Science

Jupiter’s moon Io is the most volcanically active body in the Solar System, with roughly 400 active volcanoes regularly ejecting magma into space. This activity arises from Io’s eccentric orbit around Jupiter, which produces incredibly powerful tidal interactions in the interior. In addition to powering Io’s volcanism, this tidal energy is believed to support a global subsurface magma ocean. However, the extent and depth of this ocean remains the subject of debate, with some supporting the idea of a shallow magma ocean while others believe Io has a more rigid, mostly solid interior.

In a recent NASA-supported study, an international team of researchers combined data from multiple missions to measure Io’s tidal deformation. According to their findings, Io does not possess a magma ocean and likely has a mostly solid mantle. Their findings further suggest that tidal forces do not necessarily lead to global magma oceans on moons or planetary bodies. This could have implications for the study of exoplanets that experience tidal heating, including Super-Earths and exomoons similar to Io that orbit massive gas giants.

The study was led by Ryan Park, a Senior Research Scientist and Principal Engineer at NASA’s Jet Propulsion Laboratory (JPL). He was joined by multiple colleagues from NASA JPL, the Centro Interdipartimentale di Ricerca Industriale Aerospaziale (CIRI) at the Università di Bologna, the National Institute for Astrophysics (NIAF), the Sapienza Università di Roma, the Southwest Research Institute (SwRI), and NASA’s Goddard Space Flight Center, and multiple universities. Their findings were described in a paper that appeared in the journal Nature.

An amazingly active Io, Jupiter’s “pizza moon,” shows multiple volcanoes and hot spots, as seen with Juno’s infrared camera. Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM/Roman Tkachenko

As they explain in their paper, two types of analysis have predicted the existence of a global magma ocean. On the one hand, magnetic induction measurements conducted by the Galileo mission suggested the existence of a magma ocean within Io, approximately 50 km [~30 mi] thick and located near the surface. These results also implied that about 20% of the material in Io’s mantle is melted. However, these results were subjected to debate for many years. In recent years, NASA’s Juno mission conducted multiple flybys of Io and the other Jovian moons and obtained data that supported this conclusion.

In particular, the Juno probe conducted a global mapping campaign of Io’s volcanoes, which suggested that the distribution of volcanic heat flow is consistent with the presence of a global magma ocean. However, these discoveries have led to considerable debate about these techniques and whether they can be used to distinguish whether a shallow global magma ocean drives Io’s volcanic activity. This is the question Park and his colleagues sought to address in their study:

“In our study, Io’s tidal deformation is modeled using the gravitational tidal Love number k2, which is defined as the ratio of the imposed gravitational potential from Jupiter to the induced potential from the deformation of Io. In short, if k2 is large, there is a global magma ocean, and if k2 is small, there is no global magma ocean. Our result shows that the recovered value of k2 is small, consistent with Io not having a global magma ocean.”

The significance of these findings goes far beyond the study of Io and other potentially volcanic moons. Beyond the Solar System, astronomers have discovered countless bodies that (according to current planetary models) experience intense tidal heating. This includes rocky exoplanets that are several times the size and mass of Earth (Super-Earths) and in the case of tidally-locked planets like the TRAPPIST-1 system. These findings are also relevant for the study of exomoons that also experience intense tidal heating (similar to the Jovian moons). As Park explained:

“Although it is commonly assumed among the exoplanet community that intense tidal heating may lead to magma oceans, the example of Io shows that this need not be the case. Our results indicate that tidal forces do not universally create global magma oceans, which may be prevented from forming due to rapid melt ascent, intrusion, and eruption, so even strong tidal heating – like that expected on several known exoplanets and super-Earths – may not guarantee the formation of magma oceans on moons or planetary bodies.”

Further Reading: Nature

The post New Research Suggests Io Doesn’t Have a Shallow Ocean of Magma appeared first on Universe Today.

The star HD 65907 is not what it appears to be. It’s a star that looks young, but on closer inspection is actually much, much older. What’s going on? Research suggests that it is a resurrected star.

Astronomers employ different methods to measure a star’s age. One is based on its brightness and temperature. All stars follow a particular path in life, known as the main sequence. The moment they begin fusing hydrogen in their cores, they maintain a strict relationship between their brightness and temperature. By measuring these two properties, astronomers can roughly pin down the age of a star. But there are other techniques, like measuring the amount of heavy elements in a stellar atmosphere. Older stars tend to have fewer of these elements, because they were born at a time before the galaxy had become enriched with them.

