Here's What Makes The Center of The Milky Way Galaxy So Bright

Bright Side

The center of the Milky Way is super bright because it’s packed with a lot of stars and a supermassive black hole. That black hole, called Sagittarius A*, is millions of times bigger than our sun! It pulls in gas, dust, and even stars, and as they get close, they heat up and glow, making the area shine really bright. There's also a huge cloud of hot gas and tons of stars crammed together, which adds to the glow. Some stars explode into supernovas, which are super bright, too. Dive in to explore this and other cool space facts.

Transcript

00:00Is there a giant mega sun in the center of our Milky Way?

00:04Scientists actually thought so for a while because it's the brightest place in the galaxy.

00:09It has millions of stars packed into a small area.

00:13This area is called the Gigantic Bulge.

00:17The Gigantic Bulge has millions more stars per light year than any other part of the galaxy.

00:23It can be 10 million times denser than our part of the neighborhood.

00:26In some cases, stars in this region are only 5 light days apart.

00:32That's like if there was another star in our solar system a bit further away than Pluto on a space scale.

00:38But why is this place so dense?

00:41When galaxies form, a lot of gas and dust come together under the force of gravity.

00:46This material gathers up and eventually forms stars.

00:49Gravity and angular momentum balance out and it starts looking like a flat disk with a pretty bright, bulging, dense core.

00:58The stars live their comfy lives and once they get to the finishing line, they collapse under their own huge weight.

01:05Then, the black hole forms.

01:07Black holes love to eat everything around them and the more they eat, the bigger they get.

01:13And what place is more perfect for a fine dinner than the galaxy center where all the space stuff is packed together?

01:21So it starts eating surrounding gas and dust, forming an accretion disk.

01:25As this material spirals into the black hole, it heats up and emits a lot of energy, which makes the center of the galaxy even brighter.

01:35That's why you can find both supermassive black holes and galactic bulges in the centers of all galaxies.

01:42The galactic bulge at the center of the Milky Way looks a bit like an ellipse.

01:48That's a classical bulge.

01:51Stars aren't like our sun.

01:53They move randomly in all possible directions and planes.

01:56Plus, they all move at different speeds.

01:59So gravity is going crazy there and this makes the bulge look more like a sphere or an ellipse.

02:05Since they were the first ones to form, they have some of the most ancient stars in our galaxy.

02:10But there are also some places of star formations and lots of younger, massive stars that are less than 100 million years old.

02:20As we move farther away from the center, things get a bit calmer.

02:24Stars start rotating uniformly and become stable.

02:28Right now, Earth is in one of the Milky Way's spiral arms called the Orion Arm, pretty far away from the galactic bulge.

02:35In our part of the neighborhood, stars are usually about 4 or 5 light years apart.

02:41This means that most of a galaxy is actually just black, empty space.

02:47Our black hole is called Sagittarius A star.

02:51It's a monster about 4 million times the mass of our sun.

02:55It's also about 32 million miles in size, almost like the distance between Mercury and the sun.

03:01But don't worry, it's not attracting the Milky Way inside it and it's not going to eat us.

03:07These black holes are actually super small compared to the entire galaxy, so they can only eat whatever's around.

03:14Right now, many stars orbit Sagittarius A star.

03:18And even though it emits a huge amount of energy, we can't see its light from Earth without a lot of scientific effort.

03:25But why don't we see the center itself?

03:28The galactic bulge is so bright that even though it's 26,000 light years away, we should see it shining brightly in our sky.

03:37Yet, we don't.

03:39Turns out it's all because of space dust.

03:41There's a lot of dust between us and the core, and it absorbs most of the visible light.

03:46We can only look at the galactic core using other types of light, like near-infrared, gamma-ray, and so on.

03:55NASA has images of the core in different types of light, and it shows how scarily bright the center is without the dust blocking our view.

04:04But not all bright regions are blocked by gas and dust.

04:07For example, when we look at dense clusters like the Messier 13, the stars are so close together that they look just like a white spot.

