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[♪ INTRO]
We might think we know our own cosmic neighborhood pretty well,
but scientists are discovering new objects in the solar system all the time.
Most of these are small asteroids or icy bodies,
but researchers recently spotted something unexpectedly huge heading our way.
It’s called Comet Bernardinelli-Bernstein.
And it might just be the biggest comet ever detected.
As it gets closer to earth, not only will we be able to get a good view of this giant,
but scientists will also get a chance to discover more
about the far reaches of our solar system.
The discovery came in June 2021 when researchers
analyzed data from the Dark Energy Survey.
This was an international collaborative project that ran from 2013 to 2019,
with the aim of discovering the nature of dark energy,
which seems to be causing the universe to accelerate its expansion.
To do this, astronomers built an extremely sensitive, 570 megapixel camera,
and installed it on a 4-meter telescope in Chile.
Over six years, this Dark Energy Camera, or DECam, imaged a huge portion
of the southern sky, taking pictures of up to 300 million distant galaxies,
supernovas, and cosmic structures.
And the camera’s incredible resolution also allowed it to detect objects
closer at hand, like comets and trans-Neptunian objects,
which have an average orbital distance farther than Neptune.
So two researchers from the University of Pennsylvania,
Pedro Bernardinelli and Gary Bernstein, fed the images
from DECam into a suite of supercomputers for analysis.
The supercomputers compared images taken at different times
to identify points of light that appeared to be moving across the sky.
It sounds simple enough, but with 16 billion different sources to compare
across more than 80,000 images, it’s no surprise that the supercomputers
racked up more than 15 million CPU hours.
If they’d tried this on a normal PC, it would have taken 1700 years!
But the analysis successfully identified more than 800 trans-Neptunian objects,
including one, named 2014 UN271, that snagged the scientists’ attention.
The first images to capture it were taken by DECam in 2014,
when it was about 29 astronomical units away,
or 29 times the distance from the earth to the Sun.
It was just a speck of light, but its brightness suggested it was really big.
At somewhere between 100 and 200 kilometers across,
UN271 was originally designated a minor planet.
But as soon as its detection was announced,
amateur astronomers around the world turned their telescopes to the skies
in search of this new, intriguing object.
Originally, its surface had seemed to be chemically inactive.
By this time, though, it was closer, just 20 astronomical units away,
and the new observations revealed something surprising:
UN271’s surface didn’t appear to be so inert after all.
It seemed to be surrounded with a faint haze of vapor and dust.
Such hazes are typically known as comas, and they’re a sign of comets.
They form when comets travel toward the sun in their orbit and start to heat up,
causing some of their ice to start turning into vapor.
So UN271 isn’t a minor planet, but a gigantic comet.
In fact, it’s likely the biggest ever detected, at more than ten times the diameter
and 1000 times the mass of your typical icy traveler.
The new designation also earned it a new name:
Comet Bernardinelli-Bernstein, after the scientists who discovered it.
Tracing its trajectory over the years, we now have a pretty good idea
of where this monster comet came from and where it's going.
Bernardinelli-Bernstein is what’s known as a long-period comet,
taking about five and a half million years to take a complete trip around the sun.
It likely started its inward journey from about a light year away, in the Oort Cloud.
This shell of icy debris is left over from the early years of the solar system,
and was ejected by the migration of giant planets
a few million years after their formation.
Scientists think that this may be Comet Bernardinelli-Bernstein’s
first trip into the solar system since its initial expulsion.
So they’ll be watching it closely as it comes nearer,
hoping to study a relatively unaltered Oort cloud object for the first time.
And this could help scientists learn more about
what the solar system was like back when the comet was formed.
Right now, the comet is approaching from above the solar system’s orbital plane,
and it’ll pass closest to the sun about ten years from now, on January 23rd, 2031.
Even then, it’ll still be pretty dim and distant,
so you’ll need a telescope handy to be able to see it.
It’ll be passing by at about 11 astronomical units,
which is equivalent to the orbit of Saturn.
As it warms, its coma will grow, and it will possibly gain a tail.
And researchers hope that sensitive instruments will
soon be able to probe the haze to reveal its chemical composition.
Doing so will help to answer questions about the nature of objects
in the Oort cloud, which before now has been largely out of reach.
Until then though, be sure to mark January 23rd on your 2031 calendar
as a time to find a telescope and catch a glimpse
of the biggest comet scientists have ever seen!
And while you’re waiting for the comet to swing by in 2031,
why not learn a new language?
Thanks to Babbel for sponsoring this episode of SciShow Space.
Babbel is a language-learning app that helps you not just learn a new language,
but use it in real-life situations after only five hours of practice.
It’s the #1 language-learning app in the world, and they offer 14 languages.
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You can check it out and download Babbel by clicking the link in the description.
And as a special thanks for SciShow Space viewers,
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