Going by its temperature and brightness, HD 65907 is relatively young, with an age right around 5 billion years old. And yet it contains very little heavy elements. Plus, its path in the galaxy isn’t in line with other young stars, which tend to serenely orbit around the center. HD 65907 is much more erratic, suggesting that it only recently moved here from somewhere else.

In a recent paper, an international team of astronomers dug into archival data to see if they could resolve the mystery, and they believe that HD 65907 is a kind of star known as a blue straggler, and that it has its strange combination of properties because of a violent event in its past, causing it to be resurrected.

If two low-mass stars collide, the remnants can sometimes survive as a star on its own. At first that newly merged star will be both massive and large, with its outer surface flung far away from the core due to the enormous rotation after the collision. But eventually some astrophysical process (perhaps strong magnetic fields might be to blame) drag down the rotation rate of the star, causing it to slow down and settle into equilibrium. In this new state the star will appear massive and incredibly hot: a blue straggler.

No matter what, blue straggler stars get a second chance on life. Those mergers transform small stars into big stars, and they’re just now enjoying their hydrogen-burning main sequence lives.

The astronomers believe this is the case for HD 65907. What makes this star especially unique is that it’s not a member of a cluster, where frequent mergers can easily lead to blue stragglers. Instead, it’s a field star, wandering the galaxy on its own. It must have cannibalized a companion five billion years ago, leading to its apparent youthful age.

Work like this is essential to untangling the complicated lives of stars in the Milky Way, and it shows how the strangest stars hold the keys to unlocking the evolution of elements that lead to systems like our own.

The post The Mysterious Case of the Resurrected Star appeared first on Universe Today.

In a new study, participants tended to assign greater blame to artificial intelligences (AIs) involved in real-world moral transgressions when they perceived the AIs as having more human-like minds.

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It’s axiomatic that the Universe is expanding. However, the rate of expansion hasn’t remained the same. It appears that the Universe is expanding more quickly now than it did in the past.

Astronomers have struggled to understand this and have wondered if the apparent acceleration is due to instrument errors. The JWST has put that question to rest.

American astronomer Edwin Hubble is widely credited with discovering the expansion of the Universe. But it actually stemmed from relativity equations and was pioneered by Russian scientist Alexander Freedman. Hubble’s Law bears Edwin’s name, though, and he was the one who confirmed the expansion, called Hubble’s constant, and put a more precise value to it. It measures how rapidly galaxies that aren’t gravitationally bound are moving away from one another. The movement of objects due solely to the Hubble constant is called the Hubble flow.

Measuring the Hubble constant means measuring distances to far-flung objects. Astronomers use the cosmic distance ladder (CDL) to do that. However, the ladder has a problem.

This illustration shows the three basic steps astronomers use to calculate how fast the universe expands over time, a value called the Hubble constant. All the steps involve building a strong “cosmic distance ladder” by starting with measuring accurate distances to nearby galaxies and then moving to galaxies farther and farther away. Image Credit: NASA, ESA and A. Feild (STScI)

The first rungs on the CDL are fundamental measurements that can be observed directly. Parallax measurement is the most important fundamental measurement. But the method breaks down at great distances.

Beyond that, astronomers use standard candles, things with known intrinsic brightness, like supernovae and Cepheid variables. Those objects and their relationships help astronomers measure distances to other galaxies. This has been tricky to measure, though advancing technology has made progress.

Another pair of problems plagues the effort, though. The first is that different telescopes and methods produce different distance measurements. The second is that our measurements of distances and expansion don’t match up with the Standard Model of Cosmology, also known as the Lambda Cold Dark Matter (LCDM) model. That discrepancy is called the Hubble tension.

The question is, can the mismatch between the measurements and the LCDM be explained by instrument differences? That possibility has to be eliminated, and the trick is to take one large set of distance measurements from one telescope and compare them to another.

