Astronomy

Could Black holes forge heavier elements that have yet to be discovered?

Could Black holes forge heavier elements that have yet to be discovered?

Observations

  • The heaviest elements known in abundance in nature are forged deep within stars.

  • These elements are made possible by the high densities/pressures within the stars.

  • Black holes are known to have a much higher density/pressure than any known star.

  • Black holes are also known to be a phase of stellar evolution - this suggests that the original star's internal process of forging metals would persist within the resultant black hole.

  • Scientists have forged synthetic/ephemeral heavy metals under conditions which could hypothetically be sustained within a black hole.

Hypothesis:

Black holes forge heavier elements that have not been observed on earth. The conditions needed to sustain these elements are unique to the black hole, due to its high density/pressures. These conditions can be glimpsed, but not sustained in any experimental context

Follow up questions:

  • Has this been hypothesized?

  • Where can I find research on this topic?


The problem of the superheavy elements is not that we can't forge them. Their problem is that they decay very quickly. For example, Oganesson, the heaviest element synthetised until now, has a half life of 181 ms.

In theory, even much heavier elements could be created in particle accelerators, but there is no way to even detect them.

In neutron stars, or in exploding supernovas, all the elements are created, but there is no way to even detect them. We can consider a neutron star as a large nucleus with $approx 10^{56}$ neutrons.1

In black holes, the fact is that no one knows, what is in them. They don't radiate anything (with a very little exception), and nothing leaves the singularity in them. To understand what is in them, would require currently unrealistic advances in Physics. The singularity in their center is probably not baryonic matter, though, thus we could hardly say that it would be any chemical element.

1As @PM2Ring's excellent comment says, neutron stars also have a significant number of other particles, too, not only neutrons. I also extend it that they are bound gravitationally and not by the strong interaction, which makes them in this aspect essentially different from nuclei.


The heaviest elements known in nature are forged deep within stars.

No, the heaviest elements are made on Earth in scientific laboratories, or in the extreme gravity of a neutron star's crust.

These elements are made possible by the high densities/temperature/pressures within the stars.

Many of the larger elements can be made in supernovae and neutron star collisions, not in stars. It requires extreme conditions for these elements to form.

Black holes are known to have a much higher density/temperature/pressure than any known star.

Black holes are actually very cold, they "absorb" any radiation that passes their event horizon. Outside the event horizon may be some very hot material, but it is not actually so hot compared to the core of a star.

Black holes are also known to be a phase of stellar evolution - this suggests that the original star's internal process of forging metals would persist within the resultant black hole.

No, inside the black hole everything falls, and reaches a singularity in a short amount of time.

Scientists have forged synthetic/ephemeral heavy metals under conditions which could hypothetically be sustained within a black hole.

As above, the conditions beyond the event horizon are unlike anything we have on Earth, because there is the unavoidable singularity.

After some matter has crossed the event horizon it will certainly come to the singularity. (in the same way as you will certainly reach tomorrow) And as it gets closer the tidal effects get greater, eventually ripping the atoms apart. The extreme gravity in a black hole will tend to pull matter apart not fusing it to larger atoms.

There may be nucleosynthesis in the accretion disc around a black hole. While the amount of high mass atoms made here is relatively small, it may be useful for the sake of detecting and distinguishing black holes from neutron stars or white dwarfs.


Superheavy elements have short half lives because of their extreme instability with respect to alpha decay and fission. This is a result of their high electric charge, which results in strong forces of electrical repulsion. Although theorists have predicted an "island of stability" due to quantum mechanical shell effects, this stability is a relative thing. We're still talking about half-lives on the order of seconds or less. So any such element created by astrophysical processes will not survive for very long, even if it doesn't fall into the black hole.

So conceivably in the accretion disk, outside the event horizon, you could get some fusion events resulting in the formation of superheavy elements, but those elements would not survive for very long, even if they were somehow ejected rather than infalling past the horizon. And the normal methods for detecting and characterizing superheavy elements would not work here. Normally we look for things like alpha-decay chains with characteristic alpha energies. Those would not be detectable from outside the accretion disk, since charged particles interact strongly with matter and are stopped.

The conditions needed to sustain these elements are unique to the black hole, due to its high density/pressures.

Most of the interior of a black hole (inside the event horizon) is probably an extremely good vacuum. The only high densities and pressures would be near the singularity. So any exotic matter formed at high densities and pressures would not be observable from earth or have any consequences for the outside universe, because nothing can escape from inside the event horizon.

