Astronomers Finally Found the Edge of the Milky Way

Added: 2026-05-23

[00:00:00]What if I told you astronomers may have finally found the edge of our galaxy?

[00:00:05]Not the edge of space, not the end of the universe, the actual point where the Milky Way basically stops being alive.

[00:00:14]For decades, scientists struggled with one surprisingly difficult question.

[00:00:19]Where does the Milky Way end?

[00:00:21]The problem is that galaxies don't have clean borders. There's no giant wall of stars marking the finish line.

[00:00:28]Instead, the Milky Way slowly fades outward into darkness with fewer and fewer stars the farther you travel from the center.

[00:00:36]So, instead of asking where the [music] galaxy physically ends, astronomers tried making a smarter question. Where does the galaxy stop making new stars?

[00:00:46]And now, researchers think they finally have the answer.

[00:00:50]By studying the ages and locations of more than 100,000 stars, scientists discovered that star formation in the Milky Way sharply drops off around 40,000 light-years from the galactic center.

[00:01:02]>> [music] >> That point may be the galaxy's true boundary.

[00:01:06]Inside that region, the Milky Way is still active. Gas and dust come together, collapse under gravity, and create brand new stars. In a way, this is the living part of the galaxy. But beyond that distance, something [music] changes.

[00:01:22]New stars almost completely stop forming, and yet there are still stars out there. So, where did they come from?

[00:01:31]According to the study, many of those outer stars are basically cosmic migrants.

[00:01:36]>> [music] >> They were likely born closer to the center of the Milky Way billions of years ago and slowly pushed outward over time by powerful gravitational forces.

[00:01:46]Some may have been moved by the galaxy's spiral arms. Others may have been flung outward [music] by the Milky Way's central bar. A massive structure near the core that acts a little like a gravitational slingshot.

[00:01:59]So, the outer galaxy isn't empty.

[00:02:01][music] It's more like an old quiet neighborhood filled with aging stars that drifted [music] there long ago.

[00:02:08]What makes this discovery especially interesting is that scientists still don't fully know why star formation suddenly shuts down at that distance.

[00:02:16]One idea is that the gas becomes too thin and spread out to collapse into new stars.

[00:02:22]Another possibility is that the shape of the galaxy itself disrupts the movement of gas in those outer regions.

[00:02:29]Either way, the Milky Way appears to have two very different personalities.

[00:02:34]There's the bright, [music] active inner galaxy where stars are still being born.

[00:02:39]And then there's the vast outer region where ancient stars slowly wander through a quieter cosmic landscape.

[00:02:47]And maybe the strangest part is this.

[00:02:49]Our galaxy doesn't really end [music] at all. It simply fades.

[00:02:54]There's no sharp border or a final wall, just a slow transition from busy, star-filled regions into [music] colder and older outskirts shaped by billions of years of cosmic migration. [music] For the first time though, scientists think they may finally know where that transition begins.

[00:03:14]You're traveling through space trying to get through an especially rough patch.

[00:03:19]You got to dodge asteroids, space debris, wandering black holes. No, it's not an episode of a sci-fi series. At least not completely. For the first time ever, astronomers have found a black hole that's completely alone drifting through space [music] with no stars or planets nearby.

[00:03:37]This black hole is about 5,000 [music] light-years away from us in our own Milky Way galaxy.

[00:03:43]Do we need to look for a hero with superpowers to save Earth?

[00:03:48]First things first, a black hole is a place in space where gravity pulls so much that nothing, not even light, can get out of this region.

[00:03:58]The gravity is so strong there because a huge amount of matter is squeezed into a tiny space.

[00:04:05]Supermassive black holes, hundreds of thousands [music] to billions of times the mass of our sun, are often found at the centers of galaxies.

[00:04:13]Most of them stay put or move at a very, very slow pace.

[00:04:19]But the newly discovered black hole is much weirder than anything we've seen before. First of all, it tries to avoid commitment. [music] It's lonely with no companion star or home galaxy.

[00:04:31]An even stranger thing is that it's zooming through space at a speed of 31 miles per [music] second.

[00:04:37]What might be the reason for this speedy cosmic journey?

[00:04:41]Let's look at the following imaginary scenario. One day, a really massive star exploded in a supernova.

[00:04:48]It was the very star that formed [music] our black hole.

[00:04:51]The resulting blast gave the new black hole a massive kick and sent it flying through the galaxy, starting its unbelievable voyage.

[00:04:59]Now, it's only one of a few possible explanations, but it sounds quite plausible.

[00:05:05]I bet you can't help but think, "What if this wandering [music] black hole decides to visit our solar system? Are we doomed?"

