The Universe: Supernova Consumes the Galaxy (S2, E9) | Full Episode | History

Summary

Highlights

• Supernovas are stellar explosions, shining 100 billion times brighter than the sun. 💫
• They release energy and radiation that influence the formation of new stars and planets. 🌟
• Experts estimate a supernova occurs in the universe every second. ⏰
• Supernovas can alter DNA through cosmic rays, potentially leading to new species. 🧬
• The 1987A supernova provided critical insights into supernova mechanics and behavior. 🔍

Key Takeaways

• Supernovas are the explosive end of stars, outshining entire galaxies for a brief moment. 💥
• These celestial events are crucial in creating and distributing elements essential for life and new stars. 🌌
• Scientists use high-tech tools like telescopes to investigate supernovas and uncover cosmic mysteries. 🔭
• Supernovas can occur in different types, each with unique characteristics and causes. 🌠
• The study of supernovas has led to revelations about the universe's expansion and its accelerating nature. 🚀

Overview

Chapters

• 00:00 - 02:00: Introduction to Supernovas Supernovas are described as cosmic events that signify the death of stars. They are incredibly bright, often outshining entire galaxies, and are considered the most massive and energetic events since the Big Bang. Despite their destructive nature, these catastrophic events also contribute to the creation of new cosmic phenomena.
• 02:00 - 30:00: Supernova Explosion Mechanics Supernovas are among the universe's most violent and mysterious forces, capable of catastrophic consequences such as extinguishing life on Earth if one were to explode nearby.
• 30:00 - 36:00: Historical Observations of Supernovas Supernovas are extraordinary events marking the explosive death of stars, characterized as the largest explosions in the universe.
• 36:00 - 54:00: Advancements in Supernova Research The chapter titled 'Advancements in Supernova Research' delves into the potentially catastrophic effects of supernovas, particularly the lethal radiation they emit, which can eradicate all forms of life in a planetary system. It equates scientists studying supernovas to detectives investigating a cosmic crime, using advanced tools to understand these powerful cosmic events.
• 54:00 - 72:00: Implications for the Universe The chapter titled 'Implications for the Universe' explores the use of telescopes and technology in the discovery and understanding of supernovas. Scientists utilize these tools to gather clues from after the explosion to unravel the mysteries of these cosmic events. The chapter delves into the dual nature of supernovas and the role they play in advancing our knowledge of the universe.

The Universe: Supernova Consumes the Galaxy (S2, E9) | Full Episode | History Transcription

• 00:00 - 00:30 they are cosmic killers they're the end of stars they're the deaths of stars spectacular stellar detonations 100 billion times as bright as the sun that for an instant outshine a whole galaxy the most massive energetic event in the universe since the big bang out of this exceptional cosmic catastrophe becomes creation
• 00:30 - 01:00 but if one struck near here life on earth would cease the universe the cosmic crime scene for a most violent and mysterious force supernovas [Music]
• 01:00 - 01:30 supernovas the sensational and exceptional death of stars produce the biggest blasts in the universe now only a small minority of stars actually explode but those that do just go kablam blowing themselves to smithereens releasing more energy than the sun does in its entire lifetime by more than a billion the spectacular detonation blasts vast
• 01:30 - 02:00 amounts of lethal radiation into the universe if a star at the center carriage system would go supernova and explode it would probably wipe out all forms of life in that planetary system radiation would basically sterilize all forms of life on any planet in a planetary system like homicide detectives pouring over clues to a cosmic crime scientists use state-of-the-art tools
• 02:00 - 02:30 telescopes and technology to find supernovas and to solve the mystery of how and why they occur it's an interesting thing because the explosion the event has already taken place and then we get these clues which we gather with our telescopes and try to figure out what happened as the stellar investigators know supernovas have a dual personality
• 02:30 - 03:00 they have absolute power to destroy and at the same time they are fundamental to creation itself when a supernova goes off the explosion produces a lot of light but it also produces heavy elements out of the light ones so for example iron or calcium or sodium or any of the elements of the periodic table those things came from exploding stars that went off before the sun was formed
• 03:00 - 03:30 the elements produced in these enormous stellar explosions actually make planets plants and people the calcium in your bones and the oxygen that you breathe we're all cooked up in stars and blown out into space the shock waves from exploding stars can compress nearby clouds of gas and
