- 2997 - SUPERNOVA - gold forged in exploding stars? - Astronomers are winding back the clock on the expanding remains of a nearby, exploded star. By using our Hubble Space Telescope, they retraced the speedy shrapnel from the blast to calculate a more accurate estimate of the location and time of the exploding star.
----------------------- 2997 - SUPERNOVA - gold forged in exploding stars?
- This star exploded long ago in the Small Magellanic Cloud, a satellite galaxy to our Milky Way. The star left behind an expanding, gaseous corpse, a supernova remnant named “1E 0102.2-7219“. The star was first discovered in X-rays. Like detectives, researchers sifted through archival images taken by Hubble, analyzing visible-light observations made 10 years apart.
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- The velocities of 45 tadpole-shaped, oxygen-rich clumps of ejecta flung by the supernova blast were calculated. Ionized oxygen is an excellent tracer because it glows brightest in visible light.
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- To calculate an accurate explosion age, the astronomers picked the 22 fastest moving ejecta clumps, or knots. They determined that these targets were the least likely to have been slowed down by passage through interstellar material.
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- They then traced the knots' motion backward until the ejecta coalesced at one point, identifying the explosion site. Once that was known, they could calculate how long it took the speedy knots to travel from the explosion center to their current location.
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- According to their estimate, light from the blast arrived at Earth 1,700 years ago, during the decline of the Roman Empire. However, the supernova would only have been visible to inhabitants of Earth's southern hemisphere. Unfortunately, there are no known records of this titanic event.
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- Researchers averaged the speed of all of the gaseous debris to calculate an explosion age. However, the data revealed regions where the ejecta slowed down because it was slamming into denser material shed by the star before it exploded as a supernova.
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- Researchers didn't include those knots in the sample. They needed the ejecta that best reflected their original velocities from the explosion, using them to determine an accurate age estimate of the supernova blast.
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- Hubble also clocked the speed of a suspected neutron star, the crushed core of the doomed star, that was ejected from the blast. Based on their estimates, the neutron star must be moving at more than 2 million miles per hour from the center of the explosion to have arrived at its current position.
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- That is at the extreme end of how fast astronomers think a neutron star can be moving, even if it got a kick from the supernova explosion. So the hunt may still be on for the neutron star.
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- We are made of exploded stars. Carl Sagan famously said: “We are made of star stuff.” He was referring to the origin of many elements like the calcium in our bones and the iron in our blood, that are forged exploding stars.
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- Some of the elements we know, like carbon and oxygen, are made in stars, but others , including all hydrogen, most helium, and a bit of lithium, were forged nearly 14 billion years ago through a process called Big Bang nucleosynthesis.
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- It wasn’t until the first stars formed some 100 million years after the Big Bang that the universe began to diversify into the full range of elements.
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- The idea that smaller, lighter pieces of matter could be forged into heavier ones dates back to at least the ancient Greeks. But it wasn’t until the 1920s that scientists really began to understand the specifics.
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- At that time, scientists were trying to figure out what powered the Sun. Astronomer Arthur Eddington first theorized that hydrogen atoms, the lightest element, could be squeezed together under immense temperature and pressure into helium, the second lightest element. This process, known as “nuclear fusion“, releases colossal amounts of energy.
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- Over the following decades, scientists verified the mechanism, working out many of the details. And by the mid-20th century, astronomers had a good handle on how stars made elements lighter than iron.
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- They deduced that during the prime years of their lives, stars steadily churn hydrogen into helium within their cores. And if a star is larger than about half the mass of the Sun, once it runs out of hydrogen in its core, it begins to collapse under its own uncontested gravity.
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- This collapse creates additional pressure in the star’s core, which sparks helium burning and can ultimately produce by-products such as carbon and oxygen. Stars more than twice the mass of the Sun that also have carbon and oxygen from their forbearers can produce nitrogen as well.
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- Stars up to roughly eight times the mass of the Sun eventually reach a phase of their lives known as the asymptotic giant branch. This is where their cores become inactive, and helium and hydrogen burning migrates to the stars’ outer layers.
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- At this stage, the stars begin the slow neutron-capture process. Also known as the s-process, this occurs in helium burning shells around stellar cores, which creates heavier elements like strontium, lead, and others.
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- Eventually, these relatively low-mass stars collapse into dense objects known as white dwarfs. And as they do, they can expel supersonic winds, releasing shells of gas that create beautiful, albeit short-lived, planetary nebulae.
