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Does the size of an exomoon help determine if life could form on an exoplanet it’s orbiting? This is something a February 2022 study published in Nature Communications hopes to address as a team of researchers investigated the potential for large exomoons to form around large exoplanets (Earth-sized and larger) like how our Moon was formed around the Earth. Despite this study being published almost two years ago, its findings still hold strong regarding the search for exomoons, as astronomers have yet to confirm the existence of any exomoons anywhere in the cosmos. But why is it so important to better understand the potential for large exomoons orbiting large exoplanets?

Dr. Miki Nakajima, who is an Assistant Professor of Physics and Astronomy at the University of Rochester and lead author of the study, tells Universe Today, “For Earth, the Moon plays a major role to determine the length of the day of Earth, ocean tides, and Earth’s spin axis tilt. These are extremely important parameters for life on Earth. Thus, understanding whether a planet has a moon or not would help us understand whether an exoplanet is similar to Earth or not.”

For the study, the researchers used a series of computer models to simulate how exomoons could form around an exoplanet based on the giant-impact theory that is the currently accepted model for how our Moon formed around the Earth. The researchers conducted these simulations using a variety of conditions, including rocky and icy exoplanets with the maximum target size being six Earth masses, the size and size ration of the impactor and target, along with a fixed impact velocity and impact angle for the impactor striking the target. In the end, the simulations produced some interesting results pertaining to the formation and evolution of exomoons.

“In my opinion, the most significant result is that our study made a prediction for future exomoon observations,” Dr. Nakajima tells Universe Today. “We predict that relatively small planets (< ~ 1.6 Earth radii) are good candidates to host exomoons. Up until now, most exomoon searches have focused on larger planets. So now we propose that future searches should instead focus on these smaller planets.”

As noted, this study was published almost two years ago, but its findings still hold true in terms of hypothesizing about the existence and potential future discoveries of exomoons, which could help astronomers better understand the conditions necessary for finding life beyond Earth. While the Earth’s Moon is responsible for allowing life to thrive on this planet, smaller moons throughout our solar system have demonstrated that size might not matter in terms of allowing life to potentially thrive on, or beneath, their surfaces. Examples include Jupiter’s icy moon, Europa, and Saturn’s largest moon, Titan, and its smaller icy moon, Enceladus. Given this study focused on exomoons forming around large exoplanets, what can exomoons, regardless of their size, teach us about finding life beyond Earth?

“In my opinion, a planet does not have to have a large moon to host life on its surface,” Dr. Nakajima tells Universe Today. “However, at least for Earth, the Moon plays a crucial role on the life on Earth. So, if we want to find a second Earth, a planet with a large moon would be a great candidate. I hope our study helps us to identify what planets likely host moons.”

In terms of follow-up studies that might have occurred in the two years since this study was published, Dr. Nakajima tells Universe Today that her and her colleagues have written a recent study about how the Earth’s Moon might have formed under a different process, and the paper is currently in peer-review. Additionally, Dr. Nakajima tells Universe Today she is currently participating in a proposal for NASA’s James Webb Space Telescope (JWST) with the goal of identifying exomoons orbiting relatively small exoplanets.

This 2022 study and upcoming JWST proposal both highlight how exomoons have come to the forefront for the search for life beyond Earth, and specifically beyond our solar system. While the existence of even one exomoon has yet to be confirmed, a growing list of exomoon candidates has garnered the attention of astronomers, with these exomoon candidates potentially orbiting both Jupiter- and Earth-sized worlds.

When will astronomers find the first exomoon, and how many exomoons will researchers find in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

The post Big Planets Don’t Necessarily Mean Big Moons appeared first on Universe Today.

Astronomers routinely explore the universe using different wavelengths of the electromagnetic spectrum from the familiar visible light to radio waves and infra-red to gamma rays. There is a problem with studying the Universe through the electromagnetic spectrum, we can only see light from a time when the Universe was only 380,000 years old. An alternate approach is to use gravitational waves which are thought to have been present in the early Universe and may allow us to probe back even further. 

