Space. It’s full of mysteries that have remained unsolved for centuries. But recently,
the cosmos has surpassed itself by baffling the world with a new, scary abnormality. Apparently,
something is tearing holes in the Milky Way, the galaxy that contains our Solar System!
Scientists have several theories, but none of them sound particularly reassuring.
When astronomers started the Gaia observations, a project that was organized to create a detailed
3D map of our galaxy, they didn't expect to find anything surprising. But that's exactly
what happened. Earlier this year, Harvard scientist Dr. Ana Bonaca noticed a weird disturbance
in our galaxy's stellar streams. A stellar stream is a line of stars that are moving
together through galaxies. The stellar stream we're talking about is called GD-1, and it's
stretched in an impressive line across our sky.
Anyway, this stream used to be a cohesive line, stretched by the gravity of our galaxy.
Well, not anymore! One day, Dr. Bonaca noticed a gap in the stream, and this gap had a strange
ragged edge. In fact, it looked like something terrifyingly huge recently plunged through
the stellar stream; and the sheer force of this object's gravity was so great that it
managed to drag stars in its wake. The most shocking thing was that the telescopes simply
failed to find the source of the damage. But then, what could this unseen bullet be?
One theory suggests that the intruder is a stray star. However, the hole is too enormous
for this idea to sound plausible. According to Dr. Bonaca, the hole is way bigger than
any existing star. It’d have to be a million times more massive than our Sun! That's why
this theory can be ruled out. But what if the hole in the Milky Way was
torn by a supermassive black hole like the one that dwells in the center of our galaxy?
If it was, it’d be a pretty scary scenario. If these two black holes got too close, they
wouldn't be able to escape each other's gravity, and a collision might be inevitable. And it
would be an extremely violent event. The stronger of the two holes would consume the weaker
one, and one huge, super mighty black hole would appear.
But, people have yet to witness a collision of black holes. What's more, scientists can't
predict the consequences of such a merge, even though they’ve simulated it on powerful
computers. The only obvious fact is that it would produce incredible amounts of energy
and send huge ripples through the Universe. Naturally, these ripples would be bound to
eventually hit our planet. On the other hand, two black holes in one
galaxy might refuse to merge. Imagine this: a supermassive black hole hundreds of millions
of times the mass of the Sun is spinning in the center of the Milky Way at a phenomenal
speed. Another spinning black hole approaches "ours." What do you think will happen? Right,
one of the holes, most likely the intruder, will get kicked out and sent hurtling away
like a Frisbee flying through space. And who can guarantee that it wouldn’t head toward
the Earth? Luckily for us, there aren’t any supermassive
black holes in the vicinity, so this theory fails to explain the mysterious bullet-hole
phenomenon. Naturally, astronomers have continued their
observations. But what baffles them is that there’s no large object made from ordinary,
light-reflecting matter moving away from the bullet-hole. This fact hints that the culprit
that tore our Milky Way could be... dark matter?! Dark matter is mystifying and invisible, and
it makes up more than 27 percent of all the matter in the Universe. For comparison, the
regular matter, which is virtually all the stuff we can see, makes up only a mere 5 percent
of the Universe. And the rest is dark energy, which is a bizarre phenomenon, still unclear
to researchers but associated with the never-ending expansion of the Universe.
But back to our dark matter, which gets even more confusing once you learn about the following
paradox. On one hand, scientists have never directly detected dark matter, despite conducting
tons of experiments. On the other hand, after observing dark matter's gravitational pull,
astronomers are sure that this substance does exist. They came to the conclusion that dark
matter doesn't move around much, and neither produces nor interacts with light. Well, no
wonder it's called dark! So, what if it WAS dark matter that harmed
our galaxy, and what if it reached Earth? Unlike a stream of regular matter, dark matter
wouldn't see the Earth as an obstacle. It would just pass through. But that's not the
most amazing part! The thing is that after the dark matter passes
through the planet's core, the Earth's gravitation would most likely bend the stream into dense,
thin hairs! These hairs would have "roots" and "tips," just like human hairs do. In the
"root" of a dark matter hair, the particle density would be a billion times higher than
average! Also, the root would be somewhere around 600,000 miles away from the Earth's
surface, or, in other words, two times further than the Moon. As for the "tip" of the hair,
it would be even further from Earth. How would it influence our planet and us? Well, it's
still unclear, but the chances are that people wouldn't even notice the dark matter intrusion.
(Until too late. Nah, just kidding.) At the same time, if it were indeed a dense
ball of dark matter that had damaged the Milky Way, scientists would be more than happy!
This would provide them with the perfect opportunity to study the elusive substance. On top of
that, it would prove the theory that dark matter is lumpy rather than smooth or evenly
distributed all over the Universe. However, Dr. Bonaca still doesn't rule out
the possibility that the intruder is a luminous object that, after tearing a hole in the Milky
Way, is hiding somewhere in the galaxy. But again, it seems highly unlikely because of
the huge size of the object: according to scientific estimation, it would be 30 to 65
light years across! In any case, it's hard to predict where it
would’ve ended up if it were a luminous object, and here’s the reason. The intruder
could’ve been moving at an incredibly high speed, and wouldn’t have to be very massive
to tear a hole in the stellar stream. Or, it could’ve been moving more slowly but
be very heavy. But the astronomers don't know which option it was, that's why it's next
to impossible to predict where it ended up.
Well, it seems that for now, our intruder remains a mystery that will torture the minds
of astronomers from all over the world. As if the galaxy isn't already a bizarre and
often illogical place! Just have a look at its outskirts: they're protected by a halo
of hot gas, studded with dying stars and beautiful globular clusters. The latter are spherical
groups of stars that are tightly bound by gravity and orbit the galactic core as satellites.
But that's not all! The edge of the galaxy can even contain traces of a "ghost" galaxy
- one that's older than our Milky Way! Curiously, the astronomers who discovered
the "ghost" galaxy, which is a satellite galaxy of the Milky Way, can’t explain its origin
and nature. Named Ant 2, the galaxy was dubbed "ghost" because it's weirdly dim. Besides,
for a dwarf galaxy - yep, those do exist! - Ant 2 is too large, too faint, and doesn't
have enough mass for its size. A walking paradox! However, scientists have an idea why the "ghost"
galaxy might be so abnormal. The thing is that the Milky Way could be constantly tearing
chunks of this satellite galaxy with its gravitational field. It would explain the dimness of the
galaxy and its low mass. But then, it doesn't clear up why Ant 2 is so big. Usually satellite
galaxies shrink, not grow, when they lose their mass to the Milky Way's gravitational
pull. The "ghost" galaxy’s unexplained quirks made astronomers call Ant 2 an oddball and
add it to the list of space mysteries and paradoxes. Okay, my brain exploded with that
oner.
Have you heard about any other mysteries space has in store for us? Let me know down in the
comments! If you learned something new today, then give this video a like and share it with
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