The Death of the Sun: The End of All Life on Earth? - SPACE DOCUMENTARY

[00:00:00]Look at this image. A sphere of incandescent gas 1.4 million km in diameter that has been burning for 4.6 billion years without stopping for a single second. The sun, you've been told it still has 5 billion years ahead of it, that you can sleep soundly. But here's what you're told less often. In less than a billion years, 1if of what's left, Earth will probably be uninhabitable.

[00:00:32]The oceans will be gone. Complex life will have ceased to exist on the surface. And this isn't [music] a conspiracy theory. It's what current astrophysical models predict with growing precision with their [music] certainties, their gray areas, and the real questions that still have no answers. Tonight, we're not going to tell you that scientists are lying.

[00:00:57]We're going to do [music] something rarer, give you the full picture with the raw data, the real uncertainties, and what researchers are still debating today. Hang on, because reality is far more [music] fascinating and far more urgent than what you learned in school.

[00:01:18]Let's start with the basics.

[00:01:20]What you learned in biology class is this. The sun is a yellow dwarf star on the main sequence. It has been fusing hydrogen into helium in its core for 4.6 billion years and it has roughly 5 billion years [music] left before it leaves this stable phase.

[00:01:40]Then the classic scenario, it swells into a red giant potentially engulfing Earth's orbit. then contracts [music] into a planetary nebula and ends up as a white dwarf, a stellar corpse the size of Earth, cooling for tens of billions of years.

[00:02:00]This account is correct [music] in its broad strokes, and that's where it stops for most people. Why? Because it's reassuring.

[00:02:09]5 billion years is such an enormous number that it neutralizes any anxiety.

[00:02:16]No human can really grasp it. So we move on. But this standard story contains several important ellipses, not lies, pedagogical omissions. What textbooks oversimplify to the extreme is the sun's evolutionary dynamics on intermediate time scales. Not in five billion years, in 500 million, in 1 billion, in two billion. And there the numbers change radically.

[00:02:50]Another point school skims over. Stellar models are not laws carved in stone.

[00:02:57]They are sophisticated numerical simulations based on equations from plasma physics and thermonuclear physics which have been progressively refined since the 1950s.

[00:03:09]They are extremely robust for the big trends, but they include quantified uncertainties which researchers publish in their papers [music] and which mainstream media never pick up. We're going to face them head on.

[00:03:25]First point, [music] and it's the most critical. The sun is not a static object.

[00:03:32]It shines today with a luminosity about 30% higher than it was at the formation of Earth 4.6 billion years ago. And that luminosity continues to increase progressively and inexurably.

[00:03:48]Why? A simple mechanism. As the sun converts hydrogen into helium, the density of its core increases.

[00:03:57]To maintain hydrostatic equilibrium, that is the balance between radiation pressure outward and gravity inward. The core [music] contracts slightly, its temperature rises and fusion reactions [music] speed up. Result: The emitted energy flux increases.

[00:04:18]Current models, notably those of the standard solar model developed by John Beall and his collaborators [music] and continuously updated, predict an increase in luminosity of about 1% every 100 million years.

[00:04:34]That seems small. It isn't small. A 10% increase in solar luminosity is enough to profoundly alter Earth's energy balance.

[00:04:46]Studies in planetary climate modeling, in particular [music] the work of James Casting at Penn State, published in Icarus as early as 1993 and regularly updated, show that Earth will reach this critical threshold in about 1 to 1.5 billion years. At that point, radiative forcing will become such that the oceans will begin to evaporate at an accelerated rate.

[00:05:14]Water vapor, a powerful greenhouse gas, will itself accelerate warming [music] in an uncontrolled positive feedback loop. The same mechanism that turned Venus [music] into a hellscape at 465° C.

[00:05:31]This phenomenon has a precise name, the moist greenhouse [music] runaway.

[00:05:37]On the horizon of a billion years, complex multisellular organisms will probably be unable to survive on Earth's surface. The only possible organisms would be extreophiles, microbes adapted to extreme conditions, confined to specific niches.

[00:05:57]1 billion years. That's four times less than what you retain from the school version.

[00:06:04]Launched in 2018 by NASA, the Parker Solar Probe is the fastest artificial object ever built by humanity. In 2024, it reached a record speed of 692,000 km hour during its perihelion approach to less than 6.1 million km from the sun, about 8.5 solar radi from the surface.

[00:06:29]What Parker has revealed disrupts existing models on several specific points.

[00:06:36]The first, the solar wind is structured into switchbacks, local reversals of the magnetic field that look like abrupt foldbacks.

[00:06:45]These structures had been theorized, but their frequency and intensity [music] at this proximity surprised the teams.

[00:06:52]Their generation mechanism remains partly debated between two main hypotheses.

[00:06:59]Magnetic reconnection at the surface and disturbances induced by alphane [music] waves.

[00:07:06]The second point more fundamental.

[00:07:09]Parker provided new data on the solar corona heating problem. this outer layer of the sun's [music] atmosphere that reaches more than a million degrees while the surface does not exceed 5,500° C.

[00:07:24]This paradox has lasted for 80 years.

[00:07:28]Parker did not solve the mystery, but its insitu measurements have made it possible to rule [music] out some hypotheses and strengthen others.

[00:07:38]This is not trivial. If we do not fully understand what heats the corona, our models of solar mass loss, crucial for the sun's long-term evolution, remain incomplete.

[00:07:51]These data are not hidden. They are published in Nature, the Astrophysical Journal Science.

[00:07:58]But they require an effort of translation for the general public that most mainstream media do not make.

[00:08:06]The sun follows a magnetic activity cycle of about 11 years, alternating between [music] periods of high and low radiation.

[00:08:15]We are currently in cycle 25, which began in December 2019.

[00:08:21]Contrary to initial model expectations, this cycle is proving more active than anticipated.

[00:08:28]Noah and the solar [music] cycle prediction panel had estimated a moderate maximum, but observations in [music] 2024 show activity clearly higher than projections.

[00:08:40]Historically, between 1645 and 1715, the sun went through a period of very low magnetic activity, the Monder minimum, characterized by a near absence of sunspots.

[00:08:55]This period partially corresponds to the little ice age in Europe, even if direct causality is nuanced. Other factors, volcanic activity, ocean circulation, also played a simultaneous role.

[00:09:11]What is certain, variations in the sun's magnetic activity influenced the flux of cosmic rays reaching Earth, stratospheric [music] chemistry, and marginally the radiative balance.

[00:09:25]These effects are small compared with today's anthropogenic forcing on human time scales, but they are real and documented.

[00:09:34]The Carrington event of 1859 remains the most violent space weather event [music] ever recorded.

[00:09:42]In July 2012, a coronal [music] mass ejection of comparable intensity narrowly missed Earth by 9 days of orbital offset.

[00:09:53]A 2013 study published [music] in space weather by Daniel Baker of the University of Colorado [music] estimated the potential damage to global electrical infrastructures [music] at more than $2 trillion.

[00:10:07]This risk is real documented [music] and underestimated in public policy.

[00:10:14]The standard solar model abbreviated SSM [music] is the global reference for describing the sun's internal structure and evolution.

[00:10:25]It incorporates the equations of plasma physics, thermodynamics, nuclear physics, and radiative opacities.

[00:10:34]Its predictions have been validated remarkably well by heliocismology, the study of the sun's acoustic oscillations, which function like an ultrasound of its interior.

[00:10:46]But the SSM went through a serious crisis in the early 2000s called the solar abundances problem.

[00:10:56]More precise spectroscopic measurements of the composition of the solar atmosphere, notably the work of Aspund and collaborators in 2004 to 2009, produced metal abundances, oxygen, carbon, neon, silicon significantly lower than previous values.

[00:11:16]As a result, the new chemical compositions injected into the SSM produce a helioismic profile incompatible with observations.

[00:11:28]This disagreement persists.

[00:11:31]It does not invalidate the entire model.

[00:11:34]The major predictions remain robust, but it signals that some ingredient of physics is still missing from our description of the solar interior.

[00:11:43]Several hypotheses are being explored.

[00:11:46]interactions between the core and the radiative zone, element diffusion, the role of neon.

[00:11:54]No definitive [music] consensus to date.

[00:11:57]This is a perfect example of what we are talking about in this video. Not a cover up, but a genuine open problem published, debated, and almost never [music] mentioned in mainstream media.

[00:12:11]The sun is not unique. There are hundreds of so-called solar analog stars. Stars with mass and composition similar to the suns at different stages of their lives. They serve as natural laboratories for testing models and the observations are not always perfectly consistent with the predictions. A notable case, the star 18 Scorpi, often cited as the closest twin of the sun, shows magnetic activity and rotation that are slightly different from what models predict [music] for its age. This is not alarming. Small differences in initial mass, chemical composition, and initial rotation produce [music] distinct evolutionary tracks. But it illustrates a fundamental limitation.