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- This liberates the stars’ elemental creations into interstellar space, where some of the enriched material will be recycled into new stars and planetary systems.
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- When a more massive star (greater than about eight solar masses) reaches the end of its life, it can explode as a core-collapse supernova. Such supernovae can leave behind neutron stars that produce highly neutron-rich winds.
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- In these winds, additional elements are formed through the rapid neutron-capture process, or r-process. When the nuclei of existing atoms capture extra free neutrons, the resulting product can be radioactive, meaning it will decay into a different version of itself or a new element entirely, or it can remain stable.
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- The “r-process” is very similar to the s-process, except it’s much quicker. The s-process can take decades or centuries to capture successive neutrons, with the entire elemental transformation taking tens of thousands of years.
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- A supernova can produce roughly a billion billion billion neutrons per cubic inch, so the r-process is nearly instantaneous in astronomical terms. For example, through the r-process, an iron atom can be transformed into uranium in less than a second.
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- Signatures of elements that are only created by the r-process were observed coming from the location of a confirmed neutron star merger picked up by gravitational waves.
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- Even though such mergers are rarer than supernovae, astronomers now think that neutron star mergers are the primary sites of most heavy r-process elements. This observed gravitational-wave event alone is expected to have produced an estimated three to 13 Earth-masses worth of gold.
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- Now that astronomers know how the universe forges all of its elements, the next step is working to understand exactly how much of each element is produced through various processes, as well as where they tend to occur. By building on this knowledge, researchers ultimately hope it will allow them to easily probe the complex history of any galaxy by simply looking at the ratios of its elements.
- In a remote galaxy, two neutron stars circled one another in a ballet of ultimate destruction and inevitable creation. Both objects were the remnants of massive stars, probably from a binary system, that had become supernovae long before. Each was incredibly massive, with neutrons so closely packed that their cores became diamond.
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- The dance could not go on forever and the stars collided, releasing unimaginable energy and sending gravitational waves speeding through the fabric of space-time.
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- In 2017, 1.3 billion years later, astronomers detected those waves with the “Laser Interferometer Gravitational-wave Observatory“. Albert Einstein’s prediction that the universe should be filled with such faint ripples caused by gravity from massive objects included sources such as neutron star mergers. Yet finding a disturbance in the fabric of space-time from this kind of event had proven elusive until then.
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- When news of the detection of gravitational waves broke, the media wanted to know what else happens when neutron stars collide. Astronomers explained that, beyond the destruction of the stars and the ripples in space, such events also create all the heavy elements we know in the blink of an eye. But what did the media key into? That gold comes from outer space.
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- It’s not surprising that of the many elements formed in the cataclysmic destruction of massive stars, gold should be the one that captures our imaginations the most. Elements necessary for life, such as carbon, oxygen, potassium, and sulfur, should rank higher on a list of favorites. But we have an emotional connection with gold.
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- Thousands of years ago, someone may have seen a shiny object in a stream and picked up a piece of gold. It must have looked intriguing though, because the metal is so soft, it’s not very useful.
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- Archaeologists have found a 6,500-year-old gold bead in Bulgaria and recovered a nearly 3,000-year-old gold coin from the Black Sea. The oldest known gold artifacts in England were found buried at Stonehenge, part of the grave goods belonging to a mysterious individual from Europe.
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- The ancient Egyptians had vast gold mines far south of their capital of Thebes, allowing them to encase the mummy of Tutankhamun in the precious metal. Few other ancient civilizations had such wealth. When the mummy was unwrapped, archaeologists found two daggers. One was made of what is now known to be meteoritic iron, and the other was made of pure gold.
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- It took 20th-century science to unravel this mystery. Iron, silver, and copper rust or turn colors due to reactions with oxygen. Oxygen is always hungry for electrons. Iron will give up two or three electrons to oxygen and will oxidize (rust) as a result. Other elements also fall victim to oxygen. But not gold. It’s the most nonreactive of all metals because it refuses to share electrons with oxygen.
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- Like all the heavy elements on the periodic table, there just isn’t much gold to be found. If all the gold mined in human history were formed into one solid cube, it would measure about 70 feet (21.3 meters) on a side.
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- That would be around 183,000 tons of gold. Sounds like a lot, but if melted, it would fill only three and a half Olympic-size swimming pools. In 2018, Barrick Gold Corporation’s mines in Nevada processed millions of tons of ore to recover just 4 million ounces (125 tons) of gold.
