Astronomy

Lunar settlers could avoid health problems like muscle wasting by running on the inside of a circular wall to mimic the pull of Earth’s gravity on the body

Lunar settlers could avoid health problems like muscle wasting by running on the inside of a circular wall to mimic the pull of Earth’s gravity on the body

A process to dissolve the mineral olivine in acid could provide a plentiful, energy-efficient material for carbon-negative cement

A process to dissolve the mineral olivine in acid could provide a plentiful, energy-efficient material for carbon-negative cement

A new Japanese observatory built high in the Chilean Andes mountains promises fresh views of the early universe.

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Few space images are as iconic as those of the Horsehead Nebula. Its shape makes it instantly recognizable. Over the decades, a number of telescopes have captured its image, turning it into a sort of test case for a telescope’s power.

The JWST has them all beat.

The Horsehead Nebula is about 1300 light-years away in Orion. It’s part of the much larger Orion Molecular Cloud Complex. Horsehead is visible near the three stars in Orion’s Belt in a zoomed-in image.

The Horsehead Nebula is visible in this image of Orion’s Belt. It’s in the lower left, extending horizontally, to the lower left of the belt star Alnitak. Image Credit: By Davide De Martin (http://www.skyfactory.org); Credit: Digitized Sky Survey, ESA/ESO/NASA FITS Liberator – https://www.spacetelescope.org/projects/fits_liberator/fitsimages/davidedemartin_12/ (direct link), Public Domain, https://commons.wikimedia.org/w/index.php?curid=1329999

The leading image shows JWST’s view of the Horsehead Nebula alongside two other views. The Euclid image was captured in November 2023. Euclid features a wide-angle, 600-megapixel camera, and its primary job is to measure the redshift of galaxies and the Universe’s expansion due to dark energy. It took Euclid about one hour to capture the image, showcasing the telescope’s ability to gather highly detailed images quickly.

The Hubble captured its image in 2013 and was released as the telescope’s 23rd-anniversary featured image. The venerable Hubble does a good job of revealing structures hidden by dust. There’s nothing left to say about the Hubble that hasn’t been said already. It’s the revered elder among telescopes, and if you feel no reverence towards it, its contribution to science, and the people responsible for it, you may have a bad case of ennui.

The third image is a new one from the JWST’s NIRCam instrument. It’s described as the sharpest image of the Horsehead ever taken. It shows a small part of the iconic nebula in detail we don’t usually see. The JWST is so powerful it even shows background galaxies.

A zoom-in of the JWST image. The detail is incredible. Image Credit: ESA/Webb, CSA, K. Misselt, M. Zamani (ESA/Webb)

The Horsehead Nebula is the result of stellar erosion. The nebula itself was formed by a collapsing cloud of material, and a nearby hot star called Sigma Orionis illuminates the structure. The nebula is denser than its surrounding gas and has resisted the dissipative energy of the star, while the gas that used to surround it is long gone.

This definitely isn’t the last we’ll see of Horsehead. New, powerful telescopes coming online soon, like the Giant Magellan Telescope and the European Extremely Large Telescope will likely take a crack at the nebula. Prepare to be wowed.

There’s no rush. According to astronomers, the Horsehead Nebula will eventually be eroded away, too, but not for another five million years or so.

The post Insanely Detailed Webb Image of the Horsehead Nebula appeared first on Universe Today.

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It stands to reason that stars formed from the same cloud of material will have the same metallicity. That fact underpins some avenues of astronomical research, like the search for the Sun’s siblings. But for some binary stars, it’s not always true. Their composition can be different despite forming from the same reservoir of material, and the difference extends to their planetary systems.

New research shows that the differences can be traced back to their earliest stages of formation.

Binary stars are the norm, while solitary stars like our Sun are in the minority. Some estimates place the number of binary stars in the Milky Way at up to 85%. These pairs of stars form from the same giant molecular clouds. Each cloud has a certain abundance of metals, and that abundance should be reflected in the stars themselves.

But that’s not always the case.

Sometimes, the metallicity of a pair of binary stars doesn’t agree. Astrophysicists have proposed three explanations for this.

