- 2 days ago
Space is acting weird lately and these two facts show just how strange things have gotten in our own cosmic neighborhood. First, astronomers discovered that almost all of Andromeda’s satellite galaxies are mysteriously pointing straight at the Milky Way, breaking every model we use to explain how the universe works. Then, we dive into the even bigger picture: the Milky Way and Andromeda have already begun their long-awaited collision, a process that will reshape our entire sky over billions of years. From unexplained galactic alignments to a cosmic crash already in motion - let's dive into the mysteries unfolding right next door. Animation is created by Bright Side.
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For more videos and articles visit: http://www.brightside.me
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This video is made for entertainment purposes. We do not make any warranties about the completeness, safety and reliability. Any action you take upon the information in this video is strictly at your own risk, and we will not be liable for any damages or losses. It is the viewer's responsibility to use judgement, care and precaution if you plan to replicate.
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00:00A vast galactic mystery has recently baffled astronomers.
00:04They've noticed that all but one of Andromeda's 37 satellite galaxies point toward the Milky Way.
00:11It's so extraordinary that it challenges current cosmology and might provide the answer to the dark matter question.
00:18So it happened like this.
00:20One day, scientists looked at those other satellite galaxies that go around Andromeda and spotted a really weird alignment.
00:27Now, we should keep in mind that Andromeda is kind of like our Milky Way's neighbor.
00:32It's huge, about twice as wide as the Milky Way, stretching 200,000 light-years across.
00:38It also has way more stars, around a trillion, compared to our galaxy's mere 250 to 400 billion.
00:47Just like our galaxy, it has a bunch of tiny galaxies called dwarf galaxies spinning around it.
00:53There are 37 of them.
00:54The strange thing is, almost all of those little galaxies are on the same side of Andromeda.
01:01And it's getting even creepier, because it's the side that faces the Milky Way.
01:06Only one galaxy is hanging out on the other side.
01:10Imagine tossing a bunch of marbles around a tree, with nearly every single marble landing on just one side.
01:16That's weird, isn't it?
01:18Scientists say that this discovery doesn't match what they expected at all.
01:22Their usual space models show that stuff like this should be spread out more evenly.
01:27But this isn't even close to even.
01:30It's so lopsided that they can't really explain it yet.
01:33Those models follow the main space theory we use today, called the Lambda Cold Dark Matter model.
01:39According to this theory, the little galaxy should be spread around Andromeda pretty evenly.
01:45Maybe just a bit lopsided.
01:46But in real life, their distribution is way more uneven than the model said it should be.
01:52The scientists have run tons of simulations, and only about 0.3% of them ended up close to what we actually see.
02:00And still, none of them match the real thing exactly.
02:03So, does it show the Lambda CDM model has flaws?
02:07That would be a big deal, because we normally use this model to explain how the universe works.
02:13If the real sky doesn't match what our model says, especially in a place as close and well-known as Andromeda,
02:20it might mean that we're missing something big.
02:24Another strange thing.
02:26Many of Andromeda's satellites seem to lie in a flat plane instead of being randomly distributed in all directions.
02:32This kind of flattened structure has been seen in other big galaxies too, including our own, but it's still not well understood.
02:41Maybe this satellite disk is connected to the weird cosmic asymmetry, but no one really knows how.
02:47In any case, the fact that all the tiny galaxies on Andromeda's side line up almost perfectly in the direction of the Milky Way is super weird.
02:57It makes you wonder, could our galaxy be pulling or affecting them?
03:01But the catch is that nothing like this is happening to the Milky Way's own satellites.
03:06Plus, the gravity between our two galaxies doesn't seem strong enough to do that kind of pulling.
03:13The answer might lie in one of the most mysterious things the universe has to offer.
03:18Dark matter.
03:19Let's start from the very beginning.
03:21We'll go all the way back to the early universe, just after the Big Bang.
03:25Now, back then…
03:27Hey, I wasn't around then, but I'll tell you anyways.
03:29Matter in the universe was spread out pretty evenly, but not perfectly even.
03:34In a few spots, there were just slightly higher amounts of matter than in others – tiny clumps.
