Les astronomes ont récemment découvert une planète massive, LHS 3154b, plus de 13 fois plus lourde que la Terre, et qui laisse les scientifiques perplexes. Elle est en orbite autour d'une petite étoile rouge peu lumineuse, qui ne devrait pas avoir suffisamment de matière pour former une planète aussi gigantesque. Normalement, les étoiles de ce type créent des planètes beaucoup plus petites. La découverte de LHS 3154b va à l'encontre des théories actuelles sur la formation des planètes. Cette découverte est importante car elle pourrait modifier nos connaissances sur les galaxies et la formation des planètes, en particulier autour d'étoiles comme celle-ci, qui sont très répandues. Animation créée par Sympa. ---------------------------------------------------------------------------------------- Musique par Epidemic Sound https://www.epidemicsound.com Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna ---------------------------------------------------------------------------------------- Nos réseaux sociaux : Facebook: https://www.facebook.com/sympasympacom/ Instagram: https://www.instagram.com/sympa.officiel/ Stock de fichiers (photos, vidéos et autres): https://www.depositphotos.com https://www.shutterstock.com https://www.eastnews.ru ---------------------------------------------------------------------------------------- Si tu en veux encore plus, fais un tour ici: http://sympa-sympa.com
Category
😹
FunTranscript
00:00This planet, yes, this one, should not exist, but it exists.
00:05Recently discovered, it revolves around a star much smaller and less luminous than our sun.
00:10And yet, it is huge!
00:13Such a tiny star could not have created it.
00:16It's a bit like finding an ostrich egg in a henhouse.
00:21A team from the University of Penn State has developed a tool,
00:24the Planet Detector of Habitable Zones.
00:27It is an instrument supposed to find planets around dim and cold stars.
00:32It is connected to a large telescope in Texas.
00:35The tool examines the light of the stars in what is called the near infrared,
00:40that is, beyond what our eyes can see.
00:43This gadget can detect when a star changes speed because of a planet.
00:47If the movement of a star changes slightly,
00:49it means that there must be a gravitational attraction nearby.
00:53A few years ago, this technique allowed to find the first exoplanet
00:57known around a star similar to our sun.
01:00Today, we have improved this method to take more precise measurements.
01:04Our main goal is to find planets similar to Earth.
01:08They must be rocky and located in habitable zones,
01:12that is, in regions where liquid water could exist.
01:15The Doppler technique is not yet very effective to find this kind of world.
01:20But it works quite well for cold and dim stars.
01:23This is how we discovered the impossible LHS 3154 b.
01:31Planets are generally formed in gas and dust disks.
01:34Imagine a flat cloud in rotation, composed of tiny particles.
01:39These particles gather and stick to each other.
01:42After a while, they end up combining to form a solid nucleus.
01:47This is how a planet begins.
01:50Once the nucleus is there, it attracts more dust and even gas,
01:54for example hydrogen and helium.
01:56But it is not easy to create a planet in this way.
01:59It takes a lot of things, mass and materials.
02:02This process is called the nucleus accretion.
02:05Stars are a precious help in this process.
02:08Normally, large stars have a large gravity,
02:11which allows them to accumulate all the materials necessary for the formation of planets.
02:15But the star we recently discovered is not very big.
02:18It is nine times smaller than our sun.
02:21Such a small star should not have a disk large enough to allow the formation of a heavy planet.
02:27For this, its disk should have been at least ten times larger.
02:31But this heavy planet, LHS 354 b, does exist.
02:38This mysterious planet is 13 times heavier than our Earth.
02:41Its size is similar to that of Neptune.
02:44It is about fifty light-years away from us, in the constellation of Hercules.
02:48Which, in space terms, is very close.
02:51The planet is also very close to its star.
02:54It completes a year in almost four days.
02:57This discovery led scientists to review their ideas on how planets and stars are born.
03:04New theories are emerging, such as those of gravitational instability.
03:08According to this theory, instead of assembling little by little,
03:11the matter of the disk collapses all at once, creating immediately a planet.
03:16But even with this theory, it is difficult to explain how such a heavy planet can form without a really massive disk.
03:23We will need time to shed light on all this.
03:29This is not the first planet that makes us doubt our theories.
03:32Recently, scientists have discovered another planet called Allah.
03:37This planet is orbiting around a star called Baekdu.
03:41And, just like the previous one, it should not really exist.
03:45It is far too close to its star.
03:47Stars change a lot in their lifetime.
03:50Normally, a star becomes big when it prepares to leave this world.
