00:00Wow, we just discovered a galaxy composed almost entirely of black material.
00:05A strange substance that doesn't reflect, doesn't emit, nor absorbs the light.
00:10Otherwise, this galaxy contains totally invisible things for us.
00:14So, what is there exactly?
00:19Here's Candidate Dark Galaxy 2, or CDG2.
00:23She is around 300 millions of years and we had an incredible chance to find it.
00:29The scientists estimate that 99% of the mass of this galaxy is composed of black material.
00:35This means that our telescopes can't really see it.
00:39So, black material, even if she is invisible, we are almost sure that she exists.
00:44Because it's our only logical explanation to understand how the galaxy ties together.
00:50In fact, when astronomers add all the visible material of a galaxy,
00:55like the stars, the gas and the water, the calculations don't collide.
00:59There's not enough mass to create the gravity necessary to maintain the all in place.
01:04The black material is what makes this man.
01:08Without her, the galaxies would be disintegrated in turning too fast
01:11and would propel their stars into space.
01:14That's why scientists are convinced that black material exists, even if we can't see it.
01:19But what exactly is it?
01:22Well, nobody knows it.
01:24They could be composed of a or several types of strange particles that we don't know,
01:29or maybe of a black material as lourd as lourd as the asteroids formed just after the Big Bang.
01:35But, what is the composition of the black material, it doesn't interact with the rayonnement
01:40electromagnetic, in general, the light.
01:43And it's what makes it invisible for us.
01:46Prenons a comet, for example.
01:48We can see it in space because it is made of material, and this material reflects the light of the
01:53sun.
01:54But the black material is not the same.
01:56If you put a torch on top of it, you will never see anything.
02:04But the black material interacts well with the gravity, like all the rest of our lives.
02:10And that's what makes it even more bizarre.
02:14That's why, it's also a theory largely accepted.
02:17Like we can't see it, we can't really prove it.
02:21We simply accept the idea because it's the main form of material in the universe since a little after the
02:27Big Bang.
02:28His attraction gravitational has not only helped the galaxies like ours to form it.
02:34It's also what maintains the stars in the inside today.
02:39And there, it raises more questions than answers.
02:42Because if the black material is real, and if it's what the essence of the universe is done,
02:47then there should be tons of galaxies composed almost entirely of black material,
02:52with just some stars by-ci and by-là.
02:55In theory, when they try to transform their normal material in stars,
02:59they are not as massive enough to retain their gas.
03:02And so, the major part of this gas is ejected from the galaxy.
03:06In the end, there is a huge nuage fantôme of black material,
03:10with only a few little stars inside.
03:13We should see this type of galaxies a little everywhere.
03:16But where are they?
03:19Well, we have already seen this galaxy quasi-sombres.
03:23But every time we look at it, they had nothing so special.
03:28That's what happened when we found CDG2.
03:31Because 99% of its material is black.
03:35And that's enormous.
03:37But wait!
03:38If this galaxy is almost invisible, how did we find it?
03:44Well, there are three of the most powerful tools ever built.
03:48The Hubble Hubble of NASA,
03:50the Euclide Euclide of EESA,
03:52and the terrestrial telescope Subaru.
03:54And no, they don't have the name of the automobile constructeur automobile,
03:57but of the Amas d'Etoiles des Pléiades,
04:00which we call Subaru in Japanese, right?
04:03But even with all this equipment of pointe,
04:06it remains an incredibly difficult mission.
04:10It's true.
04:10It's not obvious to know where to point out their telescope
04:13when we look for the most weak galaxies of the universe.
04:16So, scientists had to look for another thing,
04:20a sort of strange motif in space.
04:23They had an idea.
04:24Look for the Amas Globulaires.
04:27Practically every galaxy is surrounded
04:29by a group of ancient stars,
04:31called Amas Globulaires.
04:33They look like an enormous stars
04:36of stars,
04:38sometimes hundreds of thousands of thousands,
04:40all concentrated in a relatively small space.
04:43But the key point,
04:44it's where we find them.
04:45They usually gravitate around the galaxy,
04:48especially the most massive galaxies.
04:49Our Voight Lactée
04:51costs more than 150,
04:52for example.
04:53So, the reasoning of the researchers is the following.
04:57If there were tons of galaxies
04:59composed almost entirely
05:00of black matter,
05:02they could not have many stars in the center,
05:04but they would still have these Amas Globulaires
05:07floating around them.
05:09If we find a group of these Amas
05:11together,
05:12but without galaxies visible around,
05:15BINGO!
05:16So,
05:17that's how we know
05:18that's how we know
05:18that a phantom galaxy is somber
05:20in this case,
05:20at least in theory.
