From the ancient times of human civilization to this very day, we’ve always looked up
at the stars with an unwavering desire to know what’s out there. We’ve come a long
way, especially with advanced space technology on our side. But the universe still leaves
us with more questions than answers. Like what is that mysterious thing glowing in the
center of our galaxy???
It all started around 10 years ago, when NASA launched the Fermi Gamma-Ray Space Telescope.
This wasn’t your standard “point-and-shoot” telescope. It’s such an advanced piece of
equipment that it literally opened a huge window on the Universe, allowing us to see
things we wouldn’t have been able to otherwise. You might remember learning about the electromagnetic
spectrum in school. You’ve got the weakest radio waves on the far left, visible light
(that’s what the human eye can see) in the middle, and the strongest gamma rays on the
far right. So, when you observe the sky through a gamma-ray telescope rather than with your
own eyes, you’d be looking at a totally different picture!
When the astronomers started getting data back from the Fermi telescope, they noticed
that the center of our galaxy was emitting a lot more gamma radiation than, say, its
outskirts. To put it simply, something is glowing incredibly bright right in the middle
of the Milky Way! But the most perplexing thing is that no one has been able to find
an exact explanation for this phenomenon for nearly a decade!
Sure, there have been several theories. From the very beginning, some scientists hoped
that the mysterious glow was somehow connected to the long-sought-after and enigmatic “dark
matter.” This stuff’s existence has been theorized for years, and scientists are pretty
much certain that it exists. Even more so, they say it makes up about 27% of the entire
Universe. For comparison, ordinary matter like what makes up everything here on Earth
adds up to only 5% of the Universe’s composition. If you’re wondering about the remaining
68%, that would be dark energy, which oversees the fast growth of the Universe. But dark
energy is a topic for a whole ‘nother video!
For now, let’s get back to this dark matter business. There’s a theory that it works
as a sort of glue that keeps things together. Thanks to this sticky stuff, galaxies don't
split apart, stars don't collide with one another, and our Earth doesn't stray off its
orbit into open space. Let’s put that in a language that anyone can understand: pizza.
Imagine the crust is dark energy, the pepperoni, mushrooms, and all the toppings are ordinary
matter and galaxy clusters. The goopy melted cheese holding it all in place, that’s dark
matter.
Oh, and by calling it "dark" matter, scientists aren’t talking about the color. They just
mean that this space phenomenon doesn't emit either any radiation or light visible to the
human eye. Also, "matter" (if you understand this word like a “substance”) doesn't
mean that you can touch dark matter if you ever find it. It just behaves like the matter
you, as well as everything around you, are made of. For example, it has the same gravitational
pull as ordinary matter. Dark energy, however, doesn't behave this way.
Anyway, let’s go back to the glowing gamma rays in the heart of our galaxy. What does
this have to do with all that talk about dark matter? Well, some astronomers supposed that
the central region of the Milky Way was glowing with such intensity because dark matter was
getting destroyed there. While nobody has ever observed this dark matter “annihilation,”
scientists have been hypothesizing about this phenomenon for a long time. Naturally, we
wouldn't be able to see dark matter itself, but the process could be producing the radiation
the Gamma-Ray Telescope spotted. That’s why they got so excited that this could be
just the proof they needed!
Here’s the theory: if particles of dark matter collided (just like ordinary matter
particles do in particle accelerators), they’d annihilate one another. As a result, they’d
burst in a shower of other particles, including the ones that make up gamma rays. But that's
where the problem lies. If the mystifying glow was created by dark matter annihilation,
then gamma-ray particles would get distributed in space evenly. But the telescope showed
them gathering in clumps. So to the great disappointment of numerous supporters, the
theory based on dark matter was busted.
But there is an alternative explanation of why the Milky Way is glowing. The culprit
might be a group of millisecond pulsars, which are neutron stars rotating really really fast.
That is, about 1,000 times per second! You can't notice a separate pulsar since it produces
too little light. But a group of them is a different story…
Let's delve a bit deeper into the topic of pulsars. Imagine a lighthouse – its job
is to keep ships and boats from crashing into the rocks. Pulsars are the lighthouses of
the Universe, although not in the meaning that they save spacecraft from collision!
It’s more in the fact that they emit focused beams of radiation that you can only see if
you get in their path. Hence, the name of these neutron stars: they look like they're
pulsating up there in space.
When a supermassive star with a mass equal to 4 to 8 of our Suns dies, it either becomes
a supernova or turns into a black hole. But stars that are up to 3 times the mass of the
Sun aren't heavy enough to do that. That's why most of them end up collapsing and turning
into neutron stars or pulsars.
After that happens, the former star becomes much smaller. And as a result, its rotational
speed grows so dramatically that these space objects start to spin unimaginably fast. And
how about this: the incredible density of pulsars makes scientists believe that if there
was life on these stars, it would be two-dimensional, like in a comic book! That’s because the
gravity there is so strong that it would flatten anything on its surface! On top of that, it
seems that pulsars can have planets of their own, although it's unclear whether those are
original, or the pulsar just captured them one day and pulled them away from their orbits.
Our Milky Way is home to more than a billion neutron stars, and around 200,000 of them
are pulsars. If a pulsar were to enter our solar system one day, it’d be a bad situation
to say the least. The spinning invader would wreak havoc and chaos by throwing the planets
off their orbits (probably pulling away one or two of them). It’d also cause unimaginably
powerful tides that could literally rip the Earth apart. And let's not forget about its
gamma radiation! If even one jet of radiation from a pulsar hit our planet, it would destroy
the whole ozone layer in a matter of minutes! And we need that ozone to keep this planet
warm and protect it from ultraviolet radiation coming from the sun. So without it, Earth
would be uninhabitable…
Good thing that’s pretty much an impossible scenario! (Phew!) First, for all that planet-destroying
stuff to happen, a pulsar would need to get relatively close to Earth. But the closest
neutron star we know of is still 500 light-years away. Plus, the pulsar would have to be lined
up with our planet in a way for its cataclysmic jet of gamma radiation to reach us; otherwise,
it would miss.
So, is that what’s lighting up the center of our Milky Way? The pulsar theory is plausible.
Like I said before, the glow coming from there is clumpy rather than smooth. That sort of
pattern often happens when the source of the energy is one individual object, such as a
pulsar. Several studies have concluded that, due to the nature of the light, millisecond
pulsars are the best explanation for this phenomenon.
But that doesn’t mean all scientists are convinced. They state that these clumps may
be a result of the interaction of gas between stars and cosmic rays. You know, like Timon
said in the Lion King: “Hey Pumba, with you, everything’s gas.” Besides, the pulsar
theory has one more catch: why would so many of them be clustered together in a perfect
sphere around the center of the galaxy? It’s likely that the clusters of stars that orbit
the Milky Way could’ve been disrupted by the galaxy's gravity and, as a result, spilled
some stars here and there. That could’ve included pulsars that later formed a spherical
shell around the heart of the Milky Way.
But, in fact, the whole picture looks like something completely different from both pulsars
and dark matter. So, in the end, scientists are still left with more questions than answers
and a lot more researching to do for any conclusive findings. Guess we’ll just have to wait
and see!
What, in your opinion, is the source of the mysterious glow in the center of the Milky
Way? Let me know down in the comments! If you learned something new today, then give
this video a like and share it with a friend. But – hey! – don't go ejecting your dark
matter just yet! We have over 2,000 cool videos for you to check out. All you have to do is
pick the left or right video, click on it, and enjoy! Stay on the Bright Side of life!