Everything Everywhere Daily: History, Science, Geography & More - Supernovas: They're a Blast

Episode Date: July 10, 2021

One of the brightest things in the universe is caused by one of the most powerful explosions in the universe: a supernova. While they don’t happen very often, they were known to ancient peoples and their appearance would often be recorded because they were such a rare and special event. Today, astrophysicists have a much better understanding of what supernovas are and how they can help us better understand the rest of the universe. Learn more about your ad choices. Visit megaphone.fm/adchoices

One of the brightest things in the universe is caused by one of the most powerful explosions in the universe, a supernova. While they don't appear very often, they were known to ancient peoples, and their appearance would often be recorded because they were such a rare and special event. Today, astrophysicists have a much better understanding of what supernovas are and how they can help us better understand the rest of the universe. Learn more about supernovas on this episode of Everything Everywhere Daily. What if your perceptions about the past were wrong? ThruLine is a podcast that takes you back in time to uncover the parts of the story that may have gone unnoticed. It effectively turned day into night. And how it shaped the world now.

Time travel with us every week on the ThruLine podcast from NPR. This episode is sponsored by Audible.com. My audiobook recommendation today is Earth Shattering, violent supernovas, galactic explosions, biological mayhem, nuclear meltdowns, and other hazards to life in our universe by Bob Berman. The overwhelming majority of celestial space is inactive and will remain forever unruffled. But when cosmic violence does unfold, it changes the very fabric of the universe,

with mega explosions and ripple effects that reach the near limits of human comprehension. In Earth Shattering, astronomy writer Bob Berman guides us through an epic investigation into these instances of violence, both mammoth and microscopic. From the sudden creation of dazzling new stars, to the furiously explosive birth of our moon, from the uncontrollable truth about ultra-high-energy cosmic rays bombarding us, to the incredible ways in which humanity has harnessed cataclysmic energy for its gain.

You can get a free one-month trial to Audible and two free audiobooks by going to audibletrial.com slash everything everywhere, or by clicking on the link in the show notes. Supernovas, when they occur in our galaxy, are so bright that they can often be seen in the sky in the middle of the day. They don't happen that often, however. Centuries or even millennia can pass between a supernova which can be visible with the naked eye from Earth. Astronomers have detected the remnants of a supernova in the constellation Vela, which probably exploded about 10 to 20,000 years ago. It would have been strong enough to be seen by humans, but we have no records of it.

There may have been records of a supernova that occurred about 6,500 years ago. years ago from text in ancient India. The first confirmed record of a supernova occurred in the year 185. Astronomers noted the bright star which suddenly appeared out of nowhere. The light lasted for about eight months before disappearing. They noted that, unlike comets, the light didn't move in the sky. This was recorded by Chinese astronomers, but there's also reason to believe that the Romans might have recorded it as well, but those texts have long since been lost. The term Nova is a Latin term, which simply means new. It's possible that Chinese astronomers have observed 20 different supernovas over a period of 2,000 years. The problem is it's hard to know if an ancient source

actually saw a supernova or if they just saw a comet. In the year 1006, what was probably the brightest supernova ever was recorded all over the world. Chinese, Arab, and European sources all may note of the event. Arab astronomer Ali Ibn Ridwan said it was a quarter of the brightness of a full moon. In 1050,000, the supernova which created the crab nebula occurred. The last supernova in our galaxy, which humans could observe without telescopes, took place in 1604. With the advent of telescopes, however, astronomers began to see things that they couldn't explain. Some stars would suddenly become brighter for no apparent reason. In 1885, a supernova was detected in the Andromeda Galaxy,

which, for a brief period of time, was brighter than the entire galaxy. In the 20th century, astrophysicists began to figure out exactly what this phenomenon was. In 1931, Walter Bade and Fritzowiczewiki postulated that supernovas were actually giant explosions, which explained their sudden appearance and disappearance. In 1938, Bade realized that nebula's, large gas clouds, were the results of supernovas, and that the crab nebula was the leftovers from the 1054 supernova. In 1941, the categorization of supernovas was developed when they realized that there were different types of supernovas based on their spectral signature. So what is happening with supernovas? What causes such a massive explosion? This will require a bit of explaining, and there are several different concepts