Two explanations involve events occurring later in a star’s life after they’ve left the main sequence. One is atomic diffusion, where chemical elements settle into gradient layers in the star. The layers are determined by a star’s gravity and temperature. The second one involves a nearby planet. As stars age, expand, and become red giants, they engulf nearby planets. The planet would introduce new chemistry into the star, differentiating it from its binary partner.

As stars like our Sun age and leave the main sequence, they expand and become red giants, engulfing nearby planets. That can change the chemistry of the stars. Image Credit: fsgregs Creative Commons Attribution-Share Alike 3.0 Unported

The third explanation reaches back in time to the binary pair’s formation. This explanation says that the giant molecular cloud that spawned the stars wasn’t homogeneous. Instead, there were regional differences in the cloud’s chemistry, and stars formed in different locations showed noticeable differences in their chemical makeup.

A team of researchers wanted to dig into this third explanation to test its veracity. They used the Gemini South Telescope and its Gemini High-Resolution Optical SpecTrograph (GHOST) to examine the light from a pair of giant binary stars. The observations revealed significant differences in their spectra.

Sunset over Gemini South, on the summit of Mauna Kea in Hawai’i. Credit: Gemini

They presented their results in a paper titled “Disentangling the origin of chemical differences using GHOST.” It’s published in the journal Astronomy and Astrophysics. The lead author is Carlos Saffe of the Institute of Astronomical, Earth and Space Sciences (ICATE-CONICET) in Argentina. The researchers examined a pair of giant binary stars called HD 138202 + CD?30 12303.

The three explanations for chemical differences between binary stars all stem from studies of main sequence stars. The main sequence is where stars spend most of their time, reliably fusing hydrogen into helium for billions of years.

But Saffe and his colleagues took a different approach. They used Gemini and GHOST to examine a pair of binary stars that had left the main sequence behind and become giant stars. These stars are different from main sequence stars.

“GHOST’s extremely high-quality spectra offered unprecedented resolution,” said Saffe, “allowing us to measure the stars’ stellar parameters and chemical abundances with the highest possible precision.”

This table from the research shows some of the differences between the pair of giant binary stars. The third column shows their different metallicities, expressed by the Fe/H (iron hydrogen) ratio. The Star A is more metal-rich by ?0.08 dex than its companion. Image Credit: Saffe et al. 2024.

These stars experience dredge-ups. Dredge-ups are when a star’s convection zone extends from the surface all the way down to where fusion is taking place. They’re powerful convective currents that mix fusion products into the star’s surface layer when a main sequence star becomes a red giant.

This diagram of the Sun helps explain dredge-ups. The Sun is still on the main sequence, so its convective region is on its surface. But when stars like the Sun become red giants, temporary convective cells called dredge-ups can reach from the surface all the way to the fusion core. This can introduce different chemical elements onto the visible surface. Image Credit: CSIRO/ATNF/Naval Research Laboratory

However, the researchers say that dredge-ups and the atomic diffusion they drive can’t explain the wide difference between stars.

The convection currents would also rule out the second proposed explanation: planetary engulfment. With such strong currents, the chemicals from an engulfed planet would quickly be diluted. “Giant stars are thought to be significantly less sensitive than main-sequence stars to engulfment events,” the authors write.

The authors went further and calculated the amount of planetary material a giant star would need to digest to cause the difference in metallicity between the stars. “We estimate that star A would need to have ingested between 11.0 and 150.0 Jupiter masses of planetary material, depending on the adopted convective envelope mass and metallic content of the ingested planet,” the authors explain. That’s an awful lot of material. They also explain that the planets must have had extremely high metallicity for the low value of 11 Jupiter masses to cause the chemical differences.

That only leaves one explanation: inhomogeneities in the molecular cloud.

This is a two-panel mosaic of part of the Taurus Giant Molecular Cloud, the nearest active star-forming region to Earth. The darkest regions are where stars are being born. Research shows that small inhomogeneities in the cloud can produce binary stars with different metallicities. Image Credit: Adam Block /Steward Observatory/University of Arizona

“This is the first time astronomers have been able to confirm that differences between binary stars begin at the earliest stages of their formation,” said Saffe.

“Using the precision-measurement capabilities provided by the GHOST instrument, Gemini South is now collecting observations of stars at the end of their lives to reveal the environment in which they were born,” said Martin Still, NSF program director for the International Gemini Observatory. “This gives us the ability to explore how the conditions in which stars form can influence their entire existence over millions or billions of years.”