The concept of gravity waves is really quite simple. Imagine the fabric of space as an enormous sea.  The movement of any object within that lake will cause ripples that permeate through the water. Just as a sea fog will limit the visibility, the ripples can still travel through . Gravity waves are like ripples in space caused by the movement of objects. It was an idea predicted by Einstein in 1916 in his General Theory of Relativity. 

Gravity waves are not just a theory though, they have been detected. The LIGO-Virgo observatory detected gravity waves on 15 September 2015 from the merging of two black holes with 29 and 36 solar masses 1.3 billion light years away. There have since been over 100 detections so gravity waves are most certainly real. 

LIGO Observatory

Using gravity waves, Rishav Roshan and Graham White from University of Southampton believe they can probe the Universe’s earliest moments.  In the early moments of the formation of the Univserse, space was opaque becuase the Universe was full of ionised gas and electromagnetic radiation could not permeate. It is this barrier that Roshan and White believe they can break through.

In their paper, they discuss three major strategies for detecting gravitational waves; pulsar timing arrays, astrometry and interferometry. The techniques are similar and all rely upon gravity waves disturbing the space in between elements of the systemn. In the case of the interferometer, the disturbance of space between the optics of the system reveal gravity waves; in pulsar arrays, the variation in timings of pulses from known pulsar systems gives away their presence and with the astrometric technique, tiny changes in the target object’s angular velocity reveal the presence of the waves. 

Since their discovery, gravitational waves have provided invaluable information about events in the far reaches of the Universe. Now it looks like they can also be used to unlock some of the mysteries not only across space, but across time. To enable us to get a more fuller understanding of the Universe beyond the Standard Model (which was developed in the 1970’s it articulates how matter behaves taking account of the four fundamental forces; strong, weak, electromagnetic and gravitation) it seems gravity waves hold the key.

Source : Using gravitational waves to see the first second of the Universe

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On Earth, it seems to be true that life will find a way; in the deepest ocean, the saltiest ocean or the highest mountain, live seems to find a way to get a foothold. One of the key ingredients for life seems to be the necessity for water. Until now, it was thought that there was a limit to the level of salinity within which life could thrive. A team of biologists have found bacterial life thrives in salty ponds where the water evaporates leaving high levels of salt. This only serves to expand the likely envrionments across the Universe that life could evolve. 

The search for life away from planet Earth has long fascinated humanity. Studies have often focussed on salt water environments since the salt lowers the waters freezing point allowing it to remain liquid over a wider range of temperatures. There are the added benefits with salt that is a fabulous preservative for any life that may have evolved and left signs of its existence. 

The research is part of a larger program of work called Oceans Across Space and Time which is led by Cornell Iniversity and funded by NASAs Astrobiology program. It has the ambitious aim to understand how ocean worlds and life co-evolve to produce detectable signs of life, past or present! They hope to be able to help advance our understanding of teh conditions that make ocean worlds habitable and develop new ways to detect it. 

The team from Standord University paper was published their report showing the analysis of the metabolic activity in thousands of individual cells from brine ponds in California. In these ponds, the salt is harvested by allowing the water to evaporate. It is in these samples that that life has been found to survive. 

Examples of just how life has evolved in such environments can be seen in the South Bay Salt Works which were part of this study. The ponds have an amazing array of colours thanks to microbes that glow green, red, pink and orange. These amazing microbes have adapted to survive the high levels of salinity that would ordinarily have been inhospitable to other forms of life.

The ultimate goal of the study was to find out at what point cell activity such as division, cease to exist. Pure water has an activity level of 1 while salt water level is around 0.98. Prior to this study, it was believed that most activity stoped below 0.9 where salt levels become too high although laboratory studies showed that cell division would cease around 0.63. Following the study, it seems life can be sustained at levels as low as 0.54.

The results have started to change our views of the environments within which life can evolve and even be sustained. Not only does this now increase the likelihood of finding life, it enables us to widen the search for life across high salinity bodies of water and it even helps us to refocus the techniques used to continue the search.

Source : New research on microbes expands the known limits for life on Earth and beyond

The post Microbes Can Survive in Saltier Water than Previously Believed appeared first on Universe Today.

