size – or rather, its apparent strangeness – may reveal more about us and our limited understanding of comets than anything else.

 

C/2014 UN271 comes from the Oort Cloud, a massive, spherical scattering of frozen objects estimated to surround the Sun in the Solar System's deepest and most distant reaches (so far away, in fact, that it's thought to extend at least a quarter of the way to the next nearest star system, Alpha Centauri).

 

Isn't that a big deal? It is, at least in theory. The Oort Cloud, on the other hand, is so far away and impossible to detect that it's essentially a big speculative mystery, despite the fact that scientists consider it to be one of our Solar System's largest formations.

 

But every now and again, something emerges from this enigmatic mass, gravitationally drawn to the Sun from the far reaches of the cosmos.

 

Comet nucleus size comparison. (NASA/ESA/Zena Levy, STScI)

C/2014 UN271 is one of these objects, and it has the potential to reveal a lot about the Oort Cloud's frozen 'pristine' masses. These are assumed to have formed early in the Solar System before being blasted out to the furthest reaches by the gravitational influences of large planets like as Jupiter and Saturn.

 

Accordingto UCLA astronomer David Jewitt, "this comet represents essentially the tip of the iceberg for many thousands other comets that are too faint to view in the more distant portions of the Solar System."

 

"Because it is so bright at such a great distance, we've always assumed it must be a massive comet. We may now say with certainty that it is."

 

Jewitt and colleagues from the Macau University of Science and Technology, lead by first author Man-To Hui, computed the size of C/2014 UN271 in the highest resolution yet. They used Hubble images and modelling to separate the nucleus from the comet's coma, which is the lengthy tail of ice that sublimates into gases in the comet's wake.

 

The researchers states in their new study, "We confirm that C/2014 UN271 is the largest long-period comet ever detected."

 

(NASA/ESA/Man-To Hui, Macau University of Science and Technology/David Jewitt, UCLA/Alyssa Pagan, STScI)

C/2014 UN271 was discovered in a set of observational data collected by the Dark Energy Survey between 2014 and 2018, and was announced last year. Following up on the investigation, it was discovered that C/2014 UN271 had been picked up as early as 2010.

 

Even so, that early look only scratches the surface of the comet's remarkable journey. It orbits the Sun on an approximately 3-million-year elliptical orbit, the form of which indicates that it has been slowly approaching the Sun for well over a million years.

 

Bernardinelli-Bernstein will reach perihelion – its closest approach to the Sun – in 2031, at which point it will still be around 1 billion miles from the Sun before arcing back outwards on its ovoid trajectory.

 

That means we'll have almost a decade of better observing opportunities to learn more about C/2014 UN271 and its kin as the comet approaches, before it fades away into the darkness once more.

Reference: Astrophysical Journal Letters