00:00Right after its creation, the cosmos was shrouded in darkness.
00:04I mean, I wasn't there, but that's what most scientists are thinking.
00:08All of the stars were hidden behind a thick cloud of primordial gases.
00:12Then all of a sudden, something cleared up this fog, and the universe started shining
00:17as it finally woke up.
00:19But how did this happen?
00:21Eight faint recently-discovered galaxies might hold the answer.
00:26The Big Bang created our world around 13.8 billion years ago.
00:31At first, it was just a super-hot and chaotic boiling soup of particles.
00:36But over time, things cooled down, and particles could finally stick to each other.
00:40That's how the atoms appeared.
00:43Some helium, but mostly hydrogen, the very first element.
00:46And these first elements started creating thick gas clouds, which were very opaque.
00:52Then the first stars started forming.
00:54They were incredibly bright, emitting lots of light, including ultraviolet radiation.
01:00But even though these stars were shining, much of their light couldn't travel far because
01:04of that nasty hydrogen fog.
01:07The gas clouds absorbed and scattered any little light particles around.
01:11It was like the light was trapped around the stars.
01:14The Dark Ages lasted for hundreds of millions of years.
01:18Then everything changed.
01:21Recently the James Webb Space Telescope has spotted ancient dwarf galaxies from that epoch.
01:26Turns out, they're the ones we should be thanking for lighting up the universe.
01:31Back then, they were filled with early stars.
01:34These stars emitted tons of radiation that was so powerful that it managed not to just
01:39overcome, but break apart the hydrogen atoms in the fog.
01:43It turned them into charged particles, like particles that carry a little bit of electricity
01:48called ions.
01:50Little by little, the fog was cleared away.
01:53This process of clearing out the fog is called reionization, and this beautiful time is known
01:58as the epoch of reionization.
02:01Finally, the light was able to travel to all corners of the universe, which was a game-changer,
02:07just like humans' Age of Enlightenment.
02:11To find these little igniters, astronomers used a technique called gravitational lensing.
02:17Imagine light traveling through space like a straight beam.
02:20But just like everything in our world, even time, light obeys gravity.
02:25If it's too strong, it'll literally bend the light beams.
02:28So when the beams pass near a massive object, the object's gravity pulls on them, curling
02:34and twisting their path.
02:35That's why black holes look so creepy, as they stretch stars and space around them like
02:40some whirlpools.
02:42But it's not that creepy.
02:43A regular glass or magnifying glass does something similar.
02:48Hence the name gravitational lensing.
02:52When the lensing object is horrifyingly massive, it bends the light into multiple images of
02:57the same object, creating a creepy and mesmerizing structure called an Einstein ring.
03:04But if it's not that big, then the bending is less dramatic, and it just slightly distorts
03:09the shape of the background object, making it look kinda stretched.
03:14Gravitational lensing also helps scientists study things like the spooky dark matter.
03:19If the light looks stretched, and it's not just because of some obvious massive objects
03:25nearby, then it might be something invisible and heavy bending it.
03:29Since these 8 galaxies were too faint – no wonder they're almost as old as my unread
03:34emails – scientists had to use these gravity tricks to observe them.
03:40The team studied light from galaxies that are over 13 billion years old.
03:44Finally, they focused on a galaxy cluster called Abel 2744, also known as Pandora's
03:51Cluster.
03:52And these findings helped them understand how even little fellas played a huge role
03:56in transforming the early Universe.
03:59The James Webb Telescope is an incredible tool, and soon, it might help us look at even
04:05earlier times – at the cosmic dawn, when the Universe was only several millions of
04:10years old.
04:11Another great tool, called the Roman Space Telescope, is going to help it.
04:15It's also possible that these galaxies weren't the only helpers in this entire saga.
04:21These early massive stars were absolutely terrifying – they just don't make them
04:25like that anymore.
04:27Some estimates suggest they were 30 to 300 times more massive than our Sun, and millions
04:32of times brighter.
04:34Modern stars have some heavier elements in them, but back then, they used only the stuff
04:39available, hydrogen and helium, which is why they were so hot and shiny.