The early universe, according to the Standard Model of Cosmology, ought to be a fairly homogenous place, with little structure or arrangement. In 2021, however, astronomers discovered a large pattern of galaxies forming a giant arc 3.3 billion light years across. Now, a second large-scale pattern has emerged. This time, it’s an enormous circle of galaxies, nicknamed the Big Ring. Together, the Giant Arc and the Big Ring present a challenge to the Standard Model, and may send cosmologists back to the drawing board.

“The Big Ring and Giant Arc are the same distance from us, near the constellation of Boötes the Herdsman, meaning they existed at the same cosmic time when the universe was only half of its present age. They are also in the same region of sky, at only 12 degrees apart when observing the night sky,” says Alexia Lopez, a PhD student at the University of Central Lancashire who discovered both structures alongside supervisor Roger Clowes and collaborator Gerard Williger.

“Identifying two extraordinary ultra-large structures in such close configuration raises the possibility that together they form an even more extraordinary cosmological system.”

The Big Ring and the Giant Arc are made up of galaxies that are so dim and so faint they wouldn’t normally be visible. However, distant quasars (bright point sources caused by active black holes at the hearts of galaxies) shine light through the dim galaxies, where matter absorbs some of the light.

In particular, Lopez and her colleagues were looking for evidence of dim galaxies blocking a Magnesium ion called Mg-II. They found it in data from the Sloan Digital Sky Survey, giving them both the position and distance of the otherwise invisible galaxies.

This enabled Lopez to map the galaxies in three dimensions, and doing so revealed the Giant Arc and Big Ring 9.2 billion years away.

The Big Ring, spanning 1.3 billion lightyears in diameter. Credit: University of Central Lancashire.

At that point in the universe’s history, according to the Standard Model, any structure that exists shouldn’t be larger than 1.2 billion light years across. Yet both the Arc and the Ring far exceed that, and they don’t seem to be coincidental:

“We did some statistics and found that the Big Ring has a significance of 5.2 Sigma. This is exceeding that 5-Sigma golden threshold,” says Lopez, referring to the usual level of significance scientists require of themselves to confirm a discovery.

One possible explanation for large structures like these is called Baryonic Acoustic Oscillation (BAO). In the earliest moments of the universe, sound and pressure waves, shaped by gravitational interactions, could form ‘bubbles’ of matter across large scales.

BAO is allowed by the Standard Model of Cosmology. However, it tends to create spherical structures, whereas the Big Ring is two-dimensional.

So a different explanation is necessary.

At a press conference at the American Astronomical Society annual meeting on January 10, 2024, Lopez alluded to two possible alternative explanations.

The first is that the structures might be evidence for cosmic strings: one-dimensional topological defects proposed in the 1970s as part of string theory. Cosmic strings could, theoretically, have been created in the early universe and would have left their mark on the structure of matter.

The Big Ring and the Giant Arc might also be explained by an entirely different model of cosmology, such as the Conformal Cyclic Cosmology (CCC) model proposed by physicist Roger Penrose.

In this model, the universe goes through endless cycles of big bang after big bang. In CCC, there is no need for the universe to collapse back together in a Big Crunch, but rather it expands indefinitely, and all matter decays, until, mathematically, the difference between the empty expanded universe and a Big Bang singularity is just a question of scale – and when there is no matter (as at the end of the universe and at the beginning), scale is irrelevant. An expanded empty universe can become the next singularity, restarting the cycle.

Importantly, CCC would leave behind evidence of the previous cycle (what Penrose calls an Aeon) in the new Aeon. In other words, it could create structures the size of the Big Ring and the Giant Arc.

These are captivating theories. However, so far, no alternative model of the universe, not even CCC, has been able to supplant the Standard Model of Cosmology for its sheer explanatory power to describe what we observe in the universe around us. But the Standard Model does have a growing number of cracks and gaps, hinting that it might one day be improved or supplanted.

The Giant Arc and the Big Ring together represent one such crack, a place where what we know about the physics of the universe fails to explain what we observe.

It is, at the least, a reason to keep looking.

Learn More:

“A Big Cosmological Mystery,” University of Central Lancashire.

Watch the Press Conference. AAS 243, Janurary 10 2024.

The post Two Giant Structures Have Been Found Billions of Light-Years Away appeared first on Universe Today.