If we were to send a space probe inside a black hole to look for exotic matter being formed near the singularity, the probe would not be able to report its results back. Also, the region of high-density and high-pressure infalling matter would exist near the singularity, which would probably not be detectable to the probe until the probe itself had been destroyed by the same processes. (On the inside of a black hole, if general relativity is correct, you can't see the singularity. You only see infalling photons from the outside.)

If exotic matter is formed near the singularity, it will only exist for a very short time before accreting onto the singularity. (IIRC the maximum infall time for a 10-solar-mass black hole is on the order of milliseconds from horizon to singularity.) We don't really know what happens at the singularity, but we certainly can't have atomic nuclei under those conditions.


Primordial black holes may have helped to forge heavy elements

Artist’s depiction of a neutron star. Credit: NASA

Astronomers like to say we are the byproducts of stars, stellar furnaces that long ago fused hydrogen and helium into the elements needed for life through the process of stellar nucleosynthesis.

As the late Carl Sagan once put it: "The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of star stuff."

But what about the heavier elements in the periodic chart, elements such as gold, platinum and uranium?

Astronomers believe most of these "r-process elements"—elements much heavier than iron—were created, either in the aftermath of the collapse of massive stars and the associated supernova explosions, or in the merging of binary neutron star systems.

"A different kind of furnace was needed to forge gold, platinum, uranium and most other elements heavier than iron," explained George Fuller, a theoretical astrophysicist and professor of physics who directs UC San Diego's Center for Astrophysics and Space Sciences. "These elements most likely formed in an environment rich with neutrons."

In a paper published August 7 in the journal Physical Review Letters, he and two other theoretical astrophysicists at UCLA—Alex Kusenko and Volodymyr Takhistov—offer another means by which stars could have produced these heavy elements: tiny black holes that came into contact with and are captured by neutron stars, and then destroy them.

Neutron stars are the smallest and densest stars known to exist, so dense that a spoonful of their surface has an equivalent mass of three billion tons.

Tiny black holes are more speculative, but many astronomers believe they could be a byproduct of the Big Bang and that they could now make up some fraction of the "dark matter"—the unseen, nearly non-interacting stuff that observations reveal exists in the universe.

If these tiny black holes follow the distribution of dark matter in space and co-exist with neutron stars, Fuller and his colleagues contend in their paper that some interesting physics would occur.

They calculate that, in rare instances, a neutron star will capture such a black hole and then devoured from the inside out by it. This violent process can lead to the ejection of some of the dense neutron star matter into space.

"Small black holes produced in the Big Bang can invade a neutron star and eat it from the inside," Fuller explained. "In the last milliseconds of the neutron star's demise, the amount of ejected neutron-rich material is sufficient to explain the observed abundances of heavy elements."

"As the neutron stars are devoured," he added, "they spin up and eject cold neutron matter, which decompresses, heats up and make these elements."

This process of creating the periodic table's heaviest elements would also provide explanations for a number of other unresolved puzzles in the universe and within our own Milky Way galaxy.

"Since these events happen rarely, one can understand why only one in ten dwarf galaxies is enriched with heavy elements," said Fuller. "The systematic destruction of neutron stars by primordial black holes is consistent with the paucity of neutron stars in the galactic center and in dwarf galaxies, where the density of black holes should be very high."

In addition, the scientists calculated that ejection of nuclear matter from the tiny black holes devouring neutron stars would produce three other unexplained phenomenon observed by astronomers.

"They are a distinctive display of infrared light (sometimes termed a "kilonova"), a radio emission that may explain the mysterious Fast Radio Bursts from unknown sources deep in the cosmos, and the positrons detected in the galactic center by X-ray observations," said Fuller. "Each of these represent long-standing mysteries. It is indeed surprising that the solutions of these seemingly unrelated phenomena may be connected with the violent end of neutron stars at the hands of tiny black holes."


Supernova surprise creates elemental mystery

Michigan State University (MSU) researchers have discovered that one of the most important reactions in the universe can get a huge and unexpected boost inside exploding stars known as supernovae.

This finding also challenges ideas behind how some of the Earth's heavy elements are made. In particular, it upends a theory explaining the planet's unusually high amounts of some forms, or isotopes, of the elements ruthenium and molybdenum.