involved. And I'll actually start with a type 2 supernova. And just for the record, I'm aware that there are subdivisions under both type 1 and type 2 supernovas, but I'm just trying to simplify the concepts here. A type 2 supernova occurs when a single large star collapses. When a star is formed, it's made out of hydrogen gas. The gas coalesces due to gravity until the pressure becomes so great that the hydrogen atoms actually fuse into helium atoms. The heat from the fusion will cause the expansion of the gases counterbalancing the inward force of gravity. This will continue for many millions of years until the hydrogen is exhausted. Then the remaining helium will begin to fuse into carbon. As the lighter elements are exhausted, this process will continue with heavier and

heavier elements, but only to a point. Once a star starts producing iron, it'll no longer give off energy by fusing with other atoms. At this point, fusion stops, as it would require an energy input to continue fusing the atoms. Without any fusion taking place, there's no longer any heat that will counteract the gravity pulling everything together. Once this happens, the star will collapse in a fraction of a second, causing a massive explosion. What results from the explosion will depend on the size and mass of a star. If it's over 25 times the size of our sun, it might end up as a black hole. If it's about 10 to 25 times greater, it will end up as a neutron star. The other type of supernova is a type 1 supernova, and it's the result of a binary star system

made up of two stars. These stars are closer in size to our sun. They're not that big. One of the stars in the system will become a white dwarf. This is the exhausted core of a star that wasn't large enough to get to the point where it could create iron. A white dwarf is a star so dense that it's only prevented from collapsing further due to something called electron degeneracy pressure. I'm not going to dive too deep into the concept of electron degeneracy pressure, but basically, the matter is compressed so much that only quantum effects in the individual atoms are stopping it from collapsing even further. The extremely dense white dwarf then begins stealing matter from its partner star, which would

usually be, but doesn't have to be, a red giant. The white dwarf will start adding mass and growing. However, there is a hard limit to how much mass a white dwarf star can have. In fact, it is exactly 1.44 solar masses.

This exact point is known as the Chandra Saker limit, and it was proposed and named after the great Indian American physicist and Nobel Prize winner, Suburamanian Chandra Saker. Beyond the Chandra Sagar limit, the electron degeneracy pressure can no longer withstand the pull of gravity, and the star will collapse and explode. So why are these massive solar explosion so important?

There are two reasons why you should care about supernovas. The first has to do with the type 1 supernovas in particular, those from a binary star. One of the major problems in astronomy is measuring distances. Let's say you're on a dark road and you see a light in the distance. how far away is the light? The truth is, there's no way to know if you don't know what the source of the light is. It could be someone with a flashlight not that far away, or it could be someone with a massive search light miles away.

Type 1 supernovas are important, because when they explode, they all do so with exactly the same force. Because they only explode once they pass the Chandra Saker limit. Every type 1 supernova explodes with the exact same mass, and thus have the exact same luminosity. In astrophysics, this is known as a standard candle. Because these types of supernovas are all the same, by measuring the relative luminosity, astronomers can calculate the distance.

So type 1 supernovas are really handy. I'll go into how the age and size of the universe are measured in a future episode, but this will definitely be part of it. The other reason why supernovas are so important is that that is how all the heavy elements are made. As I mentioned before, a star can't create elements heavier than iron via fusion. So, how are elements heavier than iron, like lead, gold, and uranium created? Where does the energy come from to fuse these elements?

It comes from one of the only forces in the universe which has enough energy to fuse these heavy elements together. A supernova. That means that all the heavy elements on Earth, all of the elements in your body heavier than iron like copper and zinc, at one point came from a supernova. A supernova that took place probably billions of years before our solar system was even formed. So supernovas not only help us understand the rest of the universe, but they also, in a very literal sense, make up ourselves and the world. The associate producer of Everything Everywhere Daily is Thor Thompson.

Today's review comes from listener Bob DelGlornow over on audible.com. He writes, Gary is my new riding companion. Gary is my new riding buddy as I drive around town with my 11-year-old daughter and my five-month-old son. As a homeschooling dad, this counts as part of our history curriculum. Keep up the fantastic job. Thanks, Bob. While I never planned it, I've had several people tell me how they listen to the show with their kids. Just to let everyone know, I'll always keep the language clean,

and the subject matter will be as family-friendly as history will allow. Remember, if you leave a review, I might read your review on the show. Thank you.