Oorlog in de ruimte: VS voelen hete adem van Rusland en China

Volgens de New York Times zet het Pentagon spoed achter de voorbereidingen om oorlog in de ruimte te kunnen voeren.  

Washington is ervan overtuigd dat de snelle vooruitgang van China en Rusland op het gebied van ruimteoperaties een groeiende bedreiging vormt voor de Amerikaanse troepen en andere militaire middelen op de grond en satellieten in een baan om de aarde.

De details van de inspanningen van het Pentagon blijven zeer vertrouwelijk. Bepaalde documenten zijn echter onlangs vrijgegeven en gepubliceerd door de New York Times.

Daarin erkennen functionarissen van het Ministerie van Defensie in toenemende mate dat het initiatief een grote verschuiving in militaire operaties weerspiegelt, waarbij de ruimte een echt slagveld zal worden.

De VS zal niet langer alleen vertrouwen op militaire satellieten om te communiceren, navigeren, traceren en te richten op terrestrische bedreigingen, instrumenten die het Pentagon decennialang een aanzienlijk voordeel hebben gegeven in conflicten.

Het ministerie van Defensie wil een nieuwe generatie instrumenten op de grond en in de ruimte verwerven waarmee het zijn satellietnetwerk kan verdedigen tegen aanvallen en, indien nodig, vijandelijke ruimtevaartuigen in een baan om de aarde kan verstoren of uitschakelen, aldus functionarissen van het Pentagon in een reeks interviews, toespraken en verklaringen

De strategie verschilt fundamenteel van eerdere militaire ruimteprogramma's door de uitbreiding van het scala aan offensieve capaciteiten, wat heel anders is dan het voorstel voor het Strategisch Defensie-initiatief uit de jaren tachtig, dat nooit het daglicht zag en dat tot doel had satellieten te gebruiken om de Verenigde Staten te beschermen tegen aanvallen met nucleaire raketten.

• (SR and MaSi for Tagtik/Source: New York Times/Photo: Pixabay)

{ https://www.msn.com/nl-be/ }

02-08-2024 om 18:31 geschreven door peter  

It’s an ancient idea, which only increases its resonance for some. The Greek philosopher Anaxagoras was the first to propose it. He coined the term ‘panspermia’ and said that the Universe was full of life and that some of it fell to Earth. It remains on the fringe of science because it can’t explain how life started, and it’s not testable. But it is enduring.

Oumuamua’s appearance sparked renewed interest in Panspermia. After the object came and went rapidly in 2017, scientists attempted to determine what it actually was. Maybe it was a comet, maybe it was an asteroid, maybe it was a chunk of frozen hydrogen. Many hypotheses were presented. Now, we simply call it an interstellar object, or ISO.

From the perspective of panspermia, Oumuamua’s classification isn’t the most pressing concern. It was a visitor to our Solar System from elsewhere, and that’s the most salient point.

In a new paper, a trio of researchers examine how many of these types of objects might exist and what properties they’d need to protect and transport life throughout the galaxy. The paper is titled “The Implications of ‘Oumuamua on Panspermia.” The lead author is David Cao, a high school student who also served as an intern at the Johns Hopkins University Applied Physics Laboratory.

“Panspermia is the hypothesis that life originated on Earth from the bombardment of foreign interstellar ejecta harbouring polyextremophile microorganisms,” the authors write. “By utilizing ‘Oumuamua’s properties as an anchor, we estimate the mass and number density of ejecta in the ISM.”

Throughout their work, they acknowledge that “panspermia is an extraordinarily difficult theory to quantitatively model and assess.” But it’s still worth an attempt because of Oumuamua. “The recently discovered ‘Oumuamua merits a reexamination for the possibility of panspermia, the hypothesis that life seeded on Earth from the bombardment of life-bearing interstellar ejecta and that life can be transferred from one celestial body to another.”

The trio determined the minimum size of ejecta needed to protect extremophiles from radiation, especially from supernovae. Intense gamma rays can sterilize ejecta if they’re not large enough for extremophiles to survive in their interiors, shielded by rock or water ice. Ejecta also needs to be large enough to protect any lifeforms from impact with another body. But the size depends on the nature of the ejecta.

“We consider the four most common elemental compositions of asteroids (chondritic, stony and metallic) and comets (water-ice) in our own Solar System: silicate, nickel, iron, and water-ice,” they write. Nickel has the highest attenuation and the smallest minimum size needed to shelter life. Water-ice requires the maximum size.

The authors explain, “We make an assumption that the number density abundances and varying compositions of interstellar ejecta mirror the content of minor bodies in our own Solar System.” Based on that, they settled on a minimum size of 6.6 meters.

They also tried to determine the likelihood that extremophiles could have seeded Earth, though they acknowledge that many of the factors involved are poorly understood and poorly constrained. In order to seed life, an ejecta carrying extremophiles had to have arrived at Earth early, before the earliest evidence of fossilized life. “Second, we estimate the total number of impact events on Earth after its formation and prior to the emergence of life (? 0.8 Gyr).”

They calculate impact rates for objects of different sizes. For objects at least 10 meters in diameter, they calculate that about 40,000 of them could’ve impacted Earth in its first 800,000 years.

Existing estimates of the number of Earth-like planets in the Milky Way are available. Based on those, here’s what it all adds up to, keeping in mind all of the poorly constrained factors involved. “However, we find that panspermia is a plausible potential life-seeding mechanism for (optimistically) potentially up to ~ 10⁵ (100,000) of the ~ 10⁹ (one billion) Earth-sized habitable zone worlds in our Galaxy,” the authors write.

But the prospects that Earth itself was seeded by panspermia are very weak. “For the Earth in particular, we conclude that, independent of other hypotheses for the origins of life on Earth, panspermia remains improbable (< 0.001%).” In a way, it’s more of a thought experiment. The authors say that “the true relative probability for panspermia remains unknown.”

The panspermia idea will not disappear. It’s simply too compelling to discard, even though it cannot be tested.

Another way of looking at it is that Earth could be a source of panspermia rather than a receiver.

“The fraction of these rocky planets that possess magnetic fields, atmospheres, and liquid surface water capable of supporting life is currently unconstrained and unknown, but our work implies as many as 10⁴ of these worlds in our Galaxy could be populated with life today via panspermia under the most optimistic assumptions that all of these worlds are capable of supporting ejecta-transported life, with Earth as one of the potential source planets.” The number could rise to 10⁴ under the most optimistic conditions.

There are other factors to consider. We’re only beginning to determine the number of rogue planets or free-floating planets (FFPs). As we learn more about them and their abundance, the panspermia hypothesis will change. “The discovery of rogue-free floating planets (FFPs) suggests a significantly higher ISM ejecta number density than expected for large objects,” the authors explain.

Also, the number of ejecta and their mass haven’t been constant. For example, during the hypothesized Late Heavy Bombardment, a much larger number of objects were crashing into the Earth and the other Solar System bodies. How would that have affected panspermia?

“~4 Gyr ago, the Earth is thought to have experienced an unprecedented number of impact events
that consequently ejected matter into the ISM, the era of Late Heavy Bombardment,” the authors write. The rate of bombardment was between 100 to 500 times greater than the present rate. If other solar systems experienced similar events, there would be substantially more potential for panspermia.

The star formation rate also plays a role. “As more stars are formed, more mass will be ejected into the ISM in star formation regions, increasing the production of ISM ejecta number density,” the authors explain.

There are so many unknowns and so much conjecture that many scientists avoid the panspermia theory completely. But more and more data will keep coming our way, and as it does, the idea will be revised and reconsidered.