03:40Those little differences were important, because gravity could latch onto them.
03:44Over time, those denser regions started pulling in more material, slowly growing into the first structures in the universe.
03:51Astronomers believed that dwarf galaxies were the earliest and smallest building blocks of galaxy formation.
03:58Think of them like Lego bricks – tiny pieces that were later pulled together by gravity to build larger galaxies over billions of years.
04:06Now, when we talk about matter, we mean two different things.
04:10Normal matter, the kind we can see and touch, including atoms, gas, stars, planets, and everything around us.
04:17And dark matter, the invisible kind.
04:20It doesn't give off any light, doesn't absorb it, and doesn't interact with normal matter in the usual ways.
04:26The only reason we know it exists is because of its gravitational pull.
04:31There's also a lot more of it than normal matter.
04:34Scientists think that roughly 85% of all matter in the universe is dark matter.
04:40At the same time, we've never directly detected a dark matter particle.
04:44But we know dark matter is there because it bends light, it holds galaxies together,
04:49they spin too fast to stay intact otherwise, and it shapes the structure of the universe,
04:54allowing us to map its influence on larger scales.
04:57While normal matter can clump together, crash, heat up, cool down, and eventually form stars and galaxies,
05:05dark matter can't do any of that.
05:07It doesn't bump into itself or radiate heat.
05:10But it can still form big, invisible clumps, which we call dark matter halos.
05:15In the early stages of the universe, the halos acted like gravity wells.
05:20They pulled in normal matter, which sank into the centers of those halos and formed the first galaxies.
05:25So, galaxies like the Milky Way or Andromeda might be sitting inside enormous blobs of dark matter
05:32that we just can't see.
05:34So, cosmic asymmetry explained?
05:37Eh, not yet.
05:38Scientists are sure that dwarf galaxies are some of the most dark matter-dominated objects in the universe.
05:44In many cases, over 99% of their mass is likely to be dark matter.
05:48That means they give us a unique chance to study dark matter without all the messy gas and stars that exist in larger galaxies.
05:57Researchers use dwarf galaxies to figure out how dark matter clumps together,
06:01or whether there are alternative theories of dark matter, like warm or self-interacting dark matter.
06:06At the moment, the main theory is that dark matter behaves like a cold, clumpy, and slow-moving fluid.
06:14At the same time, it might not be totally cold.
06:18Maybe it has other properties.
06:19Maybe it interacts with itself or with normal matter in subtle ways we haven't discovered yet.
06:25If that's true, it could help explain why satellite galaxies form in strange patterns,
06:31like the ones around Andromeda.
06:32In other words, the Lambda-CDM model might indeed have flaws.
06:37According to it, thousands of dwarf galaxies should be orbiting around larger galaxies like the Milky Way and Andromeda.
06:44But we only see a few dozen.
06:47This is known as the missing satellites problem.
06:50There are other puzzles, too.
06:52For example, Lambda-CDM predicts that dark matter halos should be the densest at the center,
06:57but many dwarf galaxies seem to have cores of their own.
07:01Plus, dwarf satellites around galaxies like Andromeda and the Milky Way seem to lie in thin, co-rotating planes.
07:09And it's something extremely rare in Lambda-CDM simulations.
07:13And finally, some simulated dark matter halos are so massive that they should form bright dwarf galaxies.
07:19But we don't see them.
07:22No wonder astronomers are so interested in dwarf galaxies and the explanation of cosmic asymmetry.
07:27For that, we need more precise measurements of their motions and structures
07:32and simulations that add more realistic physics, like stellar feedback, turbulence, and so on.
07:38Plus, we gotta search for new dwarf galaxies in the local group and beyond,
07:43using better telescopes and deeper surveys.
07:46Now, getting back to Andromeda's weirdly positioned satellites.
07:49If the dark matter theory doesn't work out, there's another possibility that involves large-scale interactions between galaxies.
07:57It could be an old collision or near-miss that shape the current distribution of satellites.
08:03For example, some scientists think a smaller galaxy, Messier 32, might have collided with Andromeda long ago, stirring things up.