New research in The Astrophysical Journal tackles the problem by comparing Hubble Space Telescope measurements with JWST measurements. It’s titled “JWST Validates HST Distance Measurements: Selection of Supernova Subsample Explains Differences in JWST Estimates of Local H0.” The lead author is Adam Riess, a Bloomberg Distinguished Professor and Thomas J. Barber Professor of Physics and Astronomy at Johns Hopkins University. Riess is also a Nobel laureate, winning the 2011 Nobel Prize in Physics “for the discovery of the accelerating expansion of the Universe through observations of distant supernovae,” according to the Nobel Institute.

As of 2022, the Hubble Space Telescope gathered the most numerous sample of homogeneously measured standard candles. It measured a large number of standard candles out to about 40 Mpc or about 130 million light-years. “As of 2022, the largest collection of homogeneously measured SNe Ia is complete to D less than or equal to 40 Mpc or redshift z less than or equal to 0.01,” the authors of the research write. “It consists of 42 SNe Ia in 37 host galaxies calibrated with observations of Cepheids with the Hubble Space Telescope (HST), the heritage of more than 1000 orbits (a comparable number of hours) invested over the last ~20 yrs.”

In this research, the astronomers used the powerful JWST to cross-check the Hubble’s work. “We cross-check the Hubble Space Telescope (HST) Cepheid/Type Ia supernova (SN Ia) distance ladder, which yields the most precise local H0 (Hubble flow), against early James Webb Space Telescope (JWST) subsamples (~1/4 of the HST sample) from SH0ES and CCHP, calibrated only with NGC 4258,” the authors write. SH0ES and CCHP are different observing efforts aimed at measuring the Hubble constant. SH0ES stands for Supernova H0 for the Equation of State of Dark Energy, and CCHP stands for Chicago-Carnegie Hubble Program, which uses the JWST to measure the Hubble constant.

“JWST has certain distinct advantages (and some disadvantages) compared to HST for measuring distances to nearby galaxies,” Riess and his co-authors write. It offers a 2.5 times higher near-infrared resolution than the HST. Despite some of its disadvantages, the JWST “is able to provide a strong cross-check of distances in the first two rungs,” the authors explain.

Observations from both telescopes are closely aligned, which basically minimizes instrument error as the cause of the discrepancy between observations and the Lambda CDM model.

There’s a lot to digest in this figure from the research. It shows “Comparisons of H0 between HST Cepheids and other measures (JWST Cepheids, JWST JAGB, and JWST NIR-TRGB) for SN Ia host subsamples selected by different teams and for the different methods,” the authors explain. JAGB stands for J-region Asymptotic Giant Branch, and TRGB stands for Tip of the Red Giant Branch. Both JAGB and TRGB are ways of measuring distance to specific types of stars. Basically, coloured circles represent Hubble measurements, and squares represent JWST measurements. “The HST Cepheid and JWST distance measurements themselves are in good agreement,” the authors write. Image Credit: Riess et al. 2024.

“While it will still take multiple years for the JWST sample of SN hosts to be as large as the HST sample, we show that the current JWST measurements have already ruled out systematic biases from the first rungs of the distance ladder at a much smaller level than the Hubble tension,” the authors write.

This research covered about one-third of the Hubble’s data set, with the known distance to a galaxy called NGC 4258 serving as a reference point. Even though the data set was small, Riess and his co-researchers achieved impressively precise results. They showed that the measurement differences were less than 2%. That’s much less than the 8% to 9% in the Hubble tension discrepancy.

NGC 4258 is significant in the cosmic distance ladder because it contains Cepheid variables similar to both the metallicities of the Milky Way and other galaxies’ Cepheids. Astronomers use it to calibrate distances to Cepheids with different metallicities. A new composite of NGC 4258 features X-rays from Chandra (blue), radio waves from the VLA (purple), optical data from Hubble (yellow and blue), and infrared with Spitzer (red). Image Credit: Chandra

That means that our Lamda CDM model is missing something. The standard model yields an expansion rate of about 67 to 68 kilometres per second per megaparsec. Telescope observations yield a slightly higher rate: between 70 and 76 kilometres per second per megaparsec. This work shows that the discrepancy can’t be due to the different telescopes and methods.

“The discrepancy between the observed expansion rate of the universe and the predictions of the standard model suggests that our understanding of the universe may be incomplete. With two NASA flagship telescopes now confirming each other’s findings, we must take this [Hubble tension] problem very seriously—it’s a challenge but also an incredible opportunity to learn more about our universe,” said lead author Riess.