The Rubin Observatory Large Synoptic Survey Telescope will hopefully see its long-anticipated first light in early 2025. That telescope will undoubtedly detect many more ISOs and FFPs, filling in important gaps in our knowledge.

As that data comes in, expect more attention to be focused on the panspermia theory

{ https://www.universetoday.com/ }

02-08-2024 om 01:45 geschreven door peter  

Being trapped in space sounds like the stuff of nightmares. Astronauts on board the International Space Station have on occasion, had their return delayed by weather or equipment malfunction. We find ourselves again, watching and waiting as two astronauts; Juni Williams and Butch Wilmore have been stuck for months instead of their week long mission. The delays came as the Starliner system required fixes to be implemented. NASA successfully fired up 27 of its 28 thrusters in a hot-firing test and now, ground teams are preparing finally, to bring them home.

The Boeing Starliner spacecraft is officially known as the CST-100 Starliner. It was developed by Boeing as part of NASA’s Commercial Crew Program. Its purpose is to transport astronauts to the International Space Station and other low orbit craft. Starliner hit the headlines with its reusable design aimed at reducing costs and increasing launch frequency. It was first launched on 20 December 2019 as an uncrewed test flight to demonstrate docking capability with ISS. 

Since 2019 Starliner has had issues along the way but has largely seen a successful progression to becoming a key part of NASA’s launch capability. Just recently however there have been issues with the manoeuvring jets used to adjust the attitude. Engineering teams at NASA and Boeing have been working on and running tests with Mexico a new configuration. Part of the thruster system controls the flow of helium, these are the helium manifolds and they were opened to allow engineers to monitor any helium supply issues and leaks. 

The team ran a hot fire test of the reaction control system jets on 27 July to see if there were any problems with the propulsion system. They test fired 27 out of 28 jets while astronauts Wilmore and Williams sat inside the docked Starliner. The tests involved firing the jets for short bursts, one at a time. They revealed that all thrusters were back to performing well and the helium manifolds were within operational margins that were needed for a return trip from ISS. The engineering teams closed the manifolds ahead of undocking and returning the astronauts home. 

The work is not over for the engineering teams however as they are now reviewing data from the tests and from ground based testing at the White Sands Test Facility in New Mexico. Once the review of data is complete, NASA and Boeing will identify a date to return the astronauts. 

Meanwhile back on board the ISS Wilmore and Williams wait. They have been checking other Starliner systems in preparation for return, working with other Boeing teams to prepare and have been undertaking pressure tests of their space suits. They have been working alongside Expedition 71 members and have recently helped setup the BioServe centrifuge in the Harmony Module. The centrifuge supports a wide range of biological, physical and materials science projects. Facilitating the separation of substances with different densities it can work with cell cultures, DNA, protein, blood and sedimentary samples.

Source : 

• NASA, Boeing Complete Second Docked Starliner Hot Fire Test

{ https://www.universetoday.com/ }

02-08-2024 om 01:36 geschreven door peter  

Astronomers have recently spotted signs of an extended disk of dust and gas, whirling in orbit around a distant star.

While this phenomenon is a normal stage in the development of a star and its planetary system, what makes this find so spectacular is that it's the first one we've seen around a star in a whole other galaxy, outside of our own.

The feature was spotted in the Large Magellanic Cloud, a dwarf galaxy some 179,000 light-years away from the Milky Way. And, although it might seem like common sense to suppose that star formation processes are universal, we've not been able to observe their vagaries outside of our home galaxy before.

"When I first saw evidence for a rotating structure in the ALMA data I could not believe that we had detected the first extragalactic accretion disc, it was a special moment," said astronomer Anna McLeod of Durham University in the UK, when the findings were published in November.

"We know discs are vital to forming stars and planets in our galaxy, and here, for the first time, we're seeing direct evidence for this in another galaxy."

Stars are born from dense clumps in clouds of molecular gas and dust that hang out in interstellar space. When a clump grows dense enough, it collapses under gravity; spinning, it starts to draw in more material from the cloud around it. This material doesn't just fall onto the protostar any old how, though; it arranges into a disk around the star's equator, and falls down onto it in a more controlled, steady stream, like water down a drain.

Once the star is done forming, what remains of the disk stays there, clumping together to form all the other elements of a planetary system: the planets, the asteroids and meteors, the comets, the dust. That's why the Solar System's planets are more or less orbiting the Sun in a flat plane. We ourselves are like the sentient mold that grew on the leftovers of the Sun's breakfast.

The Atacama Large Millimeter/submillimeter Array (ALMA), a powerful radio telescope, has imaged quite a few such disks throughout the Milky Way, in various stages of development; some have clear gaps that are thought to be cleared by planets clumping together as they orbit. But the farther away something is, the harder it is to resolve, even with a powerful telescope.

McLeod and her colleagues embarked on their campaign to find an extragalactic stellar disk when data obtained by the Multi Unit Spectroscopic Explorer (MUSE) instrument on the Very Large Telescope revealed signs of a jet, in a system named HH 1177.

These, too, are a signature of star formation: some of the material swirling around the forming star gets whisked away along its magnetic field lines to the poles, where it is launched into space in the form of a powerful jet.

The researchers wanted to see if they could spot the disk in the dusty heart of star formation, so they used ALMA to look for signs of rotation. This can be seen in the way wavelengths of light are shortened as the source is pushed towards us, and lengthened as they are pulled away.

"The frequency of light changes depending on how fast the gas emitting the light is moving towards or away from us," explained astronomer Jonathan Henshaw of Liverpool John Moores University in the UK. "This is precisely the same phenomenon that occurs when the pitch of an ambulance siren changes as it passes you and the frequency of the sound goes from higher to lower."

Interestingly, the ALMA data showed clear signs of this rotation. The star, the team's analysis revealed, is very young and massive, still feeding from the disk around it. This is pretty normal. But there was a difference between it and the protostellar disks found in the Milky Way: the HH 1177 disk can be seen in optical wavelengths.

This, the researchers explain, has to do with the interstellar environment in the Large Magellanic Cloud. There is much less dust there; so the HH 1177 star is not as shrouded in a curtain of material as young, massive Milky Way stars usually are.

This makes the discovery an important one for studying, not just how stars form in different environments, but the limits those environments can place on star formation in general.

"We are in an era of rapid technological advancement when it comes to astronomical facilities," McLeod said. "Being able to study how stars form at such incredible distances and in a different galaxy is very exciting."

• The research has been published in Nature.
• A version of this article was first published in December 2023.

{ https://www.msn.com/en-us/channel/topic/Science/ }

01-08-2024 om 22:46 geschreven door peter  

01-08-2024 om 22:36 geschreven door peter  

Milky Way’s Thin Disk Formed Less Than One Billion Years from Big Bang, New Study Suggests

Using data from ESA’s Gaia mission, astronomers have found a large number of metal-poor stars older than 13 billion years on orbits similar to that of our Sun.

Rotational motion of young (blue) and old (red) stars similar to the Sun (orange).

Image credit: NASA / JPL-Caltech / R. Hurt / SSC / Caltech.

“The Milky Way Galaxy has a large halo, a central bulge and bar, a thick disk and a thin disk,” said Dr. Samir Nepal from the Leibniz Institute for Astrophysics Potsdam and colleagues.

“Most stars are located in the so-called thin disk of our Milky Way and follow an organised rotation around the Galactic center.”

“Middle-aged stars such as our 4.6-billion-year-old Sun belong to the thin disk, which was generally thought to have started forming around 8 to 10 billion years ago.”

Using the new Gaia dataset, the astronomers studied stars within around 3,200 light-years from the Sun.

