00:00The Pchibilsky star was discovered in the 1960s.
00:04Since then, astronomers have been intrigued by its unique chemical composition.
00:09It is suspected that the star contains ultra-rare elements,
00:12fraying the impossible.
00:14With the help of a special equipment on the telescope of the Australian European Observatory in Chile,
00:19researchers have made measurements of the magnetic field of the star.
00:23They have discovered that the period of rotation of the star,
00:26i.e. the time it takes to make a complete revolution on its axis,
00:30extends over almost 200 years.
00:32Which is extremely slow.
00:35Of course, there are even stranger objects, called hap stars.
00:40This is a category of stars of great chemical interest,
00:43which rotate extremely slowly,
00:45a rotation taking up to 1000 years.
00:48What makes these stars even more unique
00:51is the wide range of chemical elements that astronomers detect
00:54when they analyze their stellar spectrum.
00:57But if we examine the Pchibilsky star,
01:00we will see that it is at the same time similar and different from other hap stars.
01:04It contains unusually low amounts of iron and nickel.
01:08Our sun has 10 times more,
01:10and incredibly high amounts of rare and heavy elements.
01:15These could include strontium, cesium and neodymium,
01:19as well as at least two undiscovered elements.
01:22They would not occur by natural processes that we currently understand.
01:26There is a hypothesis that the presence of these heavy elements
01:30could be caused by an invisible companion of a star,
01:33like a neutron star.
01:35Some people go so far as to say that such an incredible chemical composition
01:39could be a sign of extraterrestrial technosignatures.
01:42Any specialist will tell you that this is the strangest stellar spectrum ever observed.
01:47Some even claim that there are so many chemical indicator lines
01:51that we cannot immediately understand what we are looking at
01:54by observing the star's spectrum.
01:56The Pchibilsky star also contains high levels of radioactive elements
02:00that take several thousand years to disintegrate.
02:03And this is where another mystery arises.
02:06They should have disappeared from the star a long time ago.
02:09After all, it is a billion and a half years old.
02:12Scientists have not yet been able to understand the reason for the presence of these elements.
02:17Perhaps this is due to the combination of the rare qualities of the star.
02:20It rotates very slowly, it is hot, and it has a powerful magnetic field.
02:25This could lead to the surface of the atoms which, normally,
02:28would be mixed inside the star.
02:31There is another theory that explains the presence of these radioactive elements.
02:36They could be present if they were themselves disintegrated forms of ultra-heavy elements
02:41that we have not yet discovered.
02:43So far, no one has been able to prove this theory.
02:46Even the discovery of the super-slow rotation of the Pchibilsky star
02:50does not bring us closer to the answer.
02:52It is obvious that there is a lot to learn about this bizarre star
02:56and who knows what secrets it still holds in its sleeve.
02:59Another star, no less mysterious, is called the Tabby star.
03:03It is a star similar to the Sun,
03:06located about 1500 light-years from Earth,
03:09in the constellation of the sign.
03:11Unlike our Sun,
03:13this star darkens randomly from 5 to 22%,
03:18and it lasts several days in a row.
03:20The reason could be a giant planet passing in front of the star.
03:24But in this case, the eclipses would be more regular and not so random.
03:29And if it were a planet the size of Jupiter,
03:32it should also block about 1% of the star's light,
03:36which would make it unique and different from everything we know.
03:39After the American astronomer Tabetta Tabby S. Boyajian
03:43discovered the massive and irregular fluctuations of the star in 2015,
03:47other observations followed.
03:49They showed that the star's global luminosity
03:52gradually decreases over the years.
03:54Some theories trying to explain this phenomenon are quite credible.
03:58For example, some scientists think that these variations of luminosity
04:02are intrinsic to the star.
04:04They could be caused by its magnetism
04:07or changes in the heat flux inside it.
04:11Other ideas are bolder,
04:13including some types of activities of an extraterrestrial civilization.
04:17One of the most plausible theories, however,
04:19is that the darkening is caused by fragments of an orphan exo-moon.
04:23It could have been torn from its mother planet
04:25by gravitational interactions with the star of Tabby.
