Chemical analyses find hidden elements from renaissance astronomer Tycho Brahe's alchemy laboratory

In the Middle Ages, alchemists were notoriously secretive and didn't share their knowledge with others. Danish Tycho Brahe was no exception. Consequently, we don't know precisely what he did in the alchemical laboratory located beneath his combined residence and observatory, Uraniborg, on the now Swedish island of Ven.

Only a few of his alchemical recipes have survived, and today, there are very few remnants of his laboratory. Uraniborg was demolished after his death in 1601, and the building materials were scattered for reuse.

However, during an excavation in 1988-1990, some pottery and glass shards were found in Uraniborg's old garden. These shards were believed to originate from the basement's alchemical laboratory. Five of these shards -- four glass and one ceramic -- have now undergone chemical analyses to determine which elements the original glass and ceramic containers came into contact with.

The chemical analyses were conducted by Professor Emeritus and expert in archaeometry, Kaare Lund Rasmussen from the Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark. Senior researcher and museum curator Poul Grinder-Hansen from the National Museum of Denmark oversaw the insertion of the analyses into historical context.

Enriched levels of trace elements were found on four of them, while one glass shard showed no specific enrichments. The study has been published in the journal Heritage Science.

"Most intriguing are the elements found in higher concentrations than expected -- indicating enrichment and providing insight into the substances used in Tycho Brahe's alchemical laboratory," said Kaare Lund Rasmussen.

The enriched elements are nickel, copper, zinc, tin, antimony, tungsten, gold, mercury, and lead, and they have been found on either the inside or outside of the shards.

Most of them are not surprising for an alchemist's laboratory. Gold and mercury were -- at least among the upper echelons of society -- commonly known and used against a wide range of diseases.

"But tungsten is very mysterious. Tungsten had not even been described at that time, so what should we infer from its presence on a shard from Tycho Brahe's alchemy workshop?," said Kaare Lund Rasmussen.

Tungsten was first described and produced in pure form more than 180 years later by the Swedish chemist Carl Wilhelm Scheele. Tungsten occurs naturally in certain minerals, and perhaps the element found its way to Tycho Brahe's laboratory through one of these minerals. In the laboratory, the mineral might have undergone some processing that separated the tungsten, without Tycho Brahe ever realizing it.

However, there is also another possibility that Professor Kaare Lund Rasmussen emphasizes has no evidence whatsoever -- but which could be plausible.

Already in the first half of the 1500s, the German mineralogist Georgius Agricola described something strange in tin ore from Saxony, which caused problems when he tried to smelt tin. Agricola called this strange substance in the tin ore "Wolfram" (German for Wolf's froth, later renamed to tungsten in English).

"Maybe Tycho Brahe had heard about this and thus knew of tungsten's existence. But this is not something we know or can say based on the analyses I have done. It is merely a possible theoretical explanation for why we find tungsten in the samples," said Kaare Lund Rasmussen.

Tycho Brahe belonged to the branch of alchemists who, inspired by the German physician Paracelsus, tried to develop medicine for various diseases of the time: plague, syphilis, leprosy, fever, stomach aches, etc. But he distanced himself from the branch that tried to create gold from less valuable minerals and metals.

In line with the other medical alchemists of the time, he kept his recipes close to his chest and shared them only with a few selected individuals, such as his patron, Emperor Rudolph II, who allegedly received Tycho Brahe's prescriptions for plague medicine.

We know that Tycho Brahe's plague medicine was complicated to produce. It contained theriac, which was one of the standard remedies for almost everything at the time and could have up to 60 ingredients, including snake flesh and opium. It also contained copper or iron vitriol (sulphates), various oils, and herbs.

After various filtrations and distillations, the first of Brahe's three recipes against plague was obtained. This could be made even more potent by adding tinctures of, for example, coral, sapphires, hyacinths, or potable gold.

"It may seem strange that Tycho Brahe was involved in both astronomy and alchemy, but when one understands his worldview, it makes sense. He believed that there were obvious connections between the heavenly bodies, earthly substances, and the body's organs. Thus, the Sun, gold, and the heart were connected, and the same applied to the Moon, silver, and the brain; Jupiter, tin, and the liver; Venus, copper, and the kidneys; Saturn, lead, and the spleen; Mars, iron, and the gallbladder; and Mercury, mercury, and the lungs. Minerals and gemstones could also be linked to this system, so emeralds, for example, belonged to Mercury," explained Poul Grinder-Hansen.

Read more at Science Daily

Scientists find one of the most ancient stars that formed in another galaxy

The first generation of stars transformed the universe. Inside their cores, simple hydrogen and helium fused into a rainbow of elements. When these stars died, they exploded and sent these new elements across the universe. The iron running in your veins and the calcium in your teeth and the sodium powering your thoughts were all born in the heart of a long-dead star.

No one has been able to find one of those first generation of stars, but scientists have announced a unique finding: a star from the second generation that originally formed in a different galaxy from ours.

"This star provides a unique window into the very early element-forming process in galaxies other than our own," said Anirudh Chiti, a University of Chicago postdoctoral fellow and first author on a paper announcing the findings. "We have built up an idea of the how these stars that were chemically enriched by the first stars look like in the Milky Way, but we don't yet know if some of these signatures are unique, or if things happened similarly across other galaxies."

The paper was published March 20 in Nature Astronomy.

'Fishing needles out of haystacks'

Chiti specializes in what is called stellar archaeology: Reconstructing how the earliest generations of stars changed the universe. "We want to understand what the properties of those first stars were and what were the elements they produced," said Chiti.

But no one has yet managed to directly see these first-generation stars, if any remain in the universe. Instead, Chiti and his colleagues look for stars that formed from the ashes of that first generation.

It's hard work, because even the second generation of stars is now incredibly ancient and rare. Most stars in the universe, including our own sun, are the result of tens to thousands of generations, building up more and more heavy elements each time. "Maybe fewer than 1 in 100,000 stars in the Milky Way is one of these second-gen stars," he said. "You really are fishing needles out of haystacks."

But it's worth it to get snapshots of what the universe looked like back in time. "In their outer layers, these stars preserve the elements near where they formed," he explained. "If you can find a very old star and get its chemical composition, you can understand what the chemical composition of the universe was like where that star formed, billions of years ago."

An intriguing oddity

For this study, Chiti and his colleagues aimed their telescopes at an unusual target: the stars that make up the Large Magellanic Cloud.

The Large Magellanic Cloud is a bright swath of stars visible to the naked eye in the Southern Hemisphere. We now think it was once a separate galaxy that was captured by the Milky Way's gravity just a few billion years ago. This makes it particularly interesting because its oldest stars were formed outside the Milky Way -- giving astronomers a chance to learn about whether conditions in the early universe all looked the same, or were different in other places.

The scientists searched for evidence of these particularly ancient stars in the Large Magellanic Cloud and catalogued ten of them, first with the European Space Agency's Gaia satellite and then with the Magellan Telescope in Chile.

One of these stars immediately jumped out as an oddity. It had much, much less of the heavier elements in it than any other star yet seen in the Large Magellanic Cloud. This means it was probably formed in the wake of the first generation of stars -- so it had not yet built up heavier elements over the course of repeated star births and deaths.