[00:12:58]Our knowledge [music] of stellar evolution rests on statistical averages and parametric models. For an individual star, the uncertainty margins on the precise timing of evolutionary transitions [music] can reach several hundred million years. Put differently, we know that the sun will leave the main sequence [music] in about 5 billion years. The uncertainty on that estimate is probably on the order of 500 million to 1 billion years. That's not huge.

[00:13:28]It's an accuracy of plus or minus 10 [music] to 20% over a gigantic time scale. But it's a nuance that popular discourse systematically erases by presenting [music] 5 billion years as an exact figure. Here is the central mechanism [music] that few popular explanations describe precisely. In the sun's core, thermonuclear fusion converts four hydrogen nuclei protons into one helium 4 nucleus, releasing energy in the [music] form of gammaray photons and nutrinos.

[00:14:03]The helium produced accumulates [music] in the core because it cannot yet fuse.

[00:14:08]The sun's current central temperature [music] about 15 million° is insufficient to trigger helium fusion which requires about 100 [music] million°.

[00:14:19]This gradual buildup of helium has [music] two coupled effects. First, it locally reduces the fraction of hydrogen available as fuel. [music] The core becomes depleted of fuel. Second, the increase in core density [music] leads to its gradual contraction and a rise in its temperature which accelerates the reactions increases luminosity and gradually inflates the outer layers.

[00:14:46]This process is continuous, inexurable and translates into the slow increase in luminosity mentioned in part two. There is no [music] sudden alarm signal to detect. It is a gradual drift which makes it both less spectacular for the media and more genuinely worrying over the long term. One of the most important advances for validating our models of the solar core, [music] the detection of solar neutrinos.

[00:15:14]Nutrinos are produced directly in [music] the fusion reactions of the core. They pass through the sun with virtually no interaction and reach Earth in about 8 minutes. For decades, earth-based detectors [music] measured a flux of solar nutrinos lower by a factor of three than predictions. The solar neutrino [music] problem, a major source of concern about the validity of the SSM.

[00:15:39]The resolution came in 2001 to [music] 2002 with the SN O, Sudbury Nutrino Observatory, experiments in Canada, and Super Kameio in [music] Japan. The solar neutrinos hadn't disappeared. they had transformed. The phenomenon of nutrino oscillations [music] implying that nutrinos have mass contrary to the predictions of the standard model explained the apparent deficit. This discovery earned the 2015 Nobel Prize in physics for Taki Kaja and [music] Arthur Macdonald.

[00:16:14]Result: The SSM is validated. The solar core works as [music] expected. Our fusion models are correct. It's a remarkable scientific victory and a fine example of how science corrects and [music] strengthens itself. There is no conspiracy. There is something more benal and more structural. Popular science communication [music] works through compression. A high school textbook has 400 pages to cover the entire biology and earth science [music] curriculum. A press article has 500 words. An introductory YouTube video about the solar system [music] has 8 minutes. In these formats, nuance mechanically disappears, [music] not out of ill will, but because of constraints of space and attention. What remains is the simplest narrative [music] skeleton. The sun has 5 billion years ahead of it. Period. The real question [music] in how long does Earth become uninhabitable is much more complex. depends on multiple parameters and has no one-s sentence answer.

[00:17:22]Researchers themselves when addressing the general public tend to simplify so as not to lose their audience. That is not deception. It is an adaptation to the [music] context. But the result is a population informed at 30% about a topic that deserves 100%.

[00:17:42]There is a real economic and political context [music] around the sun.

[00:17:47]Solar photovoltaic energy is today the fastest growing source of renewable electricity.

[00:17:53]In 2023, according to the International Energy Agency, global installed solar capacity exceeded [music] 1,500 gawatt and projections foresee it becoming the world's leading [music] source of electricity before 2030.

[00:18:09]In this context, public communication [music] about signals of the sun's evolution is potentially sensitive. Not because the [music] scientific facts undermine solar energy, they don't. But because any [music] poorly calibrated headline can create unnecessary public confusion.

[00:18:28]This [music] is a real case of tension between precise scientific communication and the management of public perceptions.

[00:18:35]Researchers are aware of this. Some see it as a legitimate reason to temper their communication.

[00:18:42]Others see it as a problematic paternalism.

[00:18:45]This debate exists within the scientific community. It is rarely made visible to the general public. Journals like the Astrophysical Journal, Astronomy and Astrophysics, Nature Astronomy regularly publish work that nuances or complicates dominant narratives about solar evolution. Conferences of the American Astronomical [music] Society or the European Astronomical Society address open questions about angular momentum transport in the sun. About potential instabilities in the transition zone between the radiative core and the convective [music] zone, the tacoline about couplings between magnetic activity and structural evolution. These discussions are not secret. They are accessible to anyone who wants to read them, but they are written for peers with technical vocabulary, information density, and a level of mathematical prerequisites that make them inaccessible without translation.

[00:19:46]That's where popularization has a crucial role. Not to simplify to the point of distortion, but to translate without [music] betraying.

[00:19:55]That is what this video is trying to do.

[00:19:58]This distinction is [music] fundamental and deserves to be stated clearly.

[00:20:02]Saying scientists are hiding something from you implies a deliberate intent to conceal.

[00:20:10]Saying popularization leaves out certain important nuances describes a [music] structural phenomenon well documented in the sociology of science. There are things science still does not know about the sun. the exact physics of coronal heating, [music] the details of magnetic instabilities, the precise parameters for the timing of the red giant transition.

[00:20:33]These gray areas are published, [music] discussed, funded by agencies like ESA and NASA. They are not hidden. They are simply difficult to communicate without losing precision. The real omission is not within the scientific community. It is in the transmission chain between researchers [music] and the general public. A chain in which each link, journalists, textbook publishers, [music] popularizers, optimizes for clarity at the expense [music] of fidelity.

[00:21:05]Let's recap what we've covered. The sun indeed has [music] approximately 5 billion years ahead of it before leaving the main sequence. That figure is robust, but it's not the right question.

[00:21:19]The real question is how long until Earth becomes uninhabitable?

[00:21:24]And there the answer is very [music] different. Probably less than a billion years for complex surface life because of the gradual and inexurable increase in [music] solar luminosity.

[00:21:35]The solar abundance problem shows that one ingredient is still missing in our description of the solar interior. Data from Parker Solar Probe reveal a complexity in coronal dynamics that models do not fully capture. Sun analog stars show [music] that individual evolutionary trajectories carry uncertainties of several hundred million years. None of these elements is hidden.

[00:22:00]All are published, accessible, discussed by [music] researchers. What's missing is the translation. And that is exactly what you've just listened to. The final message is this. Science advances by revising [music] its certainties. What makes the scientific approach strong is precisely that it publishes its uncertainties, corrects its errors, refineses its models as data [music] improve. This is not a weakness. It is the very definition of honest knowledge.

[00:22:33]So [music] an open question for you in the comments. If you knew with certainty that Earth will become uninhabitable in 800 million years, would that change anything about the way you think about the future of the human species? Does it strengthen the idea of space expansion?

[00:22:50]Or is that a time scale so far beyond reach that it changes nothing?

[00:23:09][music] The nebula of the universe take on shapes very similar to those of our terrestrial creatures.

[00:23:21]When we look up at the sky on a clear night, we can recognize constellations with familiar patterns. And we [music] can even guess at them since they've been lulling mankind to sleep since the dawn of time.

[00:23:36]The universe seems both familiar and unknown.

[00:23:41]Galaxies, [music] nebula, and other astronomical phenomena have long been given animal names.

[00:23:49]It's human nature to see the familiar in the unfamiliar.

[00:23:55]A nebula is an interstellar cloud of gas [music] and dust.

[00:23:59]Nebula are one of the ingredients of the universe along with stars, planets, and galaxies. [music] They play a fundamental role in the history [music] of the cosmos as it is within them that new stars are formed.

[00:24:20]Nebula play a vital role in the evolution of galaxies.

[00:24:25]By understanding [music] how nebula form and evolve, we can better understand the overall evolution of galaxies.

[00:24:37]Nebula [music] contain chemical elements that are essential building blocks for planets, stars, and life itself.

[00:24:48]They provide crucial information about the chemistry of the universe.

[00:24:54]By collecting data on nebula and the regions in which new stars are formed, scientists are gathering elements for reconstructing [music] the environment that existed in the early universe.

[00:25:10]The more distant the nebula [music] studied, the more the elements gathered helped to understand the first stages [music] of cosmic evolution.

[00:25:23]Exceptional and unique astrophysical phenomena can occur in some of these nebula.

