Scientists Just Discovered a Mysterious Entity Behind the Milky Way. And without keeping you in
further suspense, it’s behind a galactic wall. And the best way to describe it is a mysterious
intergalactic force that is pushing against our galaxy. Sure, it sounds like the set up for an
epic sci-fi flick. But truth is commonly stranger than fiction, and this mysterious entity, beyond
the boundaries of our galaxy that is pushing against us with incredible force, is nothing
but reality. We don't know exactly what it is, and we don't know how long it's been there. But
we do know its name: the Dipole Repeller. And due to billion-dollar state-of-the-art equipment, and
the best minds of this era on our planet today, it has been determined that the Dipole Repeller is a
center of effective repulsion in the large-scale flow of galaxies, first detected in 2017.
What does this mean for our earth? What does this mean for our galaxy?
Stick around and find out. Strap in. And let’s take another trip to the outskirts of our galaxy
to identify that mysterious entity behind the Milky Way. Welcome back to Space Infinity!
Astrophysicist at SUNY Stony Brook and the Flatiron Institute, Paul M. Sutter is also
host of "Ask a Spaceman" and "Space Radio," plus he’s the author of "How to Die in Space."
With all of his expertise and many years of experience in the field of cosmology, he’s able
to bring very complex physics to the table and put it into a lucid sequence for layman’s to digest.
So, we’re going to use some of his metaphors for the concrete learners who want to understand,
yet don’t have the time to study quantum or theoretical physics.
Over all, Dipole Repeller is the result of the usual process of structure formation that's been
happening in the universe since the beginning of our universe - 13.8 billion years in the making.
The Construction of Superclusters To set the stage for the dipole repeller,
we need to go big. And not only as big as our galaxy. Imagine thousands of them. Just beyond
our Milky Way galaxy, at 2.5 million light-years away, there’s another gigantic galaxy known as
Andromeda. Its close neighbour has been named Triangulum, and aside from these two galactic
neighbors, there are a few dozen dwarf galaxies. When considering all of these neighbors as a
group, they’re called the Local Group. And if you were to travel from one end to the other,
you’d be traveling for a few million light years. Now that your brain has grasped that magnificent
size, Go Bigger! The nearest big deal to our Local Group is the Virgo Cluster.
It is a massive ball comprised of over a thousand galaxies sitting 60 million light-years away.
Our Local Group and other groups in this patch of space aren't part of the Virgo Cluster
itself; rather, they belong to a greater structure known as the Virgo Supercluster.
Groups and clusters are different from superclusters because they are
gravitationally bound. Superclusters aren't; they're just collections of galaxies that are
larger than clusters. But it can get tricky because different cosmologists
might apply various definitions of the word "supercluster" and get a range of segmentations.
So, let’s use one of astrophysicist Paul M. Sutter’s representations.
“It's like a population census trying to define a metro area: Sure, there are the city limits, but
what about all the people living near a major city and working in it? Where, exactly, does it stop?”
This has been the deal of confusion when it comes to mapping our universe and separating the
galactic suburbs from the galactic city limits. Superclusters and Voids
Despite the varied definitions, scientists have general outlines. For instance,
the Virgo Supercluster appears to be just one branch of an even larger supercluster called
Laniakea. Other superclusters surround and connect with Laniakea, like the Shapley Supercluster,
the Hercules Supercluster and the Pavo-Indus Supercluster. Each of these massive structures
is hundreds of millions of light-years long. Here’s a good way to think of superclusters.
They are like the foam you see when you add too much soap to your bath or soap water when
washing your car. Between all those bits of foam are dime-sized empty spaces. In your bath, those
empty pockets are the soap bubbles themselves. In cosmology, they're the great cosmic voids.
Every supercluster defines the edge of a corresponding cosmic void. There's the Sculptor
Void, the Canis Major Void, the Boötes Void and more. Each of these voids is a vast expanse of
pretty much nothing at all. They’re just empty cosmological wastelands barely containing a few
straggling galaxies, like oasis towns in a vast desert. The largest of these voids, like Boötes,
are over 300 million light-years in diameter. The Dipole Repeller
Everything within the billion light-year proximity of our solar system is considered “Local”. With
that in mind, imagine the difficulty of mapping the Local universe let alone Superclusters and
the entire universe. That's because all the dust in the Milky Way obscures our view, and we have
to resort to fancy astronomical technology, like sensitive infrared and radio surveys,
to get a sense of what's going on deeper in space. But through these various advanced instruments,
cosmologists were able to identify the Shapley Supercluster, Laniakea's nearest neighbor. The
mass of the Shapley Supercluster is so impressive that it exerts a gravitational pull on this entire
region of space. Every galaxy, including the Milky Way, is moving in that direction.