"It's surprising," said Luke Roberts, an assistant professor at the Facility for Rare Isotope Beams, FRIB, and the Department of Physics and Astronomy, at MSU. Roberts implemented the computer code that the team used to model the environment inside a supernova. "We certainly spent a lot of time making sure the results were correct."

The results, published online on Dec. 2 in the journal Nature, show that the innermost regions of supernovae can forge carbon atoms over 10 times faster than previously thought. This carbon creation happens through a reaction known as the triple-alpha process.

"The triple-alpha reaction is, in many ways, the most important reaction. It defines our existence," said Hendrik Schatz, one of Roberts's collaborators. Schatz is a University Distinguished Professor in the Department of Physics and Astronomy and at the Facility for Rare Isotope Beams and the director of the Joint Institute for Nuclear Astrophysics -- Center for the Evolution of the Elements, or JINA-CEE.

Nearly all of the atoms that make up the Earth and everything on it, people included, were forged in the stars. Fans of the late author and scientist Carl Sagan may remember his famous quote, "We're all made of star stuff." Perhaps no star stuff is more important to life on Earth than the carbon made in the cosmos by the triple-alpha process.

The process starts with alpha particles, which are the cores of helium atoms, or nuclei. Each alpha particle is made up of two protons and two neutrons.

In the triple-alpha process, stars fuse together three alpha particles, creating a new particle with six protons and six neutrons. This is the universe's most common form of carbon. There are other isotopes made by other nuclear processes, but those make up just over 1% of Earth's carbon atoms.

Still, fusing three alpha particles together is usually an inefficient process, Roberts said, unless there's something helping it along. The Spartan team revealed that the innermost regions of supernovae can have such helpers floating around: excess protons. Thus, a supernova rich in protons can speed up the triple-alpha reaction.

But accelerating the triple-alpha reaction also puts the brakes on the supernova's ability to make heavier elements on the periodic table, Roberts said. This is important because scientists have long believed that proton-rich supernovae created Earth's surprising abundance of certain ruthenium and molybdenum isotopes, which contain closer to 100 protons and neutrons.

"You don't make those isotopes in other places," Roberts said.

But based on the new study, you probably don't make them in proton-rich supernovae, either.

"What I find fascinating is that you now have to come up with another way to explain their existence. They should not be here with this abundance," Schatz said of the isotopes. "It's not easy to come up with alternatives."

"It's kind of a bummer in a way," said the project's originator, Sam Austin, an MSU Distinguished Professor Emeritus and former director of the National Superconducting Cyclotron Laboratory, FRIB's predecessor. "We thought we knew it, but we don't know it well enough."

There are other ideas out there, the researchers added, but none that nuclear scientists find completely satisfying. Also, no existing theory includes this new discovery yet.

"Whatever comes up next, you have to consider the effects of an accelerated triple-alpha reaction. It's an interesting puzzle," Schatz said.

Although the team has no immediate solutions to that puzzle, the researchers said it will impact upcoming experiments at FRIB, at MSU, which was recently designated as a U.S. Department of Energy Office of Science (DOE-SC) user facility.

Furthermore, MSU provides fertile ground for new theories to germinate. It's home to the nation's top-ranked graduate program for training the next generation of nuclear physicists. It's also a core institution of JINA that's promoting collaborations across nuclear physics and astrophysics like this one, which also included Shilun Jin. Jin worked on the project as an MSU postdoc and has since gone on to join the Chinese Academy of Sciences.

So, although Austin expressed a little disappointment that this result contradicts longstanding notions of element creation, he also knows it will fuel new science and a better understanding of the universe.

"Progress comes when there's a contradiction," he said.

"We love progress," Schatz said. "Even when it's destroying our favorite theory."


Massive Black Hole Smashes Record

Using two NASA satellites, astronomers have discovered the heftiest known black hole to orbit a star. The new black hole, with a mass 24 to 33 times that of our Sun, is more massive than scientists expected for a black hole that formed from a dying star.

The newly discovered object belongs to the category of "stellar-mass" black holes. Formed in the death throes of massive stars, they are smaller than the monster black holes found in galactic cores. The previous record holder for largest stellar-mass black hole is a 16-solar-mass black hole in the galaxy M33, announced on October 17.

"We weren&rsquot expecting to find a stellar-mass black hole this massive," says Andrea Prestwich of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of the discovery paper in the November 1 Astrophysical Journal Letters. "It seems likely that black holes that form from dying stars can be much larger than we had realized."

