Voici un fait surprenant : un jour, notre système solaire pourrait ne plus ressembler à ce qu'il est aujourd'hui, et tout cela à cause des naines blanches. Une naine blanche est ce qui reste lorsqu'une étoile comme notre Soleil s'éteint, et cela peut provoquer un chaos sérieux. Les scientifiques pensent que lorsque le Soleil atteindra sa fin (dans environ 5 milliards d'années), il gonflera en une géante rouge, puis rétrécira en une naine blanche, envoyant les planètes voler ou les vaporisant complètement. Jupiter et Saturne pourraient survivre, mais malheureusement, Mercure, Vénus, la Terre et Mars seront probablement cuites—littéralement ! Les chercheurs qui étudient des systèmes solaires lointains ont déjà vu des naines blanches déchirer leurs anciennes planètes. Donc, même si ce n'est pas quelque chose qui nous concernera un jour, c'est un rappel étonnant de la manière dont l'espace peut être dramatique ! Animation créée par Sympa.
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Musique par Epidemic Sound https://www.epidemicsound.com
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https://www.eastnews.ru
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FunTranscript
00:00Look at this flamboyant monster. It's a white dwarf.
00:04These stars are known to swallow objects that pass by them.
00:07And, one day, these objects could well be the planets of our own solar system.
00:12According to a new study, some regions of the solar system will be attracted by a white dwarf,
00:17then crushed and finally reduced to a fine dust, like coffee beans in a blade mill.
00:22Do you like this analogy?
00:24The state of a white dwarf corresponds to the last stage of the life of a star.
00:28It is a small and very dense object, usually the size of a planet,
00:33the result of a low mass and the exhaustion of all the available nuclear fuel in its core,
00:38and the loss of its outer layers.
00:41When our sun turns into a white dwarf, which will not be long in coming,
00:46it will destroy the asteroids and the moons around Mars and Jupiter.
00:50They will be pulverized by its gravity.
00:53The Earth, it, will be swallowed before the sun even turns into a white dwarf.
00:57But this will not happen before 6 billion years.
01:01Researchers working on this subject have come to these conclusions
01:04by observing what happened to space bodies, asteroids, moons and planets
01:09that passed near three white dwarfs.
01:12For 17 years, they observed and analyzed transits,
01:15that is, the moment when the luminosity of a white dwarf decreases
01:19because a stable-orbit object passes in front of it.
01:22In the case of white dwarfs, we can predict these transits
01:25and use them to study the stars themselves
01:28and the celestial objects that pass in front of them.
01:32Thus, when an object approaches too close to a white dwarf,
01:35the immense gravity of the star tears it into increasingly smaller fragments.
01:39The scientific team has also discovered that the transits of these debris are chaotic.
01:44In addition, they usually have a strange shape,
01:47which means that they do not cease to disintegrate.
01:50The first white dwarf used to study this process
01:54seemed stable and relatively calm over the past few years.
01:58But scientists have discovered evidence of a major catastrophic event
02:02that occurred around 2010.
02:05The next star darkens irregularly every few months,
02:09before lighting up again.
02:11The behavior of the third white dwarf was close to theoretical predictions.
02:15Its transits varied in number, shape and depth.
02:18But the latest study has shown researchers
02:21that these transits have now completely ceased.
02:24This is evidence of the unpredictable nature of transits.
02:27One minute, you see them.
02:29The next moment, they have disappeared.
02:31The reason could be the chaotic environment in which they occur.
02:35As for our solar system, and our planet in particular,
02:38its destiny is rather dark.
02:40The Earth will be swallowed up by the sun in expansion
02:43before our star even turns into a white dwarf.
02:46In the rest of the solar system, further from the sun,
02:49some asteroids located between Mars and Jupiter,
02:52as well as some of Jupiter's moons, will also be destroyed.
02:55They may indeed be displaced and get too close to the white dwarf.
03:01However, astronomers are not 100% sure
03:04that this is exactly what should happen in our solar system.
03:08We just have to wait and see how things evolve
03:11over the next 6 billion years.
03:13As for the white dwarfs,
03:15scientists have recently discovered one
03:18whose surface has a strange metallic scar.
03:21This spot could be formed when the star has crumbled
03:25and swallowed up a tiny planet revolving around it.
03:28The white dwarfs, which have traces of metal in their atmosphere,
03:32are not uncommon.
03:33These traces are caused by planets falling on the stars
03:36due to their immense gravity.
03:38Experts have long thought that these metals
03:40should be evenly distributed on the surface of these polluted white dwarfs.