Navigation satellites couldn’t accomplish anything without extremely accurate clocks. But a regular clock won’t do. Only atomic clocks are accurate enough, and that’s because they tell time with electrons.

Those atomic clocks wear out over time, and that’s what the image shows.

The strange forms are reminiscent of penitentes, the unusual landscape features found in cold environments like the Atacama desert. They’re also found on Pluto, though they’re the size of skyscrapers there.

This alien-looking landscape shows penitentes in the Atacama Desert. Penitentes are made of snow that’s sculpted by the Sun and sublimation. Image Credit: ESO Photo Ambassador Babak A. Tafreshi.

The leading image has nothing to do with alien landscapes. It’s from a scanning electron microscope. It shows the surface of test glass from a project aimed at improving the lifetime of atomic clocks in the Galileo Navigation Satellite System (GNSS.) Each of these peculiar marks is smaller than one-hundredth of a millimetre. They’re the result of plasma interacting with the glass surface inside an atomic clock and degrading it over time.

The ESA is working on improving the atomic clocks in the GNSS. The system has 30 satellites, with 24 in full service and six acting as spares. Each of the satellites has four atomic clocks: two passive hydrogen maser (PHM) clocks and two rubidium clocks as backups. In 2017, six of the hydrogen and three of the rubidium clocks on some of the satellites failed. Operations weren’t affected because of the backup clocks. But failures like it are driving the ESA to improve the clocks. The clocks on the GNSS last about 20 years, and the ESA would like to extend their lifetime.

This is one of the passive hydrogen maser clocks that are inside the GNSS satellite. It’s about 50 cm (19.6 inches) long. Image Credit: Leonardo Airborne and Space Systems.

Passive hydrogen masers are based on electrons orbiting atoms. Electrons can gain and lose energy, and each time they do, they change energy states. In a PHM, a maser is used to stimulate electrons into changing energy states. When they do, they emit microwave signals at an extremely stable frequency. That stability gives the clocks on the Galileo satellites their extreme accuracy: they’re only off by one second every three million years.

PHMs are extremely complex. A detailed description of how they work is here. Two separate glass bulbs play key roles in the clock and its accuracy. One is a plasma confiner, and inside of it, hydrogen molecules are separated into hydrogen atoms. But the plasma degrades the inside of the bulb, and the degradation affects the atomic clock’s lifetime.

The leading image shows the damage on the inside of the glass bulb caused by the plasma and associated effects. The goal is to extend the life of the bulb, which extends the life of the clocks, and the life of each satellite in the GNSS.

Accuracy is extremely important in navigation satellites. Even a tiny inaccuracy can compound and lead to larger errors. That’s why these extremely complex and accurate PHMs are used. If the clocks are out by as little as three nanoseconds, then a user’s location on the Earth’s surface can be off by one meter.

But accuracy isn’t a problem. The lifetime of the PHMs is the bottleneck. The ESA and EU are planning their next generation of Galileo satellites, a system that serves over four billion users. It’s called Galileo Second Generation (G2G) and will begin deploying this year. These tests are aimed at making these and future navigation satellites have longer lives.

The post This Alien Landscape is Actually a Microscopic View of an Atomic Clock appeared first on Universe Today.

Astronomers working with TESS (Transiting Exoplanet Survey Satellite) have discovered a planet that’s been left out in the Sun too long. Or at least half of it has. The newly discovered planet is tidally locked to its star, and one side is completely molten.

The new planet was discovered orbiting a star named HD 63433. The star is young, only about 400 million years old, and it’s about the same mass and radius as the Sun. It’s also a G-type star like our Sun.

The planet is named HD 63433 d, and it’s the third planet found in the system, though the other two were found a couple of years ago. It’s rocky and about the same size as Earth, but that’s where the similarities end.

HD 63433 d is less than 500 million years old. That puts it in a particular category since of the thousands of confirmed exoplanets we’ve found, only 50 are estimated to be less than half a billion years old. It’s also the smallest Earth-like planet found this close to us. It orbits its star in about 4.2 days and is about eight times closer to its star than Mercury is to the Sun. The result?