[00:25:30]Observing them helps enrich our understanding [music] of the universe.

[00:25:35]There are several types of nebula. The [music] most common are emission nebula, reflection nebula, and obscure nebula.

[00:25:50]Emission nebula are bright. This is because their atoms are excited by ultraviolet radiation emitted by nearby young stars.

[00:26:01]The atoms in turn become a source of radiation.

[00:26:06]Reflection nebula [music] on the other hand emit no radiation themselves.

[00:26:12]They reflect the luminosity of the nearest stars, even reproducing their color.

[00:26:19]Dark nebula, on the other hand, are dense concentrations of lightabsorbing dust.

[00:26:26]They're only visible when there's a light source behind them from [music] which they can be detached.

[00:26:33]They're easy to observe and frequently even visible to the naked eye.

[00:26:39]But how were nebula discovered? and how do they form?

[00:26:46]Nebula are made up of gas [music] and dust. The gas is partly of primordial origin. It formed [music] early in the history of the universe when hydrogen and helium, the building blocks of the first stars, appeared.

[00:27:04]The heavier elements are more recent.

[00:27:07]They are formed inside stars at the end of their existence, then released into the interstellar medium.

[00:27:15]The dust that makes up nebula is a mixture of carbon at various levels of aggregation and silicates along with trace amounts of other organic matter.

[00:27:32]The gas is essentially hydrogen.

[00:27:35]Nebula are regions where the [music] interstellar medium has become denser due to gravity.

[00:27:42]This has led to the formation of clouds that attract the surrounding matter once their mass and dimension have reached a sufficient size.

[00:27:52]These clouds can become visible when newly formed stars within them excite the atoms making them luminous.

[00:28:06]Until 1780, [music] the focus of astronomers attention was on the stars.

[00:28:12]Scientists attention slowly shifted in the direction of nebula when in 1781 astronomer William Hershel discovered Uranus.

[00:28:26]King George III of England awarded him a royal pension enabling him to invest in the construction of a new more powerful telescope with which he could now study double stars.

[00:28:40]In all, the astronomer built over [music] 400 telescopes.

[00:28:45]One of these remained the world's largest telescope for almost 50 years.

[00:28:51]This gigantic device could be operated by hand.

[00:28:56]With it, Hershel described and cataloged deep sky objects.

[00:29:01]In 1786, he published the catalog of a thousand new nebula and star clusters.

[00:29:09]He already distinguished between nebula and star [music] clusters.

[00:29:14]Over a period of 20 years, he listed more than 2500 of them [music] and in 1811 completed his catalog with a list of 52 extremely duse nebulosities which turned out to be integrated flow nebula. [music] In all, William Hershel published four cataloges describing over 5,000 [music] deep sky objects.

[00:29:42]Other astronomers such as John Drier followed in his footsteps.

[00:29:48]In 1888, Drier published an NGC catalog describing over 7,800 celestial objects.

[00:29:57]Today, this catalog includes over [music] 14,600 objects.

[00:30:03]The concept of the nebula, however, belongs to William Herschel.

[00:30:09]It was Hershel himself who identified the different types of nebula.

[00:30:15]The first planetary nebula discovered was the Laalter Nebula, also known as the Dumbbell Nebula and referenced M27.

[00:30:27]Charles Messier recorded it in his catalog of duse objects, but the term planetary was proposed by William Herschel in [music] 1785.

[00:30:39]In 1927, American astronomer Edward Emerson Bernard listed 349 obscure nebula.

[00:30:50]Among the best known are the Horse Head Nebula referenced B33 and the Snake Head Nebula reference B72.

[00:31:01]By this time, a number of nebula had come to light, and scientists realized that this was an obscure world whose influence they were still unaware of.

[00:31:14]Everything was yet [music] to be discovered.

[00:31:18]Edwin Hubble's work in 1924 [music] made it possible to distinguish nebula from galaxies.

[00:31:26]Although both contain gas and dust on a very different scale and in very different concentrations, their shape, dynamics, and size are very different.

[00:31:38]Nevertheless, in a small observation instrument, their appearance is more or less the same.

[00:31:49]Nebula are warmly colored when photographed. They appear as a luminous region rich in ionized gas ejected from stars or unused during their formation.

[00:32:04]The gas and dust present in the interstellar medium can materialize when excited by stellar radiation or backlit.

[00:32:14]This is how nebula are classified.

[00:32:19][music] Emitting nebula are gaseous formations that produce their own luminescence.

[00:32:31]They absorb light from a nearby hot star and emitted at lower energies in a variety of colors.

[00:32:39]They are said to be bright as opposed to reflective nebula which simply reflect the light of nearby stars.

[00:32:48]Also known as IC277, the Seagull Nebula is a huge emission nebula seen from Earth. It is as large as four times the diameter of the full moon.

[00:33:03]The reddish glow of atomic hydrogen dominates dotted with luminous young stars that stretched the length of the nebula.

[00:33:13]The name Seagull Nebula comes from its strong resemblance to the silhouette of a bird.

[00:33:22]This cosmic cloud is an ideal place for the formation of new stars.

[00:33:28]The Seagull Nebula is located 3,800 light years from Earth and has a diameter of around 100 light years.

[00:33:38]It contains several open clusters including NGC 2343, [music] NGC 2335, Cinder 465 and Cinder 466.

[00:33:54]This nebula is difficult to observe even under ideal viewing conditions as its apparent magnitude is + 10. [music] The large number of stars in the nebula makes it impossible to see.

[00:34:12]The wings are almost impossible to see unlike the head referenced NGC 2327 which contains fewer stars.

[00:34:25][music] This is a region of compact emission in which a massive star is enclosed.

[00:34:33]There are several categories of emission nebula.

[00:34:50]Hi regions.

[00:34:53]These are regions of [music] intense activity in which stars form. The Orion constellation is home to one of the most famous examples, the Orion Nebula or M42.

[00:35:07]Its proximity to the Earth makes it one of the best known and most studied nebula [music] by scientists.

[00:35:15]Within the Orion Nebula, numerous stars and even planetary discs form.

[00:35:22]The nebula [music] glows with fluoresence.

[00:35:25]Excited by the ultraviolet radiation of bright stars, gas atoms emit light.

[00:35:32]The color emitted depends on the type of atoms.

[00:35:36]Hydrogen, which is clearly in the majority in nebula, emits predominantly red light, as does sulfur.

[00:35:46]Oxygen, on the other hand, emits green.

[00:35:49]Although our eyes are particularly poor at distinguishing colors at night, the Great Orion Nebula [music] is an exception to this rule.

[00:36:00]Its contrasts allow observers to easily distinguish the nebula's colors.

[00:36:06]At first glance, through binoculars, the Orion Nebula appears as a small cloud among the stars of Orion Sword.

[00:36:16]When viewed through a 60 to 80 millimeter telescope, its central region reveals a greenish hue.

[00:36:24]The jade hue intensifies when viewed through a more powerful telescope.

[00:36:29]As for the red, it remains indistinguishable as our eyes are blind to this color at night.

[00:36:37]The accumulation of gas [music] over tens of thousands of billions of kilome gives the Orion Nebula a dense appearance. But this is only an illusion.

[00:36:50]The Orion Nebula has been known since ancient times.

[00:36:54]Astronomers have been observing it through telescopes for almost four centuries.

[00:37:00]as if petrified since the dawn of time.

[00:37:04]Nothing in this immense interstellar cloud has ever moved.

[00:37:09]But it's only the nebula's enormous distance, almost 1500 light years, that makes us from Earth insensitive [music] to its violent disturbances.

[00:37:21]This nebula is one of the largest in our Milky Way.

[00:37:26]It extends over a diameter of 24 light years.

[00:37:30]Its mass is 2,000 times greater than that of our sun.

[00:37:36]And yet, for all its immensity, it remains almost empty.

[00:37:41]Barely a few hundred atoms are present per cubic cm.

[00:37:46]The Orion Nebula is illuminated by four super giant stars forming an asterism that identifies the Orion trapezoid.

[00:37:57]Each of these stars shines 100,000 times brighter than the [music] sun.

[00:38:03]Their powerful ultraviolet radiation heats the gas, making it luminescent.

[00:38:10]As a result, the hydrogen clouds take on a flamingo pink hue while the oxygen veils emit green radiation. [music] These four super giant stars don't just make light. They provoke a [music] powerful stellar wind blowing at over 100,000 km hour [music] or 62,000 mph.

[00:38:36]Space is violently swept away carrying clouds like storm clouds. [music] Compressed gas becomes denser and gravitation kicks in.

[00:38:48]Small globules of gas and dust form.

[00:38:52]They measure a few tens of billions of kilometers and resemble eggs that flatten on themselves under their own weight.

