Il se Passe Quelque Chose d’Étrange Avec l’Étoile Polaire – Et c'est un Événement Majeur - video Dailymotion

Sympa

L'étoile Polaire, Polaris, se comporte un peu étrangement ces derniers temps, et les scientifiques s'en étonnent. Normalement, c'est une étoile assez stable qui a été notre guide lumineux pendant des siècles, mais des observations récentes montrent qu'elle s'assombrit et s'éclaire de manière inattendue. Cela pourrait signifier qu'un grand changement se produit à l'intérieur de l'étoile, comme des modifications de son noyau ou de son processus de fusion. C'est un sujet important car Polaris a été un point de référence essentiel pour la navigation et l'astronomie depuis des siècles. Étudier son comportement inhabituel pourrait nous en apprendre davantage sur l'évolution des étoiles comme elle. C'est comme si l'étoile Polaire essayait de nous révéler un secret cosmique !  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

Transcript

00:00Locating the Polar Star is relatively easy by a clear night.

00:04You just have to identify the Big Bear.

00:07The two stars located at the end of the pot of this constellation serve as landmarks

00:11and indicate the direction of the Polar Star.

00:13Do you see it? It's the tip of the pot handle.

00:16Or, if you prefer, the tail of the Little Bear, right there.

00:21For centuries, the Polar Star has fascinated observers.

00:25Also called Polaris, it shines almost exactly above the Northern Pole,

00:30which makes it a precious landmark for any traveler without a compass or GPS on his phone.

00:37It is also the closest CFI to our planet,

00:39a type of star that oscillates periodically in brightness and size.

00:44In addition, Polaris belongs to a binary system.

00:47It has a more discreet companion, named Polaris B.

00:51From Earth, we can observe the latter in orbit around the Polar Star.

00:57But as astronomers scrutinize Polaris, their perplexity grows.

01:01The main obstacle lies in the inability to adapt to its size and distance.

01:06To estimate its parameters, as well as its age, scientists use several techniques.

01:12One of them is based on stellar evolution.

01:15After studying the brightness, color and frequency of pulsations of a star,

01:20experts can deduce its brightness, size and stage of evolution.

01:25Once these parameters are established, it becomes relatively easy to calculate its distance.

01:30This is a mathematical operation based on the comparison between its intrinsic brightness

01:35and the intensity with which it is perceived from Earth.

01:39These models are particularly reliable for stars like Polaris,

01:43whose pulsation is directly related to brightness.

01:47This relationship allows to estimate their distance with precision.

01:50Astronomers are so confident in this approach that they use it

01:54to measure distances on a large scale in the universe,

01:57making cepheids a fundamental tool in astronomy.

02:00However, other methods of analysis of the Polar Star contradict these models.

02:05Polaris is an astrometric binary star,

02:08which means that its companion star gravitates around it following a well-defined trajectory.

02:14From Earth, this orbit gives the impression of a circle drawn around the main star.

02:19The complete revolution of the secondary star takes about 26 years.

02:23Although astronomers have not yet observed in detail the entire orbit of Polaris B,

02:28they have enough elements to deduce its trajectory.

02:32By applying Newton's laws of gravitation, they can thus calculate the masses of the two stars.

02:38These calculations, crossed with the recent measurements of the Hubble Space Telescope,

02:43provide very precise estimates.

02:45They indicate that Polaris has a mass of about 3.45 times that of the Sun.

02:52However, this value is much lower than that advanced by stellar evolution models,

02:57which suggests a mass 7 times that of the Sun.

03:01There is another strange peculiarity in this stellar system.

03:05By calculating the age of the stars,

03:07researchers have discovered that Polaris B was much older than its companion.

03:11This is very rare in a binary system, because in general the two stars are the same age.

03:17One possible explanation would be that one of the measures used to determine this age is incorrect.

03:23Polaris remains a difficult star to study.

03:26Because of its position above the North Pole, it escapes the view of most telescopes.

03:31Those who have the equipment necessary to measure its properties with great precision

03:36are generally used to observe stars that are farther away and less luminous.

03:41Polaris, with its intense light, dazzles these instruments, preventing them from studying it correctly.

03:47An interesting theory suggests that the main star of the Polaris system

03:51was once a binary system, but that the two stars merged several million years ago.

03:57This collision could have rejuvenated them by bringing them additional matter,

04:01which makes them look younger than they really are.

