A Giant Oort Cloud comet will approach us
Hi Everybody knows what a comet looks like.
Films, snapshots, videos of comets are easily found on the internet,
but have you ever seen one of them on a dark night, with your naked eye?
For example, last year you probably heard about the Neowise comet.
It is a comet discovered on March 27, 2020, by the NEOWISE Space Telescope. It reached perihelion on
July 3 and its closest point to Earth on July 23. A lot of people went out to take
a look at that amazing comet. Here are some photos of the Neowise comet.
(show some pics) Amazing, uh?
What if I told you that a giant comet, coming from the Oort cloud, is approaching our solar system?
Follow me in this video to get to know more about Comet Bernardinelli-Bernstein,
also known as C/2014 UN271.
So we know pretty well what a comet looks like.
But, in order to talk about this fantastic new-discovered comet,
we need also to know what a comet exactly is. In fact, it's hard, if you're not an astronomer,
to distinguish between asteroids, comets, meteors and so on.
A comet is a body of ice, rock and dust that can be several miles in diameter and orbits the sun.
Debris from comets is the source of many meteoroids.
A meteoroid is a small rocky or metal object, usually between the size of a
grain of sand or a boulder, that orbits the sun. It originates from a comet or asteroid.
A meteor is a meteoroid that enters the earth’s atmosphere and vaporizes. Also called a “shooting
star”. What would you wish if you saw one? A meteorite is a meteor that hits Earth
without burning up in the atmosphere. A meteor shower is a collection of meteors
visible when Earth passes through a trail of debris left by a comet. This is what you usually
see in the sky in certain periods of the year, for example, the Perseids meteor shower, in august.
An asteroid is an object larger than a meteoroid that orbits the sun and is made
of rock or metal. Historically, objects larger than 10 meters across have been called asteroids.
Now that we understood the differences between all of these objects, let's talk about the news:
a giant come coming from the Oort Cloud is coming toward us.
The Oort cloud is a theoretical concept of a cloud of icy planetesimals.
It was described for the first time by famous astronomer Jan Oort.
He proposed the cloud surrounding the Sun at distances ranging from 0.03 to 3.2 light-years.
To date, we know Oort's cloud is divided into two regions: a disc-shaped inner Oort cloud,
that' called Hills cloud and a spherical outer Oort cloud.
Astronomers conjecture that the matter composing the Oort cloud formed closer
to the Sun and was scattered far into space by the gravitational effects of the giant planets
early in the Solar System's evolution. It's notable that, although no confirmed
direct observations of the Oort cloud have been made, it may be the source that replenishes most
long-period and Halley-type comets entering the inner Solar System, and many of the
centaurs and Jupiter-family comets as well. But what has the Oort Cloud to do with comets?
Well, actually the outer Oort cloud is only loosely bound to the Solar System, and thus is
easily affected by the gravitational pull both of passing stars and of the Milky Way itself.
These forces occasionally dislodge comets from their orbits within the cloud and send
them toward the inner Solar System. And that's exactly where our giant comet is coming from.
C/2014 UN721, our comet, is 1,000 times more massive than a typical comet,
making it potentially the largest ever found in modern times.
At the first glance, we didn't know it was a comet. Because of its enormous size,
astronomers thought it could be something like a dwarf planet.
But they soon realized they were wrong. They were, instead, facing a really big comet.
So the object has officially designated a comet on June 23, and it was called
the “Bernardinelli-Bernstein comet”, after its discoverers,
University of Pennsylvania graduate student Pedro Bernardinelli and astronomer Gary Bernstein.
Do you want to know how big is this comet? This fantastic ice body is estimated to have
a diameter of 62 miles to 124 miles, which makes it about 10 times wider than a typical comet.
But the comet is far away from earth, so this is a pretty rough estimation.
The size of a comet far away from Earth is often calculated based on how much sunlight it reflects.
And that's how we calculated its size. But we'll have to wait to
know a better estimation of its real size. It could be bigger, it could be smaller.
Anyway, among others, the orbital parameters of the object were studied.
Astrodynamics tells us this fantastic comet will make its closest approach to our planet in 2031
but will remain at quite a distance even then. “We have the privilege of having discovered
perhaps the largest comet ever seen — or at least larger than any well-studied one — and
caught it early enough for people to watch it evolve as it approaches and warms up,”
Bernstein said. But how did they find it?