• 03:30 - 04:00 trigger their gravitational collapse so that they begin the renewed process of formation of new stars planets and ultimately life thanks to circumstantial cosmic evidence collected experts estimate that a mighty supernova goes off somewhere in the universe once every single second [Applause]
• 04:00 - 04:30 so that's something like 30 million per year and that's been going on for the last 10 billion years or so of the universe's existence giving us a sense of how big the universe is in a typical galaxy like our milky way a supernova suddenly occurs only once or twice a century however nobody knows when the next one might come it's a completely random process so we have no idea when the next
• 04:30 - 05:00 one will occur it could be tomorrow it could be you know five minutes ago could be another hundred years we don't know if it is very close you would see a very bright event in the sky it could be even brighter than the venus or the planets or even the moon or maybe even the sun if it's bright enough if a supernova is too close to you it can definitely destroy life the flash disrupts the atmosphere burns things up
• 05:00 - 05:30 astronomers are constantly policing the skies keeping a wary eye on at least two stars in the milky way that have the potential to catastrophically explode close to earth one that threatens to blow lies in the heart of the ada carina nebula about 9 000 light years away carina is one that we know about which is a very massive star maybe even a hundred times the mass of the sun has a
• 05:30 - 06:00 very short life and it could be that the end of that life uh will take place sometime very soon another star in danger of going supernova is beetlejuice a star in the orion constellation this seething star is 15 times the size of the sun this one is even closer than ada karina to earth it's roughly 500 light years away it'll be a spectacularly brilliant sight
• 06:00 - 06:30 visible even in the daytime there's no question betelgeuse is going to blow up it could be tonight for all our ignorance it could be 10 000 years from now that's short on an astronomical time scale but it could be tonight that we're sufficiently ignorant about it so it is worth looking at every night to see whether it's flowing not only do the massive supernova explosions create and destroy stars planets and people
• 06:30 - 07:00 they also unleash powerful energy in the form of cosmic rays these highly energetic charged particles strike our planet each and every day what's more they have the capacity to alter evolution we live in a what i call a disturbed galactic ecology it is a very eruptive energetic galaxy out there and our planet is going to get pummeled by that stuff
• 07:00 - 07:30 experts say they can and do change life as we know it well we know that there are genetic mutations that take place when cosmic rays hit living things it disrupts the dna inside cells and if there were a supernova nearby there could be a lot more cosmic rays like a hundred or a thousand or a million times more than we ordinarily get if you're the old species it might lead to your demise but it also might
• 07:30 - 08:00 lead to new species being developed so a supernova could be an agent of change and it could be for better or for worse knowing that supernovas have the power to create and alter life makes it imperative that humankind unravel the riddle of what makes these stellar time bombs tick what have you got here all right so this is the supernova factory supernova the key to unlocking the mystery lies in the detailed analysis of what is ejected
• 08:00 - 08:30 into the cosmos by a supernova i'm glad this one did not escape our attention because it was a winner yeah it's a great supernova nature has given us this puzzle it says i make these objects easily and we as theorists have to figure out how nature does it as with any crime scene critical clues are contained in what is left behind like a gunshot hot gases and explosive debris are
• 08:30 - 09:00 propelled through space by these deadly stellar explosions just as these gunshots are driving a shock wave and you can hear this strong noise from the shock wave it's actually compressing the matter and heating it up a shock wave in a supernova is doing the same thing as these pieces of shrapnel are hurtling very fast through space they collide with the material around it and what forms is a shockwave the fantastic stellar detonation shoots
• 09:00 - 09:30 vast amounts of ballistic supernova evidence cosmic debris called remnants into the universe so the reference are produced as the shock wave keeps on moving out through the universe it actually produces this very picturesque image of the shock moving outward the gases that made up that star uh are ejected at tremendous velocities 10 000 miles a second and so they create an
• 09:30 - 10:00 expanding shell and eventually that can become very very large [Music] these things go for thousands of years or even tens of thousands of years so sometimes we can see the site of a supernova explosion tens of thousands of years after the event has taken place the high-speed collision of stellar debris in the shockwave produces intense heat and light in wavelengths invisible to the human eye