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- Because it is so dense and heavy, most of Earth’s gold sank to the core of our planet. Geologist estimates that 99 percent of the world’s gold is buried thousands of miles below our feet.
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- They estimate that 1.6 quadrillion tons of gold lie within the core. All this gold, if brought to the surface, would form a layer of the shimmering metal just 16 inches (40.6 centimeters) thick.
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- Compared to Earth’s total size, that’s not much gold. There is actually six times more platinum in our planet’s core, which contains about 1 part per million of gold. Gold is, in fact, quite rare.
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- During the total solar eclipse on August 18, 1868, several astronomers using spectroscopy detected a new element and, it turned out, the universe’s second most abundant one in the Sun: helium. Carbon, nitrogen, iron, and all the heavier elements of the periodic table, including gold, were eventually identified in a gaseous state in the Sun’s atmosphere.
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Eventually, scientists calculated that the Sun contains almost 2.5 trillion tons of gold, enough to fill Earth’s oceans and more. Still, that’s just eight atoms of gold for every trillion atoms of hydrogen, a tiny amount when compared to the mass of the Sun.
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- Most of us think of the first atomic bomb and splitting atoms, the process of nuclear fission, when E=mc2 comes to mind. In 1920, however, Sir Arthur Eddington, then at Cavendish Laboratory in Cambridge, England, thought that the fusing of hydrogen into helium could be the powerhouse of the Sun. Einstein’s famous equation showed that incredible energy would be released in such a process.
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- Almost two decades after Eddington and others began to explore fusion, German-American physicist Hans Bethe described the now famous proton-proton chain reaction that explains how hydrogen fuses into helium.
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- Deep within the Sun is a vast “soup” of hydrogen atoms consisting of one proton and one electron each, which are in constant, rapid motion. Most of the time, the electromagnetic force repels any collisions. Trying to stick similar poles of two magnets together gives a feel for such repulsion. But collisions happen, and protons fuse together. When four protons eventually fuse, helium–4 forms, releasing energy and making the Sun shine.
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- Our Sun contains enough hydrogen to continue this fusion process for another 5 billion years. Eventually, helium will begin to fuse, forming the final products of carbon, nitrogen, and oxygen (element No. 8). Within more massive stars, whose stronger gravity creates more pressure and heat, elements beyond oxygen can fuse.
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- But this process can continue only until iron (element No. 26) forms at the center of giant stars, and that’s when fusion shuts down. Finally, the star’s core will collapse and then rebound in a supernova explosion.
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- The proton-proton cycle is the chain reaction by which hydrogen fuses into helium in the Sun’s core. The tiny bits of mass that are converted to energy satisfy Albert Einstein’s famous equation, E=mc2.
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- As the outer layers of the star are blasted into space, one of two neutron capture reactions takes place. In both, free neutrons penetrate the nuclei of nearby atoms and are “captured” by elements released in the explosion.
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- Slow neutron capture (called “slow” because radioactive decay into other elements can occur before other neutrons are captured) creates about half of the elements heavier than iron. But that still leaves a lot of heavyweights on the periodic table. To make the rest, you need massive colliding stars that produce rapid neutron capture.
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- Once astronomers had pinpointed the source of the 2017 gravitational waves, researchers at the Max Planck Institute for Astronomy were able to detect strontium in the maelstrom of matter expanding into space at nearly 30 percent the speed of light. This element and others were formed by the rapid neutron capture reaction. The merger of these stars sent 1,022 free neutrons flying through just 1 cubic centimeter of space every second.
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- Such a high density of neutrons creates conditions that allow existing elements to quickly capture free neutrons. Strontium, thorium, uranium, and even gold form in a literal flash.
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- Off they go into the depths of space. During the nearly 14-billion-year life span of our universe, this has happened enough times to seed the nebulae that eventually collapse to form solar systems such as ours with gold and all the other heavy elements, too.
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- Gold pervades our lives. The element is in every cellphone and computer. We coat sunglasses and astronaut visors with it. Gold thread is used in electronics and in clothing. Nations pay their debts with gold. We make precious objects out of it, from jewelry to religious artifacts. We put gold in our teeth and even make toilets with it. Doctors inject patients with gold to help relieve rheumatoid arthritis. You can even eat chocolate covered in gold.
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- Carl Sagan famously said we are made from the stuff of stars. So is the world around us. The next time you glance at the gold ring on your finger or feel the gold chain around your neck, remember that they are indeed a gift from the star
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- January 23, 2021 SUPERNOVA - gold forged? 2998
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