The black hole is located in the nearby dwarf galaxy IC 10, 1.8 million light-years from Earth in the constellation Cassiopeia. Prestwich&rsquos team could measure the black hole&rsquos mass because it has an orbiting companion: a hot, highly evolved star. The star is ejecting gas in the form of a wind. Some of this material spirals toward the black hole, heats up, and gives off powerful X-rays before crossing the point of no return.

In November 2006, Prestwich and her colleagues observed the dwarf galaxy with NASA&rsquos Chandra X-ray Observatory. The group discovered that the galaxy&rsquos brightest X-ray source, IC 10 X-1, exhibits sharp changes in X-ray brightness. Such behavior suggests a star periodically passing in front of a companion black hole and blocking the X-rays, creating an eclipse. In late November, NASA&rsquos Swift satellite confirmed the eclipses and revealed details about the star&rsquos orbit. The star in IC 10 X-1 appears to orbit in a plane that lies nearly edge-on to Earth&rsquos line of sight, The Swift observations, as well as observations from the Gemini Telescope in Hawaii, told Prestwich and her group how fast the two stars go around each other. Calculations showed that the companion black hole has a mass of at least 24 Suns.

There are still some uncertainties in the black hole&rsquos mass estimate, but as Prestwich notes, "Future optical observations will provide a final check. Any refinements in the IC 10 X-1 measurement are likely to increase the black hole&rsquos mass rather than reduce it."

The black hole&rsquos large mass is surprising because massive stars generate powerful winds that blow off a large fraction of the star&rsquos mass before it explodes. Calculations suggest massive stars in our galaxy leave behind black holes no heavier than about 15 to 20 Suns.

The IC 10 X-1 black hole has gained mass since its birth by gobbling up gas from its companion star, but the rate is so slow that the black hole would have gained no more than 1 or 2 solar masses. "This black hole was born fat it didn&rsquot grow fat," says astrophysicist Richard Mushotzky of NASA Goddard Space Flight Center in Greenbelt, Md., who is not a member of the discovery team.

The progenitor star probably started its life with 60 or more solar masses. Like its host galaxy, it was probably deficient in elements heavier than hydrogen and helium. In massive, luminous stars with a high fraction of heavy elements, the extra electrons of elements such as carbon and oxygen "feel" the outward pressure of light and are thus more susceptible to being swept away in stellar winds. But with its low fraction of heavy elements, the IC 10 X-1 progenitor shed comparatively little mass before it exploded, so it could leave behind a heavier black hole.

"Massive stars in our galaxy today are probably not producing very heavy stellar-mass black holes like this one," says coauthor Roy Kilgard of Wesleyan University in Middletown, Conn. "But there could be millions of heavy stellar-mass black holes lurking out there that were produced early in the Milky Way&rsquos history, before it had a chance to build up heavy elements."


How Cygnus X-1 Challenges Theories of Stellar Evolution

The team chanced on their finding whilst conducting an ambitious project to observe Cygnus X-1 almost continuously over a full 5.6-day orbit with the network of radio telescopes that comprise VLBA and X-ray telescopes. The aim of the research was to better understand how gas being fed into a black hole from a binary partner via a spiraling accretion disc connects to powerful jets of material that launch out from near the central region at near light speed.

“We had not originally aimed to refine the distance and the mass of the black hole but realised that our data would allow us to do so, by accounting properly for the effects of the black hole orbit. But there is still a wealth of data from this rich observing campaign that we are looking to analyse more fully.”

Professor James Miller-Jones, ICRAR, Curtin University

“Black holes form from the deaths of the most massive stars when they run out of fuel and gravity takes over,” says Miller-Jones. “The mass of the resulting black hole is set by the initial mass of the star from which it formed — which we call the progenitor star — the amount of mass that star lost in winds over its lifetime, and any interactions with a nearby companion star.”

Miller-Jones continues, saying massive stars launch very powerful winds from their surfaces, which leads to significant mass loss over their few-million year lifetimes. Some of the later phases of star’s evolution have particularly strong winds — determined by the abundance of elements heavier than helium in the gas from which the star was formed. More heavy elements mean stronger winds, and ultimately, a less massive star immediately before gravitational collapse.