Mapping out its elements, the scientists were surprised to see that it had a lot less carbon than iron compared to what we see in Milky Way stars.

"That was very intriguing, and it suggests that perhaps carbon enhancement of the earliest generation, as we see in the Milky Way, was not universal," Chiti said. "We'll have to do further studies, but it suggests there are differences from place to place.

"I think we're filling out the picture of what the early element enrichment process looked like in different environments," he said.

Their findings also corroborated other studies that have suggested that the Large Magellanic Cloud made much fewer stars early on compared to the Milky Way.

Read more at Science Daily

Astrophysicists crack the case of 'disappearing' Sulphur in planetary nebulae

Two astrophysicists from the Laboratory for Space Research (LSR) at The University of Hong Kong (HKU) have finally solved a 20-year-old astrophysical puzzle concerning the lower-than-expected amounts of the element Sulphur found in Planetary Nebulae (PNe) in comparison to expectations and measurements of other elements and other types of astrophysical objects.

The expected levels of Sulphur have long appeared to be "missing in action." However, they have now finally reported for duty after hiding in plain sight, as a result of leveraging highly accurate and reliable data.

The team has recently reported their findings in Astrophysical Journal Letters.

Background

PNe are the short-lived glowing, ejected, gaseous shrouds of dying stars that have long fascinated and enthused professional and amateur astronomers alike with their colourful and varied shapes.

PNe live for only a few tens of thousands of years compared to their host stars, which can take billions of years before they pass through the PN phase on the way to becoming "white dwarfs." Consequently, PNe provide an almost instantaneous snapshot of stellar death throes.

They are a vital, scientific window into late-stage stellar evolution as their rich emission line spectra enable detailed studies of their chemical compositions.

The Enigmatic Sulphur Anomaly

Past studies showed that PNe optical spectra appeared to have a varying deficit of the element Sulphur.

This deficit was difficult to explain because Sulphur, known as an "α element," should be produced in lockstep with other elements like oxygen, neon, argon and chlorine in more massive stars.

As a result, its cosmic abundance should also be directly proportional.

Surprisingly, while strong correlations between Sulphur and Oxygen abundances have been observed in H II regions (Hydrogen ionised region) and blue compact galaxies, PNe originating from low- to intermediate-mass stars consistently exhibit lower Sulfur levels, giving rise to the so-called mysterious "sulfur anomaly" that has perplexed and annoyed astronomers for decades.

Our Work Solving the Mystery

Ms Shuyu TAN, a graduate of HKU MPhil in Physics and Research Assistant at HKU LSR, along with her supervisor Professor Quentin PARKER, the Director of LSR, utilised an unprecedented sample of exceptional high signal to noise (S/N) optical spectra for approximately 130 PNe located in the centre of our Galaxy.

This exceptional dataset had minimal background noise, allowing for a clear and detailed examination of the spectral features, helping the team effectively tackle and solve the mystery.

These PNe were observed using the world-leading European Southern Observatory (ESO) 8m Very Large Telescope in Chile.

It turns out the anomaly was essentially a result of poor data quality for Sulphur emission lines in PNe spectra.

It was found that using Oxygen as the base metallicity comparator to other elements was not accurate, and instead, Argon demonstrated a stronger correlation with Oxygen for Sulphur and has been suggested as a more reliable indicator of metallicity and a suitable comparison element.

So, when a large, carefully selected sample of PNe are spectroscopically observed at high S/N on a large telescope, not only did the data reveal a strong "lock-step" behaviour or Sulphur in PNe for the first time, as seen and expected for other types of astrophysical objects, but the anomaly itself effectively went away.

Read more at Science Daily

Reaching for the (invisible) stars

Supernovae-stellar explosions as bright as an entire galaxy-have fascinated us since time immemorial. Yet, there are more hydrogen-poor supernovae than astrophysicists can explain. Now, a new Assistant Professor at the Institute of Science and Technology Austria (ISTA) has played a pivotal role in identifying the missing precursor star population. The results, now published in Science, go back to a conversation the involved professors had many years ago as junior scientists.

Some stars do not simply die down, but explode in a stellar blast that could outshine entire galaxies. These cosmic phenomena, called supernovae, spread light, elements, energy, and radiation in space and send galactic shock waves that could compress gas clouds and generate new stars. In other words, supernovae shape our universe. Among these, hydrogen-poor supernovae from exploding massive stars have long puzzled astrophysicists. The reason: scientists have not been able to put their finger on their precursor stars. It is almost as if these supernovae appeared out of nowhere.

"There are many more hydrogen-poor supernovae than our current models can explain. Either we can't detect the stars that mature on this path, or we must revise all our models," says ISTA Assistant Professor Ylva Götberg. She pioneered this work together with Maria Drout, an Associated Faculty Member of the Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Canada. "Single stars would typically explode as hydrogen-rich supernovae. Being hydrogen-poor indicates that the precursor star must have lost its thick hydrogen-rich envelope. This happens naturally in a third of all massive stars through envelope stripping by a binary companion star," says Götberg. Now, Götberg and Drout combined their areas of expertise in theoretical modeling and observation to hunt down the missing stars. Their quest is successful: they document a first-of-its-kind star population that finally bridges a large knowledge gap and sheds light on the origin of hydrogen-poor supernovae.

Binary stars and envelope stripping

The stars that Götberg and Drout search for go in pairs: interlocked in a binary star system. Some binary systems are well-known to us Earthlings: these include the brightest star in our night sky, Sirius A, and its faint companion star Sirius B. The Sirius binary system is located only 8.6 light-years away from Earth-a stone's throw in cosmic terms. This explains Sirius A's observed brightness in our night sky.

Astrophysicists expect the missing stars to be initially formed from massive binary systems. In a binary system, the stars would orbit around one another until the more massive star's thick, hydrogen-rich envelope expands. Eventually, the expanding envelope experiences a stronger gravitational pull to the companion star than to its own core. This causes a transfer of mass to begin, which eventually leads the entire hydrogen-rich envelope to be stripped off, leaving the hot and compact helium core exposed-more than 10 times hotter than the Sun's surface. This is precisely the type of stars that Götberg and Drout are looking for. "Intermediate mass helium stars stripped through binary interaction are predicted to play important roles in astrophysics. Yet, they were not observed until now," says Götberg. In fact, there is an important mass gap between the known classes of helium stars: the more massive Wolf-Rayet (WR) stars have more than 10 times the Sun's mass, and the low-mass subdwarf stars could have around half the Sun's mass. However, models have predicted the precursors of hydrogen-poor supernovae to lie between 2 and 8 solar masses following stripping.