• 10:00 - 10:30 they include radio infrared all the way to x-rays and gamma rays fortunately for astronomers sophisticated space-based instruments like hubble spitzer and the chandra x-ray telescope can help the cosmic detectives see them all so basically every instrument and every way you can gives you a somewhat different perspective on what's going on
• 10:30 - 11:00 and then you try to put all that together as an intellectual enterprise like a fingerprint each supernova has a unique pattern and they can be analyzed in several different ways one thing we can do is measure how bright the supernova is and that's what we call the light curve the other thing that we can measure that is really helpful is what we call the spectrum we take the light from a supernova at a telescope spread it out
• 11:00 - 11:30 into a little rainbow using a prism or a grating and then measure how much light there is at each color or wavelength analysis of that line can tell us lots of interesting things like the chemical composition of the supernova the temperature the pressures and densities of the gases how quickly they're expanding and so on information gleaned from the light curve and spectrum reveals distinctions between each supernova
• 11:30 - 12:00 so it is much like a detective job where you get different clues from the light curve or from the spectrum and try to figure out what kind of star it was what made it explode what the products of the explosion were and what the effects of that explosion might be as time goes on we can see deeper and deeper into what the star originally was so we can actually get what the composition of the star was at the time it exploded
• 12:00 - 12:30 by comparing the light curves and spectra from literally hundreds of supernova cases scientists have been able to classify supernovas into two main types type 1a supernova release no hydrogen the explosions are uniform in size and luminosity type 2 supernova release large amounts
• 12:30 - 13:00 of hydrogen the explosions vary greatly in size and luminosity but why would there be such distinct types of exploding stars might they be blowing themselves apart in different ways scientists focused their efforts on uncovering the mammoth question what drives these stellar monsters to
• 13:00 - 13:30 destroy themselves like bounty hunters looking for bandits today's astronomers scour the cosmos looking for deadly supernovas with their keen eyes on the sky they belong to a long lineage of stellar observers in fact the first supernova ever witnessed by man occurred in china in
• 13:30 - 14:00 185 a.d 2 000 years ago the chinese astronomers kept very meticulous records about what they saw in the sky specifically when something new appeared they recorded how bright it was where it was how long it was there using the royal chinese records stellar investigators today have recently found the remnant of this ancient supernova it is identified as rcw 86
• 14:00 - 14:30 and is in the constellation centaurus near two bright stars known as alpha and beta centauri fourteen hundred years after the chinese discovery the first european observer witnessed a supernova on november 11th 1572 26 year old danish astronomer taiko brahe was taking a walk when he witnessed a shocking stellar phenomenon
• 14:30 - 15:00 in the northern sky it was right next to the w etched by the brightest stars in the constellation cassiopeia even though he saw it and even though he was the leading astronomer of his age he did not believe the sense of his own eyes a few years after tycho's remarkable sighting his former pupil johannes kepler made his own groundbreaking observation of a new star
• 15:00 - 15:30 he measured from star to star around it the distance and we can use that now to recreate exactly the position of where it exploded contemporary investigators took a closer look at kepler's 1604 remnant they found something very strange about it a detailed analysis of the chemical composition of the ejected and expanding gases indicated that there were two stars that somehow conjoined to produce
• 15:30 - 16:00 a gigantic explosion so how did this companion cause the stellar catastrophe many stars are in binary systems so they have a partner that is orbiting around them and we think what happens is that one star puts mass onto the other experts have since found that the companion or binary scenario is the hallmark of what is called a type 1a supernova
• 16:00 - 16:30 the type 1 supernovae we think are the explosion of white dwarfs so a star like the sun will produce a little dense nugget about the size of the earth when a star like the sun dies it ejects its outer layers and leaves behind just a small dense burnt out core called a white dwarf the ashes of the sun will be a carbon and oxygen white dwarf left by to its own devices that will
• 16:30 - 17:00 just last forever and cool off but when a star has a companion like a partner in crime it can lead to catastrophe one star puts mass onto that white dwarf pushes its mass up to the point where it becomes unstable and that there is burning that takes place in the center and very very rapidly the star goes from being a kind of boring white dwarf to being a tremendously violent and brilliant supernova