While some stars can also lose further mass in supernova explosions as they collapse to form a black hole, the evidence suggests that in Cygnus X-1, there was no explosion, and the star collapsed directly into a black hole,” says Miller-Jones. “The stronger the stellar winds during the late evolutionary phases of the star, the less massive we would have expected the black hole to be.”

An artist’s impression of the Cygnus X-1 system. This system contains the most massive stellar-mass black hole ever detected without the use of gravitational waves, weighing in at 21 times the mass of the Sun. (ICRAR)

At first, the team wasn’t totally aware of just how significant their discovery of mass disparities in the Cygnus X-1 binary system was. “I think that our biggest surprise was when we appreciated the full implications of our measurements,” Miller-Jones says. “As observational astronomers, my team and I had already found that we could revise the source distance and the black hole mass. However, it was not until I visited a colleague, Professor Ilya Mandel of Monash University, who is a theoretical astronomer, that we realised how important this actually was.”

Mandel–co-author on the resulting paper– realised that a 21-solar mass black hole was too massive to form in the Milky Way with the constraints in place due to the current prevailing estimates of the amount of mass lost by massive stars in stellar winds.

“The existence of such a massive black hole in our own Milky Way galaxy has shown us that the most massive stars blow less mass off their surface in winds than we had previously estimated. This improves our knowledge of how black holes form from the most massive stars.”

Professor James Miller-Jones, ICRAR, Curtin University

Scientists Just Found the Smallest Black Hole Yet

There are massive black holes and there are supermassive black holes. There are even ultramassive black holes.

And yet, we so rarely ponder the little ones. It's not as if a black hole that isn't, say 40 billion times as massive as our sun — like the ultramassive Holm15A* — doesn't have its own strange and spellbinding properties.

But only recently have scientists begun looking for black holes on a much smaller scale. And surprise, surprise, it didn't take long to find one.

In fact, the latest black hole, discovered by researchers at the Ohio State University, may be the smallest one detected yet.

Although, theoretically, a black hole could be microscopic in size, the black hole this team discovered is far from pocket-sized.

Publishing the results this week in the journal Science, researchers note the black hole is roughly 3.3 times as massive as our own sun — and inhabits a binary system on the fringe of our Milky Way galaxy, about 10,000 light-years away.

"It's always interesting in astronomy when you look in a new way, and you find a new type of thing," lead author Todd Thompson, an astronomy professor at Ohio State, tells Vice. "It makes you think that all your ways of looking before were biased."

Indeed, previous methods for hunting black holes may have been strongly slanted toward the heavier contenders. So far, those we've been able to detect are, on average, between five and 15 solar masses. But that's not necessarily the average size for a black hole — just the size that we've found. That's for the simple reason that when it comes to these matter-hoovering bodies, bigger is easier to find.

Supermassive black holes, like the one at the heart of our galaxy, make for disruptive neighbors — hoovering up all surrounding matter, including errant stars, with gleeful abandon. It's not hard for earthling astronomers to spot a black hole's culinary ravages — or rather the crumbs left around its mouth in the form of a radiant accretion disk.

Small black holes, on the other hand, aren't nearly as obvious, munching quietly in their corner of the cosmos and producing much less X-ray radiation for scientists to zero in on. As a result, when known black holes are tallied, the heavyweights are disproportionately represented.

But smaller rifts may be able to teach us a lot more about our universe.

"People are trying to understand supernova explosions, how supermassive black stars explode, how the elements were formed in supermassive stars," Thompson explains in a news release. "So if we could reveal a new population of black holes, it would tell us more about which stars explode, which don't, which form black holes, which form neutron stars. It opens up a new area of study."

The new discovery fills a longstanding gap on the scale of time- and space-bending anomalies. On one end, there were massive (and even more massive) black holes. On the other end were neutron stars — the cores of giant stars that collapsed on themselves. Neutron stars eventually grow into black holes, but they typically begin their existence at around 2.5 solar masses.

But the spectrum was notably blank in the middle. Where were all the small-ish black holes?

To find them, Thompson and his team relied on data from the Apache Point Observatory Galactic Evolution Experiment, or APOGEE. That installation, based in New Mexico, records light from more than 100,000 stars in our galaxy.

Researchers used APOGEE data to determine if light shifts from one star in a binary system indicated the presence of an otherwise invisible companion — a decidedly darker companion.

Under that scrutiny, the smallest known black hole made itself known, and the wealth of knowledge it contains will likely lead scientists to cast an even wider net for more of its black hole brethren.

