Des astronomes ont découvert un objet mystérieux filant à travers la Voie lactée à une vitesse incroyable ! Il se déplace si rapidement qu'il pourrait même échapper totalement à notre galaxie. Certains scientifiques pensent qu'il pourrait s'agir du noyau résiduel d'une étoile morte, tandis que d'autres croient qu'il pourrait s'agir de quelque chose que nous n'avons jamais vu auparavant. Quoi qu'il en soit, il voyage à des millions de miles par heure, laissant derrière lui une étrange traînée. L'étudier pourrait nous fournir de nouveaux indices sur les forces qui façonnent notre univers. Une chose est sûre : l'espace vient de devenir beaucoup plus étrange ! Animation créée par Sympa.
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FunTranscript
00:00At lightning speed, this mysterious object crosses our galaxy at nearly 1.6 million kilometers per hour.
00:08Its speed is such that it could even escape the gravitational grip of the Milky Way.
00:13While scientists are trying to elucidate the exact nature of this cosmic curiosity,
00:18let's launch into space to better understand the mysteries.
00:22The object in question, CWIS-J1249, is currently evolving at a distance of 400 light-years from Earth.
00:30Let's take a closer look to determine whether it could be a wandering probe.
00:35This seems unlikely due to its impressive size.
00:38It is 30,000 times more massive than Earth and represents 8% of the mass of the Sun.
00:44Such a mass ranks it in a category that Dr. Darren Baskill,
00:48a professor of astronomy at the University of Sussex, describes as
00:52« located between a star and a planet ».
00:55Stars capable of reaching such phenomenal speeds are extremely rare.
01:00Only one or two stars out of a thousand in our galactic neighborhood reach such a speed.
01:07If you were to one day observe one moving as fast as this cosmic enigma,
01:12you would see it leave the Milky Way in just a few tens of millions of years.
01:16A nod in terms of cosmic time.
01:18Let us remember that such stars can survive for tens of billions of years.
01:23Although the mysterious CWIS-J1249 only travels at 0.001% of the speed of light,
01:30its velocity remains high enough to potentially escape the gravitational attraction of our galaxy
01:36and fly into intergalactic space.
01:39To better grasp the extent of its speed,
01:41know that J1249 exceeds 2.6 times that of the fastest ever launched space probe,
01:48the Parker Solar Probe,
01:50which reached its peak in June 2024 by orbiting around the Sun.
01:55J1249 was discovered by volunteers of the Backyard Worlds project, NASA's new planet.
02:03These researchers analyze the images reported by the Wide Field Infrared Explorer and NeoWISE missions,
02:09scrutinizing all signs worthy of interest.
02:12Three of them spotted a fast and diffuse point crossing the images of WISE.
02:18When they understood the nature of their discovery, they were overwhelmed with enthusiasm,
02:23although they first thought that this space object had already been reported.
02:27However, to their great surprise, this was not the case.
02:31Currently, most scientists estimate that CWIS-J1249
02:37could be either a low-mass star or a brown dwarf.
02:41However, this type of star, larger than a planet,
02:44does not have the size necessary to maintain a nuclear fusion in its core,
02:48as our Sun does.
02:50In other words, these stars do not have enough mass
02:54for their nucleus to burn its stellar fuel and radiate.
02:57This is why brown dwarfs, often referred to as failed stars,
03:02are smaller and colder than the Sun.
03:05They even have complex atmospheres, similar to those of planets,
03:10including clouds and molecules such as water.
03:14In order to verify this hypothesis,
03:17astronomers continued their observations using terrestrial telescopes.
03:22They quickly detected an unusual chemical composition for the object,
03:26displaying iron levels and other metals much lower than those of stars
03:30or ordinary brown dwarfs.
03:32This led NASA to issue a bold hypothesis.
03:36J1249 could be one of the oldest stars ever identified in our galaxy.
03:44This upheaval raises a question.
03:46Why is this hypothetical star moving so fast?
03:50Researchers are considering several scenarios.
03:53One of them assumes that it is a remnant of a binary stellar system,
03:57in which one of the members, a white dwarf,
04:00would have exploded as a supernova after absorbing too much matter from J1249.
04:06Another hypothesis suggests that the star could come from a stellar mass
04:11that would have dislocated after meeting two black holes.
04:15According to the specialists, one way to reach such a velocity
04:19is to move towards a massive object without reaching it,
04:23which produces a gravitational wave effect.