[00:05:13]Scientists [music] tell you to relax and breathe out. This black hole is very far away, and your chances of ever encountering it are infinitesimal, if any.

[00:05:23]Plus, this black hole is [music] totally quiet and dark at the moment. One day, it might wake up and start glowing.

[00:05:30]It'll happen if it begins to eat something.

[00:05:34]In the near future, powerful new telescopes may [music] find many more wandering black holes like this one.

[00:05:41]Usually, black holes are super hard to find because they don't give off [music] any light.

[00:05:48]You can only detect them when they're eating nearby matter.

[00:05:51]That makes them glow brightly.

[00:05:54]Or when they have a companion star.

[00:05:57]In this case, it moves in a strange way, which gives away [music] the presence of a black hole.

[00:06:04]But this newly discovered black hole is lonely, totally by itself. There's no glowing, no companion star moving hectically.

[00:06:13]So, how did scientists spot our cosmic wanderer?

[00:06:17]They use something called gravitational microlensing.

[00:06:21]That's when the black hole's gravity [music] bends and magnifies the light from a star located behind it. Kind of like using a magnifying glass, [music] hence the name.

[00:06:31]This method allowed scientists to detect the black hole even though it was completely dark.

[00:06:37]All in all, black holes are fascinating things, and some of them are truly unique, like these biggest black holes ever [music] found.

[00:06:46]You see, almost every galaxy has a super massive black hole at its center.

[00:06:51]They're huge, with masses [music] millions to billions of times bigger than our sun.

[00:06:58]One of those is called Ton 618.

[00:07:01]It's a really huge and powerful black hole that's part of something called a quasar.

[00:07:07]A super bright spot in space >> [music] >> emitting incredible amounts of energy.

[00:07:12]Ton 618 is very, very far away, about 18.2 billion light-years from Earth.

[00:07:20]And it's 40 billion times heavier than our sun.

[00:07:25]There are also black holes that feed on their own kind.

[00:07:29]Black holes are known for devouring anything that gets too close.

[00:07:33]And this anything can include not only stars and gas, but also other black holes.

[00:07:40]Scientists witnessed a ginormous [music] black hole at the heart of one galaxy being swallowed by an even larger black hole in another galaxy. It was the first time we detected such an event.

[00:07:52]The discovery was made using NASA's Chandra X-ray Observatory.

[00:07:57]One black hole weighs about 30 million times the mass of the Sun, while the other has at least 1 million times the mass of the Sun.

[00:08:06]Then, there is a bullet-shooting black hole.

[00:08:09]Apparently, black holes don't just swallow matter, they can also shoot it out.

[00:08:15]For example, astronomers studied one relatively small black hole, which is about 28,000 light-years from Earth and weighs between five to 10 times the mass of the Sun.

[00:08:25]And they saw how this black hole pulled matter off a companion star, and then blasted some of it out in the form of huge bullets of gas.

[00:08:35]These bullets are super fast. They move at nearly a quarter the speed of light.

[00:08:41]Some black holes spin incredibly fast, twisting space around them at extreme speeds.

[00:08:47]One example is a black hole located in the constellation Aquila, about 35,000 light-years from Earth.

[00:08:54]This black hole spins at a staggering speed of more than 950 times per second.

[00:09:01]If you could place an object on the edge of this black hole's event horizon, it would spin around the black hole at 333 million miles per hour.

[00:09:10]That's nearly half the speed of light.

[00:09:13]The smallest black hole discovered so far has been nicknamed the Unicorn.

[00:09:19]Located 1,500 light-years away from Earth, it's around three times the mass of our Sun.

[00:09:24]>> [music] >> This makes it very close to the smallest possible size for a stable black hole.

[00:09:31]While black holes themselves are far away and difficult to study directly, scientists find new clever ways to study their properties right here on Earth.

[00:09:40]They've been able to recreate certain features of black holes in the lab.

[00:09:45]For example, black holes have a gravitational pull so strong that nothing, including light, can escape [music] once it crosses the event horizon.

[00:09:56]To understand this better, researchers have created an artificial event horizon using fiber optics.

[00:10:03]They've also been able to simulate Hawking radiation, the kind that likely escapes black holes, by setting [music] up experiments in the lab.

[00:10:11]These lab-created mini black holes help scientists understand the mysterious properties of real black holes.

[00:10:20]There are several types of black holes, and each of [music] them is born in its own unique way.

[00:10:27]Primordial black holes are believed to have formed right after [music] the Big Bang, when the universe was very young.

[00:10:34]Stellar black [music] holes form when a massive star collapses in on itself.

[00:10:39]This causes a supernova, where [music] the outer layers of the star explode into space, and the core turns into a black hole.