[00:39:01]As they [music] collapse, the gas and dust that make them up are set into rotation.

[00:39:08]At the heart of these stars, [music] a star is born.

[00:39:14]Having attracted matter to itself, it slowly pulls it out, blowing it around and beginning to shine.

[00:39:22]The four stars of Orion's trapezoid were born in this way around 200,000 years ago.

[00:39:31]By blowing the gas that gave them birth around them, they seed space and trigger the birth of new stars.

[00:39:39]The phenomenon of emission makes it possible to study nebula using selective filters that exclude certain lines from the spectrum.

[00:39:57][music] Planetary nebula are brightly colored and highly structured. They are associated with the death of low mass stars like the sun.

[00:40:09]Planetary nebula are produced by the slow expulsion of gas from the surface layers of a stars atmosphere at the end of its life.

[00:40:21]All stars of mass equal to or less than the sun end their lives by scattering the upper layers of their atmosphere into the surrounding medium.

[00:40:34]The material takes on a relatively regular disc shape reminiscent of a planet.

[00:40:43]In fact, at the time of William Hershel's first observations, he observed the small star that remained visible at the center of the nebula surrounded by a pale disc that gave the false impression that a planet was being born.

[00:41:01]Stars of greater mass also produce injections when they die, but these are much more brutal.

[00:41:09]The result is a supernova or SNR for short.

[00:41:14]Although planetary nebula and SNRs can sometimes be confused, there are many differences between them.

[00:41:24]Many [music] planetary nebula are easily accessible to professional and amateur astronomers from Earth.

[00:41:31]These include the LRA Nebula M57, the Dumbbell Nebula M27, the Roset Nebula NGC2237-9, the Owl Nebula M97, [music] and the Helix Nebula NGC7293.

[00:41:53]The discovery of this type [music] of nebula is well within the reach of amateur astronomers.

[00:42:01]139 candidate planetary [music] nebula have been proposed and some 20 have been confirmed.

[00:42:09]The LRA Nebula is the most representative of all planetary nebula.

[00:42:13][music] This star appears as a magnificent corona surrounding the star as it dies out.

[00:42:22]The stars core is completely exposed, still glowing and illuminating the gas around it.

[00:42:29]The white dwarf at the center of the LRA Nebula reaches 100,000° C or 180,000° [music] F.

[00:42:40]By comparison, the sun reaches 5,500° C.

[00:42:46]It has much more extensive [music] extensions than the main ring. Certainly the result of material ejected by the star before the nebula [music] itself was formed.

[00:43:01]Planetary nebula [music] provide information not only on the stars constitution but also on the date on [music] which it expelled matter by calculating the expansion velocity of the gases.

[00:43:16]The impressive dynamism of planetary nebula is reflected in some cases by gas moving at speeds of up to 5,000 km/s or 3,100 m/s. [music] This creates exceptional shock waves and turbulent zones.

[00:43:37]Once the star has ejected up to 35% of its envelope, it ends its life as a dwarf star.

[00:43:51]One of the closest planetary nebula to Earth is the Dumbbell M27 Nebula.

[00:43:58]It lies at a distance of around 650 light years and exploded around 12,700 years ago.

[00:44:08]The Dumbbell Nebula was the first planetary nebula to be discovered. It is characterized by an original shape with two luminous loes giving it the appearance of a bell clapper, dumbbell or apple core.

[00:44:24]This structure is known as bipolar and is found in other planetary [music] nebula but never so pronounced.

[00:44:35]This characteristically asymmetrical shape [music] is thought to have developed shortly before the stars death as the dying star blew its atmosphere in two different directions.

[00:44:50][music] M27 is one of the largest planetary nebula in the sky.

[00:44:57]Thanks to its age, it has expanded considerably.

[00:45:02]Although invisible to the naked eye, the dumbbell Nebula is easily identifiable through binoculars. [music] You can make out its dumbbell shape.

[00:45:14]Most planetary nebula contain only a single star, but a few contain a binary system.

[00:45:22]Typically, this system consists of a very hot blue O-class star and a cooler Aclass companion.

[00:45:32]The pair is rarely visible as they are tightly packed together.

[00:45:37]The blue star emits mainly in the UV spectrum while its companion emits in the visible spectrum making it impossible to observe the star at the source of the excitation. [music] Examples of double core planetary nebula include NGC 3132, NGC1514, and the Boomerang Nebula.

[00:46:07]The latter is currently the coldest place in the universe, located 5,000 lightyear from Earth in the constellation Centauri. [music] Its temperature is -272° C or -69° F.

[00:46:28]It's colder than the cosmic microwave background and the only known natural object of its kind.

[00:46:36]But why has it reached such a [music] cold temperature?

[00:46:40]At the heart of this nebula lies a star four times more massive than the sun.

[00:46:47]But this star hides a secret.

[00:46:50]3,500 years [music] ago, it was the result of the fusion of two other stars.

[00:46:56]Without this [music] fusion, the gas in the nebula would not reach such extreme temperatures today.

[00:47:03]In fact, the Boomerang Nebula's low temperature is due to its gas being expelled in very large quantities and at extremely high velocities.

[00:47:19]A team of astronomers has taken into account the envelope's expansion velocity, which is 150 km/s or 90 m/s, 10 times greater than that usually [music] expelled by a red giant.

[00:47:37]Scientists have shown that the only way to produce such a quantity of gas at such a speed would be to use energy from the interaction of two stars.

[00:47:48]A few thousand years ago, the red giant would have trapped a companion star in its envelope.

[00:47:55]The interaction of the two stars produced [music] an impetuous ejection of matter.

[00:48:01]The nebula is now shaped like an hourglass, 20,000 astronomical units long. This peculiar shape is due to the jet produced by the central star which pushes back cold gas locally.

[00:48:21]>> [music] >> Another planetary nebula containing a binary system that commands admiration for its marvelous shape is the PN M2-9 Nebula. Nicknamed the Butterfly Nebula or Twin Jet Nebula.

[00:48:41]This nebula is characterized by a surprising complexity that takes the form [music] of two wings around a heart.

[00:48:50]The core is made up of two old stars that change appearance and state to become white dwarfs.

[00:48:58]Their total disappearance will only occur in a few billion years time.

[00:49:05]In the meantime, they never cease to amaze with their sumptuous designs.

[00:49:11]Located some 4,000 lighty years from [music] Earth in the constellation ofus, the butterfly nebula owes its wings to two stars of equivalent mass that emit two great [music] expanses of gas.

[00:49:27]The smaller of the two has a mass between [music] 0.6 and 1 times the mass of the sun [music] and is already a white dwarf.

[00:49:39]Its companion is estimated to have [music] between 1 and 1.4 times the mass of the sun.

[00:49:47]It has already released [music] its outer layers.

[00:49:51]The expansion of the gas that forms these fascinating butterfly [music] wings is thought to have begun around 1,200 years ago.

[00:50:01]The nebula contains [music] inside a shell of gas two jets expelling matter at a speed of over 1 million kmh or more than 620,000 [music] mph.

[00:50:16]Scientists also recently discovered that a disc of [music] gas 15 times larger than Pluto's orbit surrounds the two stars.

[00:50:26]It [music] turns out that the star, which has already taken on the form of a white dwarf, is in the process [music] of stripping its fading companion.

[00:50:37]NGC1514, also known as the Crystal Ball Nebula, [music] is a planetary nebula located in the constellation Taurus, some 800 light years from Earth.

[00:50:51]It was [music] discovered by astronomer William Herschel in 1790.

[00:50:57]The nebula [music] is characterized by its ring pair shape.

[00:51:01]This double structure is explained by the presence of a [music] binary system of aging stars at the nebula's center.

[00:51:10]In concrete terms, the nebula appears as a double shell with a very bright envelope in the [music] center and a thinner one on the outside.

[00:51:21]At the center of the nebula, the [music] two stars revolve around a common center of gravity with a period of 4 to9 days.

[00:51:30][music] NGC6302, the Insect Nebula or M2-9, also known as the Butterfly Nebula or Caldwell 69, is a bipolar planetary nebula with one of the most complex structures ever observed in a planetary nebula.

[00:51:57]It lies around 3,500 light years from Earth in the [music] constellation Scorpius.

[00:52:05]As they age, stars can take on structures sometimes similar to flowers or insects.

[00:52:12]This is the [music] case of the insect nebula, which has a wingspan of 3 light years.

[00:52:20]Its central star at the end of its life has a temperature of over 200,000° C or 360,000° [music] F, suggesting that it was originally very large.

[00:52:34]The white dwarf's mass is around 0.64 [music] times that of the sun.

[00:52:41]It is surrounded by a dense disc of gas and dust.

[00:52:45]It is the [music] same disc that gives the nebula its hourglass-like bipolar structure.