08:12Scientists have seen some lopsided shapes in other galaxies before.
08:16But none is weird as what's going on around Andromeda.
08:20Usually, the little galaxies around big ones spread out pretty evenly, or are just a bit off.
08:26That makes scientists think Andromeda might be a super-special case.
08:30They say we need to keep looking, using better telescopes, to crack the Andromeda galaxy mystery.
08:36And perhaps, after figuring out the truth, we'll also come closer to solving the dark matter problem.
08:42So, you're driving down the highway, and an 18-wheel tractor-trailer is coming up fast behind.
08:53You've got to change lanes.
08:55You look in the mirror.
08:56Is there enough space?
08:57And you notice the words on the mirror.
08:59Objects in the mirror are closer than they appear.
09:02No kidding!
09:03Well, it's the same with the Milky Way galaxy.
09:06There's another galaxy headed this way, and like the tractor-trailer, it's closer than it looks.
09:11The Andromeda galaxy, or M31, as it was labeled originally by Charles Messier in his catalog of 110 fuzzy objects in 1774,
09:22is now officially named NGC-122.
09:26That's New Galactic Catalog 122.
09:29A spiral galaxy larger than the Milky Way, the Andromeda galaxy is so big and so close that you can see it without a telescope.
09:37In fact, it appears with the unaided eye half as wide as the moon.
09:42It's estimated that the Andromeda galaxy contains 1 trillion stars, compared with the Milky Way's estimated 300 to 400 billion measly stars.
09:52To see the Andromeda galaxy, you must allow your eyes to become dark-adapted.
09:57This might take about 10 minutes while your pupils dilate to take in as much light as possible.
10:02M31 is best seen from late summer through winter, when the great square of Pegasus the Winged Horse is overhead.
10:10Draw a line across the great square diagonally upwards from the lower corner star, then go a little further beyond the square.
10:17There it is!
10:19But you still won't be able to see how big it is, unless you peek at it from the corners of your eyes.
10:23If you stare straight at it, the galaxy will tend to fade away.
10:28You must use your peripheral vision to see how big the Andromeda galaxy appears.
10:33Peripheral vision, or averted vision, allows you to see light more sensitively at night, but without color.
10:39Sailors have used averted vision for centuries to see faint lights out on the ocean or on land.
10:45Aristotle used averted vision to observe star cluster M41 in Canis Major, as he described in his book Meteorologica.
10:52In a telescopic photograph, the Andromeda galaxy appears six times wider than the moon,
10:59because with the unaided eye, we can only see the bright center of the galaxy.
11:03A telescopic photograph shows how massive M31's spiral arms really are.
11:09And this beast of a galaxy is headed our way.
11:13We are looking at a future massive collision of galaxies of, well, galactic proportions.
11:18When that happens, humanity may need to relocate to another galaxy to inhabit.
11:24Perhaps we'll go to the pinwheel galaxy in the asterism of the Big Dipper.
11:29How do we know the Andromeda galaxy is moving towards us?
11:32With a tool called a spectroscope.
11:35After the camera, the spectroscope is the most important attachment to a telescope.
11:39Oh, except for the human eye.
11:41Our eyes only see light.
11:43You don't have this big horse in your eye.
11:45You only have the light being reflected by the horse in your eyes.
11:49The same with space.
11:50We only see the light coming from there.
11:53So, if we are going to understand space, we need to understand light.
11:57And that was not an easy task for astronomers of the 19th century.
12:01The invention of the spectroscope was a big breakthrough in understanding light coming to Earth from space.
12:07With a spectroscope, astronomers can tell which direction objects in space are moving,
12:13as well as which elements are making the light.
12:16When you hear an ambulance approaching, you hear the siren getting louder and higher.
12:20And when it passes you and goes away, you hear the siren's sound get weaker and lower.
12:26The change in pitch frequency depends entirely on the motion of the source.
12:29This is called the Doppler effect, after the Austrian physicist and mathematician Christian Johann Doppler,
12:36who first explained the effect in 1842.
12:39The ambulance siren is not changing its volume.
12:42The sound waves are being compressed as it is approaching and stretched as the ambulance recedes.