The results go a long way to explaining why a pair of binary stars can have differing compositions. But they reach even further than that. They also explain why a pair of binary stars can have such different planetary systems. “Different planetary systems could mean very different planets — rocky, Earth-like, ice giants, gas giants — that orbit their host stars at different distances and where the potential to support life might be very different,” said Saffe.

But the results also present a challenge. Astronomers use chemical tagging to identify stars that are associated with one another. Stars from the same stellar nursery are expected to have similar compositions. But that method seems unreliable in light of these findings.

The results also challenge the idea that differences in composition between binary stars can be explained by planet engulfment. Instead, those differences might stem from the stars’ earliest days of formation.

“By showing for the first time that primordial differences really are present and responsible for differences between twin stars, we show that star and planet formation could be more complex than initially thought,” said Saffe. “The Universe loves diversity!”

This artist’s concept shows a hypothetical planet covered in water around the binary star system of Kepler-35A and B. If differences in chemical compositions in stars stem from their earliest days of formation, then those differences must affect the types of planets that form around them. (Image by NASA/JPL-Caltech.)

The only drawback of this study is the sample size of one. Small sample sizes are always cautionary: they can lead to an eventual conclusion but don’t form reliable conclusions independently. The authors know this.

“We strongly encourage the study of giant-giant pairs,” the researchers conclude. “This novel approach might help us to distinguish the origin of the slight chemical differences observed in multiple systems.”

The post Binary Stars Form in the Same Nebula But Aren’t Identical. Now We Know Why. appeared first on Universe Today.

The molecular gas ejected by a dying star within the Southern Ring Nebula will one day be recycled into a new generation of stars and planets.

Check out this incredibly detailed image of the Running Chicken Nebula — IC 2944 — captured by astrophotographer Rod Prazeres.

We go about our daily lives sheltered under an invisible magnetic field generated deep inside Earth. It forms the magnetosphere, a region dominated by the magnetic field. Without that planetary protection shield, we’d experience harmful cosmic radiation and charged particles from the Sun.

Has Earth always had this deflector shield? Probably so, and the evidence is in old rocks. A team of researchers at University of Oxford and MIT found the earliest evidence for its existence in stones found along the coast of Greenland in a region called the Isua Supercrustal Belt.

Geologists have long known that iron particles in rocks “entrain” a print of the magnetic field that was in place when they formed. So, the research team uncovered rocks that formed some 3.7 billion years ago. It’s not an easy task, according to team lead Claire Nichols of the Department of Earth Sciences at Oxford. “Extracting reliable records from rocks this old is extremely challenging,” Nichols pointed out. “It was really exciting to see primary magnetic signals begin to emerge when we analyzed these samples in the lab. This is a really important step forward as we try and determine the role of the ancient magnetic field when life on Earth was first emerging.”

This 3.7-billion-year-old rock from Greenland. Entrained magnetic field fingerprints help scientists determine that our magnetosphere and magnetic field existed when this rock formed. Courtesy: Claire Nichols.

The team’s samples recorded a magnetic field strength of 15 microteslas at the time they formed. Today, Earth’s field strength is closer to 30 microteslas, so it’s obvious that our magnetic field and magnetosphere have been there for billions of years. It’s also clear that the field changes over time. The science team also found that early Earth’s magnetosphere was amazingly similar to the one it has today.

Tracking Earth’s Magnetosphere through Time

Our planet has a main dynamo at its heart. There are two cores—an inner one and an outer one. Motions in the core regions generate the magnetic field that defines our magnetosphere. Molten iron mixes and moves in the fluid outer core and the inner core solidifies. The two actions together create that dynamo. That’s what’s happening inside our planet today.

This cutaway of planet Earth shows the familiar exterior of air, water and land as well as the interior: from the mantle down to the outer and inner cores. Currents in hot, liquid iron-nickel in the outer core create our planet’s protective but fluctuating magnetic field and magnetosphere. Credit: Kelvinsong / Wikipedia

However, when Earth was first forming some 4.5 billion years ago, that solid inner core didn’t exist. Without the interaction we see today between the two parts of the core, it’s hard to know how any early magnetic field existed. That’s an open question among geologists and planetary scientists: how did it form and how was it sustained?