[00:52:52]The insect [music] nebula consists of two primary loes. A wide dark band runs through the middle of the nebula, plunging the central star into darkness at every length.

[00:53:07]This band has an exceptional chemical composition.

[00:53:11]Scientists have detected ice crystals, quartz, and numerous silicates.

[00:53:17]The characteristic [music] feature of the nebula is that it is composed of both oxygenrich and carbonrich minerals.

[00:53:26]In most cases, these minerals do not coexist.

[00:53:32]Stars are basically rich in one or the other and the transition from the first state to the second occurs as the star ages. [music] This suggests that the hydrocarbon molecules in the insect nebula were formed in an oxygenrich environment.

[00:53:51]The insect nebula is prone to strange projections of matter in [music] the part representing its wings.

[00:53:59]These jets are projected at more than a thousand km/s and asymmetrically.

[00:54:06]They intersect and form [music] disordered structures.

[00:54:11]Some researchers have speculated [music] that these ejections could be due to the central white dwarf merging with another star.

[00:54:20]However, in the absence of visibility at the center of the nebula, this hypothesis remains unconfirmed.

[00:54:29]>> [music] [music] >> A supernova defines the set of phenomena resulting from the gigantic [music] explosion of a star at the end of its life.

[00:54:45]For a time, the supernova [music] can shine brighter than an entire galaxy of billions of stars.

[00:54:53]From Earth, a supernova looks like a new star. when in fact it's the sign of a star's demise.

[00:55:01]A core collapse supernova is characterized by a massive star that stops producing energy [music] from nuclear fusion in its core.

[00:55:11]It then collapses under its own gravity.

[00:55:15][music] A thermonuclear supernova occurs when a white dwarf has stored enough material for a companion star to reach a critical mass, triggering a [music] thermonuclear explosion.

[00:55:32]The exploding star is totally destroyed [music] while the companion star may in some cases survive.

[00:55:42]When a supernova explodes, an enormous quantity of ejecta is expelled of the order of several solar masses at speeds of up to 10,000 km/s or 18,000 m/s.

[00:55:58]The shock front resulting from the rapid expansion of this material forms the visible part of the afterglow.

[00:56:08]Supernova remnants are defined by the structure produced by the expanding supernova ejecta.

[00:56:15]Many slags retain a regular shape for a long time depending on whether they have an internal energy source such as a central pulsar or not.

[00:56:34]To better understand supernova afterglows, let's look up to the sky.

[00:56:40]Against the stellar backdrop of the Milky Way, a pretty gray blob appears through a small [music] 60 mm telescope.

[00:56:49]With a 100 to 200 mm telescope, we can see a well-defined Sshape.

[00:56:57]With an even more powerful instrument, [music] it's possible to make out gaseous filaments floating in the sky.

[00:57:05]This is one of the best known and most studied examples of supernova afterglow.

[00:57:11]Messier 1 or the Crab Nebula some [music] 6,300 light years from Earth.

[00:57:18]This nebula reminds us that a supernova exploded at this very spot in the year 1054 [music] in the constellation Taurus.

[00:57:30]In July 1054, Chinese astronomers spotted a new star [music] in the Taurus constellation.

[00:57:38]They called it a guest star.

[00:57:41]However, its brilliance intensified to the point where it surpassed that of Venus.

[00:57:48]It remained visible for 3 weeks in daylight with a magnitude of between minus3 and minus5 and appeared for 2 years at night.

[00:58:00]Around 7 centuries later in 1758, the astronomer and famous comet hunter Charles Messier while searching the sky for Haley's comet spotted a small nebula in the constellation Taurus.

[00:58:17]He gave it the number one.

[00:58:20]It [music] wasn't until 1928 that Edwin Hubble made the connection between the famous guest star [music] of 1054 and this Messier 1 Nebula, nicknamed the Crab Nebula in reference to the expanding gas released by [music] the supernova.

[00:58:39]It continues to grow at a speed of,500 km/s or 930 [music] m/s.

[00:58:48]The debris forming the nebula is made up of [music] ionized helium and hydrogen and has a temperature in excess of 10,000° C or 18,000° F.

[00:59:02]It will dilute in the cosmos over the coming millennia.

[00:59:10]The Crab Nebula has a pulsar at its center called the Crab Pulsar.

[00:59:16]It rotates [music] about 30 times per second.

[00:59:20]This pulsar emits 200,000 times more energy than the sun, making it the most energetic pulsar known.

[00:59:30]Its diameter is estimated at 30 km or 18 mi.

[00:59:35]It is responsible for the central illumination of the nebula.

[00:59:40]The nebula lies in the immediate vicinity of the ecliptic plane making it an interesting source of radiation for studying other celestial bodies.

[00:59:52]By observing its radio waves or x-rays, it is possible to measure and study other nearby objects.

[01:00:03]>> [music] >> Wolf riot bubbles are located around wolf riot stars.

[01:00:13]These are defined as hot stars with masses tens of times that of the sun.

[01:00:19]They are characterized by the fact that during a relatively brief phase following the main sequence, they eject the matter around their core [music] in the form of very violent stellar winds.

[01:00:33]The core is then exposed and explodes into a supernova.

[01:00:38][music] Wolf riot bubbles are particularly active, emitting huge quantities of gas as a result of thermonuclear reactions in their cores.

[01:00:53]The two most famous of these [music] are the Crescent Nebula NGC688 and Thor's [music] helmet nebula NGC 2359.

[01:01:06]The Crescent Nebula NGC6888 is located [music] in the constellation Signis, some 5,000 lighty years from Earth.

[01:01:16]This region is particularly renowned for its wealth of nebula.

[01:01:21]The Wolf Riot star WR136 at its center generates violent [music] stellar winds that push the ejected matter outwards.

[01:01:32]This cosmic bubble, some 25 light years across paints a splendid picture of the nebula through telescopes.

[01:01:44]The structures of the crescent nebula are the [music] result of the interaction between the strong wind and matter ejected in the past.

[01:01:54]This star [music] is nearing the end of its life and is expected to explode into a supernova.

[01:02:06]>> [music] >> Thor's helmet nebula NGC2359 is a nebula [music] in the big dog constellation around 15,000 light years from the solar system. [music] It has the peculiar shape of a bubble blown by a massive star with complex filaments.

[01:02:27]The Wolf Riot WR7 star at its center is extremely hot.

[01:02:34]The nebula's emerald green color is the result of strong emissions from the oxygen atoms in the cloud. [music] [music] Reflection nebula are dust clouds that reflect the light of one or more nearby stars.

[01:02:57]>> [music] >> These stars are bright enough to make the dust visible but not hot enough to ionize the gas.

[01:03:05]Reflection nebula are hot spots for star formation.

[01:03:10]The best known and most studied reflection nebula is that surrounding the Pleiades cluster also known as M45.

[01:03:20]The Plyades cluster is a celestial figure known since at least Neolithic times.

[01:03:27]Its appearance in the morning sky heralded harvest time. Although only a small number of stars are visible to the naked eye, this cluster [music] is extremely rich, containing several thousand in all. The Plleades cluster [music] is around 100 million years old and astronomers estimate that it will disperse into the Milky Way [music] within 200 to 300 million years due to its low compactness.

[01:03:57]The blue nebula that surrounds this [music] cluster is the beauty of the photographs.

[01:04:07]Emission and reflection nebula form the group of diffuse nebula [music] distinguished by their luminous emission.

[01:04:15]On the other hand, [music] there are dark nebula.

[01:04:19]The latter are regions in which dust from the interstellar medium concentrates in immense clouds that appear in starless [music] regions.

[01:04:29]They are visible when they obscure part of an emitting or reflecting nebula.

[01:04:35]Ever since [music] human beings decided to take an interest in the sky, they have been able to observe dark spots in regions of high stellar density that appear to be devoid of stars.

[01:04:48]They have put forward two [music] hypotheses.

[01:04:51]Either these dark zones correspond to the distribution of stars or they represent dark masses appearing as opaque [music] screens.

[01:05:02]The first view was quickly discarded after the study of the celestial distribution of objects since it is unlikely [music] that immense starless pipes exist over lengths of several thousand parexs.

[01:05:15][music] So it's not surprising that there are superpositions of dark clouds.

[01:05:22]Many known nebulous objects show absorption marks in the form of small black globules or thin opaque [music] filaments.

[01:05:32]The density of these dark nebula prevents the passage of light.

[01:05:38]The Milky Way has been studied from top to bottom since the invention of the telescope.

[01:05:44]This has revealed some 200 regions in the sky that appear to be devoid of stars.

[01:05:51]In reality, they contain dark nebula with [music] stars unable to illuminate them.