"What we've done here is come up with a new way to search for black holes, but we've also potentially identified one of the first of a new class of low-mass black holes that astronomers hadn't previously known about." Thompson explains. "The masses of things tell us about their formation and evolution and they tell us about their nature."


Scientists Now Think They Know How the Universe Forges Most Heavy Metals

We are made of star stuff. With the exception of hydrogen and some helium, all the elements that we know and are made of were forged in the hot cores of giant stars billions of years ago. This includes carbon, nitrogen, oxygen and iron. Now, scientists are learning how most of the Universe’s heavy metals, like silver, gold, platinum and uranium, are generated. Without metals, life (as we know it) can not exist.

For the first time, in August 2017, two neutron stars were directly observed colliding with one another and collapsing into a black hole. The event occurred 130 million light years away. Astronomers at the Laser Interferometer Gravitational-Wave Observatories ( LIGO ) in the United States and the Virgo Interferometer in Italy detected gravitational waves , ripples in the fabric of spacetime caused by the birth of a black hole, emitting from a pair of merging neutron stars.

The resulting explosion is called a kilonova the electromagnetic counterpart of gravitational waves. Albert Einstein predicted the existence of gravitational waves nearly a century ago, and recent detection of them confirms that empty space is, incredibly, not empty. Instead, it’s referred to as the fabric of spacetime, and it contains everything in the Universe.

The biggest astronomical discovery of 2017

For astronomers, this discovery is a huge deal, because it hints at where most of the heavy metals in our Universe, such as silver, uranium, platinum and gold, come from. The project involved 4,500 astrophysicists from around the world in other words, most of them. Also, for the first time, gravitational waves were detected from such an event. It’s also the first time that a neutron star merger has been directly observed, although computer models predict that a kilonova should occur when neutron stars collide. Lighter metals like iron, barium, lead and tungsten are created when giant stars go supernova, blasting their guts into space in their final death throes.

Georgia Tech's Center for Relativistic Astrophysics

When neutron stars merge and collapse into a black hole, they generate a powerful blast of electromagnetic radiation called a gamma-ray burst . GRBs are the most extreme explosions in the universe. Because they occur as focused jets of energy, GRBs need to be facing Earth to be seen. GRBs are so energetic that one occurring in our stellar neighborhood could easily sterilize the surface of our planet. In fact, some scientists believe that a GRB could have been responsible for the Great Dying , a mass extinction event that wiped out 95 percent of all life on Earth 250 million years ago.

What are neutron stars?

Neutron stars are arguably the wildest objects in the Universe. Neutron stars are created when massive stars with cores of 1-3 solar masses go supernova. The stars’ cores collapse under their own gravity once the star begins to fuse iron. Neutron stars are only 10-12 miles across, but have the mass of roughly 1.4 suns. This makes them almost unimaginably dense just a teaspoon full of neutron star material would weigh billions of tons. For scale, this would be like shrinking all of Earth’s mass into a volume the size of a golf ball.

Neutron stars are so dense that their protons and electrons are forced together by gravity, forming a hot sphere of neutrons. It’s understandably difficult to form a visual of this. Their gravity is so strong that NASA compares their impact to “a marshmallow impacting the star's surface [hitting] with the force of a thousand hydrogen bombs.”

Amazingly, some neutron stars have planets orbiting them. In 2011, astronomers discovered a planet five times larger than Earth orbiting a neutron star. Originally a white dwarf, which is the dead core of a sun-like star, it lost most of its mass to its companion neutron star (though its diameter is about 3,000 times the diameter of its host star). The leftover material solidified into crystallized carbon, better known as diamond. The planet orbits its star in only two hours, and the distance between the planet and neutron star would fit inside the Sun. The Universe rarely makes just one of anything, so it’s therefore reasonable to suspect that our galaxy, the Milky Way, is littered with dead stars and planets that are made of diamonds.

There are two type of neutron stars: magnetars and pulsars. Magnetars have the strongest magnetic fields in the Universe. These magnetic fields are a trillion times stronger than Earth’s, and hundreds of times more powerful than typical neutron stars. Magnetars also emit powerful X-rays and gamma rays. Most neutron stars, however, are pulsars . Pulsars emit powerful jets of charged particles from their magnetic poles, a result of their fast rotation. This generates rotating beams of light, which can be seen from Earth, assuming they are pointing in our direction. Because the supernovae that created them are so powerful, pulsars rotate very rapidly. The most rapidly rotating radio pulsar so far discovered whips around at 716 times per second . Pulsars are, in a sense, cosmic lighthouses.

