00:00It would seem that the black holes may not be as unnoticeable as we thought before.
00:05They could be hidden within the stars themselves.
00:08The additional mass of some of these stars, acting like space lanterns,
00:13could explain unusual gravitational effects in the universe,
00:17while they were previously attributed to black matter.
00:20The black holes to which I refer could be those, tiny,
00:24that appeared in the dawn of time, when the universe was still young.
00:28These primordial black holes could still be found in the heart of giant stars.
00:33A team of scientists considers this hypothesis plausible,
00:37and astronomers could detect these trapped black holes
00:40thanks to the vibrations they induce at the surface of the stars.
00:44If these black holes are numerous in the universe,
00:46they could play the role of black matter, helping to maintain its cohesion.
00:52Most black holes come from massive stars that have collapsed on themselves,
00:57becoming incredibly dense.
00:59Their gravitational attraction is such that even light cannot escape their grip.
01:04Contrary to popular belief,
01:06black holes do not behave like vacuum cleaners that swallow everything in their path.
01:10They only absorb objects that approach stars from very close,
01:14generally those that cross their horizon of events.
01:17It is a point of no return where any escape becomes impossible.
01:22In 1971,
01:25the renowned physicist Stephen Hawking proposed an alternative origin for these black holes.
01:30According to him, in the first moments that followed the Big Bang,
01:34when the universe had just been born,
01:36some regions of a soup of dense particles
01:39could have reached a sufficient density to collapse into black holes.
01:43These so-called primordial black holes could vary in size,
01:47ranging from microscopic to gigantic.
01:49If they were sufficiently widespread and numerous,
01:52they could act like black matter,
01:54binding the cosmos by their immense gravity.
01:57It is estimated, moreover,
01:58that black matter would represent about 85% of the total matter of the universe.
02:05Astronomers try to detect the primordial black holes
02:08by searching for the flashes that would occur
02:11when they pass in front of distant and bright objects,
02:14amplifying their light as a lens would do.
02:16However, they have not yet observed any.
02:19If a primordial black hole was extremely small,
02:22with a mass similar to that of an asteroid
02:24and a diameter as small as a hydrogen atom,
02:27the flashes produced would not be bright enough
02:30to be detected by our current instruments.
02:33The team studying the primordial black holes
02:35then explored the implications of a universe
02:38where black matter would be made up exclusively of tiny black holes.
02:42They concluded that one of these small black holes
02:44could cross the solar system at any time.
02:47Some could even be trapped in gas clouds,
02:50thus participating in the formation of new stars
02:53and ending up nesting in their center.
02:56The researchers then built the model of a black hole
02:59at the heart of a star,
03:01where hydrogen atoms fuse to produce heat and light.
03:05Initially, they did not detect anything unusual.
03:08Even the core of a star,
03:09although extremely dense,
03:11is mostly made up of vacuum,
03:13making it difficult for a microscopic black hole
03:16to find matter to consume.
03:18This would explain why its growth would be extremely slow,
03:21to the point that it would take it more time
03:23than the age of the universe to swallow an entire star.
03:27But, what would happen if a larger black hole,
03:30with a mass comparable to that of Pluto
03:33or the asteroid Ceres,
03:34appeared at the center of a star?
03:36It could grow in a few hundred million years only.
03:39The stellar matter would spiral into the black hole,
03:42forming a disk heated by friction,
03:45which would emit radiation.
03:47When the black hole reached the size of Earth,
03:50it would emit even more radiation and shine intensely.
03:54This would disrupt the core of the star,
03:57which would then become an object fed by a black hole
04:00rather than by nuclear fusion.
04:02These objects were named Hawking stars.
04:06To cool down,
04:07the outer envelope of a Hawking star
04:09would turn into a red giant,
04:12a phase that our sun is destined to know as it ages.
04:15However,
04:16a red giant sheltering a primordial black hole in the center
04:20would be less hot than the one that would have reached this stage
04:22by conventional means.
04:24These stars are known under the name of red trennards.
04:29To determine whether these stars actually shelter a black hole,
04:32astronomers may have to focus on the frequency of their vibrations.
04:37Since a Hawking star mainly affects its core,
04:40rather than its external layers,
04:42it would resonate at a particular frequency.
04:44The generated waves could manifest themselves
04:47by variations in the pulsation and tingling of the star's light.
04:51Scientists will therefore have to examine the already identified red trennards
04:55to verify whether some present the characteristic vibrations of a black hole.
05:00Should we worry about our sun?
05:02Since it has not yet reached its phase of red giant,
05:05we cannot predict whether it will become a cold red trennard.
05:09What we know
05:10is that our star could contain these tiny black holes
05:13formed during the Big Bang.
05:15However,
05:16we currently have no way to confirm their presence.
05:21Currently,
05:22our star is about halfway through its lifespan.
05:25It produces energy continuously
05:27by fusing hydrogen atoms in its core.
05:30When it has exhausted its hydrogen,
05:32it will begin its phase of red giant
05:35and will begin to contract.
05:36This process will occur in about 5 billion years.
05:40So,
05:41don't worry too much.
05:42And this phase
05:43will last about 1 billion years
05:46before the star consumes its fusible materials
05:49and loses its external layers.
05:51It will leave behind a small white dwarf,
05:54having a mass equivalent to half that of the sun
05:57and a size comparable to that of our planet.
06:01In some cases,
06:02when a stellar nucleus completely collapses under the effect of gravity,
06:06it can turn into a black hole.
06:08However,
06:09it is not fate that awaits our sun.
06:12The fact is that it does not have enough mass to become a black hole.
06:17Several factors can influence the ability of a star
06:21to turn into a black hole,
06:23such as its composition,
06:24its rotation
06:25and the evolutionary processes it is subjected to.
06:28However,
06:29the main condition remains an adequate mass.
06:32Stars with a mass 20 to 25 times greater than that of the sun
06:36can potentially undergo the necessary gravitational collapse
06:40to become black holes.
06:42In other words,
06:43the sun is too small to turn into a black hole.
06:46But what would happen if that happened?
06:49One might think that if the sun became a black hole,
06:52our planet would inevitably be attracted to it.
06:56Nevertheless,
06:56it is important to remember that black holes do not work
07:00like gigantic space vacuum cleaners
07:02waiting for new objects to swallow.
07:05Black holes do not have an additional gravitational force
07:09beyond that generated by their incredible mass.
07:12Thus,
07:13even if the sun turned into a black hole,
07:16which is impossible,
07:17this hole would still have the same mass as our current star.
07:21The orbit of the Earth around this newly formed black hole
07:24would therefore not be altered.
07:26But many other aspects would change radically.
07:29The sun,
07:30which currently measures around 696,340 km of radius,
07:36would shrink to a radius of only 3 km.
07:40You would not really worry about the absence of the bright yellow sphere in the sky.
07:44Because other much more urgent problems would worry you.
07:47Our planet would lose its main source of heat,
07:50plunging us into a glacial darkness.
07:53Without this source of energy,
07:54photosynthesis would stop immediately,
07:57thus disturbing all food chains.
08:00In the end,
08:01life on Earth would be completely eradicated.
08:03But rest assured,
08:04our sterile and arid planet would continue to follow its orbit.
08:08That's the main thing, isn't it?
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