• 17:00 - 17:30 but why do some white dwarfs catastrophically explode that was figured out in 1930 by a brilliant young astrophysicist subrahmyan chandrasekhar the sherlock holmes of astrophysics on a boat trip from india to england during this long voyage he used the newly developed fields of quantum physics and special relativity to come up with the idea that a white dwarf
• 17:30 - 18:00 can have only a certain maximum limiting mass you cannot go beyond a certain mass about 40 percent bigger than that of our sun 1.4 solar masses and this came to be known as the chandrasekhar limit and at that point an uncontrolled runaway chain of nuclear reactions ensues
• 18:00 - 18:30 but for decades scientific investigators remain puzzled by just how this explosive chain reaction worked and what it looked like when it did computer models could never recreate what seemed to be happening in nature but then in 2006 astrophysicists from the university of chicago's prestigious flash center literally cracked the code
• 18:30 - 19:00 the chicago team was the first to create a supercomputer program capable of processing the vast amounts of data it had to be to simulate the complicated dynamics involved in the explosion of a whole star we call this extreme computing the computers we use some of them have 128 000 processors so they're really 128 000
• 19:00 - 19:30 desktop computers all linked together even with all that power it took almost 60 000 hours of computing time the astrophysicists decided not to start their simulated explosion exactly at the center of the star the reason that we decided to start slightly off-center rather than right at the center is that it's just very very improbable that the flame will ignite exactly or even really close to the center there's just no volume there
• 19:30 - 20:00 there's no there there according to the remarkable simulation in one second a flame bubble forms inside the star so what you see right in the center of the star is the bubble rising quickly growing expanding as the burning takes place and breaking through the surface of the star the molten bubble initially measures approximately 10 miles across and rises more than 1200 miles to the
• 20:00 - 20:30 surface of the star it's spreading over the star of about 3000 miles a second and it collides at the opposite point on the surface of the star and produces extremely energetic jets one that's moving outward at about 40 000 miles a second another jet that's punching in towards a star and that ignites a detonation wave which you've just seen raised to the star torrid temperatures depicted using a
• 20:30 - 21:00 standard color scale reach an unfathomable 3 billion degrees fahrenheit and you can see the moment is just detonated and going through the star takes less than half a second the whole burning phase takes less than three seconds expert analysis reveals that each type 1a supernova is remarkably similar in size and brilliance this explosion is equivalent to
• 21:00 - 21:30 completely detonating a mass the size of the sun [Music] this groundbreaking computer simulation illustrates for the first time how the explosions could occur in a type 1a supernova but type 2s seem to be a radically different animal by examining the stellar debris scientists have reasoned that type 2 supernovas are not the result of
• 21:30 - 22:00 exploding white dwarfs but rather the huge blasts of massive dying stars at least 10 times the mass of the sun [Music] but how do these mega explosions work the answer to the cosmic conundrum would come in the middle of the 20th century that's when supernova gum shoes for the first time in history pounded the intergalactic pavements systematically seeking gigantic
• 22:00 - 22:30 exploding stars like detectives on a stakeout cosmic investigators constantly scan the night sky they're looking for the telltale bright lights that are evidence of a supernova to carry out their surveillance they use an impressive array of high-tech
• 22:30 - 23:00 telescopes scattered across the globe historically we discover supernovas ground-based telescope either scanning the sky constantly to look for new supernova explosions the cosmic supernova hunt began in the 1930s maverick astrophysicist fritz zwicky led the charge he was the first to methodically search catalog and quantify new and exploding
• 23:00 - 23:30 stars he was one of the real pioneers in finding exploding stars and then he wanted to physically understand what they are the trailblazing astrophysicist proposed that these enormous and spectacular stellar events were the result of whole stars exploding swicky predicted that a certain kind of
• 23:30 - 24:00 exploding star can occur when a massive star's core collapses and then rebounds creating a colossal explosion during the collapse they said a compact remnant should be formed a ball of neutrons a neutron star essentially the ordinary matter is made out of protons and neutrons and electrons in this collapse of an iron core the the protons and the electrons that make up the iron atoms combine to make neutrons [Music]
