Journey to the Center of the Galaxy

Journey to the Center of the Galaxy

If you ever find yourself on a tour of some
of the most fantastic places in the galaxy, make sure you stop by the center. It’s a
pretty exciting place. Mainly, that’s because of the supermassive
black hole, more than 4.3 million times the mass of our Sun, that’s sitting in the middle
of the Milky Way. Black holes are what’s left over when a
star collapses, and they have an incredibly strong gravitational pull. Because of that super powerful force, the
supermassive black hole’s neighborhood is the hottest, densest, and most turbulent place
in the galaxy, stretching nearly a thousand light years across. Over time, it’s drawn in about 80 percent
of all of the dense, molecular hydrogen gas in our galaxy — the stuff that makes stars
— which is why it’s called the central molecular zone. But combine the gas clouds with the supermassive
black hole’s gravitational pull, and you get some weird effects. So not only is the region full of dark clouds,
it’s also scattered with super star clusters and the corpses of dead stars. Much of the gas in the molecular zone is clumped
up, lying along a twisted ring of dusty gas clouds around 326 light-years from the central
black hole. These gas clouds orbit the center of the Milky
Way at almost 300,000 kilometers an hour, following the same orbit like beads on a string. But the ring is a little off-center, so at
one point, the clouds end up within just 200 light-years of the black hole. And that’s when things really start to get
weird. The gravitational pull compresses the clouds
even more, and one of them is so dense that it’s nicknamed the Brick. At an average density of 10,000 atoms per
cubic centimeter, the Brick would be considered a high vacuum here on Earth. But out in space,
it’s more than 10 times the density where star formation would normally begin, and astronomers
wanted to know why. In 2012, a group of researchers got the first
glimpse inside the Brick using a set of telescopes called the Atacama Large Millimeter Array
— and in the process, they might’ve found the answer to why it hasn’t started making
stars yet. They discovered that the gas is made of both
filaments and dusty clumps, and it’s preparing to form star clusters with hundreds of high
luminosity, or super bright, high-mass stars — but the high energy environment moves the
gas around so much that the lights haven’t turned on quite yet. But eventually, the Brick will reach just
the right conditions where it can make stars, and it’ll quickly form a lot of really big,
bright ones. Then, it’ll become a lot like another cloud
in the molecular zone, called Sagittarius B2. Which is a huge cloud, almost 10 times as
massive as the Brick, and the most active site of star formation in the entire Galaxy. It probably went through that whole black-hole-squeezing
process at some point, and within the last few tens of thousands of years, it’s burst
to life with dozens of extreme, high-mass stars. And in the hottest spot in Sgr B2, there’s
a young star cluster that produces more than 10 million times the luminosity of our Sun. Those hot stars pour out so much heat and
energy that all sorts of complex chemical reactions can happen in the surrounding clouds. So that’s where we tend to find complex
organic molecules like formaldehyde, different kinds of alcohols, and ethyl formate, a molecule
that smells like rum and tastes like raspberries. But Sgr B2 won’t stick around forever. At some point, the fierce winds and radiation
from the hot stars will blow the cloud apart, leaving behind enormous super star clusters. There are a few of these, formed within the
last few million years, already in the molecular zone. Two of the most famous clusters are called
Arches and Quintuplet, and they pack stars in densities more than 100,000 times higher
than in our part of the galaxy. The Quintuplet cluster contains one of the
most luminous stars known, the Pistol star. And it probably couldn’t have formed anywhere
else in the galaxy, because it would’ve needed a lot of mass to pile up really quickly. Overall, every few million years the central
molecular zone turns so much gas into stars that it uses up 100,000 times our Sun’s
mass. But any losses are quickly replaced by gas
flowing in from farther out in the galaxy, so the star formation has continued for millions,
if not billions, of years. With such a long history of forming heavy,
bright stars, the molecular zone has another group of residents that you won’t find anywhere
else in the galaxy: lots and lots of dead stars. High mass stars burn through their fuel really
quickly, and they’ll go supernova in as little as 3.5 million years after they first
form — compare that to our Sun’s 10 billion years! After they explode, they leave behind stellar
corpses in the form of small black holes and neutron stars — tiny, high-density cores. Over the more than 10-billion-year lifespan
of the galaxy, generations of stars have formed and died in the molecular zone. So, in addition to being the busiest stellar
nursery in the galaxy, the most extreme place in the galaxy is also its largest and most
crowded graveyard. Thanks for watching this this episode of SciShow
Space, and thanks especially to our patrons on Patreon who help make this show possible.
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About the author


  1. Never heared a woman talk about astronomy. That's weird. Why can't the men who have discovered this knowledge talk in the vid? They deserved it.

  2. So we should head to the center of the galaxy because it's exciting only to get sucked into a black hole and never be heard of again?

  3. Would be kind of cool if the center of the galaxy acted as a vacuum, attracting anything without a proper gravitational pull like a dead star, or planet. Once they're in, the material is recycled and used to make new stars and planets that break away once ready.

  4. She’s better than the bald guy hairy chest guy he’s voice it’s to rough and sometimes I can barely understand. She speak so smooth and clear and I love it

  5. You know what's funny, when I was younger, I thought the bright light in the center of our galaxy was just our sun. I thought the only thing in our galaxy was our planets, and our sun. Nope. I am embarrassed to admit it, but I was WAY off.

  6. Biggest and most populated graveyard? More like richest and most unimaginable pile of heavy metals we havent even discivered yet

  7. but now imagine: the things she is talking about the brick might be happening right now but the light still needs hundreds of yeara ro reach us.

  8. welp time to sleep and i feel scared that the center of "EVERY GALAXY IS A SUPER MASSIVE BLACKHOLE" not telling its 100% true but i think its almost every galaxy is like that and science ruins your happy life knowing the truth

  9. How can supermassive black holes (whatever you call them) which are formed by died stars, being more powerful than still alive stars. Isnt something died being weaker than the surviving one!?

  10. She was so fast that I didn't understand anything. I hope she went to go potty later and relieved herself.

  11. I hope a star doesn't form inside me from all that taco bell I ate earlier, because the gas it's created inside me is a least 10,000 atoms per cubic cm.

  12. Just wondered where the center was, didn't really need a weird girl doing some kind of hand jive on here spewing things to act like she's smart or something.

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