Astronomers were taking a look at some archival images from the DES, the Dark energy Survey.
The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions
of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that
will reveal the nature of the mysterious dark energy that is accelerating the expansion of
our Universe. DES began searching the Southern skies on August 31, 2013.
One of the highest-performance, wide-field CCD imagers in the world, DECam was designed
specifically for the DES and operated between 2013 and 2019. DECam was built and tested at
DOE’s Fermilab. At present DECam is used for programs covering a huge range of science.
DES was tasked with mapping 300 million galaxies across a 5000-square-degree area of the night sky,
but during its six years of observations, it also observed many comets and trans-Neptunian
objects passing through the surveyed field. A trans-Neptunian object,
or TNO, is an icy body that resides in our Solar System beyond the orbit of Neptune.
Bernardinelli and Bernstein spotted the comet using the National Center for Supercomputing
Applications and Fermilab, identifying 800 TNOs from archival survey data.
At first, the images of the comet didn't show a classic tail between 2014 and 2018.
But an independent observation in 2021 (after the comet's existence was made
public) showed the comet now has a coma of gas and dust surrounding it. Bingo!
Let's see what we can say about the current position of the comet in our solar system.
Comet Bernardinelli-Bernstein is currently located at the equivalent distance of Uranus,
of about 20 astronomical units (AU) from the sun. One AU is the Earth-sun distance — about
93 million miles, or 150 million kilometres. Unluckily, the comet has a small brightness,
because it shines at magnitude 20. This means that, if you're an amateur astronomer,
it will be out of reach of your amateur telescope, and we are very sorry about that!
Just for a term of comparison, most people can see objects of magnitude
5 or 6 with the naked eye in dark conditions. Remember that the magnitude scale is a little
bit strange: a bigger magnitude corresponds to a lower brightness.
So we said the comet is actually 20 AU distant from us.
What will be its closest distance in the next years?
When the comet swings closer to Earth in 2031, it will still be at 11 AU.
This means it will be just a little more distant than Saturn's orbit from the sun.
Even then, amateur skywatchers will still need to
use very large telescopes to see it. This comet doesn't like to be papped!
But what makes our Bernardinelli-Bernstein comet so special?
The special thing about our giant comet is
that it hasn't visited the inner solar system in 3 million years.
At that time, our famous ancestor “Lucy” was still walking on Earth.
What will happen next? Comet Bernardinelli-Bernstein will of course be
followed by the astronomical community because we need to understand the composition and origin of
this massive object. Also, there may be many more undiscovered comets of this size waiting in the
Oort Cloud far beyond Pluto and the Kuiper Belt. And they could give us a better understanding
of the evolution and birth of our solar system. Since these giant comets are thought to have been
scattered to the far reaches of the solar system by the migration of Jupiter, Saturn, Uranus,
and Neptune early in their history, finding huge objects like Comet Bernardinelli-Bernstein
is crucial to our understanding of the early history of our planetary system.
Some of you may ask: we know we can send probes of comets, exactly as we did with
the Rosetta mission. So will the astronomical community send spacecraft on this giant comet?
Well, this is hard to say, and it's hard to predict.
Space missions tend to be shorter than the lifespans of ground-based scopes.
But it still remains possible that a future telescope or mission could be
funded by 2031 for comet observations that are not yet approved or even planned.
The major space agencies may also task existing
spacecraft across the solar system to look at Comet Bernardinelli-Bernstein,
as happened near Mars in 2014 when Comet Siding-Spring zoomed past the Red Planet.
Meanwhile, we can feast our eyes with these spectacular images from
the approaching on the surface of the comet 67 P/Churyumov-Gerasimenko from the Rosetta mission.
The Rosetta mission goal was initially set for a rendezvous with Comet 46 P/Wirtanen. After
the postponement of the initial launch, a new target was set: Comet 67 P/Churyumov-Gerasimenko.
On its 10-year journey to the comet, the spacecraft also passed by two asteroids.
Rosetta's main objective was to rendezvous with and enter orbit
around Comet 67P/Churyumov-Gerasimenko, performing observations of the comet's nucleus and coma. On
12 November 2014, at 17:32 GMT, Rosetta's Philae lander made the first-ever landing on a comet.
"This video ends here! Thanks for watching everyone! What are your thoughts about this video?
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science needs you, and you need science! See you next time for another amazing video.”