How do neutron stars create gold and other heavy metals?

As neutron stars approach each other, their rotational speed increases. Protons and neutrons are flung out into space in hot clouds of plasma, or superheated gas. “It’s like taking two jelly donuts and slamming them together,” said Dan Kasen, a member of the team of thousands that made the discovery. The intense heat and outward pressure of the expanding gas forces the nuclei of atoms together into metals like iron, silver, gold and uranium. As they drift through interstellar space, these heavier elements mix with other elements, eventually becoming part of rocky planets like Earth. The LIGO discovery found the amount of gold equivalent to ten Earths .

Iron and heavier elements are also created when giant stars explode as supernovae. The fusion of iron is what kills stars fusing iron requires more energy than a star can produce in its core, and once a star begins fusing iron, a supernova occurs within a few seconds. This miniscule drop in outward pressure allows gravity to take over, and gravity always wins. The core collapses into a neutron star (or black hole in even more massive stars), and the outer layers are blown out into space. As this occurs, heavy elements like nickel, lead and cobalt are forged from the enormous pressure and high temperatures generated in the explosion. Stars big enough to create iron and other metals only live for a few million years, as they burn through their fuel faster than smaller stars like the Sun.

Does the Sun forge heavy elements too?

Nope. Stars like the Sun don’t have enough mass to forge heavy elements. Still, the Sun fuses a whopping 660 million tons of hydrogen into helium every second . In about one or two billion years, the Sun will begin to run out of hydrogen. As it starts to fuse helium into elements like carbon and oxygen, its outer layers will expand from the more intense pressure coming from the core, becoming a red giant .

At this point, Earth will be destroyed. The outer layers will form a planetary nebula (and they are gorgeous) , gradually dissipating into space. The Sun will then become a white dwarf star a super-dense Earth-sized ball of cooling stellar ash, made mostly of carbon. Eventually, white dwarf stars cool to the point of being black dwarfs. Black dwarfs have never been observed and are entirely theoretical, however, because the Universe isn’t old enough for any to have formed… yet.

Stars are the best example of how good the Universe is at recycling material. Stars like our Sun are, in fact, the children and grandchildren of massive stars that went supernova in the distant past, blasting into space the materials needed to form suns, planets and, of course, life. We are the Universe, and the Universe is us.


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National corporate funding for NOVA is provided by Draper. Major funding for NOVA is provided by the David H. Koch Fund for Science, the NOVA Science Trust, the Corporation for Public Broadcasting, and PBS viewers.


Step Three: Stellar Black Holes

Scientists now know that neutron stars like the one in the Crab Nebula are not the last word, so to speak, in the awesome story of stellar collapse. That distinction belongs to the black hole. Light is just barely able to escape the deep gravity well of a neutron star, so in a sense it almost qualifies for black hole status. In fact, says John Gribbin, "A neutron star sits on the very threshold of being a black hole." 21 One major factor that sets black holes apart from neutron stars, however, is that no light can escape from a black hole light and everything else that gets too close to a black hole becomes trapped inside its gravity well forever.

A stellar black hole forms from the collapse of a star having more than eight times the mass of the Sun. So powerful is the force of the inrushing matter that it bypasses both the white dwarf and neutron star stages and compresses that matter into an even denser state. In fact, the matter keeps on falling down the star's gravity well in a sort of neverending death spiral. This is because the gravity well of a black hole is like a bottomless pit, from which nothing can escape.

Not surprisingly, this densest of superdense objects jams an extremely large amount of material into a very small volume of space. A stellar black hole is surprisingly small, therefore. One formed during the death of a star having eight solar masses would probably be only about the size of a small house. It is important to remember that most of the former star's original matter is still inside the black hole. (Some of its matter was ejected into space during the supernova accompanying the star's collapse.) That means that the object's gravitational pull will be roughly the same as that of the original star. Any planets orbiting the star before its collapse would continue orbiting the black hole, which would not capture and consume them unless they strayed too close to it.

