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Explore the eerie phenomena of zombie stars devouring each other and the recent discovery of a supermassive black hole, 33 times the mass of the sun, lurking dangerously close to our solar system. These cosmic giants reveal the terrifying and fascinating nature of the universe.
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00:00Stargazers, come up here, because I have exciting news.
00:05Astronomers have just completed the full mapping of two pairs of stars outside our Milky Way galaxy
00:11that are chowing down on their stellar neighbors.
00:14Not only does it give us a better understanding of stars in general,
00:18but it can also help us measure distance in the night sky.
00:23Did you know that more than half of the stars in our Milky Way are paired?
00:28And while it's unlikely that other galaxies have a significant number of binary stars too,
00:34they're usually too faint to see.
00:37But these so-called symbiotic stars, where one star consumes the other,
00:42are extremely bright and easier to observe.
00:45And, according to scientists, measuring the orbits of these symbiotic star systems
00:51is an essential step towards learning whether other galaxies create binary stars
00:56like those in our Milky Way.
00:59Now, let's get down to the nitty-gritty.
01:02A pair of stars may be born together, but due to their masses, they age differently.
01:09The more massive one burns through its material faster,
01:12reaching the end of its lifetime first, and leaves behind a compact white dwarf.
01:18White dwarfs are small and dim,
01:20but can pack the mass of the sun into an object the size of Earth.
01:25If close enough, their gravity can pull material from their companion,
01:30creating a signal that astronomers can identify from far away.
01:35Draco C1 and Lin 358 are the symbiotic stars that have been fully mapped.
01:41The stars in Draco C1 take roughly three Earth years to orbit one another,
01:47while Lin 358's components take just over two.
01:52These are the first full orbital measurements of any symbiotic star system outside the Milky Way.
01:58The new measurements will help astronomers better understand star formations in other galaxies.
02:06In some symbiotic stars, the white dwarf can slurp enough material from its companion
02:11that it explodes in a supernova.
02:14These supernovae are incredibly bright and can be seen across the universe.
02:20They all start out with the same brightness for a nearby observer,
02:24making them like a sort of standard candle for measuring the universe.
02:28While Draco C1 and Lin 358 are unlikely to explode as supernovae anytime soon,
02:35understanding how they work can provide us with a better understanding
02:39of how these standard candles evolve.
02:44If you're here to complete your knowledge of weird stars in the universe,
02:48don't be disappointed. We're not finished just yet.
02:51Have you ever wondered about the biggest stars in the universe?
02:56Scientists have recently discovered a gigantic star called UI Scuddy.
03:02This bad boy is located about 9,500 light-years away from Earth
03:07and is truly out of this world.
03:09It's about 1,700 times larger than our Sun,
03:13which means if it were in our solar system, it would reach past Jupiter's orbit.
03:18There's more. UI Scuddy isn't just massive, it's also super bright.
03:24It's what scientists call a red supergiant.
03:27And it shines with a brightness of about 340,000 times that of our Sun.
03:34If you're thinking about getting a tan from this star,
03:37think again though, it's way too far away for that.
03:41How does a star like UI Scuddy even form, you might wonder?
03:45Well, it starts out like any other star.
03:48A cloud of gas and dust collapses under its gravity and starts to heat up.
03:54Eventually, the temperature becomes hot enough in the core of the cloud
03:58to ignite nuclear fusion, and a star is born.
04:02But UI Scuddy didn't stop there.
04:05It kept devouring more and more gas and dust, growing larger and larger.
04:10This process continued until it became the giant we know today.
04:15As fascinating as UI Scuddy is, it's not the only big star out there.
04:20There are others, like VY Canis Majoris,
04:24which was once thought to be the biggest star until UI Scuddy stole the show.
04:29VY Canis Majoris is still a force to be reckoned with though.
04:33It's about 1,400 times larger than our sun and located about 5,000 light years away from us.
04:41But here's the kicker.
04:43Stars like UI Scuddy and VY Canis Majoris aren't even the biggest things in the universe,
04:49not by a long shot.
04:51There are objects called hypergiants that make these stars look like ants in comparison.
04:57One such hypergiant is Stevenson 218, located about 20,000 light years away.
05:04It's about 2,150 times larger than our sun and shines with the brightness of 7 million suns.
05:12And just when you thought things couldn't get any crazier,
05:16there's a mysterious object called the Great Attractor
05:19that's pulling everything in our local group of galaxies towards it.
05:23We don't know what it is or what's causing it.
05:27But one theory is that it's a massive cluster of hypergiants.
05:31We'd be minuscule in comparison.
05:35The next star is so metal, it's practically headbanging all the time.
05:40Jokes aside, scientists have discovered a star that's called a heavy metal subdwarf.
05:46Now that's a band name.
05:47It's a type of star that's seriously heavy metal.
05:50This star has more metal in its composition than any other star we've seen before.
05:56Such stars are said to contain metal elements like iron, nickel, and chromium.
06:01This heavy metal subdwarf has about 10,000 times more iron than our sun.