03:54This is what is called the red giant stage.
03:57Such a star tends to destroy or repel neighboring planets, creating a huge mess.
04:03Since it revolves around a red giant, Allah must have been swallowed or destroyed a long time ago.
04:08But it is still there.
04:10Baekdu has already begun to burn helium and has become smaller than expected.
04:14But Allah does not seem to care.
04:18Scientists call Allah the forbidden planet.
04:21His discovery questions what we thought of the survival of planets near aging stars.
04:27And we have two theories.
04:29According to the first, Baekdu was once composed of two stars.
04:32A white dwarf and a red giant.
04:34Allah was in orbit around the two.
04:36And they merged before the red giant took its full size.
04:40If Allah was able to survive, it was because of the additional helium of the white dwarf that prevented the red giant from growing excessively.
04:48According to the second theory, Allah would have formed from the debris created during the fusion of the two stars.
04:54In this case, Allah would be a very young planet in orbit around an old star.
04:58Astronomers continue to study Allah and look for other planets of this type.
05:05Another strange planet, named LTT 9700M109B, scares us a little because it is too bright.
05:12This planet reflects 80% of the light of its star.
05:16Ordinary mirrors reflect between 85 and almost 100% of the light.
05:22Which means that this mysterious planet must have the appearance of a rough mirror with reflections of aluminum or silver.
05:29This planet is also the size of Neptune.
05:31It is located 260 light years from us and was discovered by the TESS probe of NASA.
05:37It makes a complete rotation around its star in just 19 hours.
05:41It is very close to its star and therefore extremely hot, reaching temperatures near 2000 ° C.
05:49Normally, planets as close to their star lose their atmosphere and turn into bare rocks.
05:55But this one happily decided to do it to its head.
06:01This time, we know the secret of its survival.
06:04It owes it to shiny metallic clouds composed of glass and titanium.
06:08These clouds make titanium rain on the hot surface of the planet.
06:13They reflect a lot of light, which prevents the planet from becoming too hot and losing its atmosphere.
06:20A bit like a mirror shield.
06:22The size of this planet also surprised scientists.
06:25It is much larger than Earth.
06:27Generally, planets that are so close to their star are either very, very large gas giants or small rocky planets.
06:35Well, this planet is a small gas giant.
06:38Scientists did not expect it to survive so close to its star.
06:42It is the brightest planet ever discovered.
06:45Even brighter than Venus.
06:47Despite its appearance, it is probably not suitable for life due to its extreme temperatures and its strange metallic rain.
06:57Finally, our last case is a planet called WASP-107b.
07:02Scientists discovered it using the James Webb Space Telescope.
07:06It is located about 200 light years from Earth, in the constellation of the Virgin.
07:11It is also very fast.
07:13It loops an orbit around its star in just 6 days.
07:17This is a super-Neptune-type exoplanet.
07:20It looks like Jupiter in some respects, especially in its size and its very high temperatures.
07:25But the main difference is that it is much lighter, weaker and less dense.
07:31It is the least dense planet we have discovered so far.
07:34After some additional research, we also discovered that it has a tail composed of helium, which it releases during its transit.
07:42It slowly loses its atmosphere due to the extreme ultraviolet radiation of its star.
07:47And so its tail looks exactly like that of a comet.
07:51A comet of Jupiter.
07:55But this is only the beginning.
07:57The low density of this planet, its plushy appearance, has allowed astronomers to study its atmosphere in detail.
08:03And they discovered surprising elements, like water vapor and clouds,
08:08made up of fine particles of silicate, which look like very fine sand.
08:13Its high star does not emit much light at high energy.
08:16But as WASP-107b is very dense, this light can penetrate deeply into its atmosphere.
08:22It results from sulfur dioxide, this smell that comes out when you scratch a match.
08:28In other words, it is a cloudy planet on which it rains sand and smells like matches.
08:34Researchers believe that sand clouds in its atmosphere are formed in the same way as clouds on Earth.
08:40They simply contain particles of sand instead of water droplets.
08:44These sand droplets condense, fall, turn into silicate vapor in the hot layers of the planet,
08:51then rise to form clouds again.
08:55But this planet could not form where it is.
08:58According to astronomers, it probably got closer to its star little by little, attracted by a heavier neighbor.
09:05And it follows a retrograde orbit, that is, it turns in the opposite direction of the rotation of its star.
09:11All these discoveries change the way we understand planets and their atmospheres.
09:16And so, we can better understand the mysteries of our own solar system.