Not just a needle in the haystack

Before Götberg and Drout's study, only one star was found to fulfill the expected mass and composition criteria and was called "Quasi-WR" (or "Almost Wolf-Rayet"). "Yet, the stars that follow this path have such a long lifetime that many must be scattered all over the observable universe," says Götberg. Did the scientists simply not "see" them? Thus, Götberg and Drout drew on their complementary expertise. With the help of UV photometry and optical spectroscopy, they identified a population of 25 stars that are consistent with the expectations for intermediate-mass helium stars. The stars are located in two well-studied neighboring galaxies, the Large and the Small Magellanic Clouds. "We showed that these stars were bluer than the stellar birthline, the bluest phase in a single star's lifetime. Single stars mature by evolving towards the redder region of the spectrum. A star only shifts in the opposite direction if its outer layers are removed-something that is expected to be common in interacting binary stars and rare among single massive stars," explains Götberg.

The scientists then verified their candidate star population using optical spectroscopy: they showed that the stars had strong spectral signatures of ionized helium. "Strong ionized helium lines tell us two important things: first, they confirm that the stars' outermost layers are dominated by helium and, second, that their surface is very hot. This is what happens to stars left as an exposed, compact, helium-rich core following stripping," says Götberg. Yet, both stars in a binary system contribute to the observed spectra. Thus, this technique allowed the researchers to classify their candidate population depending on which star contributed the most to the spectrum. "This work allowed us to find the missing population of intermediate-mass, stripped helium stars, the predicted progenitors of hydrogen-poor supernovae. These stars have always been there and there are probably many more out there. We must simply come up with ways to find them," says Götberg. "Our work may be one of the first attempts, but there should be other ways possible."

From graduate students at a conference to group leaders

The idea behind this project sparked in a discussion following a talk by Götberg at a conference that she and Drout attended during their graduate studies. Both scientists, then Early Career Researchers reaching for the stars, are now group leaders in their field. Götberg joined ISTA in September following her research at the Carnegie Observatories in Pasadena, California, as a NASA Hubble postdoctoral fellow. At ISTA, Götberg joins the Institute's growing ranks of young group leaders in astrophysics and leads her own group focused on studying the binary interactions of stars.

Read more at Science Daily

Ancient stars made extraordinarily heavy elements

How heavy can an element be? An international team of researchers has found that ancient stars were capable of producing elements with atomic masses greater than 260, heavier than any element on the periodic table found naturally on Earth. The finding deepens our understanding of element formation in stars.

We are, literally, made of star stuff. Stars are element factories, where elements constantly fuse or break apart to create other lighter or heavier elements.

When we refer to light or heavy elements, we're talking about their atomic mass.

Broadly speaking, atomic mass is based on the number of protons and neutrons in the nucleus of one atom of that element.

The heaviest elements are only known to be created in neutron stars via the rapid neutron capture process, or r-process.

Picture a single atomic nucleus floating in a soup of neutrons.

Suddenly, a bunch of those neutrons get stuck to the nucleus in a very short time period -- usually in less than one second -- then undergo some internal neutron-to-proton changes, and voila!

A heavy element, such as gold, platinum or uranium, forms.

The heaviest elements are unstable or radioactive, meaning they decay over time.

One way that they do this is by splitting, a process called fission.

"The r-process is necessary if you want to make elements that are heavier than, say, lead and bismuth," says Ian Roederer, associate professor of physics at North Carolina State University and lead author of the research.

Roederer was previously at the University of Michigan.

"You have to add many neutrons very quickly, but the catch is that you need a lot of energy and a lot of neutrons to do so," Roederer says.

"We have a general idea of how the r-process works, but the conditions of the process are quite extreme," Roederer says.

"We don't have a good sense of how many different kinds of sites in the universe can generate the r-process, we don't know how the r-process ends, and we can't answer questions like, how many neutrons can you add? Or, how heavy can an element be? So we decided to look at elements that could be made by fission in some well-studied old stars to see if we could start to answer some of these questions."

The team took a fresh look at the amounts of heavy elements in 42 well-studied stars in the Milky Way.

The stars were known to have heavy elements formed by the r-process in earlier generations of stars.

By taking a broader view of the amounts of each heavy element found in these stars collectively, rather than individually as is more common, they identified previously unrecognized patterns.

Those patterns signaled that some elements listed near the middle of the periodic table -- such as silver and rhodium -- were likely the remnants of heavy element fission.

The team was able to determine that the r-process can produce atoms with an atomic mass of at least 260 before they fission.

"That 260 is interesting because we haven't previously detected anything that heavy in space or naturally on Earth, even in nuclear weapon tests," Roederer says.

"But seeing them in space gives us guidance for how to think about models and fission -- and could give us insight into how the rich diversity of elements came to be."

Read more at Science Daily

'Teenage galaxies' are unusually hot, glowing with unexpected elements

Similar to human teenagers, teenage galaxies are awkward, experience growth spurts and enjoy heavy metal -- nickel, that is.

A Northwestern University-led team of astrophysicists has just analyzed the first results from the CECILIA (Chemical Evolution Constrained using Ionized Lines in Interstellar Aurorae) Survey, a program that uses NASA's James Webb Space Telescope (JWST) to study the chemistry of distant galaxies.

According to the early results, so-called "teenage galaxies" -- which formed two-to-three billion years after the Big Bang -- are unusually hot and contain unexpected elements, like nickel, which are notoriously difficult to observe.

The research will be published on Monday (Nov. 20) in The Astrophysical Journal Letters. It marks the first in a series of forthcoming studies from the CECILIA Survey.

"We're trying to understand how galaxies grew and changed over the 14 billion years of cosmic history," said Northwestern's Allison Strom, who led the study. "Using the JWST, our program targets teenage galaxies when they were going through a messy time of growth spurts and change. Teenagers often have experiences that determine their trajectories into adulthood. For galaxies, it's the same."

One of the principal investigators of the CECILIA Survey, Strom is an assistant professor of physics and astronomy at Northwestern's Weinberg College of Arts and Sciences and a member of Northwestern's Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Strom co-leads the CECILIA Survey with Gwen Rudie, a staff scientist at Carnegie Observatories.

'Chemical DNA' gives insight into galaxy formation

Named after Cecilia Payne-Gaposchkin, one of the first women to earn a Ph.D. in astronomy, the CECILIA Survey observes spectra (or the amount of light across different wavelengths) from distant galaxies. Strom likens a galaxy's spectra to its "chemical DNA." By examining this DNA during a galaxy's "teenage" years, researchers can better understand how it grew and how it will evolve into a more mature galaxy.

For example, astrophysicists still don't understand why some galaxies appear "red and dead" while others, like our Milky Way, are still forming stars. A galaxy's spectrum can reveal its key elements, such as oxygen and sulfur, which provide a window into what a galaxy was previously doing and what it might do in the future.

"These teenage years are really important because that's when the most growth happens," Strom said. "By studying this, we can begin exploring the physics that caused the Milky Way to look like the Milky Way -- and why it might look different from its neighboring galaxies."

In the new study, Strom and her collaborators used the JWST to observe 33 distant teenaged galaxies for a continuous 30 hours this past summer. Then, they combined spectra from 23 of those galaxies to construct a composite picture.

"This washes out the details of individual galaxies but gives us a better sense of an average galaxy. It also allows us to see fainter features," Strom said. "It's significantly deeper and more detailed than any spectrum we could collect with ground-based telescopes of galaxies from this time period in the universe's history."