04:26This phenomenon is used to accelerate space probes,
04:30allowing them to explore the solar system in a reasonable time scale.
04:34The speed of J1249 could be explained by a similar mechanism.
04:39The star could have been born in the overpopulated core of the galaxy,
04:43move towards another star without hitting it,
04:46and thus gain an extreme speed.
04:49Let's now let the astronomers continue their investigations
04:52to confirm this fascinating hypothesis.
04:55Meanwhile, let's go to the binary system 55 Cancri,
04:59located 41 light-years from Earth.
05:02This system houses an amazing planet.
05:0555 Cancri E, alias Jonsen.
05:10This super-Earth, 8 times more massive than our planet,
05:14orbits around its star in a little more than 17 hours,
05:17a much shorter year than a terrestrial day.
05:20In addition, the planet is 25 times closer to its star than Mercury is to the Sun,
05:26which explains why its surface reaches an infernal temperature of 2400°C.
05:32It's hot enough to melt most of the known metals.
05:36In 2010, researchers discovered that the high star of 55 Cancri
05:41had a particularly high carbon-oxygen ratio.
05:45If this same ratio also applied to the planet,
05:48it could receive immense amounts of carbon,
05:51and the most incredible.
05:53This carbon could exist in the form of diamonds.
05:56This would make 55 Cancri a real planet of jewels.
06:02Unfortunately, later studies revealed that this carbon-oxygen ratio
06:07was less extreme than initially thought,
06:10making the existence of a gem-encrusted world unlikely.
06:14However, the composition of the planets does not always reflect
06:17exactly that of their high star.
06:19If an external process had enriched the amount of carbon in 55 Cancri E,
06:24it could still remain the most precious planet in the universe.
06:28It would certainly be worth the detour.
06:30But let's leave behind us this diamond planet to go to Vega,
06:34one of the brightest and most important stars in the night sky.
06:38The brightness of the other stars is evaluated compared to Vega's,
06:43on a scale where its own magnitude is zero.
06:46A magnitude star is 1.25 times less luminous than Vega,
06:51while a magnitude star is 1.25 times brighter.
06:56Vega was also a polar star, although it is no longer the case.
07:00Today, the axis of the Earth points to Polaris, the North Star.
07:05However, the axial inclination of the Earth draws a circle
07:08over a period of about 26,000 years,
07:10and Vega will become the polar star again in about 12,000 years.
07:14Patience.
07:15What really distinguishes Vega from the other stars
07:18is that it does not have a perfect spherical shape.
07:21Unlike the Sun, which rotates slowly and is practically spherical,
07:25Vega makes a complete rotation in just 12 hours and a half.
07:29This rapid rotation causes an equatorial inflation,
07:32giving it an ovoid appearance.
07:34And now, prepare for the most dangerous meeting of all.
07:38But before that, a warning is necessary.
07:41Although space is of inconceivable immensity,
07:44it is extremely sparsely populated.
07:47The average density of the universe is equivalent to 6 protons in a volume of 1 m3.
07:52Some regions, called empty or super-empty,
07:55contain even less matter.
07:57These areas are colossal.
07:59They can extend over 30 to 300 million light years,
08:03and almost nothing can be found.
08:05We also find in the universe places where time and space are deformed
08:09in order to challenge any human understanding.
08:12Like the binary black holes systems,
08:14where two massive black holes gravitate around each other
08:18before finally merging.
08:20As they approach in a spiral,
08:22they emit powerful gravitational waves
08:25that propagate through space-time.
08:28The first detection of these waves was made in 2015
08:31by the Laser Interferometer Gravitational Wave Observatory, LIGO,
08:36when it recorded the final collision of a pair of black holes.
08:40During the 20 milliseconds preceding the fusion,
08:43these black holes released more gravitational energy
08:46than the total energy emitted by all the stars of the observable universe
08:50during the same period.
08:52But the universe has much more to offer.
08:54By exploring more,
08:56you could come across exoplanets like Corot T7b,
08:59where rock clouds form and pour down stone wells,
09:03or KILT 9b, the hottest known planet,
09:08with surface temperatures reaching 4,300 °C,
09:12or TRES-2b,
09:15the darkest planet ever discovered.
09:18It absorbs more than 99% of the light it receives,
09:22making it darker than coal.
09:25Thus, on a vast and almost unfathomable scale of the cosmos,
09:29fast and mysterious objects,
09:31strange planets and immense voids
09:34remind us how much there is still to discover in the universe.