04:17Most of our telescopes can't separate them from each other.

04:20The satellite galaxy M32, our neighbor near the Andromeda galaxy, has about 84 stars per light year.

04:28It's so dense that stars can't be resolved even by the Hubble Space Telescope.

04:33To get the idea, our solar system is two light years long.

04:38We'd see about 168 stars outside our window if we were there.

04:44Our closest star is Alpha Centauri.

04:47It's about four light years away from the sun.

04:50If it was just a couple of light days away, it would shine much brighter than the full moon.

04:55So if we somehow managed to survive in crazily dense star regions, the sky would be white all day long.

05:02But it's unlikely that we'd make it.

05:05As we get closer to the center of the Milky Way, the chances of finding life get super slim.

05:11The gravity of stars is going wild with chaotic movements, so there are barely any planets around.

05:17On those miracle planets, the radiation from cosmic rays is skyrocketing.

05:22Supernova blasts and star collisions nearby become an everyday occasion.

05:28And all the gas around makes it basically impossible to breathe or even see properly.

05:34At the same time, as we move further away, there are fewer stars around.

05:39Elements that are super useful for life like carbon, oxygen, and iron are produced by stars.

05:45So they also drop.

05:47Too much radiation is awful.

05:49But too low radiation means that there's not enough energy to support chemical reactions, like photosynthesis.

05:55Which is why if there is extraterrestrial life, it would most likely be somewhere in the middle of different galaxies.

06:03But some galaxies get their brightness from a so-called active galactic nucleus.

06:09These are extremely energetic regions at the center of some galaxies.

06:13They shine much brighter than any stars imaginable, although it mostly shines only in certain parts of the electromagnetic spectrum.

06:22The brightness comes not from the stars, but from the accretion disk around their supermassive black holes.

06:30As the material slowly falls into a black hole, it gathers around it and creates this flat, spinning disk of gas, dust, and other stuff.

06:39Since the gravity and friction there are insane, this disk heats up and starts emitting enormous amounts of energy.

06:47Also, this disk spins incredibly fast, almost at the speed of light.

06:52Because of that, collisions there happen all the time, and they're unimaginably powerful.

06:59They release even bigger amounts of energy.

07:01Most galaxies don't have an AGN.

07:05Those that do, like the galaxy M87, in the Virgo constellation, are called active galaxies.

07:13There are also different types of AGNs.

07:16The Saifert galaxies, radio galaxies, and finally, the winners of our space brightness competition, quasars.

07:23Imagine things so bright that they can outshine the entire galaxy they belong to.

07:29Quasars are a specific type of active galactic nucleus, the most extreme and luminous form.

07:36They belong to the supermassive black holes, the biggest ones in our universe.

07:41Quasars are like a combination of several things.

07:44First, they're the brightest accretion disks in our world, because of their behemoth black holes eating everything around.

07:51But they have some cool features.

07:53For example, they have powerful jets of particles that shoot out from the poles of the black hole at nearly the speed of light.

08:01These jets add up to the brightness of the quasar, although they can only be seen in radio wavelengths.

08:08The energy they emit is so intense that they can be seen billions of light-years away.

08:13However, the nearest quasar to us is 600 million light-years away, so we can't see them with backyard telescopes.

08:21So, when we look at a galaxy through a telescope, we usually see only the brighter core, not the outer parts.

08:28Unfortunately, our eyes just aren't made to see things like the active galactic nucleus.

08:34So, these stars are the brightest things we can see.

08:38But what a beautiful sight it is!

08:40That's it for today.

08:41So, hey, if you pacified your curiosity, then give the video a like and share it with your friends.

08:46Or, if you want more, just click on these videos and stay on the bright side!

08:50Who would like to watch this side?

08:51Who would like to see anything else when you are running out?

08:54Do ready steps for this?

08:55Don't forget to watch any hands.

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08:57Let's go around for a sec.

08:58Here.

08:58You in mind, let's go around for a minute.

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09:01In route for a different friend.

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