Spectra surprises

The ultra-deep spectrum revealed eight distinct elements: Hydrogen, helium, nitrogen, oxygen, silicon, sulfur, argon and nickel. All elements that are heavier than hydrogen and helium form inside stars. So, the presence of certain elements provides information about star formation throughout a galaxy's evolution.

While Strom expected to see lighter elements, she was particularly surprised by the presence of nickel. Heavier than iron, nickel is rare and incredibly difficult to observe.

"Never in my wildest dreams did I imagine we would see nickel," Strom said. "Even in nearby galaxies, people don't observe this. There has to be enough of an element present in a galaxy and the right conditions to observe it. No one ever talks about observing nickel. Elements have to be glowing in gas in order for us to see them. So, in order for us to see nickel, there may be something unique about the stars within the galaxies."

Another surprise: The teenage galaxies were extremely hot. By examining the spectra, physicists can calculate a galaxy's temperature. While the hottest pockets with galaxies can reach over 9,700 degrees Celsius (17,492 degrees Fahrenheit), the teenage galaxies clock in at higher than 13,350 degrees Celsius (24,062 degrees Fahrenheit).

"This is just additional evidence of how different galaxies likely were when they were younger," Strom said. "Ultimately, the fact that we see a higher characteristic temperature is just another manifestation of their different chemical DNA because the temperature and chemistry of gas in galaxies are intrinsically linked."

Read more at Science Daily

The remains of an ancient planet lie deep within Earth

In the 1980s, geophysicists made a startling discovery: two continent-sized blobs of unusual material were found deep near the center of the Earth, one beneath the African continent and one beneath the Pacific Ocean. Each blob is twice the size of the Moon and likely composed of different proportions of elements than the mantle surrounding it.

Where did these strange blobs -- formally known as large low-velocity provinces (LLVPs) -- come from? A new study led by Caltech researchers suggests that they are remnants of an ancient planet that violently collided with Earth billions of years ago in the same giant impact that created our Moon.

The study, published in the journal Nature on November 1, also proposes an answer to another planetary science mystery. Researchers have long hypothesized that the Moon was created in the aftermath of a giant impact between Earth and a smaller planet dubbed Theia, but no trace of Theia has ever been found in the asteroid belt or in meteorites. This new study suggests that most of Theia was absorbed into the young Earth, forming the LLVPs, while residual debris from the impact coalesced into the Moon.

The research was led by Qian Yuan, O.K. Earl Postdoctoral Scholar Research Associate in the laboratories of both Paul Asimow (MS '93, PhD '97), the Eleanor and John R. McMillan Professor of Geology and Geochemistry; and Michael Gurnis, the John E. And Hazel S. Smits Professor of Geophysics and Clarence R. Allen Leadership Chair, director of Caltech's Seismological Laboratory, and director of the Schmidt Academy for Software Engineering at Caltech.

Scientists first discovered the LLVPs by measuring seismic waves traveling through the earth. Seismic waves travel at different speeds through different materials, and in the 1980s, the first hints emerged of large-scale three-dimensional variations deep within the structure of Earth. In the deepest mantle, the seismic wave pattern is dominated by the signatures of two large structures near the Earth's core that researchers believe possess an unusually high level of iron. This high iron content means the regions are denser than their surroundings, causing seismic waves passing through them to slow down and leading to the name "large low velocity provinces."

Yuan, a geophysicist by training, was attending a seminar about planet formation given by Mikhail Zolotov, a professor at Arizona State University, in 2019. Zolotov presented the giant-impact hypothesis, while Qian noted that the Moon is relatively rich in iron. Zolotov added that no trace had been found of the impactor that must have collided with the Earth.

"Right after Mikhail had said that no one knows where the impactor is now, I had a 'eureka moment' and realized that the iron-rich impactor could have transformed into mantle blobs," says Yuan.

Yuan worked with multidisciplinary collaborators to model different scenarios for Theia's chemical composition and its impact with Earth. The simulations confirmed that the physics of the collision could have led to the formation of both the LLVPs and the Moon. Some of Theia's mantle could have become incorporated into the Earth's own, where it ultimately clumped and crystallized together to form the two distinct blobs detectable today at Earth's core-mantle boundary today; other debris from the collision mixed together to form the Moon.

Given such a violent impact, why did Theia's material clump into the two distinct blobs instead of mixing together with the rest of the forming planet? The researchers' simulations showed that much of the energy delivered by Theia's impact remained in the upper half of the mantle, leaving Earth's lower mantle cooler than estimated by earlier, lower-resolution impact models. Because the lower mantle was not totally melted by the impact, the blobs of iron-rich material from Theia stayed largely intact as they sifted down to the base of the mantle, like the colored masses of paraffin wax in a turned-off lava lamp. Had the lower mantle been hotter (that is, if it had received more energy from the impact), it would have mixed more thoroughly with the iron-rich material, like the colors in a stirred pot of paints.

The next steps are to examine how the early presence of Theia's heterogeneous material deep within the earth might have influenced our planet's interior processes, such as plate tectonics.

Read more at Science Daily

Massive space explosion observed creating elements needed for life

Scientists have observed the creation of rare chemical elements in the second-brightest gamma-ray burst ever seen -- casting new light on how heavy elements are made.

Researchers examined the exceptionally bright gamma-ray burst GRB 230307A, which was caused by a neutron star merger. The explosion was observed using an array of ground and space-based telescopes, including NASA's James Webb Space Telescope, Fermi Gamma-ray Space Telescope, and Neil Gehrels Swift Observatory.

Publishing their findings today in Nature (25 Oct), the international research team which included experts from the University of Birmingham, reveal that they found the heavy chemical element tellurium, in the aftermath of the explosion.

Other elements such as iodine and thorium, which are needed to sustain life on earth, are also likely to be amongst the material ejected by the explosion, also known as a kilonova.

Dr Ben Gompertz, Assistant Professor of Astronomy at the University of Birmingham, and co-author of the study explains: "Gamma-ray bursts come from powerful jets travelling at almost the speed of light -- in this case driven by a collision between two neutron stars. These stars spent several billion years spiralling towards one another before colliding to produce the gamma-ray burst we observed in March this year. The merger site is the approximate length of the Milky Way (about 120,000 light-years) outside of their home galaxy, meaning they must have been launched out together.

"Colliding neutron stars provide the conditions needed to synthesise very heavy elements, and the radioactive glow of these new elements powered the kilonova we detected as the blast faded. Kilonovae are extremely rare and very difficult to observe and study, which is why this discovery is so exciting."

GRB 230307A was one of the brightest gamma-ray bursts ever observed -- over a million times brighter than the entire Milky Way Galaxy combined. This is the second time individual heavy elements have been detected using spectroscopic observations after a neutron star merger, providing invaluable insight into how these vital building blocks needed for life are formed.

Lead author of the study Andrew Levan, Professor of Astrophysics at Radboud University in the Netherlands, said: "Just over 150 years since Dmitri Mendeleev wrote down the periodic table of elements, we are now finally in the position to start filling in those last blanks of understanding where everything was made, thanks to the James Webb Telescope."