• 24:00 - 24:30 a neutron star is an incredibly dense object now if you were to take a large building like the empire state building in new york and compress it to the density of a neutron star it would be about the size of a marble they have a very high density and in fact a teaspoon of neutron star material would weigh as much as 1 billion tons on earth scientists today believe that only huge
• 24:30 - 25:00 stars at least 10 times the mass of the sun have the potential to generate this core collapse type explosion a massive star generates energy by fusing hydrogen to helium it can fuse helium into carbon and oxygen and it keeps on going all the way up to make iron iron is the most tightly bound nucleus so when a star has made iron it's really at the end of the lawn and it's ready for disaster
• 25:00 - 25:30 the iron core forms in the last day of the star's life and then it becomes so massive that essentially it collapses under its own weight it just collapses gravitationally very quickly it takes less than a second for the core of the star to crunch down from something about the size of the earth to a neutron star which is maybe 10 or 15 miles across but this dense iron core doesn't settle
• 25:30 - 26:00 down peacefully into its new life as a neutron star but instead of reaching an equilibrium configuration right away the neutron star rebounds off of itself just as the gymnast rebounds off of the trampoline and goes upward again well this rebounding neutron star collides with the material surrounding it and imparts some of its energy to that
• 26:00 - 26:30 colliding material thus initiating an ejection [Music] however unlike a gymnast for whom gravity ultimately prevails pulling him back to earth in a core collapse scenario something else continues to drive the ejection outward the question became what was this mysterious force driving the blast into space
• 26:30 - 27:00 experts calculated that in order for a successful explosion to occur one more ingredient was needed they suspected something called neutrinos ghostly energy-bearing particles that had been predicted but never observed astrophysicists believe that during a core collapse when the electrons are pushed so close to protons in the nuclei
• 27:00 - 27:30 of atoms that they combine to become neutrons in the process they release these tiny mysterious neutrino particles the neutrinos are kind of interesting particles they don't have any electric charge so they don't interact with light they only interact by what physicists call the weak force and the weak force is aptly named it means that these particles can go right through the earth they can go through long chunks of matter
• 27:30 - 28:00 so they're they're like ghosts they just go through things [Music] for centuries modern astronomers had been studying the remnants of supernovas in faraway galaxies from the distant past but in 1987 they would get a front row seat to an explosion of their very own it was the brightest supernova scene in nearly four centuries long after the
• 28:00 - 28:30 development of the telescope so we could use our full arsenal of equipment to study this fantastic blast in 1987 the most fantastic stellar event near our galaxy since the invention of the telescope occurred the first to witness it was young chilean astronomer oscar delhalde
• 28:30 - 29:00 his and astronomy's good fortune came on the night of february 23rd 1987. a telescope operator at the las campanas observatories oscar duhalde put water on for coffee and went outside to take a look at the sky and when oscar went out there he looked at the large magellanic cloud which he knows very well and he noticed that there was an extra star so he discovered this supernova
• 29:00 - 29:30 explosion by basically running outside the telescope building and saw with his own eyes when a star explodes astrophysicists like investigators looking for clues to a crime know that the first few hours after the stellar death are the most critical so in 1987 when the closest supernova in nearly 400 years appeared they knew they
• 29:30 - 30:00 had to act fast it was only about 170 000 light years away a mere stone's throw for an astronomer supernova 1987a was in a small galaxy called the large magellanic cloud a dwarf galaxy that orbits around our much bigger milky way galaxy being the first supernova of that year the exceptional and nearby exploding star was simply labeled
• 30:00 - 30:30 sn 1987 a but this time dozens of seasoned astronomers all over the planet were ready for action armed with sophisticated tools and telescopes they turned their minds and machines to the heavens and closely scrutinized supernova 1987a knowing that an exploding star is at its hottest in the first few hours
• 30:30 - 31:00 and is emitting lots of light in ultraviolet wavelengths the astral detectives sprung into action at the time of the explosion we saw the fastest moving stuff was coming toward us at a tenth of the speed of light so that was the actual star blowing up scientists had their explosion now they wanted to know the name of the victim