They discovered a surprising number of very old stars in thin disk orbits; the majority of these are older than 10 billion years, some of them even older than 13 billion years.

These ancient stars show a wide range of metal compositions: some are very metal-poor (as expected), while others have twice the metal content of our much younger Sun, indicating that a rapid metal enrichment took place in the early phase of the Milky Way’s evolution.

“These ancient stars in the disk suggest that the formation of the Milky Way’s thin disk began much earlier than previously believed, by about 4-5 billion years,” Dr. Nepal said.

“This study also highlights that our Galaxy had an intense star formation at early epochs leading to very fast metal enrichment in the inner regions and the formation of the disk.”

“This discovery aligns the Milky Way’s disk formation timeline with those of high-redshift galaxies observed by the NASA/ESA/CSA James Webb Space Telescope and the Atacama Large Millimeter Array (ALMA).”

“It indicates that cold disks can form and stabilize very early in the Universe’s history, providing new insights into the evolution of galaxies.”

“Our study suggests that the thin disk of the Milky Way may have formed much earlier than we had thought, and that its formation is strongly related to the early chemical enrichment of the innermost regions of our Galaxy,” said Dr. Cristina Chiappini, an astronomer at the Leibniz Institute for Astrophysics Potsdam.

“The combination of data from different sources and the application of advanced machine learning techniques have enabled us to increase the number of stars with high quality stellar parameters, a key step to lead our team to these new insights.”

• The paper will be published in the journal Astronomy & Astrophysics.
• Samir Nepal et al. 2024. Discovery of the local counterpart of disc galaxies at z > 4: The oldest thin disc of the Milky Way using Gaia-RVS. A&A, in press; arXiv: 2402.00561

{ https://www.sci.news/ }

01-08-2024 om 21:04 geschreven door peter  

Warp Drive Collapse Should Generate Gravitational Waves, Theoretical Astrophysicists Claim

The principle idea behind a warp drive is that instead of exceeding the speed of light directly in a local reference frame, a ‘warp bubble’ could traverse distances faster than the speed of light — as measured by some distant observer — by contracting spacetime in front of it and expanding spacetime behind it.

Clough et al. proposed a formalism for studying warp drive spacetimes dynamically and produced the first fully consistent numerical-relativity waveforms for the collapse of a warp drive bubble.

Despite originating in science fiction, warp drives have a concrete description in general relativity, with University of Wales astrophysicist Miguel Alcubierre first proposing a spacetime metric that supported faster-than-light travel.

Whilst there are numerous practical barriers to their implementation in real life, such as the requirement for an exotic type of matter with negative energy, computationally, one can simulate their evolution in time given an equation of state describing the matter.

In a new work, theoretical astrophysicists studied the signatures arising from a warp drive ‘containment failure.’

“Even though warp drives are purely theoretical, they have a well-defined description in Einstein’s theory of general relativity, and so numerical simulations allow us to explore the impact they might have on spacetime in the form of gravitational waves,” said Dr. Katy Clough, a researcher at Queen Mary University of London.

“The results are fascinating. The collapsing warp drive generates a distinct burst of gravitational waves, a ripple in spacetime that could be detectable by gravitational wave detectors that normally target black hole and neutron star mergers.”

“Unlike the chirps from merging astrophysical objects, this signal would be a short, high-frequency burst, and so current detectors wouldn’t pick it up.”

“However, future higher-frequency instruments might, and although no such instruments have yet been funded, the technology to build them exists.”

“This raises the possibility of using these signals to search for evidence of warp drive technology, even if we can’t build one ourselves.”

“In our study, the initial shape of the spacetime is the warp bubble described by Alcubierre,” said Dr. Sebastian Khan, a researcher at Cardiff University.

“While we were able to demonstrate that an observable signal could in principle be found by future detectors, given the speculative nature of the work this isn’t sufficient to drive instrument development.”

The authors also delve into the energy dynamics of the collapsing warp drive.

The process emits a wave of negative energy matter, followed by alternating positive and negative waves.

This complex dance results in a net increase in the overall energy of the system, and in principle could provide another signature of the collapse if the outgoing waves interacted with normal matter.

“It’s a reminder that theoretical ideas can push us to explore the Universe in new ways,” Dr. Clough said.

“Even though we are sceptical about the likelihood of seeing anything, I do think it is sufficiently interesting to be worth looking.”

“For me, the most important aspect of the study is the novelty of accurately modeling the dynamics of negative energy spacetimes, and the possibility of extending the techniques to physical situations that can help us better understand the evolution and origin of our Universe, or the processes at the centre of black holes,” said University of Potsdam’s Professor Tim Dietrich.

“Warp speed may be a long way off, but this research already pushes the boundaries of our understanding of exotic spacetimes and gravitational waves.”

“We plan to investigate how the signal changes with different warp drive models.”

• The team’s paper was published online in the Open Journal of Astrophysics.
• Katy Clough et al. 2024. What no one has seen before: gravitational waveforms from warp drive collapse. Open Journal of Astrophysics 7; doi: 10.33232/001c.121868

{ https://www.sci.news/ }

01-08-2024 om 20:58 geschreven door peter  

Twee nieuw ontdekte gassen in de atmosfeer van Venus zouden kunnen wijzen op sporen van leven: de ontdekking

Door Janine

NASA/JPL

Venus, de tweede planeet van het zonnestelsel, lijkt qua omvang en massa sterk op de aarde, maar verder is het een van de meest onherbergzame plaatsen die we tot nu toe kennen. De atmosfeer, die bestaat uit gassen die giftig voor ons zijn, is het onderwerp geweest van recente ontdekkingen die de aanwezigheid lijken te suggereren van twee gassen die door levende organismen worden geproduceerd. Kunnen we daarom spreken van sporen van leven op Venus? Laten we het samen ontdekken!

Zoeken naar leven op andere planeten: het belang van biomarkers

Zoals we in de inleiding zeiden, is Venus een plek die net zo fascinerend is om te bestuderen als onherbergzaam, voor welke vorm van leven dan ook die ons bekend is. Het oppervlak bereikt temperaturen van 450°C, terwijl de atmosfeer ongeveer 90 keer dichter is dan die van de aarde. Een onherbergzame plek, waar echter leven zou kunnen voorkomen op hoogten van minstens 50 kilometer boven het oppervlak, waar de omstandigheden minder extreem zijn. Maar hoe kom je erachter of er organismen op Venus leven?

Een van de methoden die wetenschappers gebruiken, bestaat uit het analyseren van de chemische samenstelling van de planeten. Meestal is het inderdaad mogelijk om verbindingen te identificeren die geen verband houden met het leven, maar soms is het mogelijk om zogenaamde biomarkers te vinden, dat wil zeggen chemische verbindingen die op aarde door bepaalde organismen worden geproduceerd. En die zouden kunnen duiden op een soortgelijk proces op andere planeten of andere hemellichamen. Op Venus beweren sommige wetenschappers bijvoorbeeld sporen van fosfine en ammoniak te hebben gevonden. Maar wat betekent dat?

Fosfine en ammoniak in de atmosfeer van Venus: wat betekent het?

Unsplash - Not the actual photo

Er zijn twee specifieke biomarkers gedetecteerd in de atmosfeer van Venus, tijdens observaties die al een paar jaar duren en die, zo lijkt het, zijn bevestigd. De eerste biomarker is fosfine, een verbinding die op aarde door sommige microben wordt geproduceerd in zuurstofvrije omgevingen en in kleine hoeveelheden door vulkanen. Sommige wetenschappers beweren al jaren dat fosfine een teken van buitenaards leven op Venus zou kunnen vertegenwoordigen. In het bijzonder vestigde Dave Clements van Imperial College London in een onderzoek uit 2023 opnieuw de aandacht op de kwestie en ontdekte dat fosfine wordt vernietigd door de werking van de zon. Maar over zijn vorming is nog niets bekend: zou het leven kunnen zijn?