12:48The spectroscope shows that light waves show the same Doppler effect as sound waves.
12:53They are compressed as the star or galaxy is approaching us and appear stretched when it is receding.
13:00Therefore, the light from an approaching galaxy will appear slightly bluer, the blue shift, a slight increase in frequency.
13:07And the light from a receding galaxy will appear slightly redder than normal, or redshift, a slight decrease in the light's frequency.
13:14In 1929, Edwin Hubble, after whom the Hubble spacecraft is named, published his spectroscopic study of 46 galaxies,
13:24the light from all but one of which was redshifted, moving away.
13:28Hubble's study provided the first evidence that the universe was expanding.
13:32The farther away a galaxy was from the Milky Way, the faster it was moving away.
13:37This was also the first evidence that the universe began with a big bang.
13:42The one galaxy whose light was blue shifted, moving towards the Milky Way, was M31, the Andromeda galaxy, the closest galaxy.
13:51250,000 miles per hour seems a pretty high speed at which to have a collision.
13:57That's the speed's spectroscopic measurements of the blue shift of Andromeda indicate.
14:01It's going to be a big mess when it happens.
14:04But when is it going to happen?
14:06To determine when the two galaxies will collide, we need to determine the distance between them.
14:11And for that, we need, boom, supernovas.
14:15Type 1A supernovas are what are called standard candles.
14:19Just as we know how bright a candle shines, we know how bright a type 1A supernova shines, its absolute magnitude.
14:26A type 1A supernova appears when a white dwarf collapses under the pressure of all the gas it has been gravitationally slurping from a companion star.
14:37Looking at the Andromeda galaxy and measuring the apparent brightness of a supernova in the galaxy, it is possible to calculate its distance away from us.
14:46Because the intensity of light dims inversely with the square of its distance away, which is called the inverse square law,
14:53By comparing the apparent brightness of a supernova in the Andromeda galaxy with its absolute brightness,
14:59well, we get an approximate distance of 2.5 million light years.
15:04Since one light year is approximately 6 trillion miles, and the Andromeda galaxy is 2.5 million light years away,
15:11even though it is approaching at the speed of about 250,000 miles, we have about 4 billion years before the big collision.
15:19So, you can wait until after lunch, maybe dinner, to start packing.
15:23As an aside, if we see the Andromeda galaxy as it was 2.5 million years ago,
15:28and it has been moving toward the Milky Way all this time, how big in the sky would it appear now?
15:34Quite as big as that tractor-trailer in your rearview mirror.
15:38But do we really have 4 billion years before the galaxies crash?
15:42There are several other factors to consider.
15:45The minor galaxies that are gravitationally linked to both the Milky Way and the Andromeda galaxy
15:50will be swallowed up by their host galaxies.
15:53Considering the lopsided mass distribution that will result,
15:57the galactic collision of the Milky Way and Andromeda will be affected.
16:01Some scientists are saying it won't be a direct hit, but more of a sideswipe.
16:05And then there's the galactic halos of each galaxy.
16:09Here's what Project Amiga has found out about the halo of stars and gas surrounding the Andromeda galaxy.
16:16Using the Hubble Space Telescope, researchers were able to observe
16:19how the light from bright distant quasars were being absorbed
16:23by the mostly invisible gas around the Andromeda galaxy.
16:26Look at the results!
16:28Notice M31 in the center.
16:29If the same is true of the Milky Way, and there's no reason to think it would be different,
16:35then the halos of the two galaxies are touching now.
16:38The collision has already begun.
16:41There is also a question about what effect the dark matter clouds around each galaxy
16:45might have on an impending collision, or are having now.
16:49But enough of speculation.
16:51In 4 billion years, the Sun will have increased brightness on its way to becoming a red giant star.
16:56And humans will have already found another galaxy to inhabit.
17:01Happy traveling, dear humans!
17:03That's it for today.
17:04So hey, if you pacified your curiosity, then give the video a like and share it with your friends.
17:09Or if you want more, just click on these videos and stay on the bright side!
17:13Have a great time, mm-hmm.
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