06:08In their discovery, astronomers used a technique called spectroscopy,
06:13which involves analyzing the light that comes from the star
06:16to determine what elements it's made of.
06:19By looking at the spectrum of light,
06:21scientists were able to see that this star
06:24had an unusual amount of metal in its composition.
06:28There's more.
06:29This heavy metal subdwarf isn't just a regular star with a lot of metal.
06:33It's also really weird in other ways.
06:37For one thing, it's smaller and cooler than our sun.
06:40And for another, it's really old.
06:43We're talking about a star that's been around for almost as long as the universe itself.
06:49What does this all mean?
06:51Well, scientists are hoping that by studying this heavy metal subdwarf,
06:56they can learn more about the early universe.
06:58Since this star is so old that it was around when the universe was just beginning to form,
07:04it's seen a lot of stuff.
07:06By studying its composition and characteristics,
07:10scientists can get a better understanding of what the universe was like in its early days.
07:16This next star is one of the coolest things in outer space.
07:20Her name is Vega, and it's one of the brightest stars in the night sky.
07:25Some recognize it as the shiny point of light in the constellation Lyra.
07:29And get this, it's only about 25 light years away from us,
07:34which, in astronomical terms, is practically next door.
07:38Scientists have been studying Vega for a long time,
07:42and they've learned some pretty interesting things.
07:44For starters, Vega is a young star, only a few hundred million years old.
07:49That might sound like a long time, but compared to our sun,
07:53which is around 4.6 billion years old,
07:56Vega is practically a newborn.
07:58Vega is also a very hot star,
08:01with a surface temperature of around 17,000 degrees Fahrenheit.
08:06To put that into perspective,
08:07the surface of our sun is only about 10,000 degrees Fahrenheit.
08:12So if you think it's hot outside today,
08:14just be glad you're not hanging out on Vega.
08:18Another interesting thing about this star
08:20is that it's surrounded by a disk of dust and gas.
08:23This disk is called a debris disk,
08:26because it's made up of leftover material from when the star formed.
08:30Scientists think that this debris disk
08:32is similar to the one that surrounded our solar system when it was young.
08:37Vega is also a source of cosmic rays.
08:40These rays are high-energy particles
08:43that zip around space at incredible speeds.
08:46They're made up of protons, electrons, and other particles,
08:50and scientists aren't exactly sure where they come from.
08:53But they do know that Vega is one of the places where cosmic rays originate.
08:58But wait, there's more!
09:00Vega is also a famous star in pop culture.
09:04It's been used in a lot of movies and books as a source of inspiration,
09:09mostly because of its brightness and cool features.
09:12Astronomers have discovered the most massive stellar black hole
09:16ever spotted in our home Milky Way galaxy.
09:19This newly found space monster is 33 times bigger than the Sun
09:23and sits 2,000 light-years away from us.
09:27Until recently, the largest stellar black hole found residing in our galaxy
09:31has been around 20 times as big as our star in terms of mass.
09:35As for the average stellar-mass black hole,
09:37it's usually about 10 times as hefty as the Sun.
09:41Scientists from the European Southern Observatory's Gaia mission
09:45spotted the giant black hole after a star started to wobble
09:49while orbiting in that area.
09:51The black hole got the name of Gaia BH3.
09:54The proximity of this space object to Earth
09:57makes it the second-closest black hole to our planet ever discovered.
10:01The nearest one is called Gaia BH1.
10:04It's hanging out around 1,560 light-years away from us.
10:10This uncomfortably close neighbor has a mass of about 9.6 times that of the Sun.
10:16It means that it's way smaller than the newly found black hole.
10:20Gaia BH3 is located in the Aguila constellation.
10:25From Earth, it seems to have the shape of an eagle.
10:28Interestingly, astronomers didn't expect to find a high-mass black hole
10:33lurking so relatively close to Earth and remaining undetected for so long.
10:38Okay, we can probably admit that this stellar black hole is just a small fry
10:42compared to supermassive black holes
10:44like the one that dominates the center of the Milky Way.
10:47I'm talking about Sagittarius A-star.
10:51This space giant has a mass of 4.2 million times that of the Sun.
10:57While a stellar black hole forms when a star collapses,
11:01supermassive black giants have their own ways of seeing the light of day.
11:05They are usually the result of mergers of progressively larger and larger black holes.
11:10We'll talk about that later.
11:12First, let's speak a bit more about how stellar black holes form.
11:17When stars near the end of their lives, they typically inflate,
11:21lose a lot of mass, and cool to form what we know as white dwarfs.
11:26Such massive stellar black holes as Gaia BH3
11:30are believed to form when a star doesn't contain heavy elements
11:34and loses not so much mass over its lifetime.
11:37Such stars are called metal-poor.
11:40Afterward, instead of cooling into a white dwarf,
11:43this star collapses into a black hole.
11:46The companion of Gaia BH3 is a very metal-poor star.
11:51It suggests that the star that collapsed and formed BH3 was metal-poor, too.
11:57Astronomers know of about 50 stellar black holes in the Milky Way.
12:03Some black holes are larger than others.
12:06You see, the universe is filled with black holes.