03:44But a new study has led to the discovery of a white dwarf
03:47with a strange concentrated metal spot.
03:50This star was observed for two months
03:52using the Very Large Telescope installed in Chile.
03:55Researchers have discovered an opaque metal spot.
03:58It was located above one of the magnetic poles of the star
04:01and blocked part of its light during its rotation.
04:04Based on this observation,
04:06astronomers concluded that the material
04:08could have been attracted to the star
04:10by the powerful magnetic field of the latter.
04:13This process is similar to the one
04:15that causes the auroras of Boreal on Earth,
04:17where charged particles follow the magnetic field to the surface.
04:23The planet destroyed by the white dwarf
04:25was very likely small,
04:27the same size as the asteroid Vesta in the solar system,
04:30which is only 525 km in diameter.
04:33These debris are now clearly visible at the surface of the high star.
04:36It is therefore easier for researchers
04:38to examine the geochemistry of the planet
04:40before it is devoured.
04:42Such a study could even turn out
04:44to be one of the best ways to observe
04:46the small worlds located beyond the solar system,
04:48even if they have already disappeared.
04:50There could be many other bright stars like this one.
04:53The star in question was the first,
04:55but probably not the last.
04:57Even better, astronomers have already discovered
05:00two white dwarfs that seem to have similar scars.
05:04The repeated observation of these stars
05:06could help us to dig even more secrets
05:08and make other discoveries.
05:10Another strange white dwarf,
05:12discovered not so long ago,
05:14seems to have ceased to cool
05:16due to the formation of internal crystals.
05:20This discovery questions existing theories
05:23about the aging of stars
05:25as well as the methods of estimating their age.
05:27But scientists may have understood
05:29the reason for this phenomenon.
05:32White dwarfs are considered dead stars,
05:35that is, they do not cease to cool
05:38and that this process can generally
05:40not be reversed or interrupted.
05:42But in 2019, the Gaia satellite
05:45of the European Space Agency
05:47discovered a certain number of white dwarfs
05:49that had ceased to cool
05:51for more than 8 billion years.
05:53This could mean that some white dwarfs
05:55can generate a lot of additional energy
05:58and this goes against the classic theory
06:00of the dead star.
06:02At first, astronomers could not understand
06:05how this could happen.
06:07More than 97% of the stars of the Milky Way
06:10turn into white dwarfs.
06:12Astronomers have long thought
06:14that these stars were at the end of their lives.
06:16After exhausting their nuclear energy reserves,
06:18they cease to produce heat
06:20and cool down.
06:22The dense plasma they contain
06:24ends up freezing and the star solidifies from the inside.
06:26The whole process can take
06:28billions of years.
06:30But new data indicates
06:32that in some white dwarfs,
06:34this dense plasma does not cease to freeze.
06:36On the contrary,
06:38the solid crystals that form during the cooling
06:40become less dense
06:42and begin to float upwards.
06:44And so they move the liquid,
06:46heavier, downwards.
06:48The movement of this matter towards the center of the white dwarf
06:50releases gravitational energy.
06:52This energy is enough
06:54to interrupt the cooling process
06:56of the star for billions of years.
06:58This explanation actually corresponds
07:00to the properties of the white dwarfs
07:02that we have observed.
07:04But this is the first time
07:06that such a process is identified
07:08in a completely different type of star.
07:10And this is incredibly fascinating.
07:12We have here a completely new astrophysical phenomenon.
07:14But why does this happen
07:16in some stars and not in others?
07:18This probably depends
07:20on the composition of the object.
07:22Indeed, some white dwarfs
07:24come from the fusion of two different stars.
07:26When they collide
07:28and form a white dwarf,
07:30the composition of the star changes,
07:32and the formation of these floating crystals occurs.
07:34This discovery
07:36could force astronomers
07:38to review the methods they used
07:40until now to determine the age of the stars.
07:42Nowadays,
07:44we often use the state of a white dwarf
07:46as an age indicator.
07:48The colder a star is,
07:50the older we think it is.
07:52But today, we know that the cooling process
07:54of some dwarfs can be delayed.
07:56And this vacillates the certainties
07:58concerning the methods used.
08:00Some stars could be much older
08:02than we thought,
08:04with a gap of several billion years.
08:06This phenomenon recently discovered
08:08means that some of these stars
08:10are able to shine almost normally
08:12for billions of additional years.
08:14This complicates the measurements
08:16and questions the use of white dwarfs
08:18in the reconstruction of galactic history.
08:20Stay tuned.