The side of the planet that faces the star gets no reprieve from the star’s powerful radiation. The planet’s dayside reaches 1,257 C (2,294 F.) That means it’s blistering hot lava and will likely spend billions of years in this state. This rules out any potential habitability, and habitability is the holy grail of exoplanet research.

But HD 63433 d is more than just another lifeless exoplanet. It’s a valuable piece of the puzzle in the quest to understand how planets form and evolve. This type of planet is such an important target in science that TESS has an entire project aimed at them: THYME.

The discovery is presented in a new paper titled “TESS Hunt for Young and Maturing Exoplanets (THYME). XI. An Earth-sized Planet Orbiting a Nearby, Solar-like Host in the 400 Myr Ursa Major Moving Group.” It was published in The Astronomical Journal and presented in a Jan. 10 presentation at the 2024 American Astronomical Society Meeting. The lead author is Benjamin Capistrant, a graduate student in astronomy at the University of Florida.

“Young terrestrial worlds are critical test beds to constrain prevailing theories of planetary formation and evolution,” the authors write. The fact that HD 63433 d is half lava doesn’t change that. Studying it will help planetary scientists study atmospheric loss. Also, the light from its star is so bright that it enables accurate spectroscopy.

This figure from the research illustrates how rare exoplanets like HD 63433 d are. The x-axis is the distance from Earth, and the y-axis is the planetary radius. Each grey circle is a known exoplanet, while each blue pentagon is a known exoplanet younger than 500 million years old. The yellow star represents HD 63433 d, the nearest, young, Earth-sized exoplanet discovered to date. Image Credit: Capistrant et al. 2024

“The apparent brightness of the stellar host makes this transiting multiplanet system favourable to further investigations, including spectroscopic follow-up to probe the atmospheric loss in a young Earth-sized world,” the authors explain.

The first few hundred million years in the life of a planet is critical. Young solar systems are dynamic places. Collisions between planets and gravitational interactions can force planets to migrate or follow eccentric orbits. There are also abundant impacts by asteroids and planetesimals, which can go on for a long time. In regions of dense star formation, neighbouring stars can even affect the planets in nearby systems.

“Detailed observations of planetary systems in such environments are, therefore, crucial to understanding the general formation history of the exoplanet population,” the authors explain.

This artist’s illustration shows an exoplanet tidally locked to its star. The side facing the star is so hot it’s molten rock. Image Credit: NASA/Kepler Mission/Dana Berry

Besides its size and proximity to Earth, why is HD 63433 d important? It comes down to exoplanet atmospheres.

“Currently, one of the most important inquiries in exoplanet science is understanding in which circumstances planets keep or lose their thick primordial hydrogen/helium atmospheres and what physical processes drive this phenomenon,” the authors write.

There’s a mass gap in the radius distribution of small exoplanets that scientists refer to as the small planet radius gap. For some reason, there’s a scarcity of small planets between about 1.5 and 2 times Earth’s radius. There’s no reason to think that planets don’t form at these radii, so scientists believe planets lose mass and end up smaller.

A histogram of planets with given radii from a sample of 900 Kepler systems. The decreased occurrence rate between 1.5 and 2.0 Earth radii is apparent. [Fulton et al. 2017]

Planetary scientists aren’t sure what drives the mass loss that creates the gap, but two primary mechanisms could be responsible. One is extreme ultraviolet photoevaporation. Young stars emit powerful UV radiation that can drive the atmosphere away from a planet into space.

The other mechanism is core-powered mass loss. With this mechanism, the luminosity of the cooling planetary core provides the energy for atmospheric loss. These cores start out hot due to their assembly and formation, as the gravitational energy that binds them together is converted into heat. As the cores cool, the heat can drive away the atmosphere.

These mechanisms work on different time scales, and that’s why the youthful HD 63433 d is such a compelling subject for study. Since its radius is below the radius gap, it’s likely rocky. But if mass loss takes longer than 500 million years, it could still have a thick atmosphere. “Because Earth-sized planets orbiting young, Sun-like stars have so far been difficult to detect, HD 63433 d presents a particularly compelling case study for atmospheric investigations of close-orbiting Earth-sized planets,” write the authors.