Another question relates to how much the planetary magnetic field has varied over time. Answering that one would help geologists understand just when the solid inner core formed. It would also show how much heat has escaped our planet from deep inside over time. Heat escape drives plate tectonics, which uses large “plates” of rock to shift things around on the surface over hundreds of millions of years.

What Do the Rocks Tell Us?

Rocks have a long and complex history. They form as a molten mixture that solidifies, or in the case of sandstones, are laid down in layers that then harden. In the case of molten rocks, they have magnetic field fingerprints entrained at the time of formation. In measuring those fingerprints, geologists account for any heating that could “reset” the magnetic signatures over time. The Greenland rocks are relatively pristine, meaning they haven’t been significantly heated since they formed. That means their magnetic fingerprints haven’t changed since formation.

Lava cooling after an eruption. This rock has an entrained magnetic field fingerprint from the time it formed. Credit: kalapanaculturaltours.com

Rocks also get weathered by wind, temperature changes and erosion, but the Isuan samples seem to be relatively pristine, according to Benjamin Weiss of MIT. “Northern Isua has the oldest known well-preserved rocks on Earth,” Weiss said. “Not only have they not been significantly heated since 3.7 billion years ago but they have also been scraped clean by the Greenland ice sheet.”

Rocks Through Time

The rocks the team studied date back to the Archean Eon—the second-oldest geologic eon in Earth’s history. That period began about 4 billion years ago, and during that time Earth was largely an ocean world with a limited amount of continental surface. Since then, Earth’s surface has changed a great deal, destroying or burying rocks from earlier times. So, finding rocks that date back that far in time is a big deal.

The Isuan rocks are relatively unchanged since they formed, and bear proof of a magnetic field existing less than a billion years after the planet formed. That same early magnetic field could have played a role in the development of our planet’s atmosphere, by assisting in removing xenon gas. Other old rocks may well tell scientists more about the birth of the magnetic field. There are rocks in Canada, Australia and South Africa that could give unique insight into the formation of the field and its role in making Earth habitable for life.

For More Information

Researchers Find Oldest Undisputed Evidence of Earth’s Magnetic Field
Possible Eoarchean Records of the Geomagnetic Field Preserved in the Isua Supracrustal Belt, Southern West Greenland

The post Earth Had a Magnetosphere 3.7 Billion Years Ago appeared first on Universe Today.

New time-lapse videos from the Chandra X-ray Observatory show the Crab Nebula and the Cassiopeia A supernova remnant over more than 20 years.

The post What Happens After a Supernova Blows? Watch and Find Out appeared first on Sky & Telescope.

A video outlining China's moon base plans depicts a wide number of concepts, including surface sample return operations, a lander and rover, and supporting orbital satellites.

When the first stars in the Universe formed, the only material available was primordial hydrogen and helium from the Big Bang. Astronomers call these original stars Population Three stars, and they were extremely massive, luminous, and hot stars. They’re gone now, and in fact, their existence is hypothetical.

But if they did exist, they should’ve left their fingerprints on nearby gas, and astrophysicists are looking for it.

The hunt for the Universe’s Population 3 (Pop III) stars is important in astrophysics. They were the first to form astronomical metals, elements heavier than hydrogen and helium. Only once these metals were available could rocky planets form. Their metals also fed into the next generation of stars, leading to the higher metallicity we observe in stars like our Sun.

Since Pop III stars were so massive and hot, they didn’t last long. None would have survived to this day. But the powerful JWST can expand the search for these crucial stars by looking back in time for their ancient light. That’s what the JWST-JADES (James Webb Space Telescope Advanced Deep Extragalactic Survey) is all about.

Researchers working with JADES data have found tantalizing evidence of Pop III stars in GN-z11, a high-redshift galaxy that’s one of the furthest galaxies from Earth ever observed. Their findings are in the paper “JWST-JADES. Possible Population III signatures at z=10.6 in the halo of GN-z11.” The lead author is Roberto Maiolino, a professor of Experimental Astrophysics at the Cavendish Laboratory (Department of Physics) and the Kavli Institute for Cosmology at the University of Cambridge. The research will be published in the journal Astronomy and Astrophysics.