[01:05:58]The material is thus condensed and opaque to radiation, positioning itself in front of brightly lit regions of [music] the Milky Way.

[01:06:09]To study these dark nebula, you need to get as far [music] away as possible from pollution and artificial light.

[01:06:17]within them. A tiny fraction of the incident light crosses the matter barrier formed by the clouds.

[01:06:24]This makes them veritable radiation traps.

[01:06:29]Astronomers have therefore used derivative techniques such as infrared or radio to observe them.

[01:06:36][music] These dark clouds are neither too thick nor too dense. Infrared techniques are able to penetrate them and observe the objects behind them.

[01:06:47]Dark nebula are among the coldest and largest [music] bodies in our galaxy.

[01:06:53]They are made up of molecular hydrogen and a variety of dusts whose grains, a mixture of silicut, graphite, ice, and various ferrris metals provide sufficient opacity.

[01:07:08]Nebula can also be distinguished by their thickness.

[01:07:12]The largest of them can contain up to 100 solar masses of dust.

[01:07:24]One of the best examples of this type of nebula is the charcoal bag.

[01:07:29]This large dark nebula occupies an area on the celestial vault equivalent to some 30 full moons.

[01:07:38]It can be found 600 light years away in the southern cross [music] constellation in front of luminous sections of the Milky Way.

[01:07:48]Spanish explorer Vicente Janes Penzon first spotted this [music] dark spot in 1499.

[01:07:57]He was the navigator and commander of Lan Ninia, one of the three ships that first landed in America under the command of Christopher Columbus.

[01:08:07]The nebula was nicknamed Mellin's dark cloud because of its opacity and in comparison with the two bright melenic clouds.

[01:08:18]Seen with a naked eye from the southern hemisphere, the charcoal bag can be spotted lurking against the stars of the southern cross.

[01:08:28]With binoculars, it's easy to spot thanks to its [music] irregular contours.

[01:08:34]This coal black nebula is so vast that it doesn't fit entirely within the field of a telescope.

[01:08:42]Nevertheless, a telescope can observe one of the most beautiful star clusters nearby.

[01:08:48]It's called the jewel box because its stars are compared to sparkling gems.

[01:08:56]The obscure Horsehead [music] Nebula, also known as Barnard 33, is located in one of the youngest regions of the sky, the constellation Orion.

[01:09:09]At the end of December, during the winter solstice, the night darkened hemisphere [music] of Earth comes face to face with a stellar region of our galaxy.

[01:09:20]stars, each more beautiful and brilliant than the last, light up the Milky Way like rubies, diamonds, and sapphires.

[01:09:28]The brightest and closest is Sirius.

[01:09:32]A h 100 times further on is the super giant Riel, which along with Beetlejuice, Bellatrix, and Scythe forms the constellation Orion.

[01:09:45]Not far from the center of this constellation, patience and perseverance are required to find the Horsehead Nebula just below the [music] star Alnetac.

[01:09:57]Here, immense clouds of gas give birth to new stars.

[01:10:02]This nebula is made up of interstellar gas and dust that light is unable to penetrate.

[01:10:08]It [music] is therefore invisible to the naked eye.

[01:10:12]Its horse head shape is caused by the presence of a dense cloud of gas and dust.

[01:10:18]At the base of the head are young stars in the process of forming.

[01:10:24]The Horse Head Nebula is about 7 light years long and lies almost 1500 light years from us. It does not radiate and is very dense and cold.

[01:10:39]>> [music] >> Some nebula are said to be chaotic [music] because they are unique in that they are both emitting and dark at the same time.

[01:10:51]The gases they contain take on highly varied appearances and the environment is disturbed.

[01:10:59]Examples include the Sorcerers [music] Nebula NGC7380, the IC1318 Nebula, and the North American Nebula NGC7000. [music] Close to DAB, the brightest star in the Signis lies the North American Nebula NGC7000 [music] in the Signis constellation.

[01:11:26]It is closely accompanied by a neighboring nebula nicknamed the Pelican, IC5070.

[01:11:34]The mass of gas contained in [music] these two nebula is estimated at 5,000 solar masses.

[01:11:43]Between them, they form the visible part of an immense hydrogen cloud.

[01:11:49]Scientists thought that the nearby super giant star [music] DANB would provide them with the energy they needed to flues.

[01:11:58]As it turns out, this star isn't hot enough at 8,230° C or 14,900° F. And the nebula needs to be heated by a star with a temperature above 30,000° C or [music] 54,000° F.

[01:12:19]What's more, DAB is too far from the nebula complex. The ionizing star is actually at the rear of the nebula.

[01:12:28]Its surface temperature exceeds [music] 40,000° C or 72,000° F. and it belongs to a binary system.

[01:12:40]The light emitted cuts the contours of the clouds in such a way as to remind us from Earth of the North American continent.

[01:12:49]The Swan Wall is a region reminiscent of Mexico and Central America.

[01:12:55]It is in this region of the nebula that we find the highest rate of star formation.

[01:13:02]The North American Nebula is only visible in excellent skies.

[01:13:07]Although it emits a not inconsiderable light of magnitude 5, it extends over such a vast area that it is difficult to see.

[01:13:17]It covers an area more than 10 times that of the full moon.

[01:13:23]The Sorcerer's Nebula NGC7380 is so named because seen in profile, its contours evoke the figure of a sorcerer.

[01:13:34]From above, you can make out his hat, eye, nose, mouth, and long beard.

[01:13:40]This nebula is located in the Sephiius constellation, some 8,000 lighty years from Earth. It is surrounded by an open cluster.

[01:13:51]The nebula and cluster form a favorable environment for the birth of [music] new stars and the creation of new planets.

[01:13:59]The sorcerer's nebula is not easily identifiable on the celestial vault. It requires very good observation conditions as well as the use of precise [music] instruments such as a telescope with a diameter of at least 200 mm.

[01:14:18]The IC1318 [music] nebula, also known as the butterfly nebula, is located in the constellation Signis.

[01:14:29]This brightly emitting nebula has a dark nebula [music] at its center.

[01:14:34]Its circumflex shape is clearly visible in the photographs.

[01:14:42]Since 1976, another category of nebula has also been described.

[01:14:48]Integrated flow nebula or IFNS.

[01:14:53]An integrated flux nebula is illuminated solely by the luminous halo emitted by the entire [music] galaxy it inhabits, the so-called integrated flux.

[01:15:06]This type of nebula has been observed in the Milky Way. These clouds are made up of dust [music] present in the interstellar medium at all galactic latitudes.

[01:15:17]Their colors stand out in very long exposure photographs, but do not show up in binoculars or telescopes unless the optics are very bright and the observation [music] site is shielded from artificial light.

[01:15:33]The best known nebula owe their success to their proximity to the Earth.

[01:15:39]Astronomers, whether professional or amateur, choose objects that are easily accessible and within reach of their instruments.

[01:15:49]Within the Milky Way, most of the nebula observed are located close to the sun within a radius of 5,000 light years between the Orion arm and the Karina [music] Sagittaria arm.

[01:16:04]Nebula in the direction of the galactic bulge are difficult to spot as the stars and dust clouds there are far too [music] dense.

[01:16:14]As for the rest of the universe beyond the Milky Way, it also contains some astonishing nebula [music] outside the Milky Way. It's difficult to identify specific individual nebula with the same notoriety as those in our own galaxy.

[01:16:38]Nevertheless, there are some complex nebulous [music] regions in other galaxies that are well known to astronomers and astronomy enthusiasts.

[01:16:48]We won't necessarily find individual planetary nebula like those in the Milky Way. The galaxy itself may contain various nebulous regions due to star formation processes. [music] Specific observations and discoveries may vary over time due to [music] advances in astronomy and imaging.

[01:17:15]The brightness of the melenic clouds is comparable to that of the Milky Way. In the southern hemisphere and in the absence of light pollution, they both appear distinctly without the need for observational instruments.

[01:17:31]If you use binoculars, their characteristic shapes are [music] clearly visible.

[01:17:37]The large cloud galaxy measures the equivalent of 20 full moons lined up end to end.

[01:17:44]The small cloud galaxy, on the other hand, is three times smaller.

[01:17:49]The Magelinic clouds are the Milky Way's [music] two largest satellite galaxies.

[01:17:55]The large cloud is 160,000 light [music] years from the sun, while the small cloud is 200,000 lighty years away.

[01:18:05]Although not the closest to the Milky Way, the galaxies of the Magelenic clouds are still the easiest to observe.

[01:18:14]They are certainly ancient barred spiral galaxies distorted by the gravitational pull of the Milky Way.

[01:18:22]The small cloud galaxy [music] contains around 3 billion stars while the large cloud galaxy has 10 times [music] that number.

