00:00It seems that scientists have discovered a strange object in space and they do not know exactly if it is a star or a planet.
00:08What we know is that it is located 1400 light years from us.
00:13Which leads us to wonder about what we thought we knew about the universe.
00:18Let me explain the dilemma.
00:20We can determine if an object is a star or a planet depending on its mass or the amount of matter it contains.
00:28Stars have a large mass, which gives them a strong gravity that compresses them strongly.
00:33This compression creates high temperatures inside.
00:36As a result, they shine with a thousand lights.
00:40Planets have a smaller mass and their gravity is therefore weaker.
00:44They do not undergo the same compression and therefore do not have the high temperatures of stars.
00:49If planets shine, it is because they reflect the light of their stars, as our beautiful Earth does with our sun.
00:56Well, this strangeness is between the two.
00:59We consider that it is a brown dwarf, a particular type of large-sized gas proto-star.
01:06Brown dwarfs generally resemble Jupiter in terms of atmosphere, but they are much larger, with a diameter of 13 to 80 times higher.
01:15If a brown dwarf has a mass more than 80 times higher than that of Jupiter, then it can start to burn hydrogen like any star does.
01:24This is how stars shine in the sky.
01:27But normally, brown dwarfs are not as hot as stars.
01:31Their inability to burn hydrogen has even earned them the nickname of missed star.
01:36They burn at about 2200 ° C, which is colder than most stars.
01:43But this object defies the norm.
01:45Its temperature reaches the incredible bar of 7700 ° C.
01:50Let's put this into perspective.
01:52The hottest day in history was recorded in the Valley of Death, in California, more than 100 years ago, with a temperature of 57 ° C.
02:02The people of the time must have had the impression of melting with everything around them.
02:08Now imagine that you are getting closer to the sun, as if you were traveling to Venus.
02:15Venus can reach the insane temperature of 460 ° C.
02:21But there is not only the distance that matters.
02:24Mercury is the planet closest to the sun.
02:27But it is colder than Venus.
02:30If Venus is so hot, it is because of the greenhouse effect.
02:34Did you know that a long time ago, Venus could have been a place where it was good to live?
02:39Or at least, it could have sheltered forms of life.
02:42But at some point, it began to trap carbon dioxide, and it ended up creating a thick fog that did not let the heat escape.
02:51That's why it's so hard to explore.
02:54The probe that managed to spend the most time on Venus only lasted two hours.
02:59It's still longer than what I can do at work.
03:03After that, I melt.
03:05So yes, you get to the sun.
03:09Its surface burns at an incredible temperature of 5,500 ° C.
03:14And what is fascinating is that this strange brown star we are talking about is even hotter than that.
03:21Of course, it is not hotter than the heart of the sun, whose temperature can reach 15 million ° C.
03:28But it is still very impressive and unusual for a brown dwarf to be so hot.
03:34This is at least what everyone thought, until we realized the reason for this phenomenon.
03:39The brown dwarf is remarkably close to another star, which, it, falls into the category of white dwarfs.
03:46They are so close to each other that our mysterious brunette makes an orbit around her white friend in just two or three hours.
03:54As if we were old there.
03:57As they are very close, they are in a state of gravitational lock, like the moon and the earth.
04:03This means that this brown dwarf always presents only one of its faces to its white dwarf.
04:08The other face is always in the dark.
04:11For this reason, our brown dwarf is overheated only on one side.
04:15It is therefore this illuminated face that confused us,
04:18while the temperature of its nocturnal face corresponds to what we expect from a brown dwarf.
04:23But these extreme conditions will not last long.
04:26Such a high temperature causes the molecules of its atmosphere to disintegrate into individual atoms,
04:32and as these molecules fragment, our brown dwarf slowly disappears.
04:38If you think this brown dwarf is hot, what would you say about Eta Carinae?
04:42It is a star located at about 7,500 light-years from Earth, in the constellation of the Cairn.
04:49It belongs to a category of stars called the blue luminous variables.
04:54An astronomer noticed it for the first time in the 17th century.
04:58But at the time, it was just an ordinary star of average luminosity.
05:02Nearly 200 years later, another astronomer came across it.
05:06But this time, it was a very bright star, one of the brightest in the sky.
05:12A few years later, it reached its highest level of luminosity
05:16during a major event called the Great Eruption.
05:19At that time, the star was easily visible in our night sky.
05:24It released a surprising amount of light,
05:27as important as that emitted during the explosion of a supernova.
05:31And it stayed that way for a few years, which is not the case of exploding stars.
05:36When the event reached its peak, it decided it was time to say goodbye.
05:41But it still hesitates a little, which means it is still alive, but it is less luminous than before.
05:48There is also a nebula around Eta Carinae.
05:52It is a gas and dust shell that formed during the Great Eruption.
05:56It even blocked part of the star's light.
05:59Eta Carinae is a binary stellar system.
06:03In other words, two stars orbit each other.
06:07One of them has a temperature of about 14,700°C,
06:11the other of 34,650°C.
06:14The main star of the Eta Carinae system, the most massive of the two,
06:18is 100 times heavier than our Sun.
06:21Because of its enormous mass, scientists predict that this star could explode
06:26during a powerful event known as a supernova, but not before several thousand years.
06:31You may have already guessed what is the hottest phenomenon in the universe.
06:35Yes, a supernova.
06:37It is thanks to it that we know that the life of a star is over.
06:41These are the most powerful explosions in space.
06:44They occur when a star is between 8 and 40 times more massive than our Sun.
06:51Its core can no longer produce enough energy
06:54through a process called fusion,
06:57so that the star can no longer withstand its own gravity.
07:01It is therefore a kind of stellar exhaustion.
07:04The star can no longer face such a heavy workload
07:07and its core is let go.
07:09During a supernova, the temperatures at the center of the star
07:12can be 6,000 times higher than in the center of the Sun.
07:16It also happens that a particular type of star, called white dwarf,
07:20suddenly resumes its nuclear fusion and, boom,
07:23you get a supernova again.
07:26Kepler's supernova occurred at the beginning of the 17th century
07:29and was the last really important to be directly observed from Earth.
07:34On average, supernovas in our galaxy occur three times a century.
07:39A supernova of lesser importance occurred in 1987
07:44when a blue supergiant named SN 1987A
07:49exploded in one of the satellite galaxies of our Milky Way,
07:53the Great Magellan Cloud.
07:55This explosion was so powerful that it could be observed with the naked eye,
07:59although it occurred at an incredible distance,
08:02at 168,000 light years from our planet.
08:05What a beautiful day, isn't it?
08:08We can also talk about the hottest thing ever created,
08:12made in an amazing place, Switzerland.
08:15No, it's not a super hot chocolate.
08:19A group of scientists created a subatomic soup
08:23called quark and gluon plasma.
08:25During this experiment, the temperature became
08:28250,000 times higher than that of the heart of the Sun,
08:31the goal was to recreate the conditions that existed shortly after the Big Bang
08:35when the universe was still in a state of chaos.
08:38Well, let's go even further.
08:40In theory, things can get even hotter.
08:44Have you heard of Planck's temperature?
08:47It is an extremely high temperature,
08:50with numbers that we can't even imagine.
08:53A supernova is a warm tea compared to this madness.
08:56And who knows what the matter does at these temperatures?
08:59That's all for today.
09:01You are back in your comfortable universe.
09:04Bye!
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