The survival of a planet and the survival of living things that might inhabit it are two different things, however. A majority of life forms that happen to exist on planets orbiting a star that becomes a black hole will die from powerful radiation released during the catastrophic collapse and supernova. And any life that has the misfortune to survive this disaster will quickly freeze to death after the star stops radiating light and heat. Clearly, the formation of a stellar black hole is one of the most awesome and potentially lethal events that can occur in nature.


Universe’s Earliest Supernovae Ejected Powerful Jets, Astronomers Say

A team of astronomers from MIT has observed evidence that the Universe’s first stars exploded as asymmetric supernovae, strong enough to scatter heavy elements across the early Universe. The findings appear in the Astrophysical Journal.

An artist’s impression of a supernova. Image credit: NASA / CXC / M.Weiss.

Several hundred million years after the Big Bang, the very first stars flared into the Universe as massively bright accumulations of hydrogen and helium gas. Within the cores of these stars, thermonuclear reactions forged the first heavy elements, including carbon, iron, and zinc.

These first stars were likely immense, short-lived fireballs, and astrophysicists have assumed that they exploded as similarly spherical supernovae.

But now astronomers at MIT and elsewhere have found that these stars may have blown apart in a more powerful, asymmetric fashion, spewing forth jets that were violent enough to eject heavy elements into neighboring galaxies. These elements ultimately served as seeds for the second generation of stars, some of which can still be observed today.

“When a star explodes, some proportion of that star gets sucked into a black hole like a vacuum cleaner,” said MIT’s Dr. Anna Frebel.

“Only when you have some kind of mechanism, like a jet that can yank out material, can you observe that material later in a next-generation star.”

In 2005, Dr. Frebel and colleagues found that a star called HE 1327-2326 is an ancient, surviving star that is among the Universe’s second generation of stars.

At the time, the star was the most metal-poor star ever observed, meaning that it had extremely low concentrations of elements heavier than hydrogen and helium — an indication that it formed as part of the second generation of stars, at a time when most of the Universe’s heavy element content had yet to be forged.

“The first stars were so massive that they had to explode almost immediately,” Dr. Frebel said.

“The smaller stars that formed as the second generation are still available today, and they preserve the early material left behind by these first stars. Our star has just a sprinkle of elements heavier than hydrogen and helium, so we know it must have formed as part of the second generation of stars.”

An artist’s rendering of how the first stars in the Universe may have looked. Image credit: N.R. Fuller, National Science Foundation.

In 2016, the team used the Cosmic Origins Spectrograph onboard the NASA/ESA Hubble Space Telescope to observe the star.

The astronomers made a list of heavy elements that they suspected might be within such an ancient star, that they planned to look for in the Hubble data, including silicon, iron, phosphorus, and zinc.

“We found that, no matter how we measured it, we got really strong abundance of zinc,” said MIT’s Dr. Rana Ezzeddine.

The researchers then ran over 10,000 simulations of supernovae and the secondary stars that form in their aftermath.

They found that while most of the spherical supernova simulations were able to produce a secondary star with the elemental compositions they observed in HE 1327-2326, none of them reproduced the zinc signal.

As it turns out, the only simulation that could explain the star’s makeup, including its high abundance of zinc, was one of an aspherical, jet-ejecting supernova of a first star.

Such a supernova would have been extremely explosive, with a power equivalent to about a nonillion times that of a hydrogen bomb.

“We found this first supernova was much more energetic than people have thought before, about 5-10 times more,” Dr. Ezzeddine said.

“In fact, the previous idea of the existence of a dimmer supernova to explain the second-generation stars may soon need to be retired.”

The results may shift scientists’ understanding of reionization, a pivotal period during which the gas in the Universe morphed from being completely neutral, to ionized — a state that made it possible for galaxies to take shape.

“People thought from early observations that the first stars were not so bright or energetic, and so when they exploded, they wouldn’t participate much in reionizing the Universe,” Dr. Frebel said.

“We’re in some sense rectifying this picture and showing, maybe the first stars had enough oomph when they exploded, and maybe now they are strong contenders for contributing to reionization, and for wreaking havoc in their own little dwarf galaxies.”

These first supernovae could have also been powerful enough to shoot heavy elements into neighboring ‘virgin galaxies’ that had yet to form any stars of their own.

Rana Ezzeddine et al. 2019. Evidence for an Aspherical Population III Supernova Explosion Inferred from the Hyper-metal-poor Star HE 1327-2326. ApJ 876, 97 doi: 10.3847/1538-4357/ab14e7