[01:18:32]Within the latter, we find one of the largest nebula known in the universe, [music] the Tarantula Nebula.

[01:18:42]A vast patch of [music] interstellar fog is visible within the large Magelinic Cloud. This is the Tarantula Nebula, also known as NGC 2070.

[01:18:55]Seeing the images of this nebula, it's easy to understand why this sprawling mixture of gas and [music] stars is likened to a spider.

[01:19:05]Located 160,000 light years from Earth, [music] the Tarantula Nebula seems rather modest. But it's its remoteness that's misleading.

[01:19:16]If the tarantula were as close to us as the Orion Nebula, it would cover a quarter of our sky and be visible [music] even in broad daylight.

[01:19:27]Within this gigantic gaseous labyrinth, lies some of the most massive [music] stars known to man.

[01:19:34]Like a colossal matrix of stars, the Tarantula Nebula [music] exceeds 1,800 lightyear in diameter.

[01:19:42]It is the largest nebula known to date.

[01:19:46]Its star formation [music] rate is higher than in any other region of the Milky Way.

[01:19:52]Shielded from light pollution, the nebula appears as a small bright spot in the immediate vicinity of the large melenic cloud.

[01:20:02]Its magnitude of around five makes it easily [music] visible to the naked eye.

[01:20:08]At the heart of the nebula is a dense cluster of hot stars that produce the ultraviolet radiation that ionizes the surrounding gas.

[01:20:18]This is what makes the nebula visible.

[01:20:21]The cluster of stars is called R136A.

[01:20:26]It includes the most massive [music] star ever observed.

[01:20:31]R136A1 beats the sun in every respect. It is comparatively [music] 30 times wider, 8 million times brighter, and has a surface temperature 10 times higher than the sun.

[01:20:46]The nebula contains a large number of star forming stars.

[01:20:51]It turns out that star formation in this nebula is quite different from that in other galaxies such as the Milky Way.

[01:20:58]Scientists have discovered that the star forming regions within the tarantula nebula are producing stars at a far greater rate than in the Milky Way.

[01:21:09]These discoveries provide new insights [music] into the history of stellar creation.

[01:21:15]The chemical composition of the tarantula is similar to certain star forming regions that existed when the universe was very young only a few billion [music] years ago.

[01:21:28]This subject of study continues to enter scientists as they seek to learn even more about this nebula. [music] The Tarantula Nebula emits a reddish light due to the excitation of hydrogen.

[01:21:43]The powerful light rays from giant stars burn the gas so intensely that they eventually explode into supernovas.

[01:21:53]In 1987, at the edge of the Tarantula Nebula, a supernova visible to the naked eye lit up the sky, leaving behind an afterglow that is now well known and still observed.

[01:22:14]In 1987, the large melenic cloud galaxy was the site of the brightest supernova recorded in the last 400 years.

[01:22:24]A star with a mass equivalent to 20 solar masses exploded.

[01:22:30]SN1987A was the first supernova explosion of the 20th century to be observed with a naked eye, far from light pollution.

[01:22:41]It was then observed [music] continuously in all usable ranges of electromagnetic radiation.

[01:22:48]This supernova is one of astronomy's most important objects as it is the first time that the progenitor star is known [music] before the explosion.

[01:23:00]The phenomenon occurred on the night of February 23rd, 1987, some 165,000 light years from Earth.

[01:23:10]It was the closest supernova observed outside our galaxy.

[01:23:15]Around 3 months later in May, its brightness peaked at an apparent magnitude of around plus three before declining over the following months.

[01:23:27]The progenitor [music] star is a blue super giant with an initial mass of around 20 solar masses.

[01:23:35]It is named Sandelique -69° [music] 202A and formed 10 million years ago.

[01:23:43]Scientists were astonished that it was a blue super giant and not a red one since at the time it was considered that only red super giants evolved into supernovas.

[01:23:55]Thanks to the Hubble telescope, scientists were able to analyze Sandelique -69° [music] 202A and deduced that it must have evolved from a red to a blue [music] super giant before exploding.

[01:24:11]In fact, three rings of gas orbit SN1987A, dating back 20,000 years before the explosion.

[01:24:21]The star must have lost mass before its explosion which explains its change in type.

[01:24:28]Its rings have adopted a distinctive morphology.

[01:24:32]The two outer rings are hourglass shaped while a smaller inner ring forms the neck.

[01:24:39]This characteristic may be linked to the violent solar winds that sculpted this extraordinary shape.

[01:24:47]The two outer rings may also have been illuminated [music] by the gas ejected in the supernova.

[01:24:54]The supernova afterglow has always been visible. It is the object of intense observation since it is the [music] youngest known afterlow.

[01:25:05]All these years of observation of SN1 1987A are of immense value.

[01:25:11]The data enable scientists to better understand the final stages in the evolution of stars.

[01:25:18]Supernovas are of considerable importance in the history of the universe.

[01:25:24]They expel the elements that form at [music] the heart of stars such as iron, oxygen, nitrogen, and carbon.

[01:25:33]Depending on the strength of the explosion, they can also feed energy into gas clouds, helping to give birth to new stars.

[01:25:43]By studying supernova 1987a from the moment of its explosion, astronomers have gained a better understanding of the very first stages in the dispersal of the afterglow and the effects this will have on the supernova's environment.

[01:26:08]The Lobster Nebula is located in the smallest of the dwarf galaxies [music] in the Magelinic Cloud. It spans about 400 light years and is about 5,500 light years from Earth. A blue glow from the emission of ionized hydrogen gas surrounds this star forming region.

[01:26:29]The surrounding nebula appears as a mixture of gas, dark dust, stars in formation, and newborn stars.

[01:26:38]This complex architecture is the result of interactions between interstellar winds, magnetic fields, gravitational interactions, and radiation pressure.

[01:26:51]The Lobster Nebula harbors an open cluster near its center containing stars of exceptional brilliance and mass.

[01:27:00]This is the Pismus 24 open cluster.

[01:27:04]This [music] cluster contains many massive stars.

[01:27:08]Among them, Pismus 241 is 776,000 times brighter than the sun. Its mass approaches 300 solar masses.

[01:27:21]It is in fact a system of at least three stars.

[01:27:25]Pismus 24 is one of the most active sites of massive star formation.

[01:27:35]NGC 346 is an emission nebula associated with an open cluster. It lies within the small melenic cloud in the constellation of the toucan.

[01:27:47]It [music] was discovered by astronomer James Dunlop in 1826.

[01:27:54]NGC 346 lies some 200,000 light years away.

[01:27:59]This [music] intense star forming region has a diameter of around 200 lightyear.

[01:28:06]NGC 346 is a true wonder of the southern sky. By studying it, astronomers have been able to discover a population of embriionic stars in formation.

[01:28:20]These are arranged along the [music] dark bands of visible dust. The very young stars continue to collapse into their initial clouds, emitting a light that is reddened by the dust between them and the Earth.

[01:28:33]This stellar nursery closely resembles those that remain in the primordial universe.

[01:28:45]Scientists estimate that 2% of the 200 billion galaxies in the universe interact with a nearby galaxy.

[01:28:53]Such is the case with the famous Hound Dog Galaxy, also known as the Whirlpool Galaxy and referenced M51.

[01:29:03]It lies at an abysmal distance of 23 million lighty years from us. Messier 51 is the common name for the two stars because Charles Messier did not split them at the time.

[01:29:18]In fact, they are a pair of interacting galaxies. [music] The small galaxy NGC5195 lies a few [music] tens of thousands of light years behind its big sister NGC5194.

[01:29:35]The former is so distorted by the interaction which has been going on for almost a billion years that astronomers can't classify it.

[01:29:45]The interaction of these two [music] galaxies is causing outbreaks of new stars.

[01:29:51]In the larger of the two galaxies, [music] no fewer than 100 ionized nebula have been detected.

[01:30:00]No one knows how the encounter will end.

[01:30:03]Will the two stars separate and drift apart or merge into a single galaxy?

[01:30:10]Our planet's nocturnal orientation away from the galactic disc that illuminates summer and winter nights is directed in spring towards the constellations with the fewest [music] stars and interstellar gas such as Leo, Virgo, the Big Dipper, and the Hounds.

[01:30:29]It's in these endless transparent regions of the sky seemingly devoid of stars that astronomers enjoy observing the most distant objects under the best conditions.

[01:30:42]Among them, the Hound Dog Spiral is one of the brightest and most beautiful galaxies known. [music] Despite its impressive diameter of over 60,000 light years, it is invisible to the naked eye.

[01:30:57]It is populated by over 200 billion stars.

[01:31:02]The pair of galaxies is bound together by the force of gravity.

[01:31:07]The spiral structure of NGC-5194 is strongly disrupted by the passage of its smaller companion.