This discovery is important because the planet is such a valuable target for future, more detailed observations of its atmosphere. “It would be valuable to interrogate the planet’s mass using precise radial velocities and determine whether the composition is indeed rocky, as expected based on observations of older planets,” the researchers explain.

The first step is confirming that HD 63433 d is, in fact, a rocky planet. The JWST has a role to play in this, as its MIRI instrument has already been used to capture the thermal emissions of rocky exoplanets. These measurements provide a benchmark astronomers can use to compare JWST observations of HD 63433 d with other rocky planets. “Moreover, the star’s unusual brightness should provide plenty of photons to make these sensitive measurements,” the authors write.

Most rocky planets, Earth included, are magma ocean planets after they initially form. Repeated impacts keep the planet’s surface molten. But some, like HD 63433 d, remain half-molten for billions of years. That may doom them to eternal lifelessness, but as this research shows, they have much to tell us.

It could be the key that unlocks the mystery of the small planet radius gap.

The post Half of this Exoplanet is Covered in Lava appeared first on Universe Today.

According to the most widely accepted scientific theory, our Solar System formed from a nebula of dust and gas roughly 4.56 billion years ago (aka. Nebula Theory). It began when the nebula experienced gravitational collapse at the center, fusing material under tremendous pressure to create the Sun. Over time, the remaining material fell into an extended disk around the Sun, gradually accreting to form planetesimals that grew larger with time. These planetesimals eventually experienced hydrostatic equilibrium, collapsing into spherical bodies to create Earth and its companions.

Based on modern observations and simulations, researchers have been trying to understand what conditions were like when these planetesimals formed. In a new study, geologists from the California Institute of Technology (Caltech) combined meteorite data with thermodynamic modeling to better understand what went into these bodies from which Earth and the other inner planets formed. According to their results, the earliest planetesimals have formed in the presence of water, which is inconsistent with current astrophysical models of the early Solar System.

The research was conducted in the laboratory of Paul Asimow, the Eleanor and John R. McMillan Professor of Geology and Geochemistry at Caltech. The team was led by assistant professor Damanveer Grewal, the leader of the CosmoGeo Lab at Arizona State University (ASU) and a former postdoctoral scholar with the Division of Geological and Planetary Sciences at Caltech. Grewal and Asimow were joined by planetary scientists from the Massachusetts Institute of Technology (MIT), the University of California Los Angeles (UCLA), and Rice University.

Sample from a rare meteorite family revealing that its parent planetesimal had a layered structure with a molten core and solid crust (similar to Earth). Credit: Carl Agee, Institute of Meteoritics UNM/MIT

Grewal and his colleagues specialize in studying the chemical signatures of iron meteorites to gather information about the early Solar System. These meteorites are remnants of the metallic cores of the first planetesimals that did not accrete to form a planet and continue to orbit within our Solar System today. Over many eons, some of these objects fell into Earth’s gravity well and ultimately crashed to the surface. The chemical composition of these meteorites is of particular interest since it reveals a great deal about the environments in which they formed.

For one thing, the composition of planetesimals can reveal whether they (and Earth) formed closer to or farther away from the Sun. If the former scenario were the case, cooler conditions would have allowed Earth to retain water ice as a building block. If the latter is correct, Earth would have formed dry and obtained its water by some other means later on, which is what current astrophysical models suggest. According to these models, water was delivered to the inner Solar System via comets and asteroids billions of years ago, a period known as the Late Heavy Bombardment.

While water is no longer present in these meteorites, scientists can infer its existence from the presence of other elements. These include iron oxide (FeO), which occurs when iron is oxidization by exposure to water. A sufficient excess of water will drive the process further, creating ferric oxide (Fe2O3) and ferric oxyhydroxide, or FeO(OH) – the ingredients of rust. While the earliest planetesimals would have lost all traces of iron oxide long ago, Grewal and his team were able to determine how much was present by examining the metallic nickel, cobalt, and iron contents of these meteorites.

These three elements should be present in roughly equal ratios relative to other materials in the meteorite, which means that any “missing” iron would have been depleted through oxidation. As Asimow explained in a Caltech news release:

“Iron meteorites have been somewhat neglected by the planet-formation community, but they constitute rich stores of information about the earliest period of Solar System history, once you work out how to read the signals. The difference between what we measured in the inner solar system meteorites and what we expected implies an oxygen activity about 10,000 times higher.”