04:04This phenomenon could also explain other anomalies,

04:07because the stars from such collisions do not correspond to the classical evolution model.

04:12However, it is important to note that none of these hypotheses have yet been confirmed.

04:17The polar star is of paramount importance.

04:20Because of the incessant rotation of the Earth, the stars seem to move through the sky.

04:25And this movement, combined with the inclination of the planet, is at the origin of the seasons.

04:30If we drew a straight line extending the axis around which the Earth rotates,

04:34and if we extended it over more than 300 light years beyond the North Pole,

04:38we would end up with the polar star.

04:41Polaris remains practically immobile in the sky, constantly pointing north.

04:45This makes it an essential navigation tool,

04:48especially before the appearance of GPS systems.

04:51If you were at the equator, the polar star would be just above the horizon,

04:55while at the North Pole, it would be directly above you.

04:59By measuring the height of the star in the sky,

05:02it is possible not only to orient yourself,

05:05but also to determine your position on Earth with great precision.

05:09It is curious to note that there are no stars equivalent to the South Pole,

05:13because there are no stars bright enough directly above this region.

05:18However, it is possible that such a star will appear one day.

05:22This phenomenon could be linked to the precession,

05:25the movement similar to that of a spinning top,

05:28which leads to a progressive change in the orientation of the Earth's poles.

05:32Thus, in the next 26,000 years, it is possible that the North Star changes,

05:37going from Polaris to other stars.

05:39One day, Vega will take the place of the Polar Star.

05:43It is the fifth brightest star in the night sky

05:46and the second brightest in the northern celestial hemisphere.

05:49Vega is also called Alpha Lyrae,

05:52the main star of the Lyra constellation.

05:55It has played a central role for civilizations since Antiquity,

05:59thanks to its great luminosity and its blue color,

06:02which make it very recognizable.

06:04Vega was already the Polar Star several thousand years ago

06:08and should find this title in about 12,000 years.

06:11This star is only 25 light-years from Earth

06:15and is only 450 million years old,

06:18much less than our solar system,

06:21aged 4.6 billion years.

06:24Astronomers study it to better understand the stellar systems in formation.

06:29Vega is almost directly above our heads in summer,

06:33or the Middle North latitude.

06:35It hides behind the horizon for only 7 hours a day

06:38and is visible every night of the year.

06:41Traveling further south,

06:43we see that Vega disappears under the horizon for longer periods,

06:46but in Alaska, in northern Canada and in certain regions of Europe,

06:50it never sets.

06:52Its blue-white light has been noticed in many cultures,

06:55including the oldest,

06:57from the Chinese to the Polynesians and the Hindus.

07:00The name Vega can be translated as

07:02Chute or Rapt,

07:04referring to the period when this constellation was seen

07:07as a flying vulture rather than a lyra.

07:09Vega was also the first star to be photographed,

07:13after the sun, of course.

07:15In 1850, astronomers from Harvard's observatory

07:19used a 38-centimeter refractor to capture it in image.

07:24Twenty years later,

07:26an amateur astronomer analyzed Vega's light,

07:29thus revealing the different elements that make up the star.

07:32In 2006, thanks to telescopic observations,

07:35scientists discovered that Vega rotated at a speed such that

07:39its poles were several thousand degrees warmer than its equator.

07:43The star rotates every 12 and a half hours,

07:46reaching 90% of its critical rotation speed,

07:50i.e. the speed at which an object may disintegrate.

07:53In 2013, researchers announced the discovery

07:57of an asteroid belt around Vega,

07:59suggesting the possibility of planets among these space rocks.

08:02This belt is divided into two areas,

08:04an exterior region composed of icy asteroids

08:07and an interior region with warmer rocks.

08:10Scientists can study bright stars like Vega

08:13thanks to NASA's TSS mission,

08:16whose name means Transiting Exoplanet Survey Satellite.

08:20Launched in 2018,

08:22this satellite dedicated to observing the entire sky

08:25has as its main objective the search for exoplanets.

08:28But it also allows to analyze stellar variability.

08:32By studying stars like Vega,

08:34TESS helps scientists better understand

08:36the first stages of star evolution.

Il se Passe Quelque Chose d’Étrange Avec l’Étoile Polaire – Et c'est un Événement Majeur

Category

Transcript

Recommended