• 31:00 - 31:30 they dug through a catalog that lists all known stars and their positions in the sky when they struck pay dirt they found the star that exploded it was tagged sk69202 they also determined that it was a huge star 20 times the mass of the sun examining the spectral evidence
• 31:30 - 32:00 scientists could see strong lines of hydrogen sn1987a bore the hallmarks of a type ii core collapse supernova but to confirm their suspicions and prove the core collapse theories experts had to have one more piece of physical evidence they needed neutrinos those ghostly particles that scientists predicted would be unleashed during the
• 32:00 - 32:30 blast in the early 1980s scientists had built a handful of neutrino detectors around the world they consisted of tanks deep underground filled with tons of pure water but these detectors had yet to capture a single supernova neutrino we've had this story for a long time that most of the energy of a supernova
• 32:30 - 33:00 explosion the core collapse supernova explosion goes into neutrinos but we've never seen those neutrinos as luck would have it on february 23 1987 they got their neutrinos two detectors one beneath the city of kamika japan and the other under lake erie in ohio captured a dozen of the elusive particles there were light detectors on this uh
• 33:00 - 33:30 volume of water that were used to see this little flash caused by the neutrino india interacting with matter inside the tank for the first time ever scientists on earth saw tangible evidence of the mysterious neutrino particles generated in the core of an exploding star astronomers now knew the theories first proposed in the 1930s were right
• 33:30 - 34:00 supernova 1987a showed beyond a shadow of a doubt that the massive iron core of a very massive star collapsed and formed a neutron star because in that process a lot of neutrinos should be emitted with the deployment of powerful space-based telescopes astronomers today have built on the astonishing discoveries made in the wake of supernova 1987a
• 34:00 - 34:30 in 2006 30 year old astronomer robert quimby would once again turn conventional thinking on its head and revolutionize the way astronomers searched for supernovas most supernova searches they just want to find as many supernovas as possible so they'll look once every two weeks every one week just just so you can find them and so you can look at as many fields as possible and get as many supernovas as
• 34:30 - 35:00 possible so i decided to look at a limited number of fields and look at them as often as i can the enterprising cosmic gum shoe programmed his robotic telescope to systematically sweep the targeted field every night like an interstellar searchlight it honed in on and methodically scanned the same small dark corner of the cosmos looking for supernovas suspects i had software that can very quickly
• 35:00 - 35:30 process the data and tell me if there's anything there that wasn't there before and when that happens if i think it could be a supernova i'll get a spectrum of it and then that spectrum of it will tell me exactly what it is is it a supernova what type is it etc on september 18 2006 quimby got his big break he found the brightest supernova ever this is my fourth supernova i didn't think that i should be so lucky
• 35:30 - 36:00 and others looked at the spectra and they started taking their own measurements of the photometry how bright it was and they figured out that in fact 2006 gy was brighter than any other published supernova very slowly took over two months 70 days to get the maximum light and then faded again so it was a supernova unlike anything we'd ever seen before discovered by this fourth year graduate student at the university of texas
• 36:00 - 36:30 analysis of the remnant indicated that the star before it exploded was a hundred times the size of the sun and with lots of hydrogen showing in its spectrum the brightest supernova ever recorded wore the stamp of a type 2 event then quimby topped himself when he finally analyzed a seemingly insignificant supernova he found earlier called sn 2005 ap
• 36:30 - 37:00 he made a stunning discovery it was something like 100 billion times as bright as the sun as compared to for a type 1a supernova the peak may be only 6 billion times as bright as the sun it was even brighter than sn 2006 gy like circumstantial evidence astonishing discoveries of new ultra bright supernovas like 2005 ap and others
• 37:00 - 37:30 have opened up a whole new avenue of inquiry into exploding stars and their mo the basic idea we have is that perhaps this is connected somehow to gamma ray bursts gamma rays are the most powerful form of light known in the universe by analyzing supernovas investigators are getting closer than ever to solving some of the most confounding riddles in the cosmos
• 37:30 - 38:00 how one of them makes gamma rays and the other makes an ordinary supernova is still one of the big mysteries nobody really knows how that works what astronomers do know is that supernovas and the gamma-ray bursts associated with them are the brightest beacons in the universe on the galactic highway that is the cosmos supernovas serve as celestial signposts pointing astronomers to the beginning and the end of time and space