De tweede biomarker is ammoniak, onlangs geïdentificeerd door Jane Greaves van Cardiff University, die samen met Dave Clements een conferentie gaf op de National Astronomy Meeting 2024. Beiden betogen hoe de aanwezigheid van fosfine en ammoniak ons ​​kan helpen de atmosfeer van Venus beter te begrijpen en, waarom niet, ook de mogelijke aanwezigheid van leven.

Sporen van leven op Venus?

Veel geleerden zijn het erover eens dat Venus in het verleden mogelijk omstandigheden heeft gehad die meer leken op die op aarde, inclusief de mogelijkheid om leven te huisvesten. Het is echter moeilijker om de aanwezigheid van fosfine en ammoniak in de atmosfeer van de planeet te verklaren met bekende chemische processen. Hier op aarde worden de twee stoffen geproduceerd door biologische of hoogstens industriële processen, maar op Venus?

Het is duidelijk dat het te vroeg is om conclusies te trekken, maar het onderzoek van Clements en Greaves heeft tenminste de verdienste dat het met de vinger in de juiste richting wijst. Er zullen veel preciezere detecties nodig zijn door de James Clerk Maxwell-telescoop, gericht op Venus, en veel meer tijd. Tegelijkertijd is het normaal om verbaasd te zijn over de mogelijkheid om iets te ontdekken dat nog nooit eerder is gezien, ook al is het een klein organisme dat op 50 kilometer hoogte zweeft, op een verder onherbergzame planeet.

{ https://www.curioctopus.nl/ }

01-08-2024 om 18:37 geschreven door peter  

Runaway Star Might Explain Mysterious Black Hole Disappearing Act

By JET PROPULSION LABORATORY

The telltale sign that the black hole was feeding vanished, perhaps when a star interrupted the feast. The event could lend new insight into these mysterious objects.

At the center of a far-off galaxy, a black hole is slowly consuming a disk of gas that swirls around it like water circling a drain. As a steady trickle of gas is pulled into the gaping maw, ultrahot particles gather close to the black hole, above and below the disk, generating a brilliant X-ray glow that can be seen 300 million light-years away on Earth. These collections of ultrahot gas, called black hole coronas, have been known to exhibit noticeable changes in their luminosity, brightening or dimming by up to 100 times as a black hole feeds.

But two years ago, astronomers watched in awe as X-rays from the black hole corona in a galaxy known as 1ES 1927+654 disappeared completely, fading by a factor of 10,000 in about 40 days. Almost immediately it began to rebound, and about 100 days later had become almost 20 times brighter than before the event.

The X-ray light from a black hole corona is a direct byproduct of the black hole’s feeding, so the disappearance of that light from 1ES 1927+654 likely means that its food supply had been cut off. In a new study in the Astrophysical Journal Letters, scientists hypothesize that a runaway star might have come too close to the black hole and been torn apart. If this was the case, fast-moving debris from the star could have crashed through part of the disk, briefly dispersing the gas.

This illustration shows the black hole after the debris from the star has dispersed some of the gas in the disk, causing the corona to disappear.

Credit: NASA/JPL Caltech

“We just don’t normally see variations like this in accreting black holes,” said Claudio Ricci, an assistant professor at Diego Portales University in Santiago, Chile, and lead author of the study. “It was so strange that at first we thought maybe there was something wrong with the data. When we saw it was real, it was very exciting. But we also had no idea what we were dealing with; no one we talked to had seen anything like this.”

Nearly every galaxy in the universe may host a supermassive black hole at its center, like the one in 1ES 1927+654, with masses millions or billions of times greater than our Sun. They grow by consuming the gas encircling them, otherwise known as an accretion disk. Because black holes don’t emit or reflect light, they can’t be seen directly, but the light from their coronas and accretion disks offers a way to learn about these dark objects.

The authors’ star hypothesis is also supported by the fact that a few months before the X-ray signal disappeared, observatories on Earth saw the disk brighten considerably in visible-light wavelengths (those that can be seen by the human eye). This might have resulted from the initial collision of the stellar debris with the disk.

Digging Deeper

The disappearing event in 1ES 1927+654 is unique not only because of the dramatic change in brightness, but also because of how thoroughly astronomers were able to study it. The visible-light flare prompted Ricci and his colleagues to request follow-up monitoring of the black hole using NASA’s Neutron star Interior Composition Explorer (NICER), an X-ray telescope aboard the International Space Station. In total, NICER observed the system 265 times over 15 months. Additional X-ray monitoring was obtained with NASA’s Neil Gehrels Swift Observatory — which also observed the system in ultraviolet light — as well as NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and the ESA (the European Space Agency) XMM-Newton observatory (which has NASA involvement).

When the X-ray light from the corona disappeared, NICER and Swift observed lower-energy X-rays from the system so that, collectively, these observatories provided a continuous stream of information throughout the event.

Although a wayward star seems the most likely culprit, the authors note that there could be other explanations for the unprecedented event. One remarkable feature of the observations is that the overall drop in brightness wasn’t a smooth transition: Day to day, the low-energy X-rays NICER detected showed dramatic variation, sometimes changing in brightness by a factor of 100 in as little as eight hours. In extreme cases, black hole coronas have been known to become 100 times brighter or dimmer, but on much longer timescales. Such rapid changes occurring continuously for months was extraordinary.

“This dataset has a lot of puzzles in it,” said Erin Kara, an assistant professor of physics at the Massachusetts Institute of Technology and a co-author of the new study. “But that’s exciting because it means we’re learning something new about the universe. We think the star hypothesis is a good one, but I also think we’re going to be analyzing this event for a long time.”

It’s possible that this kind of extreme variability is more common in black hole accretion disks than astronomers realized. Many operating and upcoming observatories are designed to search for short-term changes in cosmic phenomena, a practice known as “time domain astronomy,” which could reveal more events like this one.

“This new study is a great example of how flexibility in observation scheduling allows NASA and ESA missions to study objects that evolve relatively quickly and look for longer-term changes in their average behavior,” said Michael Loewenstein, a coauthor of the study and an astrophysicist for the NICER mission at the University of Maryland College Park and NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, Maryland. “Will this feeding black hole return to the state it was in before the disruption event? Or has the system been fundamentally changed? We’re continuing our observations to find out.”

More About the Missions

NICER is an Astrophysics Mission of Opportunity within NASA’s Explorer program, which provides frequent flight opportunities for world-class scientific investigations from space utilizing innovative, streamlined, and efficient management approaches within the heliophysics and astrophysics science areas.

NuSTAR recently celebrated eight years in space, having launched on June 13, 2012. A Small Explorer mission led by Caltech and managed by NASA’s Jet Propulsion Laboratory in Southern California for the agency’s Science Mission Directorate in Washington, NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp. in Dulles, Virginia. NuSTAR’s mission operations center is at the University of California, Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center at GSFC. ASI provides the mission’s ground station and a mirror data archive. Caltech manages JPL for NASA.

ESA’s XMM-Newton observatory was launched in December 1999 from Kourou, French Guiana. NASA funded elements of the XMM-Newton instrument package and provides the NASA Guest Observer Facility at GSFC, which supports the use of the observatory by U.S. astronomers.