04:44But they also had very short lifespans, lasting just a few million years.
04:48For example, our Sun is 4.6 billion years old and is still going strong, thankfully.
04:55At the end of their lives, they went supernova.
04:58These colorful bursts of energy were so strong that they forged the first heavier elements
05:03in our world and spread them across the Universe, planting first seeds for the future planets.
05:09Meanwhile, the stars themselves didn't just disappear.
05:14They collapsed under their own gravity, creating the first black holes.
05:18The black holes are also known for producing insane amounts of radiation, so it's possible
05:24that they might've helped speed up the clearing of the fog.
05:28Ironically, they helped the Universe shine brighter while sucking up the light at the
05:32same time.
05:34Recent discoveries show that black holes might be much, much older than we used to believe.
05:39They probably helped new stars and galaxies form.
05:42They were millions or even billions of times the mass of the Sun.
05:46The James Webb telescope has already found a pair of early quasars – that's what
05:51we call the bright centers of galaxies – powered by supermassive black holes.
05:55It's a curious pair of quasars that are merging just 900 million years after the Big
06:01Bang.
06:02This might be the earliest and most distant pair of merging quasars ever found.
06:08The telescope has also been studying things that are called cosmic lighthouses.
06:13In scientific language, they're pulsars.
06:16Pulsars are super-dense remnants of massive stars.
06:19They form from stars that were once 4-8 times more massive than our Sun.
06:25One of the greatest things about them is how fast they spin.
06:28They're one of the fastest objects in the Universe.
06:31They might do around 700 rotations in just one second.
06:35They got their name because they behave like lighthouses – basically flickering radio
06:40waves.
06:41These beams of radiation sweep across the sky, creating a pulse-like signal that we
06:45detect.
06:47A star basically works like this – there's nuclear fusion happening inside of its core.
06:54Atoms get fused in each other, move at crazy speeds, bump, all meanwhile releasing an unbelievable
07:00amount of energy.
07:01That's why they emit tons of light and heat.
07:04Of course, all this pressure tries to push outward, sweating like crazy to expand a star.
07:10The greatest the fusion is, the more powerful and insane the star gets.
07:15On the other hand, there's gravity that's pulling inward, trying to compress the star
07:19and keep it a nice small dense ball.
07:22As long as there's balance, the star keeps living.
07:25But when it gets old and spends all of its nuclear fuel, it becomes too weak to generate
07:30the energy it needs and can't fight against gravity anymore.
07:34That's when it basically collapses under its own weight, going supernova.
07:40What's left behind is the star's core, but now it's crushed down to an incredibly
07:45small size, about 12 to 17 miles across.
07:49It's roughly the size of a city.
07:51This dense core is known as a neutron star.
07:55The material in a neutron star is so dense that just a teaspoon of it would weigh as
08:00much as 4 billion tons, like 10,000 Empire State Buildings.
08:06And all this collapse sets off a trigger, causing the neutron star to spin super fast,
08:11creating a pulsar.
08:12It's kind of like when an ice skater spins faster when they pull their arms in.
08:18Pulsars often have a smaller star friend orbiting them, although it's not always a friendly
08:23relationship.
08:24Not long ago, astronomers discovered a pulsar that was surrounded by lots of energetic material
08:29for some reason.
08:31They realized that all this material was the remnants of another much larger star.
08:36Turns out, the pulsar had been slowly destroying its friend with its terrifying radiation and
08:41particles until it basically ate the neighbor away.
08:45It's similar to how a black widow spider consumes its mate, so systems like this were
08:50called black widow pulsars.
08:53In any case, these lighthouses most likely helped the reionization process as well.
08:59A long time ago, they could be very energetic stars in small galaxies and could emit enough
09:04radiation to transform the early universe.
09:07The James Webb Telescope's mission is to find more of these lighthouses and see what
09:12role they played in the universe's evolution.
09:16That's it for today!
09:17So, hey, if you pacified your curiosity, then give the video a like and share it with your
09:21friends!
09:22Or, if you want more, just click on these videos and stay on the Bright Side!
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