• 38:00 - 38:30 nasa's powerful swift satellite launched in 2004 was designed specifically to sweep the sky and detect gamma ray bursts in the universe [Music] like cosmic first responders astrophysicists at nasa's goddard space
• 38:30 - 39:00 flight center in baltimore maryland are standing by 24 7 waiting for a 9-1-1 call from swift basically less than two minutes after swift discovered a gamma reverse the satellite sends down emails directly to our blackberries when a recent supernova recorded as sn 2006 aj appeared the swift satellite caught the shocking gamma rays it
• 39:00 - 39:30 generated and that gum reverse was very interesting because first of all it was a very long duration gamma ray burst usually gamma breasts are very short-lived phenomena only fractions of a second or few seconds but this gummy bears was visible for like 35 minutes we saw three days later a supernova explosion going off at the exact same location and this solved one of the important mysteries of gamma ray burst because we found out at least parts of gamma ray bursts are due to
• 39:30 - 40:00 massive stars that are exploding astronomers today can see hundreds of supernovas and the deadly gamma-ray bursts they generate on the cosmic highway scientists use these stellar headlights to ascertain the bounds and breadth of the universe you can use supernova to probe the universe because if they're very dim you know they were very far away and then you can study the curvature of space-time and all the cosmology that
• 40:00 - 40:30 you can study with them for example if you're on a desert highway and you're looking out at the lights of the cars you can tell which are nearby and which are far away from the apparent brightness of the lights the ones that are nearby look bright the ones that are far away look dim measuring how far away things are very systematically will tell you about the size the age the shape history the future of the universe it turns out that type 1a supernovas are
• 40:30 - 41:00 the best suited for this purpose one of the things that's really interesting about the type 1a supernova the ones that are exploding white dwarfs is that there is this fixed mass this chandrasekhar mass that sets how big the explosion is how much stuff is involved and the consequence of that is that many of these have very nearly the same brightness if the explosion produces the same amount of light then we can measure how much light we
• 41:00 - 41:30 see and figure out how far away the supernova is this is known as the standard candle principle type 1a supernovae are like standard candles they all have about the same peak power the same peak luminosity so if you look at them from different distances they appear different apparent brightnesses they look dimmer if they're farther away and brighter if they're more nearby so if we find type 1a supernovae in
• 41:30 - 42:00 distant galaxies and measure their apparent brightness and compare that with the known power of a nearby type 1a supernova we can determine the distance of that supernova and hence of the galaxy in which it's located the trailblazing technique has also led astro investigators to some radical conclusions basically we can use the distances to supernovae to figure out what the universe is doing
• 42:00 - 42:30 how old it is and we now know that from various lines of evidence that it's a little less than 14 billion years old but in particular found out the universe was accelerating when we thought it was decelerating in the grip of the gravitational materials in it that just caused an intellectual revolution like throwing a ball up towards the ceiling and rather than having it come back down into your hand it goes faster and faster and faster towards the ceiling it's completely counter-intuitive basically all the tech's astronomy textbooks out there all said that the universe should be decelerating that is
• 42:30 - 43:00 gravity should be slowing down the expansion rates but what this result showed is that instead of slowing down it was actually expanding faster and faster and faster while the examination of supernovas has helped scientists unravel many monumental cosmic mysteries experts believe that if they continue to follow the clues left behind when huge stars explode
• 43:00 - 43:30 they'll be able to answer the biggest unanswered questions today scientists know that some days soon we could each witness for ourselves the marvelous and almighty force of a supernova our galaxy is a hundred thousand light years across so that means there's light from a thousand supernovas that's on its way to us now
• 43:30 - 44:00 it could even happen in our very own milky way in our galaxy we are expected to have on average about two supernova explosions per century the problem is that the last supernova that we saw in our galaxy is almost 400 years ago so our galaxy is long overdue if it did happen in our own galaxy we like the titans of space and time tycho kepler chandrasekhar and zwicky would bear witness to the most
• 44:00 - 44:30 destructive and the most creative force in the universe the supernova you