GSFC manages the Swift mission in collaboration with Penn State in University Park, Pennsylvania, the Los Alamos National Laboratory in New Mexico, and Northrop Grumman Innovation Systems in Dulles, Virginia. Other partners include the University of Leicester and Mullard Space Science Laboratory of the University College London in the United Kingdom, Brera Observatory in Italy, and the Italian Space Agency.

• Read Astronomers Watch a Black Hole’s Corona Mysteriously Disappear, Then Reappear for more on this research.
• Reference: “The Destruction and Recreation of the X-Ray Corona in a Changing-look Active Galactic Nucleus” by C. Ricci, E. Kara, M. Loewenstein, B. Trakhtenbrot, I. Arcavi, R. Remillard, A. C. Fabian, K. C. Gendreau, Z. Arzoumanian, R. Li, L. C. Ho, C. L. MacLeod, E. Cackett, D. Altamirano, P. Gandhi, P. Kosec, D. Pasham, J. Steiner and C.-H. Chan, 16 July 2020, Astrophysical Journal Letters.
  DOI: 10.3847/2041-8213/ab91a1

{ https://scitechdaily.com/ }

01-08-2024 om 01:47 geschreven door peter  

Runaway 'failed star' races through the cosmos at 1.2 million mph

CWISE J1249+3621,was originally discovered by citizen scientists working with the Backyard Worlds: Planet 9 project, which uses data from NASA's Wide-field Infrared Survey Explorer (WISE) to detect faint, moving objects relatively close to the sun.

Related: 

• Hubble Space Telescope discovers 'failed stars' are bad at relationships too

After several citizen scientists flagged the object, a team of astronomers followed up using the Keck I Telescope, one of two 10-meter twin telescopes located on the dormant volcano Maunakea, in Hawai'i.

"We discovered a very low-mass object, right on the star/brown dwarf mass boundary, that has an extreme velocity, moving fast enough that it may actually be unbound to the Milky Way galaxy," study team leader Adam Burgasser, of the University of California San Diego, told Space.com. "It joins a collection of 'hypervelocity' stars that have been found over the past few decades, most of which are thousands of light-years from the sun, whereas this source is a 'mere' 400 light-years away."

Burgasser added that the team's observations included an analysis of CWISE J1249+3621's atmosphere. This indicated that the potential brown dwarf also has an unusual chemical composition. The team aimed to use the information they gathered about the motion and composition of CWISE J1249+3621 to speculate on its possible origins.

"This discovery mainly opens up a new pathway to studying brown dwarfs that are in remote regions of the Milky Way, including its center, its halo and its various globular clusters and satellites," Burgasser said. "All of these systems are too far away to study brown dwarfs in detail directly, but if they get thrown at us, it's much easier!"

A young star, similar to the renegade star PG 1610+062, gets ejected from the Milky Way by a hungry black hole. So long! 

(Image credit: A. IRRGANG, FAU)

What is this rogue star running from?

Brown dwarfs form just like stars do — from giant clouds of gas and dust, called molecular clouds, that develop overly dense patches that collapse under the influence of their own gravity. However, unlike a regular star such as the sun, brown dwarfs fail to gather enough material from the remains of the cloud that birthed them to reach the mass needed to generate the pressures and temperatures in their cores that kickstart the fusion of hydrogen to helium. This is the process that defines a "main sequence" star. Hence, the "failed star" moniker foisted on brown dwarfs.

Brown dwarfs have masses ranging from around four times that of Jupiter to around 80 times that of the gas giant. (For comparison, the sun is 1,000 times more massive than Jupiter.) The mass of CWISE J1249+3621 is exciting because it puts it right at the hypothetical boundary between a star and a brown dwarf.

"The low mass is significant because it's by far the lowest-mass, high-velocity 'star' found to date. The original hypervelocity stars found about 20 years ago were massive O stars [around 50 times as massive as the sun] and B stars [up to 16 times as massive as the sun], a likely selection bias because these stars are rare and would need to be found at large distances," Burgasser said. "Our discovery indicates that whatever process (or processes) causes these stars to run away must operate at both high and low masses."

The UC San Diego researcher explained that the team is really excited to try to answer what sent this stellar body careening through the Milky Way.

"The star could have been kicked out of the center of Milky Way by our supermassive black hole, Sagittarius A*, a process commonly used to explain the origins of other hypervelocity stars," Burgasser said. "Notably, our star is moving into the center, not away, but it might be on a return trip after being ejected previously."

He added that it is also possible that the brown dwarf is on the run from a "cosmic vampire." The rogue stellar body may have been part of a binary system with a white dwarf stellar corpse that was ripping material away from it. This gruesome feeding eventually causes the white dwarf to erupt in a cosmic explosion called a Type Ia supernova. This would destroy the white dwarf and provide the "kick" that sent this runaway racing through the Milky Way at incredible speeds.

"Another possibility is that the star was launched out of a globular cluster through dynamical interactions with black holes in the center of the cluster; recent simulations show that this should happen several times over the age of the Milky Way," Burgasser said. "Any of these processes above, given a fast enough kick, could have launched it out, or in the case of an 'extragalactic' star, it just happens to be passing through."

He added that, currently, the team can't rule out the possibility that this potential brown dwarf is an intruder in our galaxy that came from outside the Milky Way. But the fact that it's passing through the plane of our Milky Way makes that a less likely case.

"The orbit is certainly the most surprising aspect of this object; it is moving radially in and out of the center of the Milky Way and almost perfectly in the plane," Burgasser said. "Most of the high-velocity stars we see are on much more chaotic or inclined orbits. I think this is a real clue to its real origin."

Related: 

• Brown dwarfs: The coolest stars or the hottest planets?

Runaway brown dwarfs, if that is indeed what CWISE J1249+3621 is, appear to be rare, but this could be because of their cool and faint nature, which makes them difficult to detect. This means that the population of rogue brown dwarfs could be much larger than current detection rates indicate.

"These types of stars are exceedingly rare; only a few dozen have been found out of billions of stars examined, and, as noted, this is the first low-mass one. And this object in particular is difficult to see because it's a very cool and dim star, nearly 10,000 times fainter than the sun and emitting most of its light at infrared wavelengths," Burgasser said. "It's hard to say how common these bodies are, with only one found so far, but since this is so close, we speculate that there may be many more.

"That speculation is informed partly by the fact that the majority of stars in the Milky Way are low mass, and about one in five are brown dwarfs, and that these objects are the easiest to 'throw around' since they are so low mass."

The team now intends to follow up on the investigation of CWISE J1249+3621's atmosphere in greater detail to see if its chemical abundances reveal something about its origin. They will also attempt to discover more of these low-mass stellar runaways, a hunt in which citizen scientists will play an integral role.

"We definitely want to find more of these objects, and our citizen scientists have identified several more high-velocity candidates to follow up," Burgasser concluded. "Citizen scientists were absolutely essential to this study! They were the ones who identified this source as an interesting target worth investigating. Without them, we'd still have hundreds of thousands of faint little dots to sort through."

The team's research is discussed in a pre-peer-reviewed paper featured on the repository site arXiv.

{ https://www.space.com/ }

01-08-2024 om 01:38 geschreven door peter  

World's largest telescope continues taking shape on Chilean mountain (photos)

Part of the dome will have large sliding doors, which will remain closed during the day and open at night, allowing the telescope to survey the sky. Once complete, the telescope will hunt for Earth-like exoplanets in search of signs of life outside of our own solar system and probe the early universe to study the first galaxies that formed after the Big Bang, among other tasks.

Assembly has begun on the beam structure for the sliding doors, which will help protect the telescope from the high daytime temperatures and dusty desert environment. 