What could be missing from the Lambda CDM model?

Marc Kamionkowski is a Johns Hopkins cosmologist who helped calculate the Hubble constant and recently developed a possible new explanation for the tension. Though not part of this research, he commented on it in a press release.

“One possible explanation for the Hubble tension would be if there was something missing in our understanding of the early universe, such as a new component of matter—early dark energy—that gave the universe an unexpected kick after the big bang,” said Kamionkowski. “And there are other ideas, like funny dark matter properties, exotic particles, changing electron mass, or primordial magnetic fields that may do the trick. Theorists have license to get pretty creative.”

The door is open, theorists just have to walk in.

The post The JWST Looked Over the Hubble’s Shoulder and Confirmed that the Universe is Expanding Faster appeared first on Universe Today.

Water oxidation offers a promising path to achieve sustainable energy by efficiently generating oxygen. This study investigates how optimizing Ru(II) photosensitizers, metal oxide catalysts, and pH conditions can enhance water splitting efficiency. By introducing a simplified method to estimate catalyst performance, researchers make it easier to design more effective systems. These findings provide crucial insights for advancing clean energy solutions and accelerating the transition to renewable energy.

A new comprehensive literature review of the benefits and challenges of integrating haptics-enhanced virtual reality training, or VR-haptics for short, in dental education curricula highlights the transformative potential of VR-haptics in dental education.

A fragment of 'lost' music found in the pages of Scotland's first full-length printed book is providing clues to what music sounded like five centuries ago. Scholars have been investigating the origins of the musical score -- which contains only 55 notes -- to cast new light on music from pre-Reformation Scotland in the early sixteenth-century. Researchers say the tantalizing discovery is a rare example of music from Scottish religious institutions 500 years ago, and is the only piece which survives from the northeast of Scotland from this period.

Conventional wisdom assumes the ratio of gases in a planet's atmosphere should match the ratio of gases in the natal disk that birthed it. For the first time, researchers compared gases in a still-forming planet's atmosphere to its natal disk. The team found the planet surprisingly was less carbon-rich than the disk.

Researchers have developed a molecule that allows an important ion channel to be regulated -- a breakthrough with therapeutic potential.

Artificial intelligence (AI) systems tend to take on human biases and amplify them, causing people who use that AI to become more biased themselves, a new study finds.

Galaxy clusters -- the big cities of the universe -- are home to many giant elliptical galaxies that have completed their growth and are not forming stars. However, it is still unclear what has shut down star formation. In a new study, researchers utilized the James Webb Space Telescope to observe an ancestor of galaxy clusters, revealing the role of supermassive black holes in slowing star formation and allowing them to evolve into giant elliptical galaxies.

To guard against harmful waterborne pathogens, many consumers, including managers of health-care facilities, install antimicrobial silver-containing showerheads. But researchers now report that these fixtures are no 'silver bullet.' In real-world showering conditions, most microbes aren't exposed to the silver long enough to be killed. However, the composition of rare microbes in water from these showerheads varied with each type of fixture tested.

Scientists recently led a team that found, for the first time, that Chiron has surface chemistry unlike other centaurs. Its surface it has both carbon dioxide and carbon monoxide ice along with carbon dioxide and methane gases in its coma, the cloud-like envelope of dust and gas surrounding it.

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Scientists have spotted a massive black hole in the early universe that is 'napping' after stuffing itself with too much food. Like a bear gorging itself on salmon before hibernating for the winter, or a much-needed nap after Christmas dinner, this black hole has overeaten to the point that it is lying dormant in its host galaxy.

Scientists have developed swarms of tiny magnetic robots that work together like ants to achieve Herculean feats, including traversing and picking up objects many times their size. The findings suggest that these microrobot swarms -- operating under a rotating magnetic field -- could be used to take on difficult tasks in challenging environments that individual robots would struggle to handle, such as offering a minimally invasive treatment for clogged arteries and precisely guiding organisms.

Scientists have developed swarms of tiny magnetic robots that work together like ants to achieve Herculean feats, including traversing and picking up objects many times their size. The findings suggest that these microrobot swarms -- operating under a rotating magnetic field -- could be used to take on difficult tasks in challenging environments that individual robots would struggle to handle, such as offering a minimally invasive treatment for clogged arteries and precisely guiding organisms.