GRB 230307A lasted for 200 seconds, meaning it is categorised as a long-duration gamma-ray burst. This is unusual as short gamma-ray bursts, which last less than two seconds, are more commonly caused by neutron star mergers. Long gamma-ray bursts like this one are usually caused by the explosive death of a massive star.

The researchers are now seeking to learn more about how these neutron star mergers work and how they power these huge element-generating explosions.

Dr Samantha Oates, a co-author of the study while a postdoctoral research fellow at the University of Birmingham (now a lecturer at Lancaster University) said: "Just a few short years ago discoveries like this one would not have been possible, but thanks to the James Webb Space Telescope we can observe these mergers in exquisite detail."

Read more at Science Daily

A supernova in distant space allows us to understand the origin of the elements in the universe

A supernova is a stellar explosion, which occurs when the lives of some really massive stars come to an end. In this violent epilogue, the star expels the material from its outer layers by means of a shock wave, allowing us to see the various elements it was composed of.

The research team developed a model of the gravitational field of the galaxy that acted as a lens, and that way it was possible to determine that the light from these three images travelled along three different paths, differing in distance by a few days. This accounts for the three colours obtained in the images, because a variation in the colour emitted takes place as the gas in the supernova expands and cools. The higher the temperature is, the bluer the light emitted will be, and as the temperature falls, the light emitted tends towards red. So the blue image is a photograph of the supernova a few hours after the stellar explosion, while the green and red images correspond to 2 and 8 days, respectively, after the explosion.

This information enabled the radius of the star that exploded to be determined; it was a red super-giant with a radius equal to 500 times that of the Sun, and exploded 11.5 billion years ago, long before the Earth was born, specifically at the moment when our Galaxy is thought to have formed. The images of this supernova captured by the Hubble Space Telescope are highly magnified by the gravitational field of a nearby galaxy that acts as a lens and allows us to see much further in distance and in time than all local supernovae in nearby galaxies.

The study of the explosions of these red super-giant stars tallies with the current understanding of how the heavier atomic elements were created inside stars and during supernova explosions: elements forged inside stars are released in these supernova explosions to become the next generation of gas and material from which solar systems and life as we know it are created. Without these explosions, the gas in today's galaxies would only include the hydrogen and helium that formed during the Big Bang and would not support complex life that requires other heavier chemical elements. Moreover, this supernova observed through a gravitational lens demonstrates that an event taking place in the distant Universe can be witnessed several times, so in principle we could focus our instruments in advance to get a detailed view of the eruption of a star turning into a supernova.

From Science Daily

Pushing the boundaries of chemistry: Properties of heaviest element studied so far measured at GSI/FAIR

An international research team has succeeded in gaining new insights into the chemical properties of the superheavy element flerovium -- element 114 -- at the accelerator facilities of the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt. The measurements show that flerovium is the most volatile metal in the periodic table. Flerovium is thus the heaviest element in the periodic table that has been chemically studied. With the results, published in the journal Frontiers in Chemistry, GSI confirms its leading position in the study of the chemistry of superheavy elements and opens new perspectives for the international facility FAIR (Facility for Antiproton and Ion Research), which is currently under construction.

Under the leadership of groups from Darmstadt and Mainz, the two longest-lived flerovium isotopes currently known, flerovium-288 and flerovium-289, were produced using the accelerator facilities at GSI/FAIR and were chemically investigated at the TASCA experimental setup. In the periodic table, flerovium is placed below the heavy metal lead. However, early predictions had postulated that relativistic effects of the high charge in the nucleus of the superheavy element on its valence electrons would lead to noble gas-like behavior, while more recent ones had rather suggested a weakly metallic behavior. Two previously conducted chemistry experiments, one of them at GSI in Darmstadt in 2009, led to contradictory interpretations. While the three atoms observed in the first experiment were used to infer noble gas-like behavior, the data obtained at GSI indicated metallic character based on two atoms. The two experiments were unable to clearly establish the character. The new results show that, as expected, flerovium is inert but capable of forming stronger chemical bonds than noble gases, if conditions are suitable. Flerovium is consequently the most volatile metal in the periodic table.

Flerovium is thus the heaviest chemical element whose character has been studied experimentally. With the determination of the chemical properties, GSI/FAIR confirm their leading position in the research of superheavy elements. "Exploring the boundaries of the periodic table has been a pillar of the research program at GSI since the beginning and will be so at FAIR in the future. The fact that a few atoms can already be used to explore the first fundamental chemical properties, giving an indication of how larger quantities of these substances would behave, is fascinating and possible thanks to the powerful accelerator facility and the expertise of the worldwide collaboration," elaborates Professor Paolo Giubellino, Scientific Managing Director of GSI and FAIR. "With FAIR, we are bringing the universe into the laboratory and explore the limits of matter, also of the chemical elements."

Six weeks of experimentation

The experiments conducted at GSI/FAIR to clarify the chemical nature of flerovium lasted a total of six weeks. For this purpose, four trillion calcium-48 ions were accelerated to ten percent of the speed of light every second by the GSI linear accelerator UNILAC and fired at a target containing plutonium-244, resulting in the formation of a few flerovium atoms per day.

The formed flerovium atoms recoiled from the target into the gas-filled separator TASCA. In its magnetic field, the formed isotopes, flerovium-288 and flerovium-289, which have lifetimes on the order of a second, were separated from the intense calcium ion beam and from byproducts of the nuclear reaction. They penetrated a thin film, thus entering the chemistry apparatus, where they were stopped in a helium/argon gas mixture. This gas mixture flushed the atoms into the COMPACT gas chromatography apparatus, where they first came into contact with silicon oxide surfaces. If the bond to silicon oxide was too weak, the atoms were transported further, over gold surfaces -- first those kept at room temperature, and then over increasingly colder ones, down to about -160 °C. The surfaces were deposited as a thin coating on special nuclear radiation detectors, which registered individual atoms by spatially resolved detection of the radioactive decay. Since the decay products undergo further radioactive decay after a short lifetime, each atom leaves a characteristic signature of several events from which the presence of a flerovium atom can unambiguously be inferred.

One atom per week for chemistry

"Thanks to the combination of the TASCA separator, the chemical separation and the detection of the radioactive decays, as well as the technical development of the gas chromatography apparatus since the first experiment, we have succeeded in increasing the efficiency and reducing the time required for the chemical separation to such an extent that we were able to observe one flerovium atom every week," explains Dr. Alexander Yakushev of GSI/FAIR, the spokesperson for the international experiment collaboration.

Six such decay chains were found in the data analysis. Since the setup is similar to that of the first GSI experiment, the newly obtained data could be combined with the two atoms observed at that time and analyzed together. None of the decay chains appeared within the range of the silicon oxide-coated detector, indicating that flerovium does not form a substantial bond with silicon oxide. Instead, all were transported with the gas into the gold-coated portion of the apparatus within less than a tenth of a second. The eight events formed two zones: a first in the region of the gold surface at room temperature, and a second in the later part of the chromatograph, at temperatures so low that a very thin layer of ice covered the gold, so that adsorption occurred on ice.