[00:10:48]As for supermassive black holes, they're thought [music] to have formed alongside the galaxies they're in.

[00:10:54]The size of the black hole is usually related to the size and mass of the galaxy.

[00:11:01]Despite what [music] many believe, black holes don't roam the universe randomly looking to swallow planets. They obey gravity like anything else in space. So, for a black hole [music] to affect Earth, it would have to be very close, much closer than any black hole is to us right now.

[00:11:18]Even if a black [music] hole the same mass as the Sun replaced our Sun, Earth wouldn't fall into it. The black hole would still have the same gravity as the Sun, and Earth would continue [music] orbiting it just like it orbits the Sun today. It would get much colder, though, so we wouldn't survive such a replacement in any case.

[00:11:37]But, don't worry. Our sun will never turn into a black hole. It doesn't have enough mass to do so.

[00:11:43]Instead, in about 5 billion years, when the sun reaches the end of its life, it will become a red giant star.

[00:11:51]After using up its fuel, it will shed its outer layers, creating a glowing ring of gas called a planetary nebula.

[00:11:59]What's left [music] will be a cooling white dwarf star.

[00:12:03]At breakneck speed, this mysterious object is zipping through our galaxy.

[00:12:08]It's moving at a staggering 1 million miles per hour. That's so fast, it might potentially escape the Milky Way altogether.

[00:12:16]While scientists are trying to understand exactly what this space weirdo is, we're going into space to learn more about it.

[00:12:23]The object [music] is currently moving at a distance of 400 light-years away from Earth. Let's have a closer look and try to figure out if it could be a runaway probe.

[00:12:33]Nah, it's way too large for that. The object [music] is around 30,000 times the mass of Earth and 8% of the mass of the sun. What a giant. Such a size places it in a category that Dr. Darren Baskill, an astronomy lecturer at the University of Sussex, describes as somewhere between a star and a planet.

[00:12:53]Stars moving at such extreme speeds are super rare. Only one or two out of every thousand local stars travel so incredibly fast.

[00:13:02]So, if one day you found a star moving as rapidly as our cosmic enigma, you'd see it leave our home Milky Way galaxy in just a few tens of millions of years.

[00:13:13]In terms of space and cosmic distances, it's a blink of an eye period of time.

[00:13:18]After all, such stars can live for tens of billions of years. Even though the mysterious object is only moving at 0.001% of the speed of light, it's still potentially fast enough to eventually break free from the gravitational pull of our galaxy and fly into intergalactic space.

[00:13:39]Let's put this speed into perspective.

[00:13:41]J1249 is traveling 2.6 times faster than the fastest space probe ever [music] launched.

[00:13:49]I'm talking about the Parker Solar Probe.

[00:13:52]The Parker Probe [music] reached this speed in June 2024 while looping around the sun.

[00:13:59]J1249 was discovered by citizen scientists volunteering for NASA's Backyard Worlds Planet 9 project. These volunteers sift through online images taken by NASA's Wide-field Infrared Explorer and NEOWISE missions.

[00:14:16]They're looking for anything interesting.

[00:14:18]Three of those volunteers spotted a faint, fast-moving object as it moved across WISE images.

[00:14:25]When they realized what they were looking at, they were incredibly excited, but thought someone had already reported the space object. But surprisingly, that wasn't the case.

[00:14:36]At the moment, most scientists believe that CWISE J1249 could either be a low-mass star or a brown dwarf.

[00:14:45]That's a type of star that is larger than a planet, but too small to support nuclear fusion in its core like our sun does.

[00:14:52]In other words, such stars don't have enough mass and their cores can't [music] burn their star fuel, radiating starlight. That's why brown dwarfs, often referred to as failed stars, are smaller and cooler than the sun. They even have complex planet-like atmospheres, which have clouds [music] and molecules. For example, H2O.

[00:15:15]Anyway, to confirm or disprove this theory, astronomers continued to observe the object with the help of ground-based telescopes.

[00:15:23]Soon, they found out that the object had an unusual composition with much less iron and other metals compared to typical stars or brown dwarfs.

[00:15:33]It allowed NASA to claim the unthinkable.

[00:15:36]J1249 could be one of the oldest stars ever found in our galaxy. Okay, that's certainly a game-changer, but why is this potential star moving so fast?

[00:15:48]The research team has a few theories.

[00:15:50]For example, the object might be the remains of a binary star system where its companion, a white dwarf, exploded in a supernova after pulling too much material from J1249.

[00:16:03]Another possibility is that our mysterious traveler may have originated from a cluster of stars that dispersed after coming across two black holes.

[00:16:13]According to experts, one way to get to such extreme speeds is to fall toward an object and [music] miss it.