[01:31:16]The galaxy's sumptuous brilliance is due to the gravitational tidal forces generated by the small galaxy.

[01:31:24]In the same way that the moon influences the oceanic masses of the earth, NGC5195 acts on the gas masses of NGC-5194.

[01:31:35][music] This interaction suppresses interstellar gas which condenses into new stars.

[01:31:45]As a result, the spiral disc of the Hound Dog Galaxy [music] is rich in nebula.

[01:31:52]In close-up photographs of the galaxy's disc, we can see its youth and vitality [music] in the brilliant nebula illuminated by the thousands of super giant stars they give birth to a few hundred million years ago.

[01:32:07]Only stars 1,000 to 10,000 times brighter than the sun are visible.

[01:32:13]The billions of others are too dim to be [music] seen individually.

[01:32:26]The barred spiral galaxy NGC1313 is located in the constellation Reticle.

[01:32:34]It is one of the smallest and least luminous constellations in the southern hemisphere and contains one of the most remarkable celestial objects.

[01:32:46]This galaxy lies some 13.5 million lightyear from Earth. This gravitationally isolated galaxy shares some characteristics with the melenic clouds.

[01:33:00]Its spiral arms are weakly coiled and attached to the end of its bar. They are uneven, revealing globules of gas.

[01:33:10]What's more, they don't rotate at the center of the bar, which is also a sign that the galaxy has undergone disturbances.

[01:33:19]Its morphology suggests that its past must have been highly turbulent.

[01:33:25]NGC 1313 is thought to have interacted with a smaller galaxy in the past.

[01:33:32][music] This highly active galaxy features a large number of nebula surrounded by gas.

[01:33:39]The arms of the galaxy feature numerous star forming sites and open clusters of young stars.

[01:33:47]The radiation from all these fledgling stars generates gas that creates beautiful patterns of light and [music] dark nebula.

[01:33:59]NGC1313 is a star forming galaxy, a feature that remains enigmatic [music] as the galaxy remains relatively isolated.

[01:34:10]Indeed, in most galaxies of this type, the high rate of star formation is due to a meeting or even a merger of two galaxies. [music] In the constellation Perseus, NGC 1275 is a lenticular galaxy around 250 million lighty years from Earth with a diameter of over 250,000 lightyear.

[01:34:43]This vast galaxy is characterized by highly complex dynamics that set it apart from other galaxies.

[01:34:52]Located at the heart of the Perseus galaxy cluster, it is bathed in hot diffuse gas with an average temperature of several tens of millions of degrees.

[01:35:04]It is this gas that forms most of the luminous mass [music] of galaxy clusters.

[01:35:09]The matter that forms the environment is highly complex.

[01:35:14]On the one hand, the hot gas causes cooling and on the other, the super massive black hole with a mass equivalent to around 340 [music] million solar masses generates powerful high energy jets that prevent the gas from cooling [music] completely.

[01:35:32]The result is a sumptuous network of filaments surrounding NGC 1275.

[01:35:40]This large nebula extends over 250 light years, equivalent to 2 and 1/2 times the size of the Milky Way.

[01:35:50]The motion of the network of filaments is not uniform, but rather chaotic.

[01:35:56]This dynamic may be intimately linked to the heating and cooling of the gas that feeds the black hole at the heart of the galaxy.

[01:36:12]NGC 2403, also known as Caldwell 7, is a spiral galaxy in the constellation Giraffe, around 8.5 million lighty years from the Milky Way.

[01:36:25]In the galaxy's eastern outer arm lies NGC 2404, [music] an open cluster of stars.

[01:36:33]It is associated with an emission nebula.

[01:36:39]NGC 2403 spiral arms are illuminated by bright red nebula, a few bluish open clusters, and dark veins of dust.

[01:36:51]At its heart, the nucleus is bright but relatively small.

[01:36:56]According to some scientists, this galaxy is gravitationally part of the Messier 81 group.

[01:37:05]Around 15 million light-years from Earth, Messier 83, a spiral galaxy, [music] is majestically visible.

[01:37:14]Beside it is a small quai elliptical nebula, the dwarf galaxy NGC5253.

[01:37:23]Although it may seem rather insignificant at first glance, it is a site of intense [music] star formation.

[01:37:31]This compact blue dwarf galaxy [music] is located in the constellation Centauri.

[01:37:38]It has a magnitude of 10.5.

[01:37:41]It is one of the closest blue compact dwarf galaxies [music] to us.

[01:37:47]Vivid blue and violet colors are visible through observational instruments due to its [music] active star formation.

[01:37:56]NGC5253 is home to very active star forming regions. Although it contains little dust, hydrogen, and helium, the basic elements for star formation.

[01:38:10]These molecular clouds strongly resemble the clouds [music] that form the first stars in the early universe.

[01:38:17]This is why scientists like to study [music] compact blue dwarf galaxies to better understand the primordial [music] process of star formation.

[01:38:29]NGC 5253 features a central starburst zone rich in hot young stars concentrated in a star cluster.

[01:38:40]Its morphology is not uniform due to the intense consumption of gas.

[01:38:46]At its heart is a gigantic supercluster of over a million stars, [music] each 3 million years old. The total luminosity of this supercluster is [music] equivalent to around a billion times that of the sun.

[01:39:02]From Earth, it is completely invisible as it is obscured by a giant dust cloud.

[01:39:14]The local group is a collection of 60 galaxies spanning 10 million light years.

[01:39:20]Among them, the Milky Way and the Andromeda galaxy are the main members.

[01:39:26]The third largest galaxy is the Triangulum, also known as M33. [music] To spot the triangulum galaxy with a naked eye, you need a [music] pure black sky and the eyes of an eagle.

[01:39:41]Nevertheless, it is easily visible through binoculars.

[01:39:46]Its oval disc is uniformly bright, although a slight excess of brightness towards the center betrays the presence of the bulge.

[01:39:55]Through a 300 to 400 millimeter telescope, we can easily [music] observe its sumptuous spiral arms.

[01:40:03]The triangulum galaxy has particularly well-developed spiral arms, which appear spectacularly when viewed from the front.

[01:40:13]Yet, it remains modest in [music] comparison to the Milky Way and Andromeda galaxies, containing just 40 billion stars.

[01:40:23]Its very active arms are filled with regions of ionized gas within which [music] stars are born by the hundreds.

[01:40:31]The largest of these nebula is NGC 604, the Triangulum Nebula.

[01:40:42]The Triangle [music] Nebula, also known as NGC 604, spans 1500 light years and shines 6,000 times brighter than the Orion Nebula.

[01:40:55]Its immense tentacles of cold gas extend far beyond the visible disc.

[01:41:01]It was discovered by astronomer [music] William Hershel on September 11th, 1784.

[01:41:09]It lies nearly 3 million lightyear from Earth.

[01:41:13]If it were at the same distance as the Orion [music] Nebula, it would surpass the brilliance of Venus.

[01:41:21]It's an emission nebula with around 200 [music] stars at its heart with masses ranging from 15 to 60 solar [music] masses.

[01:41:31]It is this same cluster of stars that irradiates the gas with energetic ultraviolet light, stripping electrons from atoms and producing the special glow of nebula.

[01:41:47]A hot sparse gas that emits X-rays fills the bubbles and cavities of the nebula.

[01:41:55][music] The tarantula, the crab, the lobster, the owl, the butterfly, and many others are silent witnesses to the grandeur and complexity of our universe.

[01:42:13]This journey through the nebula helps us understand the significant importance of these stellar objects.

[01:42:21]Since mankind first discovered and studied nebula, new data have been added to our understanding of star formation, galactic evolution, and cosmic chemistry.

[01:42:37]These vast clouds [music] of gas and dust, which often take on the appearance of creatures and animals, can be [music] found everywhere in the Milky Way and beyond.

[01:42:50]They are ideal places for the formation of new stars and planets [music] and shape the cosmic architecture.

[01:42:58]The study of nebula continues to fuel our quest for understanding.

[01:43:03]The mysterious secrets of the early universe are gradually being revealed, reminding us [music] of the complexity of the universe around us.

[01:43:15]To what extent do nebula hold the answers to the fundamental enigmas of our [music] universe?

[01:43:24]The exploration of nebula is far from over and they remain a dynamic area of research in astronomy. [music] Despite the enormous progress scientists have made in understanding nebula over the decades, there is still much to discover.

[01:43:47]Astronomers are trying to understand many mysteries such as the precise details [music] of star formation inside nebula, the exact mechanisms of their evolution or their role in galactic evolution.

[01:44:02]New technologies, [music] more powerful telescopes, space missions, and advances in observation techniques continue to open up new perspectives.

[01:44:14]Many more revelations await us in [music] these vast stellar clouds.

[01:44:23][music]