From experiments with lead, mercury and radon atoms, which served as representatives of heavy metals, weakly reactive metals as well as noble gases, it was known that lead forms a strong bond with silicon oxide, while mercury reaches the gold detector. Radon even flies over the first part of the gold detector at room temperature and is only partially retained at the lowest temperatures. Flerovium results could be compared with this behavior.

Apparently, two types of interaction of a flerovium species with the gold surface were observed. The deposition on gold at room temperature indicates the formation of a relatively strong chemical bond, which does not occur in noble gases. On the other hand, some of the atoms appear never to have had the opportunity to form such bonds and have been transported over long distances of the gold surface, down to the lowest temperatures. This detector range represents a trap for all elemental species. This complicated behavior can be explained by the morphology of the gold surface: it consists of small gold clusters, at the boundaries of which very reactive sites occur, apparently allowing the flerovium to bond. The fact that some of the flerovium atoms were able to reach the cold region indicates that only the atoms that encountered such sites formed a bond, unlike mercury, which was retained on gold in any case. Thus, the chemical reactivity of flerovium is weaker than that of the volatile metal mercury. The current data cannot completely rule out the possibility that the first deposition zone on gold at room temperature is due to the formation of flerovium molecules. It also follows from this hypothesis, though, that flerovium is chemically more reactive than a noble gas element.

International and interdisciplinary collaboration as the key to understanding

The exotic plutonium target material for the production of the flerovium was provided in part by Lawrence Livermore National Laboratory (LLNL), USA. In the Department of Chemistry's TRIGA site at Johannes Gutenberg University Mainz (JGU), the material was electrolytically deposited onto thin titanium foils fabricated at GSI/FAIR. "There is not much of this material available in the world, and we are fortunate to have been able to use it for these experiments that would not otherwise be possible," said Dr. Dawn Shaughnessy, head of the Nuclear and Chemical Sciences Division at LLNL. "This international collaboration brings together skills and expertise from around the world to solve difficult scientific problems and answer long-standing questions, such as the chemical properties of flerovium."

"Our accelerator experiment was complemented by a detailed study of the detector surface in collaboration with several GSI departments as well as the Department of Chemistry and the Institute of Physics at JGU. This has proven to be key to understanding the chemical character of flerovium. As a result, the data from the two earlier experiments are now understandable and compatible with our new conclusions," says Christoph Düllmann, professor of nuclear chemistry at JGU and head of the research groups at GSI and at the Helmholtz Institute Mainz (HIM), a collaboration between GSI and JGU.

How the relativistic effects affect its neighbors, the elements nihonium (element 113) and moscovium (element 115), which have also only been officially recognized in recent years, is the subject of subsequent experiments. Initial data have already been obtained as part of the FAIR Phase 0 program at GSI. Furthermore, the researchers expect that significantly more stable isotopes of flerovium exist, but these have not yet been found. However, the researchers now already know that they can expect to find a metallic element.

Read more at Science Daily

Astronomers map mysterious element in space

A research team led by Lund University in Sweden has provided an important clue to the origin of the element Ytterbium in the Milky Way, by showing that the element largely originates from supernova explosions. The groundbreaking research also provides new opportunities for studying the evolution of our galaxy. The study is published in Astronomy & Astrophysics.

Ytterbium is one of four elements in the periodic table named after the Ytterby mine in the Stockholm archipelago. The element was first discovered in the black mineral gadolinite, which was first identified in the Ytterby mine in 1787.

Ytterbium is interesting because it may have two different cosmic origins. Researchers believe that one half comes from heavy stars with short lives, while the other half comes from more regular stars, much like the sun, and that they create Ytterbium in the final stages of their relatively long lives.

"By studying stars formed at different times in the Milky Way, we have been able to investigate how fast the Ytterbium content increased in the galaxy. What we have succeeded in doing is adding relatively young stars to the study," says Martin Montelius, astronomy researcher at Lund University at the time of the research, and now at the University of Groningen.

It has been speculated that Ytterbium was thrown into space by supernova explosions, stellar winds and planetary nebulae. There, it accumulated in large space clouds from which new stars formed.

By examining high-quality spectra of about 30 stars in the sun's vicinity, the researchers were able to provide important experimental support for the theory of the cosmic origin of Ytterbium. It seems that Ytterbium largely originates from supernova explosions.

"The instrument we used is a super-sensitive spectrometer that can detect infrared light in high resolution. It was used with two telescopes in the southern United States, one in Arizona and one in Texas," says Martin Montelius.

Since the Ytterbium analysis was done using infrared light, it will now be possible to study large areas of the Milky Way that lie behind impenetrable dust. Infrared light can get through the dust in the same way that red light from a sunset can get through the Earth's atmosphere.

Read more at Science Daily

Chemical history of the Milky Way revealed by new catalog of tens of millions of stars

University of Notre Dame researchers, along with collaborators in China and Australia, published a new sample catalog of more than 24 million stars that can be used to decipher the chemical history of elements in the Milky Way Galaxy.

The research, published this month in The Astrophysical Journal, represents about one-hundredth of a percent of the roughly 240 billion stars in the Milky Way. It marks a milestone for Timothy Beers, the Grace-Rupley Professor of Physics at Notre Dame, who has spent most of his career planning and executing ever-larger surveys of stars to decipher the galaxy's formation and chemical evolution -- a field called galactic archaeology. Researchers employed a new approach to measure the light from each star to infer the abundances of heavy metals such as iron. They also measured their distances, motions and ages.

"The elemental abundances of individual stars trace the chemical enrichment of the Milky Way galaxy, from when it first began to form stars shortly after the Big Bang to the present," Beers said.

"Combining this information with the stellar distances and motions allows us to constrain the origin of different components in the galaxy, such as the halo and disk populations," he continued. "Adding age estimates puts a `clock' on the process, so that a much more complete picture of the entire process can be drawn."

Previous spectroscopic work by Beers and collaborators provided the information for the tens of thousands of stars that were used to calibrate the new approach, based on precision photometric measurements. The recent research used large photometric samples obtained with the Australian SkyMapper Southern Survey and the European Gaia satellite mission to calibrate estimates of metallicity.

Until recently, the only means to obtain accurate estimates of the content of heavy metals, such as iron, for large numbers of stars was by taking low- and medium-resolution spectra that could be analyzed to extract this information. The process was long and painstaking.

Beers is most interested in the stars with the lowest metallicities -- very metal-poor stars with iron abundances less than 1 percent that of the sun -- because they were born early in the history of the universe, and therefore reveal the origin of elements in the periodic table. In the early 1980s, when Beers started his work, researchers knew of only about 20 very metal-poor stars. This new catalog brings the total of what Beers refers to as "fossils of the night sky" to more than 500,000.

Containing more than 19 million dwarf and five million giant stars, the new catalog is expected to advance the knowledge of how the Milky Way was formed in a variety of ways, Beers said. These include characterizing the structure of the galactic thin/thick disks -- the structural components of spiral galaxies -- as well as the population of stars and globular clusters that surround most disk galaxies, called the stellar halo. The catalog of stars will also help researchers identify the trails of stars left behind from disrupted dwarf galaxies and globular clusters.