Artist concept of Earth during the Late Heavy Bombardment period. Credit: NASA’s Goddard Space Flight Center.

The team’s results indicate that meteorites believed to have originated in the inner Solar System had roughly the same amount of missing iron as meteorites from the outer Solar System. This suggests that both groups formed in a part of the Solar System where conditions were cool enough for water. It further implies that planets accreted water from the beginning, which could have profound implications for theories of how life emerged on Earth. “If water was present in the early building blocks of our planet, other important elements like carbon and nitrogen were likely present as well,” said Grewal. “The ingredients for life may have been present in the seeds of rocky planets right from the start.”

This represents a significant challenge for our current models for how the Solar System formed and evolved, which could indicate that conditions in the early inner Solar System were much cooler than previously thought. The results could also mean that Earth and its fellow rocky planets formed farther from the Sun and gradually migrated to their current orbits. However, as Asimow acknowledged, there is a degree of uncertainty when it comes to the study of ancient planetesimals, which means the results may not contradict current astrophysical models:

“However, the method only detects water that was used up in oxidizing iron. It is not sensitive to excess water that might go on to form the ocean. So, the conclusions of this study are consistent with Earth accretion models that call for late addition of even more water-rich material.”

Their study, titled “Accretion of the earliest inner Solar System planetesimals beyond the water snowline,” recently appeared in Nature Astronomy. Their research was made possible thanks in part to funding provided by NASA and through a Barr Foundation Postdoctoral Fellowship.

Further Reading: Caltech, Nature Astronomy

The post The Meteorites That Made Earth Were Filled With Water appeared first on Universe Today.

We think of magnetic fields as a part of planets and stars. The Earth and Sun have relatively strong magnetic fields, as do more exotic objects such as neutron stars and the accretion disks of black holes. But magnetic field lines also run throughout galaxies, and even between the vast voids of intergalactic space. Magnetic fields are quite literally everywhere, and we aren’t entirely sure why. One idea is that faint magnetic fields formed during the earliest moments of the Universe. If that’s the case, we might be able to prove it through the distribution of dark matter.

The idea of mapping primordial magnetic fields with dark matter is a bit subtle. As far as we know, dark matter only interacts with regular matter gravitationally. It doesn’t interact with magnetic fields, so the mere presence of a magnetic field shouldn’t affect dark matter in any way. But magnetic fields do interact with charged regular matter such as electrons, and those electrons interact with dark matter gravitationally.

So the idea is that intergalactic magnetic fields would tend to cluster electrons and ionized intergalactic hydrogen along their field lines, making those regions of the intergalactic voids just slightly denser than the rest of the void. This would cause dark matter to cluster a bit along the field lines as well. The gravitational effect would be extremely tiny, but over the entire history of the Universe, it would add up. So if primordial magnetic fields did form in the early Universe, tendrils of dark matter should be present along the same lines.

Artist rendering of the dark matter halo surrounding our galaxy. Credit: ESO/L. Calçada

In a recent work in Physical Review Letters the authors argue that this effect would produce minihalos of dark matter. Just as galaxies are surrounded by a halo of dark matter due to gravitational clustering, faint halos of dark matter should exist around primordial magnetic field lines to do the gravitational tug of ionized matter along the field lines.

What’s interesting about this idea is that over time the charged ions and electrons would interact with the primordial magnetic fields and tend to cancel them out. The ions and electrons could even merge to create neutral hydrogen, so in the modern Universe, there would be no trace of these early magnetic fields in regular matter. But the microhalos of dark matter would still exist, and they could be seen through the gravitational lensing of distant light sources. These tendrils of dark matter could be the only evidence remaining of the earliest magnetic fields in the cosmos.

This study is purely theoretical, and current telescopes aren’t sensitive enough to measure the gravitational lensing effect of microhalos. But it’s interesting to see how dark matter can carry the history of the Universe in its structure, even for things that have long faded from view.

Reference: Ralegankar, Pranjal. “Dark Matter Minihalos from Primordial Magnetic Fields.” Physical Review Letters 131 (2023): 231002.

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