Related: 

• The Milky Way's heart shines over construction site of world's largest telescope

Construction photos from June also show progress on the support structure in the center of the dome that will eventually hold the ELT's 128-foot-wide (39 meters) primary mirror (M1), which weighs a whopping 200 tons. The mirror will rest on the white lattice structure, which will allow M1 to move smoothly during observations and compensate for varying gravity loads, wind conditions, vibrations or changes in temperature. 

"Notice the cranes and vehicles at the bottom, which show off just how enormous the ELT is!" ESO officials said in a statement releasing the updated images. 

The primary mirror will be made up of 798 individual hexagonal segments, making it the largest segmented mirror ever built for a telescope. The ELT will have a total of five mirrors, all of which have different shapes, sizes and roles but will work together to observe the cosmos. 

The secondary mirror, M2, will hang above M1, reflecting the light collected by it to the tertiary mirror, M3. The hole in the middle of the white lattice structure will house the central tower, which will hold the M3, M4 and M5 mirrors.

{https://www.space.com/ }

01-08-2024 om 01:17 geschreven door peter  

Astronaut traveling to Titan loses his grip on reality in 1st 'Slingshot' trailer (video)

• https://youtu.be/tibvd41bhCg

It seems that acclaimed actor Laurence Fishburne ("The Matrix") has some uncanny attraction to sci-fi projects centered around doomed spaceships, having co-starred in 2016's "Passengers" and the 1997 cult classic, "Event Horizon." 

Now he's sharing the screen with the Academy Award-winning Casey Affleck ("Manchester By the Sea") and Tomer Capone ("The Boys") in Bleecker Street's upcoming outer space thriller, "Slingshot," and we've got the first full trailer to share to prove our point. 

The basic plot revolves around a harrowing 1.5-billion-mile trek to Saturn's moon Titan and one astronaut's inability to distinguish nightmares from real-life due to the side effects of a drug meant to induce hibernation sleep for the long haul.

"Slingshot" arrives in theaters on Aug. 30, 2024 as perhaps a bit of a sleeper hit in the late summer box office bonanza, and with Håfström at the helm this has all the makings of a future sci-fi classic. 

Directed by Mikael Håfström ("1408") from a screenplay by R. Scott Adams ("Donner Pass") and Nathan Parker ("Moon"), this riveting production also stars Emily Beecham ("Cruella") and David Morrissey ("The Colour Room," "The Walking Dead").

Check out the official synopsis:

"A psychological thriller starring Casey Affleck and Laurence Fishburne, 'Slingshot' follows an elite trio of astronauts aboard a years-long, possibly compromised mission to Saturn's moon Titan. As the team gears up for a highly dangerous slingshot maneuver that will either catapult them to Titan or into deep space, it becomes increasingly difficult for one astronaut to maintain his grip on reality." 

As seen in this trippy trailer, Affleck's unhinged character is not dealing with the extreme mental rigors of the mission very well and is hallucinating heavily as the Odyssey 1 spacecraft prepares to whip around Jupiter to provide the craft with a super speed boost necessary to properly reach the moon of Titan. 

Casey Affleck and Laurence Fishburne in 'Slingshot' 

COURTESY OF BLUESTONE ENTERTAINMENT PRODUCTION

RELATED STORIES:

• New 'Transformers One' trailer reveals the root of Optimus Prime and Megatron's rivalry
•  'Star Trek: Strange New Worlds': Pike and crew go full Vulcan in first Season 3 clip (video)
• 'Star Trek: Lower Decks' Season 5 trailer launches the crew on one last wacky mission (video)

"Slingshot" was mostly filmed at Korda Studios in Budapest, Hungary and was produced by Richard Saperstein, Istvan Major, and Beau Turpin. Ivett Havasi, Shara Kay, Michael Hollingsworth, Tom Nohstadt, Ron Cundy, Nikolett Barabás, Jonathan Krauss, Brooklyn Weaver and Joanna Plafsky serve as the film's executive producers. 

Bleecker Street's "Slingshot" streaks into theaters on Aug. 30, 2024.

{ https://www.space.com/ }

01-08-2024 om 01:04 geschreven door peter  

POSTED BY CAROLYN COLLINS PETERSEN

Space Debris From Every Angle

Near-Earth space is an orbiting junkyard of space debris. Everything from old rocket parts and pieces of dead satellites to cameras and tools floats in orbit. None of it serves a useful function any longer, but it does threaten other spacecraft. In fact, some missions have been damaged by this orbital debris and the problem will get worse as we launch more missions to space.

So, it makes sense to remove the existing space junk, but how to do that? A company in Japan called Astroscale is working with the Japan Aerospace Agency (JAXA) to figure that out.

On July 15 and 16th, Astroscale maneuvered a demonstration satellite called ADRAS-J into place around its target. Its goal was to do a “Fly-around observation” of a rocket upper stage that launched the Greenhouse Gases Observing Satellite (GOSAT) in 2009. ADRAS-J was launched earlier this year on a trajectory to chase down space debris. The early July portion of the mission saw ADRAS-J fly around the object and get high-quality images of the object. In addition, it took data about the rocket motor’s motion in space (including its orbital parameters) and assessed its condition. The effort was successful and the teams captured great images of the motor from every angle.

The maneuvers ADRAS-J made are technically challenging, requiring fine guidance control of the ADRAS-J module. Luckily, the target object was fairly easy to approach and move around. In on-orbit maneuvers like this one, it’s important to control the relative position and attitude of the servicer unit (ADRAS-J). Such control allows it to move around the object and zero in on specific parts for further work. The rocket motor was fairly stable. However, not all bits of space junk are as stable as the rocket motor targeted for this experiment.

Challenges to Working with Space Debris

Given the huge collection of space junk out there, not everything is going to be easy to capture. Future “clean-up efforts” could involve so-called “non-cooperative targets” whose motions are more chaotic, or are dangerous to approach. Those could be very challenging. So, it’s important to have the detailed shape and surface reflectance of the real target object. For most pieces of space junk that information isn’t readily available.

For example, it’s also useful to know the changing visibility of the target object, and the influence of earth-reflected light, which disturbs the navigation sensor (the so-called Earth background problem in non-cooperative relative navigation). These add to the complexity of the mission. That’s because the servicer spacecraft must overcome those challenges for relative navigation while achieving highly accurate relative six-degree-of-freedom control around the target.

The ADRAS-J mission is part of the “Commercial Remove of Debris Demonstration” initiative from JAXA to acquire and test debris removal in space. If it’s successful, that should help clear up space for future missions leaving Earth. Astroscale Japan, Inc. will continue to operate ADRAS-J and will carry out “Astroscale missions” to further test the hardware and maneuvering capabilities.

The next step will be to perform a “Mission termination service”. That involves the transfer of a target piece of space junk to a safe orbit. This will be done in cooperation with JAXA, which has already provided extensive technical advice, testing facilities, and other activities supporting ADRAS-J’s development and operation.

Why Clean Up Space Junk?

Tens of thousands of artificial objects orbit above Earth. That includes more than 5,000 operating satellites, plus space stations, and Starlinks, and other stuff shot into orbit since the late 1950s. Eventually, as the old adage says, “what goes up must come down.” In fact, some of it does come back to Earth, which also poses a safety issue.

In the case of dead rocket motors and other nonworking pieces of space junk, not only will they come down to Earth, but they get in the way of spacecraft launches. That includes crewed launches carrying astronauts to the space stations, the Moon, and beyond.

The danger isn’t just that a collision will hurt somebody in space or on the ground. Tiny pieces of space junk can knock holes in solar panels and instruments. Bits of dust and paint flecks and other materials literally “sandblast” spacecraft on the way up. Space shuttles showed a lot of this damage. All this space debris began littering our spaceways starting with the first launches in the late 1950s. The materials are tracked by the North American Aerospace Defense Command (NORAD), and their catalogs include details of all the objects including satellites, weapons, fairings, upper stages, cameras, tools, and other pieces of debris from satellites destroyed by collisions and other actions.