Read more at Science Daily

Where does gold come from? New insights into element synthesis in the universe

How are chemical elements produced in our Universe? Where do heavy elements like gold and uranium come from? Using computer simulations, a research team from the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, together with colleagues from Belgium and Japan, shows that the synthesis of heavy elements is typical for certain black holes with orbiting matter accumulations, so-called accretion disks. The predicted abundance of the formed elements provides insight into which heavy elements need to be studied in future laboratories -- such as the Facility for Antiproton and Ion Research (FAIR), which is currently under construction -- to unravel the origin of heavy elements. The results are published in the journal Monthly Notices of the Royal Astronomical Society.

All heavy elements on Earth today were formed under extreme conditions in astrophysical environments: inside stars, in stellar explosions, and during the collision of neutron stars. Researchers are intrigued with the question in which of these astrophysical events the appropriate conditions for the formation of the heaviest elements, such as gold or uranium, exist. The spectacular first observation of gravitational waves and electromagnetic radiation originating from a neutron star merger in 2017 suggested that many heavy elements can be produced and released in these cosmic collisions. However, the question remains open as to when and why the material is ejected and whether there may be other scenarios in which heavy elements can be produced.

Promising candidates for heavy element production are black holes orbited by an accretion disk of dense and hot matter. Such a system is formed both after the merger of two massive neutron stars and during a so-called collapsar, the collapse and subsequent explosion of a rotating star. The internal composition of such accretion disks has so far not been well understood, particularly with respect to the conditions under which an excess of neutrons forms. A high number of neutrons is a basic requirement for the synthesis of heavy elements, as it enables the rapid neutron-capture process or r-process. Nearly massless neutrinos play a key role in this process, as they enable conversion between protons and neutrons.

"In our study, we systematically investigated for the first time the conversion rates of neutrons and protons for a large number of disk configurations by means of elaborate computer simulations, and we found that the disks are very rich in neutrons as long as certain conditions are met," explains Dr. Oliver Just from the Relativistic Astrophysics group of GSI's research division Theory. "The decisive factor is the total mass of the disk. The more massive the disk, the more often neutrons are formed from protons through capture of electrons under emission of neutrinos, and are available for the synthesis of heavy elements by means of the r-process. However, if the mass of the disk is too high, the inverse reaction plays an increased role so that more neutrinos are recaptured by neutrons before they leave the disk. These neutrons are then converted back to protons, which hinders the r-process." As the study shows, the optimal disk mass for prolific production of heavy elements is about 0.01 to 0.1 solar masses. The result provides strong evidence that neutron star mergers producing accretion disks with these exact masses could be the point of origin for a large fraction of the heavy elements. However, whether and how frequently such accretion disks occur in collapsar systems is currently unclear.

Read more at Science Daily

Mystery of heavy elements in galactic cosmic rays

Scientists have used data from the Southwest Research Institute-led Magnetospheric Multiscale (MMS) mission to explain the presence of energetic heavy elements in galactic cosmic rays (GCRs). GCRs are composed of fast-moving energetic particles, mostly hydrogen ions called protons, the lightest and most abundant elements in the universe. Scientists have long debated how trace amounts of heavy ions in GCRs are accelerated.

The supernova explosion of a dying star creates massive shockwaves that propagate through the surrounding space, accelerating ions in their path to very high energies, creating GCRs. How heavy ions are energized and accelerated is important because they affect the redistribution of mass throughout the universe and are essential for the formation of even heavier and more chemically complex elements. They also influence how we perceive astrophysical structures.

"Heavy ions are thought to be insensitive to an incoming shockwave because they are less abundant, and the shock energy is overwhelmingly consumed by the preponderance of protons. Visualize standing on a beach as waves move the sand under your feet, while you remain in place," said SwRI's Dr. Hadi Madanian, the lead author of the paper about this research published in Astrophysical Journal Letters. "However, that classical view of how heavy ions behave under shock conditions is not always what we have seen in high-resolution MMS observations of the near-Earth space environment."

Shock phenomena also occur in the near-Earth environment. The Sun's magnetic field is carried through interplanetary space by the supersonic solar wind flow, which is obstructed and diverted by the Earth's magnetosphere, a bubble of protection around our home planet. This interaction region is called the bow shock due to its curved shape, comparable to the bow waves that occur as a boat travels through water. The Earth's bow shock forms at a much smaller scale than supernova shocks. However, at times, conditions of this small shock resemble those of supernova remnants. The team used high-resolution in-situ measurements from the MMS spacecraft at the bow shock to study how heavy ions are accelerated.

"We observed intense amplification of the magnetic field near the bow shock, a known property associated with strong shocks such as supernova remnants. We then analyzed how different ion species behaved as they encountered the bow shock," Madanian said. "We found that these enhanced fields significantly modify the trajectory of heavy ions, redirecting them into the acceleration zone of the shock."

While this behavior was not expected to occur for heavy ions, the team identified direct evidence for this process in alpha particles, helium ions that are four times more massive than protons and have twice the charge.

Read more at Science Daily

Alien radioactive element prompts creation rethink

The first-ever discovery of an extraterrestrial radioactive isotope on Earth has scientists rethinking the origins of the elements on our planet.

The tiny traces of plutonium-244 were found in ocean crust alongside radioactive iron-60. The two isotopes are evidence of violent cosmic events in the vicinity of Earth millions of years ago.

Star explosions, or supernovae create many of the heavy elements in the periodic table, including those vital for human life, such as iron, potassium and iodine.

To form even heavier elements, such as gold, uranium and plutonium it was thought that a more violent event may be needed, such as two neutron stars merging.

However, a study led by Professor Anton Wallner from The Australian National University (ANU) suggests a more complex picture.

"The story is complicated -- possibly this plutonium-244 was produced in supernova explosions or it could be left over from a much older, but even more spectacular event such as a neutron star detonation," lead author of the study, Professor Wallner said.

Any plutonium-244 and iron-60 that existed when the Earth formed from interstellar gas and dust over four billion years ago has long since decayed, so current traces of them must have originated from recent cosmic events in space.

The dating of the sample confirms two or more supernova explosions occurred near Earth.

"Our data could be the first evidence that supernovae do indeed produce plutonium-244," Professor Wallner said

"Or perhaps it was already in the interstellar medium before the supernova went off, and it was pushed across the solar system together with the supernova ejecta."

Professor Wallner also holds joint positions at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Technical University Dresden in Germany, and conducted this work with researchers from Australia, Israel, Japan, Switzerland and Germany.

Read more at Science Daily

How planets form controls elements essential for life

The prospects for life on a given planet depend not only on where it forms but also how, according to Rice University scientists.

Planets like Earth that orbit within a solar system's Goldilocks zone, with conditions supporting liquid water and a rich atmosphere, are more likely to harbor life. As it turns out, how that planet came together also determines whether it captured and retained certain volatile elements and compounds, including nitrogen, carbon and water, that give rise to life.

