00:00Chbilsky's star was discovered in the 1960s.
00:04Since then, astronomers have been intrigued by its unique chemical makeup.
00:08The star is suspected to contain ultra-rare elements verging on the almost impossible.
00:15Using special equipment on the European Southern Observatory's telescope in Chile, researchers
00:20took readings of the star's magnetic field.
00:23They discovered that the star's rotation period, which is the time it takes to finish
00:27one revolution on its axis, stretches out over almost 200 years, which is super slow.
00:35Of course, there are even more bizarre objects called app stars.
00:40They're a chemically interesting category of stars that rotate extremely slowly, with
00:44one rotation taking up to 1,000 years.
00:48What makes these stars even more peculiar is a wide range of chemical elements astronomers
00:53detect when analyzing their stellar spectrums.
00:57But if we look at Chbilsky's star, we'll see that it's both similar to and different
01:02from other app stars.
01:04It contains unusually low amounts of iron and nickel.
01:07Our sun has 10 times more and incredibly high amounts of rare, heavy elements.
01:13Those might include strontium, cesium, and neodymium, as well as at least two undiscovered
01:19elements.
01:20They wouldn't occur through any natural processes we currently understand.
01:25There's a hypothesis that the presence of such heavy elements could be caused by a star's
01:30unseen companion, like a neutron star.
01:33Some people go as far as to say that such an incredible chemical makeup could be a sign
01:38of an alien technosignature.
01:41Any specialist will tell you that it's the strangest stellar spectrum they've ever observed.
01:46Some even claim that there are so many chemical indicator lines you can't immediately understand
01:50what you're looking at while observing the star's spectrum.
01:54Chbilsky's star also contains high levels of radioactive elements that take a few thousand
02:00years to decay.
02:02And here's where another mystery lies.
02:04They should have long vanished from the star.
02:08After all, it's almost a billion and a half years old.
02:11Scientists haven't managed to figure out the reason for the presence of these elements
02:15yet.
02:16Maybe it's the combination of the star's rare qualities.
02:19It spins very slowly, it's hot, and it has a strong magnetic field.
02:24This could raise to the surface atoms that would normally be mixed inside the star.
02:30There's another theory that explains the presence of these radioactive elements.
02:34They could be there as if they were themselves decayed forms of ultra-heavy elements that
02:38we haven't discovered yet.
02:40So far, no one has been able to prove this theory.
02:44Even the discovery of Chbilsky's star's super-slow rotation doesn't bring us closer to the answer.
02:49It's obvious that there's a lot to learn about the bizarre star, and who knows which secret
02:54it still has up its sleeve.
02:57Another not-less-mysterious star is called Tabby's star.
03:01It's a sun-like orb around 1,500 light-years away from Earth, sitting in Cygnus the Swan.
03:09Unlike our sun, this star dims randomly by 5-22%, and it lasts for days at a time.
03:16The reason could be a giant planet passing in front of the star, but then the eclipses
03:21would be more regular and not so random.
03:25And if it was a Jupiter-sized planet, it would also need to block around 1% of the star's
03:30light, which would make it unique and unlike anything we know.
03:34After American astronomer Tabitha Boyajian discovered the star's massive and irregular
03:39fluctuations in 2015, further observations followed.
03:44They show that the overall magnitude of the star has been gradually dimming over the years.
03:50Some theories trying to explain this phenomenon are quite believable.
03:54For example, some scientists think that these brightness changes are intrinsic to the star.
03:59They could be caused by its magnetism, or changes in heat flow in its interior.
04:04Other ideas are more daring, including some kinds of activity of an extraterrestrial civilization.
04:11One of the most plausible theories, though, is that the dimming is caused by the chunks
04:15of an orphaned exomoon.
04:17It could have been pulled away from its parent planet by gravitational interactions with
04:22Tabby's star.
04:23As the moon approached the star, it exploded, sending dust clouds into stellar orbit.
04:29These countless chunks of rock and dust are now moving between Tabby's star and Earth
04:33in a giant, clumpy cloud.
04:36It could indeed explain why we observe such irregular brightness variations.
04:40Usually, when astronomers spot a spiral arm structure, it turns out to be a galaxy.
04:47But not in this case.
04:48SAO 206462, located 460 light-years away from our home planet, is a young star.
04:56It's surrounded by a circular disk of gas and clearly defined spiral arms.
05:01The bizarre star was spotted during an exoplanet search with the help of the Subaru telescope
05:06located in Hawaii.
05:08Instead of finding fully-fledged planets around a young star, astronomers discovered planets
05:13that were still in formation.
05:16These baby planets are growing out of the disk of gas and dust surrounding the star.
05:21The disk extends out to around 80 astronomical units, which is twice the orbit of Pluto.
05:28At least two of these planets have stretched the disk into its extremely unusual spiral shape.
05:34A different planet is responsible for each arm.
05:40In our home galaxy, there is a giant star that is a real stellar wind machine.
05:46At the moment, this monster is just waiting to burst and send a wave of radiation and
05:51hot gas towards Earth.
05:53All because it's a Wolf-Rayet, a star which is at that precarious point before it goes
05:58supernova.
06:00Its core doesn't have any more helium left to burn.
06:03Instead, the star is forced to churn through much heavier elements, for example, oxygen.
06:09Unfortunately, it disrupts the careful balance between gravity and fusion, leading to the
06:14star shedding its layers.
06:16When the oxygen eventually runs out, the star will go supernova.
06:20But this time, the show will be different.
06:23The thing is, WR104 is one half of a binary pair, which means that two stars are feeding
06:30into each other, spinning up their stellar winds.
06:34It will continue until they start going incredibly fast.
06:38Is the potential explosion going to harm Earth?
06:41On the one hand, we're far away enough for even a directed supernova to not hurt our
06:46planet.
06:47At the same time, there is a threat of an extremely dangerous gamma-ray burst.
06:51Luckily for us, it takes a very specific and unlikely train of events for a Wolf-Rayet
06:56to produce a gamma-ray burst.
06:58Plus, even if it does, the star might be pointed far away enough for the danger to miss us.
07:04Anyway, astronomers are still watching the star, just in case.
07:09A star sitting in the constellation of Centaurus keeps a secret not many know about.
07:14At first glance, it looks like a dim white dwarf.
07:18But when astronomers analyzed it, it turns out to be incredibly dense.
07:22Take the mass of the Sun and cram it into something that is only a third the diameter
07:27of Earth.
07:28This space wonder is also rather cool.
07:31Its core temperature is a mere 11,900 degrees Fahrenheit.
07:35For comparison, the Sun's core temperature is around 27 million degrees Fahrenheit.
07:41At such low temperatures, stars begin to vibrate.
07:44And then, scientists can use these vibrations to sneak a peek inside a star.
07:49And in the case with the star in question, which was later named Lucy, they discovered
07:54that its carbon core had crystallized.
07:57In other words, it formed a giant diamond 10 billion trillion trillion carats in size.
08:02Since the discovery of Lucy, a few other crystallized stars have been spotted.
08:07Some of them have diamond hearts the size of our planet.
08:10The last bizarre star for today is called Vega, and it's squashed.
08:15The star's bulging waistline is caused by an extremely high spin rate.
08:19Vega rotates once every 12 and a half hours.
08:22This pushes the material around its equator outward.
08:25It also leads to the phenomenon known as gravity darkening when stellar material further from
08:30the center of the star experiences less gravity, which makes it cooler and darker.
08:36So when Vega faces Earth pull and on, it looks perfectly round.
08:41But the dark halo around its middle is a telltale sign of Vega's oblate shape.
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