It makes sense to clean up the junk that doesn’t fall back to Earth (and hopefully burn up in the atmosphere). That’s why JAXA and other agencies are looking at proactive ways to approach, apprehend, and safely store the debris (or deorbit it to vaporize, if possible). The first steps with ADRAS-J are proofs of concept that should lead to a larger clean-up job and a safer near-Earth environment for future missions.

For More Information

• CRD2 Phase I / ADRAS-J Update: Fly-Around Observation Images of Space Debris Released
  ESA: about Space Debris

{ https://www.universetoday.com/ }

31-07-2024 om 23:11 geschreven door peter  

POSTED BY EVAN GOUGH

No Merger Needed: A Rotating Ring of Gas Creates A Hyperluminous Galaxy

Some galaxies experience rapid star formation hundreds or even thousands of times greater than the Milky Way. Astronomers think that mergers are behind these special galaxies, which were more abundant in the earlier Universe. But new results suggest no mergers are needed.

These galaxies are called Hyper Luminous Infrared Galaxies (HyLIRGs), and they emit most of their energy in the infrared. New research examined a HyLIRG that’s 10,000 times brighter than the Milky Way in infrared. Instead of a chaotic merger, they found an organized rotating ring of gas that they say is responsible for the galaxy’s abundant star formation.

Their results are in a paper in Nature Astronomy titled “Detailed study of a rare hyperluminous rotating disk in an Einstein ring 10 billion years ago.” The lead author is Daizhong Liu, a Research Professor at Purple Mountain Observatory near Nanjing, China.

HyLIRGs are the rarest type of starburst galaxy, and they’re the most extreme type. They’re found only in the distant, ancient Universe. The galaxy is named PJ0116-24 and has a redshift of z=2.125. That redshift value means the light we’re seeing was emitted about 10.5 billion years ago, and the distant galaxy is now about 16 billion light-years away. At that distance, astronomers had to use gravitational lensing to look at the galaxy. That not only magnified the galaxy, it created an Einstein Ring.

The researchers used a pair of telescopes to observe the galaxy. The Very Large Telescope traced the warm gas with its Enhanced Resolution Imager and Spectrograph (ERIS) instrument, and the Atacama Large Millimetre/submillimetre Array traced the cold gas. By combining the observations from both, the astronomers found an organized ring of rotating gas. If a merger had occurred and triggered the galaxy’s abundant star formation, an organized structure like this wouldn’t have been present. Instead, the galaxy’s morphology would be much more chaotic.

The authors write, “A widely accepted scenario is that HyLIRGs are the distant higher-luminosity tail of the local ultra-luminous IR galaxies with extreme starburst activities triggered by major mergers.” Another possibility is that these galaxies are very young and are experiencing their maximum star formation rates associated with youth. The problem is that astronomers haven’t observed enough of them to be certain exactly what’s going on.

This galaxy was identified by the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts project (PASSAGES), which found about 20 HyLIRGs. PJ0116-24 is the brightest one found in the southern sky.

The authors write, “We found PJ0116-24 to be highly rotationally supported with a richer gaseous substructure than other known HyLIRGs. Our results imply that PJ0116-24 is an intrinsically massive and rare starburst disk probably undergoing secular evolution.” Its star formation rate (SFR) is 1,490 solar masses yr^-1.

Simulations predict that the maximum SFR is greater than or equal to 1,000?solar masses yr^-1. If these observations are correct, then they show that a galaxy can reach its maximum SFR even if it is alone and hasn’t been involved in a merger.

“Unlike almost all other extreme HyLIRGs, which are major mergers, PJ0116-24 does not obviously have massive companions or disturbed kinematics as evidence for major mergers,” the authors explain in their paper.

The galaxy also shows much higher metallicity than others in the early Universe. “These diagnostics indicate solar to supersolar metallicity,” the authors write. “This is much higher than in non-starburst galaxies at the same redshifts.”

Amit Vishwas is a postdoc at the Cornell Center for Astrophysics and Planetary Sciences. He’s a co-author of this paper and a previous paper in 2023 that used the JWST to observe another galaxy at an earlier epoch with similar gas conditions and metallicity. PJ0116-24 is about five times more massive and luminous than that one. Vishwas says both of these galaxies are helping astronomers build a better picture of how galaxies evolve.

“In both cases, gravitational lensing helped us zoom in to study the details of the interstellar medium of these galaxies,” Vishwas said in a press release. “I believe these new observations are helping us build an argument for the way galaxies evolve and build up – efficiently converting gas to stars in rapid growth spurts separated by long periods of relative calm.”

“The robust confirmation of PJ0116-24 as the most rotationally supported HyLIRG from this work is key evidence suggesting that secular evolution, that is, without recent major mergers, can be responsible for maximal star formation in the Universe,” the authors conclude in their work.

{ https://www.universetoday.com/ }

31-07-2024 om 23:04 geschreven door peter  

POSTED BY MARK THOMPSON

When Earth Danced with Polar Moons

The origins of the Moon have been the cause of many a scientific debate over the years but more recently we seem to have settled on a consensus. That a Mars-sized object crashed into Earth billions of years ago, with the debris coalescing into the Moon. The newly formed Moon drifted slowly away from Earth over the following eons but a new study suggests some surprising nuances to the accepted model. 

According to current theory, the Moon formed around 4.5 billion years ago, shortly after the Solar System’s birth. It began with a massive collision between the early Earth and a Mars-sized protoplanet called Theia. The impact sent debris into orbit around the Earth which eventually coalesced to create the Moon. There is plenty of evidence to support this theory chiefly the composition of Earth’s mantle and lunar rocks.

The majority of the debris cloud settled back down on the Earth, a large proportion formed the Moon but some of it was ejected from the Earth-Moon system. In the paper recently authored by Stephen Lepp and his team from the University of Nevada they explored the dynamics of the material ejected from the impact. 

Shortly after the Moon formed it was orbiting Earth at a distance about 5% of its current value (average distance – 384,400km) but slowly, due to tidal effects between Earth and Moon it drifted away to its current altitude. Its surface was largely molten magma which gradually cooled and solidified forming the familiar crust, mantle and core that we see today. Heavy bombardment scarred the lunar surface with impact basins and craters and volcanic activity led to the slow formation of the lunar maria. 

The orbit of the Moon around the Earth has settled into a slightly elliptical one with an eccentricity of 0.0549. It is not a perfect circle and moves from 364,397km to 406,731km from Earth. The system wasn’t so stable in the early days of the Earth-Moon system and the particles in the accreting Moon had more erratic journeys. 

One of the terms that describes evolving orbits is nodal precession (where the orbital intersections slowly move around the orbit). There are two types and the first relates to where particles in an orbit slowly precess about the angular momentum vector of the Earth-Moon system. The other occurs around highly eccentric binary systems when the inclination of the orbiting object is large. The particle precesses about the binary eccentricity vector. Taking into account the Earth and orbits of particles in the debris cloud as the Moon started to form, such orbits described would be unstable.

The team showed that of all the possible orbits of particles, those in polar orbits were the most stable. They went further and showed that they existed around the Earth-Moon binary system after the Moon formed. As the separation of the Earth and Moon slowly increased through tidal interactions the region of space where polar orbits could exist decreased. Today, with the Moon at its current distance from Earth, there are no stable polar orbits since the nodal precession driven by the Sun is dominant

The team conclude that the presence of polar orbiting material can drive eccentricity growth of a binary system like the Earth and Moon. If a significant amount of material found its way into a polar orbit then the eccentricity of the Earth-Moon system would have increased.  