In a study published in Nature Geoscience, Rice graduate student and lead author Damanveer Grewal and Professor Rajdeep Dasgupta show the competition between the time it takes for material to accrete into a protoplanet and the time the protoplanet takes to separate into its distinct layers -- a metallic core, a shell of silicate mantle and an atmospheric envelope in a process called planetary differentiation -- is critical in determining what volatile elements the rocky planet retains.

Using nitrogen as proxy for volatiles, the researchers showed most of the nitrogen escapes into the atmosphere of protoplanets during differentiation. This nitrogen is subsequently lost to space as the protoplanet either cools down or collides with other protoplanets or cosmic bodies during the next stage of its growth.

This process depletes nitrogen in the atmosphere and mantle of rocky planets, but if the metallic core retains enough, it could still be a significant source of nitrogen during the formation of Earth-like planets.

Dasgupta's high-pressure lab at Rice captured protoplanetary differentiation in action to show the affinity of nitrogen toward metallic cores.

"We simulated high pressure-temperature conditions by subjecting a mixture of nitrogen-bearing metal and silicate powders to nearly 30,000 times the atmospheric pressure and heating them beyond their melting points," Grewal said. "Small metallic blobs embedded in the silicate glasses of the recovered samples were the respective analogs of protoplanetary cores and mantles."

Using this experimental data, the researchers modeled the thermodynamic relationships to show how nitrogen distributes between the atmosphere, molten silicate and core.

"We realized that fractionation of nitrogen between all these reservoirs is very sensitive to the size of the body," Grewal said. "Using this idea, we could calculate how nitrogen would have separated between different reservoirs of protoplanetary bodies through time to finally build a habitable planet like Earth."

Their theory suggests that feedstock materials for Earth grew quickly to around moon- and Mars-sized planetary embryos before they completed the process of differentiating into the familiar metal-silicate-gas vapor arrangement.

In general, they estimate the embryos formed within 1-2 million years of the beginning of the solar system, far sooner than the time it took for them to completely differentiate. If the rate of differentiation was faster than the rate of accretion for these embryos, the rocky planets forming from them could not have accreted enough nitrogen, and likely other volatiles, critical to developing conditions that support life.

"Our calculations show that forming an Earth-size planet via planetary embryos that grew extremely quickly before undergoing metal-silicate differentiation sets a unique pathway to satisfy Earth's nitrogen budget," said Dasgupta, the principal investigator of CLEVER Planets, a NASA-funded collaborative project exploring how life-essential elements might have come together on rocky planets in our solar system or on distant, rocky exoplanets.

"This work shows there's much greater affinity of nitrogen toward core-forming metallic liquid than previously thought," he said.

The study follows earlier works, one showing how the impact by a moon-forming body could have given Earth much of its volatile content, and another suggesting that the planet gained more of its nitrogen from local sources in the solar system than once believed.

In the latter study, Grewal said, "We showed that protoplanets growing in both inner and outer regions of the solar system accreted nitrogen, and Earth sourced its nitrogen by accreting protoplanets from both of these regions. However, it was unknown as to how the nitrogen budget of Earth was established."

Read more at Science Daily

Rare blast's remains discovered in Milky Way's center

 Astronomers may have found our galaxy's first example of an unusual kind of stellar explosion. This discovery, made with NASA's Chandra X-ray Observatory, adds to the understanding of how some stars shatter and seed the universe with elements critical for life on Earth.

This intriguing object, located near the center of the Milky Way, is a supernova remnant called Sagittarius A East, or Sgr A East for short. Based on Chandra data, astronomers previously classified the object as the remains of a massive star that exploded as a supernova, one of many kinds of exploded stars that scientists have catalogued.

Using longer Chandra observations, a team of astronomers has now instead concluded that the object is left over from a different type of supernova. It is the explosion of a white dwarf, a shrunken stellar ember from a fuel-depleted star like our Sun. When a white dwarf pulls too much material from a companion star or merges with another white dwarf, the white dwarf is destroyed, accompanied by a stunning flash of light.

Astronomers use these "Type Ia supernovae" because most of them mete out almost the same amount of light every time no matter where they are located. This allows scientists to use them to accurately measure distances across space and study the expansion of the universe.

Data from Chandra have revealed that Sgr A East, however, did not come from an ordinary Type Ia. Instead, it appears that it belongs to a special group of supernovae that produce different relative amounts of elements than traditional Type Ias do, and less powerful explosions. This subset is referred to as "Type Iax," a potentially important member of the supernova family.

"While we've found Type Iax supernovae in other galaxies, we haven't identified evidence for one in the Milky Way until now," said Ping Zhou of Nanjing University in China, who led the new study while at the University of Amsterdam. "This discovery is important for getting a handle of the myriad ways white dwarfs explode."

The explosions of white dwarfs is one of the most important sources in the universe of elements like iron, nickel, and chromium. The only place that scientists know these elements can be created is inside the nuclear furnace of stars or when they explode.

"This result shows us the diversity of types and causes of white dwarf explosions, and the different ways that they make these essential elements," said co-author Shing-Chi Leung of Caltech in Pasadena, California. "If we're right about the identity of this supernova's remains, it would be the nearest known example to Earth."

Astronomers are still debating the cause of Type Iax supernova explosions, but the leading theory is that they involve thermonuclear reactions that travel much more slowly through the star than in Type Ia supernovae. This relatively slow walk of the blast leads to weaker explosions and, hence, different amounts of elements produced in the explosion. It is also possible that part of the white dwarf is left behind.

Sgr A East is located very close to Sagittarius A*, the supermassive black hole in the center of our Milky Way galaxy, and likely intersects with the disk of material surrounding the black hole. The team was able to use Chandra observations targeting the supermassive black hole and the region around it for a total of about 35 days to study Sgr A East and find the unusual pattern of elements in the X-ray data. The Chandra results agree with computer models predicting a white dwarf that has undergone slow-moving nuclear reactions, making it a strong candidate for a Type Iax supernova remnant.

"This supernova remnant is in the background of many Chandra images of our galaxy's supermassive black hole taken over the last 20 years," said Zhiyuan Li, also of Nanjing University. "We finally may have worked out what this object is and how it came to be."

In other galaxies, scientists observe that Type Iax supernovae occur at a rate that is about one third that of Type Ia supernovae. In the Milky Way, there have been three confirmed Type Ia supernova remnants and two candidates that are younger than 2,000 years, corresponding to an age when remnants are still relatively bright before fading later. If Sgr A East is younger than 2,000 years and resulted from a Type Iax supernova, this study suggests that our galaxy is in alignment with respect to the relative numbers of Type Iax supernovae seen in other galaxies.

Along with the suggestion that Sgr A East is the remnant from the collapse of a massive star, previous studies have also pointed out that a normal Type Ia supernova had not been ruled out. The latest study conducted with this deep Chandra data argue against both the massive star and the normal Type Ia interpretations.

These results have been published today in The Astrophysical Journal, and a preprint is available online. The other co-authors of the paper are Ken'ichi Nomoto of The University of Tokyo in Japan, Jacco Vink of the University of Amsterdam in The Netherlands, and Yang Chen, also of Nanjing University.

Read more at Science Daily