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The things we can see in the night sky are captivating,
but what’s even more mind-boggling are the things we can’t see with our eyeballs.
Like back in the 1950s and 60s,
astronomers discovered these two massive structures emitting radio waves.
But new research set to be published in the Astrophysical Journal
suggests they’re actually the same thing, a massive cylinder of light, created by long-dead
stars.
If you haven’t heard the news, we’re living in a spiral galaxy.
And the position of the solar system is about here,
in what’s called the Local Arm.
It’s a tiny arc of stars, gas, and dust wedged between two larger arcs.~
But even more locally, our solar system, along with many others,
sits inside a feature known as the Local Bubble,
a peanut-shaped region of space filled with a lot less hydrogen than average.
And astronomers believe the Local Bubble formed after a bunch of stars exploded
and pushed everything away,
which is probably why there’s less hydrogen than in other places.
Scientists also hypothesize that our Sun hasn’t been in the Local Bubble for very long,
astronomically speaking: only a few million years.
And this won’t last forever because stars migrate over time.
But in the meantime, sitting inside a bubble can influence our view of outer space.
Which brings us back to those two massive radio structures.
They’re known as the North Polar Spur, or NPS,
which is roughly perpendicular to our galaxy,
and the Fan Region, which runs parallel to our galaxy.
From our perspective here on Earth, they appear on opposite sides of the sky.
So they’ve always been studied as distinct features,
even though they do share some similar properties, like the light they emit.
Both radio structures emit synchrotron radiation,
which is created when charged particles, like electrons, are accelerated.
And, in this case, the acceleration happens through an external magnetic field.
If the light of the NPS and Fan Region originates from the same physics concept,
they may share a common origin story.
Instead of being two separate structures,
they might be a single massive one with our solar system sitting right inside its walls.
At least that’s what a 1965 paper suggested.
Or, more specifically, an aside in that paper.
Basically, they knew that synchrotron radiation is brightest
when it’s coming from a direction perpendicular to the magnetic field making it.
And they applied that to the Local Arm’s magnetic field.
Perpendicular to that,
there would be two patches of synchrotron radiation…
right where the NPS and Fan Region happen to be.
Inspired by the paper’s aside note,
a team of astronomers decided to do more research into this phenomenon.
They created simplified computer models of the sky in radio wavelengths,
generating synchrotron radiation based on magnetic field strength, direction,
and distribution of electrons.
But unlike more traditional models, which center things on the center of the Milky Way
these were centered on us.
Which isn’t a thing you’d think astronomers would want to do,
after Copernicus and the whole overturning of the Earth
being the center of the universe thing.
But this vantage point was able to connect the NPS and Fan Regions.
Which showed how the structures ran parallel to one another,
with the solar system sandwiched between them.
A couple other structures, similar to the NPS and Fan Regions,
generally known as filaments, were also matched up.
The most important outcome of the model was that
the radio structures looked like part of a larger cylindrical structure, sort of like
a cosmic tunnel.
The team estimated that both the NPS and Fan Region
stretch about a thousand light-years long,
and the closest parts of each lie about 350 light-years from Earth,
which is roughly where the edge of the Local Bubble is.
The model also suggested that the common origin of these structures comes from supernova shockwaves.
The explosions that helped create the Local Bubble
would have compressed interstellar gas at the bubble’s edge,
increasing the magnetic field strength and the amount of charged particles around,
the perfect ingredients to make the synchrotron radiation we’re detecting.
As time passed, the overall structure, and therefore each filament’s shape,
was distorted and lengthened, following the spiral structure of the Local Arm.
This is the first research to demonstrate that the NPS, Fan Region,
and other local filaments could share a common origin.
But there’s still more to investigate, since the team’s models weren’t particularly
complex,
and astronomers also need to work out what these structures are really made of.
Which is pretty important if we're trying to study phenomena outside the Local Bubble,
and especially the Local Arm.
Our data could be contaminated by signals coming from the “stuff” creating these
filaments
. It’d be like looking through a dirty window, but possibly thinking that dirt is off in
the distance.
So, this model supports the hypothesis that matter is being ejected out one end of the
Local Bubble
and our solar system will eventually escape the bubble.
Which is noteworthy, because similar features have been observed in other galaxies.
Which means that the Local Bubble may, in fact, be a Local Chimney, a
nd we’re living inside the walls.
Just don’t expect Cosmic Santa to come down with presents.
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