However, there is another concern. The projected mass of the Shapley Supercluster
isn’t quite enough to account for our velocity. So, cosmologist figure there must be an additional
pull other than the Shapley Supercluster coming from another direction. This is the
Dipole Repeller, a hypothetical void, perhaps even a supervoid that is sitting on the opposite side
of the Milky Way. As the Shapley pulls us with its massive gravity, the Dipole Repeller does
the same in kind with its massive nothingness. Astronomers have discovered that there is a vast
wall across the southern border of the local cosmos; a vast assemblage of galaxies hidden
behind our own, in the “zone of avoidance also known as the “South Pole Wall.” Another good way
to describe it is thousands of galaxies taking structures like beehives of trillions of stars
and dark worlds, as well as dust and gas — aligned in a curtain arcing across at least 700 million
light-years of space. It winds behind the dust, gas and stars of our own galaxy, the Milky Way,
from the constellation Perseus in the Northern Hemisphere to the constellation Apus in the far
south. Unfortunately, trying to see it is pointless since the entire conglomeration
is behind the Milky Way. This area has been quaintly called the zone of avoidance.
This is Not the Only Intergalactic Wall An international team of astronomers led
by Daniel Pomarède of Paris-Saclay University and R. Brent Tully of the University of Hawaii
announced that this new addition to the Local Universe, the South Pole Wall is the poster
child among the other known great intergalactic walls and cosmographic space marks including,
the Sloan Great Wall, the Hercules-Corona Borealis Great Wall and the Bootes Void.
As mentioned previously, the galaxies in the wall cannot be seen, but Dr. Pomarède
and his colleagues were able to observe their gravitational effects by assembling data from
telescopes around the world. With these studies combined with Dr. Tully and his colleagues,
they have been able to study the distances of 18,000 galaxies as far away as 600 million
light-years away. By comparison, the most distant objects we can see — quasars and
galaxies that formed shortly after the Big Bang — are about 13 billion light years away.
All of these discoveries are confirming Edwin Hubble’s theory of the expanding universe that was
realized in 1929. Host of “Ask a Spaceman” might tell you, distant galaxies are flying away from
us as if they were dots on an inflating balloon; and the farther they are, the faster they recede
from us, according to the Hubble law. And this is where we get into redshift
as that motion away from Earth causes their light to be shifted to longer, redder wavelengths and
lower frequencies, like retreating ambulance sirens. Astronomers have been using “redshift”
for many discoveries since it is easy to measure. It’s basically a proxy for relative
distance in the universe. By measuring the galaxy distances independently, the “Cosmicflows” team,
as Dr. Pomarède and his colleagues call themselves, were able to differentiate
the motion caused by the cosmic expansion from motions caused by gravitational irregularities.
Due to these methods, scientists have found that the galaxies between Earth
and the South Pole Wall are sailing away from us slightly faster than they otherwise should be,
by about 30 miles per second. Then, they’re drawn outward by the enormous blob of matter in
the wall. And galaxies beyond the wall are moving outward more slowly than they otherwise should be,
reined in by the gravitational drag of the wall. Keep this astonishing concept of space in
mind. Studies and surveys show that the sheer volume of some of these walls are
easily 1.4 billion light-years long packed with clouds easily 600 million light-years in radius.
According to Dr. Tully, “We’d have to anticipate that our view of the filament is clipped; that
it extends beyond our survey horizon.” Meaning, the universe just might be too big for us to map.
Yet regarding the South Pole Wall near our solar system, Dr. Pomarède noted, in nearby cosmological
terms. “One might wonder how such a large and not-so-distant structure remained unnoticed.”
In the ever expanding universe, there is always something more to see. And luckily for you,
you’ve already hit that like button and subscribed to Space Infinity to consistently learn more and
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