04:28As the moon approached the star, it exploded,
04:32sending dust clouds into stellar orbit.
04:35These countless pieces of rock and dust
04:38are now moving between the star of Tabby and the Earth
04:41in a huge cloud.
04:43This could explain why we observe such irregular variations of luminosity.
04:49Usually, when astronomers spot a spiral-arm structure,
04:53it is generally a galaxy.
04:55But not in this case.
04:57SAO 206462,
05:00located 460 light years from our planet,
05:03is a young star.
05:05It is surrounded by a gas circumstellar disk
05:07with clearly defined spiral arms.
05:10The strange star was spotted during an exoplanet search
05:13with the help of the Subaru telescope,
05:15located in Hawaii.
05:17Instead of finding planets completely formed around a young star,
05:21astronomers discovered planets that were still in formation.
05:24These planets in gestation develop from the gas and dust disk
05:28surrounding the star.
05:30This disk extends up to about 80 astronomical units,
05:34which is twice the orbit of Pluto.
05:36At least two of these planets have stretched the disk
05:39to give it its extremely unusual spiral shape.
05:43A different planet is responsible for each arm.
05:47In our original galaxy, there is a giant star
05:50which is a real stellar forward machine.
05:52For now, this monster is just waiting for the moment to explode
05:55and send a wave of radiation and hot gas to Earth.
05:59All this because it is a Wolf Rayet,
06:01a star that is so precarious before exploding into a supernova.
06:05Its core has no more helium to burn.
06:08Therefore, the star is forced to consume much heavier elements,
06:12for example oxygen.
06:14Unfortunately, this disturbs the delicate balance
06:17between gravity and fusion,
06:19leading the star to get rid of its layers.
06:22When oxygen runs out,
06:25the star will become a supernova.
06:27But this time, the show will be different.
06:30Indeed, WWR 104 is part of a binary couple,
06:34which means that two stars feed each other,
06:37thus accelerating their stellar wind.
06:40This will continue until it starts spinning at an incredibly fast speed.
06:45Will the potential explosion harm Earth?
06:48On the one hand, we are far enough away
06:51so that a supernova can not damage our planet.
06:55At the same time, there is a threat of an extremely dangerous Gamma superjump.
06:59Fortunately for us,
07:01we need a very specific and unlikely sequence of events
07:04for a Wolf Rayet star to produce a Gamma superjump.
07:07In addition, even if this happens,
07:10the star could be sufficiently oriented so that danger avoids us.
07:13Anyway, astronomers continue to observe the star, just in case.
07:18A star located in the Centauri constellation
07:21hides a secret that few people know.
07:23At first glance, it looks like a pale white dwarf.
07:27But when astronomers analyzed it,
07:29it turned out to be incredibly dense.
07:32Imagine the mass of the sun compressed into an object
07:35that is only a third of the diameter of the Earth.
07:38This wonder of space is also rather cold.
07:41Its central temperature is only 6600 ° C.
07:45For comparison, the central temperature of the sun is about 15 million ° C.
07:51At such low temperatures,
07:53the stars begin to vibrate.
07:55And then, scientists can use these vibrations
07:58to look inside a star.
08:00And in the case of the star in question,
08:02which was later named Lucy,
08:04they discovered that its carbon nucleus had crystallized.
08:07In other words, it formed a giant diamond
08:09of 10 billion thousand billion carats.
08:12Since the discovery of Lucy,
08:14some other crystallized stars have been spotted.
08:17Some of them have diamond hearts the size of our planet.
08:21The final bizarre star for today is called Vega,
08:24and it is flattened.
08:26The inflated size of the star
08:28is caused by an extremely high rotation speed.
08:31Vega makes a complete rotation every 12 and a half hours.
08:35This pushes the material around its equator outward.
08:38It also causes the phenomenon known as gravitational darkening,
08:42when the stellar material,
08:44farthest from the center of the star,
08:46undergoes less gravity,
08:48making it fresher and darker.
08:50Thus, when Vega faces the Earth
08:52with the pole facing us,
08:54it seems perfectly round.
08:56But the dark halo around its center
08:58is a revealing sign of Vega's flattened shape.
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