05:22One team
05:23of the University of Toronto
05:24has tried the coup
05:25and they found it.
05:27They were stupéfaits
05:28when Hubble
05:29was sent to send
05:30images of four Amas Globulaires
05:32regrouped
05:33at the interior
05:33of Persée,
05:34a massive mass
05:35of thousands of galaxies.
05:36They decided to recouper
05:39the data
05:39with the two other telescopes
05:41and have detected
05:42a weak lueur fantomatique
05:44surrounding
05:45these four Amas.
05:46This halo
05:47ténu
05:48was the proof
05:49that it was
05:49there.
05:50There was a very
05:51galaxy sombre
05:52just there.
05:53They called
05:55CDG2.
05:56The first studies
05:57indicate that this galaxy
05:58bright with
05:59an eclipse of
05:591 million
06:00stars
06:01similar to the Sun.
06:02It may seem a lot,
06:03but at the spatial level,
06:05it is
06:05incredibly low.
06:07In fact,
06:08these Amas
06:09stars
06:09represent around
06:1016%
06:11of all
06:12what we can observe.
06:13And that's how
06:15we can see
06:15a galaxy
06:16composed of
06:1799%
06:18of something
06:18that we can't see,
06:20but that we know
06:21to be there.
06:21Or rather,
06:22that we are quite sure
06:23that it is there.
06:25Astronomers say
06:26that it's perhaps
06:26one of the galaxies
06:27the most rich
06:28in black matter
06:28ever discovered.
06:30But if the major part
06:32is invisible,
06:33it's a bit crazy.
06:34I mean,
06:35could it hide something?
06:38Well,
06:39it's hard to say.
06:40For now,
06:41it looks like
06:41a massive system
06:42maintained by
06:43gravity,
06:44composed of enormous
06:45clouds of black matter
06:46with some amas
06:47of stars floating around
06:48and almost no stars
06:50at the center.
06:52But the team
06:53has a theory
06:53about what happened
06:54to CDG2
06:56in the past.
06:57They think
06:58that they had
06:59enough material
07:00to form
07:01the stars
07:02but with the time,
07:04these stars
07:04have been
07:05destroyed
07:05by the galaxy
07:06nearby.
07:08And that's how
07:09the galaxy
07:10fantôme
07:11that is
07:11today.
07:12But before
07:13to celebrate
07:13this discovery,
07:15everyone is not
07:16convinced.
07:19Some astronomers
07:20admit
07:20that the
07:21galaxies
07:21probably exist
07:23and recognize
07:24that CDG2
07:25is really
07:26habitable.
07:27But they
07:27are not totally
07:28convinced
07:29by the study.
07:31They think
07:31that the team
07:32must prove
07:32that these
07:33amas
07:34are
07:34well
07:34globules.
07:36After all,
07:38this could be
07:38simply
07:38the galaxies
07:39which seem
07:40proches
07:40from our point of view.
07:43The only way
07:44to be sure,
07:45is to analyze
07:45the spectre
07:46of their
07:47lumière.
07:48In general,
07:48it would be
07:49decomposed
07:50this
07:50in long
07:51length
07:51to identify
07:52the signatures
07:53of the elements,
07:54the stars
07:54and the gas
07:55that it contains.
07:56It would be
07:57exactly
07:58what these
07:59amas
07:59are composed.
08:00Then,
08:05there is a difference
08:05between saying
08:06that a galaxy is
08:07principalmente
08:07sombre
08:08and saying
08:09that it is
08:09totally
08:09sombre.
08:10What the scientists
08:12are looking for
08:12really,
08:13it is a totally
08:14sombre
08:14composed of
08:16black matter.
08:18Unfortunately,
08:19CDG2
08:19is not
08:20even a little
08:21light.
08:23There is also
08:24this
08:25audacious
08:25which
08:27could not exist
08:28at all.
08:29Maybe
08:29there is no
08:30substance
08:31there.
08:31A new study
08:33suggests
08:33that this
08:34bizarre attraction
08:35that we observe
08:36in the galaxy
08:37could simply
08:38signify
08:39that the gravity
08:39can behave differently
08:41when the distances
08:42become immense.
08:44So,
08:44instead of
08:45an universe
08:45full of invisible material
08:47that we can't find,
08:48this idea
08:49suggests
08:49that we can't understand
08:51the rules
08:52of the gravity
08:52in the deep space.
08:54In this theory,
08:56the black matter
08:56has not disappeared.
08:57It is simply
08:58a sign of
08:58that the gravity
08:59could be more strange
09:00than we thought.
09:01So, yes,
09:03CDG2
09:03could be the key
09:04of a bigger mystery
09:06than what we imagined
09:07at the beginning.
09:08It is more
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