Source : 

• Polar orbits around the newly formed Earth-Moon binary system

{ https://www.universetoday.com/ }

31-07-2024 om 22:57 geschreven door peter  

I have always found Mariana’s Trench fascinating, it’s like an alien world right on our doorstep. Any visitor to the oceans or seas of our planet will hopefully get to see fish flitting around and whilst they can survive in this alien underwater world they still need oxygen to survive. Breathing in oxygen is a familiar experience to us, we inflate our lungs and suck air into them to keep us topped up with life giving oxygen. Fish are different, they get their oxygen as water flows over their gills. Water is full of oxygen which at the surface comes from the atmosphere or plants. But deep down, thousands of meters beneath the surface, it is not so easy. Now a team of scientists think that potato-sized chunks of metal called nodules act like natural batteries, interacting with the water and putting oxygen into the deep water of the ocean. 

Thanks to robotic underwater explorers the sight of life teeming around thermal vents on the bottom of the deep ocean is not unusual. At those depths, no sunlight can penetrate to facilitate photosynthesis in plants. Somehow though, oxygen is present in the dark, deep regions of the ocean and its the rocks that a team of scientists led by Andrew Sweetman have been exploring.

The production of oxygen by plants is well understood. Light is captured by a pigment known as chlorophyll where it is then converted into chemical energy and stored in the glucose. During photosynthesis, carbon dioxide from air and water from soil are combined in a series of chemical reactions to produce glucose and oxygen that we use to breathe. This oxygen from the plants plays a role in maintaining levels in the atmosphere and the oceans and seas. The study challenges this somewhat simplified explanation. 

The team focussed on measuring how much oxygen was being consumed by organisms in the depths of the ocean. Water sampled from the deep showed a surprising rise in oxygen levels instead of an anticipated decline. The study was repeated a few years later from the same location in a study commissioned by a mining company. Again they saw a rise in oxygen levels. Clearly something in the deep ocean was creating oxygen, but what?

Lab tests ruled out the possibility of microbes but the region being studied was peppered with lumps of rock known as polymetallic nodules. The nodules are known to form when manganese and cobalt precipitate out of water and form around shells. The nodules where theorised to be the source of the oxygen but the mechanism was not understood. 

The answer came when Sweetman heard a reporter calling the nodules ‘a battery in a rock’. Putting batteries in saltwater results in bubbles of hydrogen and oxygen which is the result of a process known as electrolysis. The team measured the voltage on the nodules and found just one of them to be 0.95 volts – a little lower than the required 1.5 volts for saltwater driven electrolysis but the team were onto something, suspecting multiple rocks could cluster together to increase voltage. 

The discovery of rocks on the bottom of the ocean generating oxygen is fascinating on its own but it has profound impacts on the search for life elsewhere in the universe. We have already discovered ice covered water worlds among the moons around some of the outer planets. It’s likely there will be others in planetary systems around other stars. If these worlds are common then it is quite likely that oxygen is being released through electrolysis from similar metallic nodules and perhaps, supporting entire ecosystems.  

Source :

• Evidence of dark oxygen production at the abyssal seafloor

{ https://www.universetoday.com/ }

31-07-2024 om 22:50 geschreven door peter  

31-07-2024 om 16:41 geschreven door peter  

NASA’S DART MISSION SNAPPED PICTURES UNTIL IT CRASHED INTO AN ASTEROID. HERE’S WHAT THOSE IMAGES REVEAL

NASA got up close and personal to an asteroid pair near Earth.

BY DORIS ELÍN URRUTIA

 

JHU Applied Physics Laboratory

The footage is a treasure trove. On Tuesday, teams published five scientific papers in the journal Nature Communications. Each contains new insights into what these rocks are like, and how tricky it may be for future planetary defense missions to strike another asteroid to avoid an impact’s calamity on Earth.

Here are five discoveries about this binary asteroid system so briefly encountered on September 26, 2022.

1. THE LARGER ASTEROID HAS AN OLDER SURFACE THAN THE LITTLE MOON.

Didymos and its moonlet Dimorphos are related to one another. But scientists still don’t know exactly how. One investigation looked at 16 craters on the larger asteroid, Didymos.

DRACO, the Didymos Reconnaissance and Asteroid Camera for OpNav scientific camera, was one image source. It took many photos of Didymos and smaller Dimorphos before impacting the latter’s surface.

The craters suggest that the Didymos surface is about 12.5 million years old. But the Dimorphos surface is a fraction of that, only about 90,000 years to 300,000 years old.

2. DIDYMOS IS A PILE OF RUBBLE.

Observations confirmed theoretical expectations: It’s essentially a clump of leftovers from a catastrophic event in the ancient past.

Scientists noticed Didymos boulders appear too large to have been excavated by whatever made the craters. Something grander was responsible, and its mess, rounded up through gravitational attraction, is now Didymos. The large boulders are heirlooms passed down from an ancient parent rock.

3. WE NEED TO KNOW MUCH MORE ABOUT FRACTURES ON DIMORPHOS’ BOULDERS.

Asteroid boulders live in an airless environment. But, they can be altered through thermal fatigue. As the Sun shines on them, cracks form.

The Dimorphos fractures were identified with the help of independent contributors who located them across boulders of different sizes. This work adds to what’s already been gleaned about the Near-Earth asteroid population from previous NASA, Japanese, and European missions.

The picture emerging from the data is that, should a kinetic impactor like DART slam into another space rock, the thermal cracks “may contribute to an enhancement in the ejected mass,” one study says.

4. ECLIPSES MAY BE ONGOING.

On the flip side, eclipses could be having an opposite effect: cooling rocks down.

Based on limited data about how Dimorphos now spins after DART struck it, scientists think the moonlet remains tidally-locked to Didymos. This means Dimorphos shows the same face to Didymos, like the Moon does with Earth. If this relationship is fostering eclipses, a periodic drop in temperature could be happening on the asteroids.

Like thermal fatigue from solar radiation, the cooling effect of eclipses must also be factored into deflection techniques. This asteroid duo provides a unique chance to investigate this. Other closely-studied asteroids and comets have no companion to block out light.

5. THE DIDYMOS SURFACE IS WEAKER THAN DRY SAND ON EARTH.

One major thing researchers want to know before visiting any celestial object is how much weight you can put on it. This is called bearing capacity. It reveals a lot about the formation history of the Solar System. And in the case of planetary defense, bearing capacity also informs how to build something that can effectively knock a space rock off a collision course with Earth.

“The low surface strength of Dimorphos likely contributed to DART’s significant impact on its orbit,” NASA officials wrote in an announcement published Tuesday. This also seems to be a trait of the larger asteroid, Didymos.

Researchers looked at DRACO’s final full image of Didymos before it slammed into the moonlet Dimorphos. DART didn’t touch Didymos. But boulders on its surface left tracks. Scientists studied nine of these paths. They determined that the bearing capacity of Didymos is “at least 3 orders of magnitude less than the bearing capacity of dry sand on Earth, or lunar regolith [dirt].”

Researchers have already learned so much about Near-Earth asteroids from the DART mission. Thanks to the European Space Agency’s upcoming Hera mission to survey the duo in October 2026, even more discoveries could emerge.

{ https://www.inverse.com/ }

31-07-2024 om 16:31 geschreven door peter  

{ https://www.universetoday.com/ }

31-07-2024 om 01:40 geschreven door peter  

31-07-2024 om 01:31 geschreven door peter