[00:16:21]Such gravitational slingshots are how space probes are accelerated to extreme speeds, which allows us to explore the solar system up close over reasonable time scales.

[00:16:32]The same technique could also explain the speed of J1249.

[00:16:37]The star could have been born in the crowded center of our galaxy.

[00:16:42]Then, it might have fallen toward a star, missed, and in the process was [music] accelerated to extreme speeds.

[00:16:52]Well, let's leave astronomers to search for more evidence to confirm this exciting theory.

[00:16:57]Meanwhile, we're heading further to the binary star system 55 Cancri.

[00:17:03]It lies 41 light-years away from Earth and hosts an amazing planet, 55 Cancri e, also known as Janssen.

[00:17:13]This is a scorched super-Earth, eight times the mass of our planet, and it orbits its star in just over 17 hours.

[00:17:22]Yep, the year on this planet is shorter than one day on Earth.

[00:17:26]Plus, it's 25 times closer to its star than Mercury is to our sun.

[00:17:31]No wonder the planet's surface reaches blistering temperatures of 4,350° Fahrenheit.

[00:17:38]That's hot enough to melt nearly any known metal.

[00:17:42]Back in 2010, a study found out that the host star of 55 Cancri E had an unusually high carbon to oxygen ratio.

[00:17:51]If this ratio was also true for the planet, it would mean that 55 Cancri E might have huge quantities of carbon.

[00:17:59]And the coolest thing? It would be in the form of diamonds.

[00:18:03]It make this space body a literal diamond planet.

[00:18:07]Sadly, some follow-up studies discovered that the carbon to oxygen ratio on the planet was less extreme than originally thought.

[00:18:14]It makes the idea of a diamond-encrusted world less feasible.

[00:18:19]On the bright side, planets don't always have to match [music] the composition of their host stars exactly.

[00:18:25]If some other process topped up the carbon on 55 Cancri E, [music] it could still be the most precious planet known in the universe.

[00:18:33]Definitely worth a visit.

[00:18:36]But, let's leave the diamond planet behind and fly to Vega, which holds a special place as one of the brightest and most important stars in the sky.

[00:18:45]The brightest of other stars is measured against the brightness of Vega on a special magnitude scale, where Vega's magnitude is zero.

[00:18:54]A star with a magnitude of one is 2.5 times dimmer than Vega.

[00:18:59]And a star with a magnitude of -1 is 2.5 times brighter.

[00:19:05]Vega is also a pole star, although not at the moment.

[00:19:10]Right now, Earth's axis points toward Polaris, the North Star. But, Earth's axial tilt draws a circle over 26,000 years, [music] and Vega will again be the polestar in about 12,000 years. Just [music] you wait.

[00:19:24]But, the coolest thing about Vega, which sets it aside from other stars, is that [music] it's not shaped like a perfect sphere. Unlike the Sun, which rotates slowly and is almost spherical, Vega spins very fast, completing one rotation in just 12.5 hours.

[00:19:41]And it causes [music] it to bulge at the equator, taking on an egg-shaped appearance.

[00:19:47]And now, get ready for the most dangerous encounter of them all. But first, I must warn you.

[00:19:53]>> [music] >> Even though space is unimaginably vast, it's populated extremely sparsely.

[00:19:59]The universe's average density is equivalent to six protons in 35 cubic feet. But, some areas, known as voids or supervoids, contain [music] even less matter.

[00:20:10]These regions are enormous and can span 30 to 300 million light-years. And there's [music] almost nothing there.

[00:20:19]There are also places in the universe where time and space are distorted in ways that challenge our human comprehension, like binary black hole systems, where two massive black holes dance around each other before eventually merging.

[00:20:34]As they spiral closer, they release immense gravitational waves that ripple across space-time.

[00:20:41]The first detection of such waves was made by the Laser Interferometer Gravitational Wave Observatory in 2015, [music] when it recorded the final collision of a black hole pair.

[00:20:52]In the final 20 milliseconds [music] before the merger, the black holes released more gravitational energy than the total energy emitted by all the stars in the observable universe during the same period.

[00:21:04]But, that's not all the universe has to offer. Once you start exploring, you can come across exoplanets like CoRoT-7b, where rock clouds form and send pebbles raining from the skies. Or KELT-9b, [music] the hottest known planet with surface temperatures reaching 7,800° Fahrenheit. Or TrES-2b, the darkest planet ever discovered. It absorbs over 99% of the light it receives, making it blacker than coal.

[00:21:35]So, as you can see, in the vast, almost incomprehensible scale of the cosmos, [music] mysterious, fast-moving objects, strange planets, and immense voids serve as a reminder of how much we have yet [music] to learn about the universe.

[00:21:55]>> [music]