12:09Some of them are sprinkled randomly throughout galaxies.
12:13Others, those giants we know as supermassive black holes,
12:17sit at the center of galaxies.
12:19While stellar black holes are usually just a few times bigger than the sun,
12:23such space monsters can weigh from a million to a billion solar masses.
12:29But even though they're so much heavier than our star,
12:32they're packed into a relatively small area.
12:35On a cosmic scale, of course.
12:37The size of our solar system or so.
12:40Some astronomers think supermassive black holes could form
12:43by several stars colliding and collapsing at once,
12:46while other experts state that such space objects
12:50might have started growing several billion years ago.
12:53At first, a small seed appears somewhere out there in space,
12:58which then gradually increases in mass to form a black hole.
13:02This seed does it through the process of accretion,
13:06which basically means gathering more and more matter around itself.
13:10Besides the absence of any precise information about the formation of black holes,
13:15there's also the black hole information paradox.
13:19If a black hole has some mass,
13:21and as we know, these spaced objects have a lot of it,
13:25then, according to the first law of thermodynamics,
13:28it should have a temperature.
13:30And, according to the second law of thermodynamics,
13:33it should also radiate heat.
13:35Stephen Hawking showed that black holes are supposed to emit radiation too.
13:40These days, this kind of radiation is called Hawking radiation.
13:44It should form at the boundary of a black hole,
13:46but after proving it, Hawking pointed out a paradox.
13:50If a black hole is capable of evaporating,
13:52some of the information it contains can be lost forever.
13:57The problem is that the information contained in thermal radiation
14:00emitted by a black hole gets degraded.
14:03It doesn't repeat any information about the matter swallowed by a black hole before.
14:07Such an irreversible loss of information contradicts one of the basic principles of quantum mechanics.
14:15Physical systems that change over time cannot create or destroy information.
14:20It means we must be missing something.
14:23Both physicists and mathematicians have tried to come up with different ideas,
14:27but they ended with pretty weird results.
14:30Some have even claimed that the universe could be holographic.
14:34It means that the universe that we know and love
14:37is actually the result of some mysterious interactions at the infinitely distant boundary.
14:42I told you, black holes are really strange.
14:47At the same time, we have definitely found space objects
14:50that seem to have the properties of black holes.
14:53For example, look at this image of black hole M87 star.
14:58It certainly looks like a physical object,
15:01but what if black holes don't exist at all?
15:06There's an idea that black holes are actually gravastars,
15:09a blend of gravity, vacuum, and stars.
15:12This theory was first proposed in 2001 by Emil Mottola and Pavel O. Mazur.
15:19They hypothesized that at one point during the collapse of a large star,
15:23intense gravity might transform its matter into a new state.
15:28It's similar to what occurs when atoms are cooled to such low-energy states
15:32that they start acting like a single super-atom.
15:35When we speak of gravastars,
15:38a star might collapse to the point of the event horizon,
15:41or the point of no return,
15:43and then its matter is transformed into a new state.
15:46It exerts enough outward pressure
15:49to prevent the star from collapsing into a physics-defying singularity.
15:53In gravastars, an ultra-thin, ultra-cold,
15:56and ultra-dark, indestructible shell
15:59surrounds heavily wrapped space-time.
16:02This new form of matter turns out to be very durable,
16:05but it's also a bit flexible, like a bubble.
16:08So anything that's trapped by the intense gravity of a gravastar
16:12and smashed into it gets obliterated
16:14and then assimilated into the shell of this bizarre space structure.
16:19One of the benefits of the gravastar theory
16:21is getting away with those messy paradoxes
16:24connected with information and singularities.
16:26But even though this idea sounds kind of cool,
16:30it doesn't explain the phenomena we observe.
16:32And we've definitely observed something that looks like black holes.
16:37On the other hand, look at this shadow.
16:39It isn't caused by the trapping of light in the event horizon.
16:43It's a slightly different phenomenon known as the gravitational redshift.
16:47It makes light lose energy when it moves through a region
16:51with a powerful gravitational field.
16:53So, potentially, it could be a gravastar.
16:57When the light emitted from the regions
16:59close to the alternative objects reaches our telescopes,
17:02most of its energy is already lost to the gravitational field,
17:06which causes the appearance of this shadow.
17:09And still, like with black holes,
17:12things get complicated when you add rotation to the equation.
17:16Many experts are sure that gravastars would not be able
17:19to remain stable during rotation.
17:21But wait, it gets even more bizarre.
17:24There are suggestions that the insides of gravastars
17:27could contain a series of thicker shells.
17:30Those are known as nestars,
17:33something like a Matryoshka doll.
17:35Of course, these theories aren't perfect yet.
17:38Astronomers still have a lot of work
17:40trying to build functioning models.
17:42There's also a chance that both black holes and gravastars exist.
17:46But then, we've got another problem on our hands.
17:49How can we distinguish between the two?
17:51Some theories suggest that these different kinds of space objects
17:55should also emit very different gravitational radiation.
17:59It could allow us to figure out
18:01whether we're looking at a gravastar
18:02or a traditional black hole.
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