“Finding the first generation of stars formed out of pristine gas in the early Universe, known as Population III (Pop III) stars, is one of the most important goals of modern astrophysics,” Maiolino and his colleagues write in their paper. “Recent models have suggested that Pop III stars may form in pockets of pristine gas in the halo of more evolved galaxies.”

GN-z11 is one such galaxy. At a redshift of z = 10.6034, the JWST sees the galaxy as it existed about 13.4 billion years ago, corresponding to about 400 million years after the Big Bang.

Pop III stars were massive and could be as much as 1000 times more massive than the Sun. These massive stars would’ve been exceptionally hot, which can provide a clue to their presence. Astrophysicists think all that heat could’ve doubly ionized nearby helium. So they search for the expected signature of that helium: prominent HeII nebular lines called the HeII?1640 emission line. To indicate the presence of Pop III stars, the HeII lines need to be unaccompanied by any metal lines.

The JWST observed the galaxy with its NIRSpec-IFU (Integrated Field Unit) and found a tentative detection of HeII?1640.

This figure from the research shows the detection of doubly-ionized Helium at 1.903 µm. in the galaxy GN-z11. Image Credit: Maiolino et al. 2024.

Detecting the doubly-ionized helium line was only the first step. Pop III stars aren’t the only objects that could’ve ionized the helium. To determine if the ancient stars were responsible, the researchers examined the galaxy and isolated several features.

Along with the HeII?1640, they also found Lyman-alpha emissions and CIII, or doubly-ionized carbon.

This figure from the research shows the detection of different emissions. The red star in the top images indicates the position of the continuum of GN-z11. The bottom row shows the lines mapped onto a JWST NIRCam image. The ‘fewer exposures’ on the top row indicates a lack of exposures in the upper portions of the panels due to a telescope-pointing error. Image Credit: Maiolino et al. 2024.

In the images above, the researchers note several features that are clues to the source of the helium ionization.

The HeII emissions show a plume extending to the west of GN-z11. It could be tracing gas photoionized by the galaxy’s active galactic nucleus (AGN.) Since CIII is so weak there, it could indicate very low metallicity gas photoionized by the AGN.

The image also shows a clump of HeII to the northeast of GN-z11. The researchers call this clump the “most intriguing” feature found. They analyzed the clump in the image below.

This figure from the research shows the spectra of the HeII clump. The observed emissions (blue) line up with the expected emissions from a galaxy at redshift z=10.600. Image Credit: Maiolino et al. 2024.

So what does this all add up to? Did the researchers find Pop III stars?

The spectral feature in the clump is strong evidence of photoionization by Pop III stars, according to the authors. “This wavelength corresponds to HeII?1640 at z=10.600, and it is fully consistent with the redshift of GN-z11,” they write. The same emission was detected over a larger area to the northeast, possibly with a second, fainter clump.

The authors say that the AGN could’ve photoionized the helium close to the galaxy’s center, but it can’t explain the HeII further away. Pop III stars are the best explanation, according to the authors.

Other evidence for Pop III stars comes from the emissions widths of the HeII lines. The high width suggests photoionization by metal poor Pop III stars rather than by Pop II stars with higher metallicity.

The extent of the ionization also indicates a certain mass for the Pop III stars, and the indicated mass agrees with simulations.

There’s another possibility: a direct collapse black hole (DCBH). “We also considered the alternative possibility of photoionization by a DCBH in the HeII clump,” the authors write. But the emission width should be lower in that scenario, although not by a lot. “Hence, this scenario remains another possible interpretation,” the authors write.

If future observations confirm the presence of Pop III stars in GN-z11, that’s a pretty big deal. But even if we have to wait for that confirmation, this research shows how powerful the JWST is again.

“These results have demonstrated the JWST’s capability to explore the primitive environment around galaxies in the early Universe, revealing fascinating properties,” the researchers conclude.

The post Astronomers Think They’ve Found Examples of the First Stars in the Universe appeared first on Universe Today.

NASA's exoplanet hunter TESS may have detected its first free-floating planet with a little help from Einstein.

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The G7 group of wealthy, developed economies has agreed to phase out coal-fired power, the most polluting form of energy, by 2035

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