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Supermassive black holes are elusive creatures. Massive gravitational beasts that can power immensely bright quasars, or can lurk quietly among the bright stars of a galactic core. We mostly study them indirectly through their bright accretion disks or powerful jets of plasma they create, but we have been able to observe them more directly, such as our images of M87* and Sag A*. But what still eludes us is capturing a direct image of the enigmatic photon ring. A new work in Acta Astronautica proposes how this might be done.

Black holes are nothing more and nothing less than a warped structure of space and time. They are defined by the presence of an event horizon, which is a closed surface boundary through which light can cross only once. It is the point of no return. Anything that crosses the event horizon of a black hole is forever held in its gravitational trap. But there are other defining structures near a black hole, such as the photon shell. This is the inner limit of stable circular orbits for photons. In theory, light in the photon shell can orbit the black hole forever, though, in reality, small gravitational fluctuations would make the orbits unstable over time. If the event horizon has a radius of R, then the photon shell has a radius of 1.5R.

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The structures of a simple black hole. Credit: John F. Lindner, The College of Wooster

We can’t observe the event horizon or the photon shell directly, but the next closest feature we can observe. Known as the photon ring, it is the thin circle of light caused by photons that have grazed the black hole so closely their paths are deflected directly toward us. For a simple black hole, the photon ring has a radius of about 2.6R. For a real, rotating black hole things are a bit more complicated, since the spin of a black hole boosts a photon’s energy in the direction of rotation, but in either case, the photon ring is the closest black hole structure we can observe from a distance. As such, it could tell us a great deal about black holes and whether Einstein’s gravitational theory is accurate.

The photon ring of M87* is captured in the EHT images of the black hole we currently have, but it’s not distinct. Some research has argued that we can pull out the photon ring data from the background, but this has been disputed. A major problem with capturing the photon ring is that the current is at its limit of resolution. It took all we could do just to get the blurry images of M87* and Sag A* we have. There are plans to build a next-generation Event Horizon Telescope (ngEHT), with more observatories and more sensitive detectors, but even this might not be enough to see the photon ring.

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Proposed elliptical orbits for the VLBI. Credit: Hudson, et al

So this new study proposes a constellation of space-based Very Long Baseline Interferometers (VLBI). Antennas could be placed in a wide Earth orbit, or orbit a the L2 Lagrange point between the Earth and the Moon. Without the interference of Earth’s atmosphere, the receivers of this constellation could capture radio light at shorter wavelengths than ground-based observatories. By placing the antennas in elliptical orbits, the array could achieve an effective baseline much wider than the diameter of the Earth. Both of these features would allow astronomers to capture high-resolution images of both M87* and Sag A* and observe their photon rings. The proposed telescope would also be able to capture lower-resolution images of other
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Moon Dust Could Contaminate Lunar Explorers’ Water Supply

Aldrin bootprint C second impression

Water purification is a big business on Earth. Companies offer everything from desalination to providing just the right pH level for drinking water. But on the Moon, there won’t be a similar technical infrastructure to support the astronauts attempting to make a permanent base there. And there’s one particular material that will make water purification even harder – Moon dust. 

We’ve reported plenty of times about the health problems caused by the lunar regolith, so it seems apparent that you don’t want to drink it. Even more so, the abrasive dust can cause issues with seals, such as those used in electrolyzers to create rocket fuel out of in-situ water resources. It can even adversely affect water purification equipment itself. 

Unfortunately, this contamination is inevitable. Lunar dust is far too adhesive and electrostatically charged to be kept completely separate from the machinery that would recycle or purify the water. So, a group of researchers from DLR in Germany decided to test what would happen if you intentionally dissolved lunar regolith.

Fraser interviews Dr. Kevin Cannon, an expert in lunar dust mitigation.

The short answer is, unsurprisingly, nothing good. Dissolved lunar regolith causes pH, turbidity, and aluminum concentrations all exceed World Health Organization benchmarks for safe drinking water. This happened even with short exposure times (2 minutes) and static pH values, as they used a 5.5 pH buffer in part of the experiments. 

They didn’t use actual lunar dust for these experiments, but a simulant modeled on the regolith returned during the Apollo 16 mission. It mimics the regolith that is thought to be most similar to the Artemis landing sites. In addition to the pH changes and the amount of exposure time (which went up to 72 hours), the authors also varied the amount of dissolved oxygen in the system and the particle size of the simulant.

Those negative results occurred for every test variation, no matter what combination of the four control variables was used. Ultimately, that means engineers will have to devise a system to filter the water from these deposits before it can be recycled into the overall water system.

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After taking the first boot print photo, astronaut Buzz Aldrin moved closer to the little rock and took this second shot. His boot was already completely covered in adhesive dust.
Credit: NASA

The paper explored some potential solutions for that water purification system. Each of the limits that were violated requires its purification methodology. In the author’s estimation, lowering the turbidity is the first requirement. To do so, they suggest doing standard filtration or allowing the dust particles to settle. 

Removing aluminum is next in importance, with another experiment showing that plants that grew in lunar soil showed signs of aluminum toxicity. Additional ions, including calcium, iron, and manganese, also need to be removed, as they were above acceptable levels in some test batches but not all. Removing these ions would require a reverse osmosis process or ion exchange. Ion removal is vital to a fully functional electrolyzer system as well. 

The authors seemed to be ultimately going after a platform to test and validate water purification processes for future lunar exploration missions. Given the results from their experimentation, there will undoubtedly be future rounds of testing and plenty of technology development to work on solving these technical challenges. Ultimately, astronauts will have to drink water on the Moon – and it won’t be coming just from bottles from Earth.

Learn More:
Freer, Pesch, & Zabel – Experimental study to characterize water contaminated by lunar dust
UT – The Moon Is Toxic
UT – Astronauts Will Be Tracking Dust Into the Lunar Gateway. Is This a Problem?
UT – Lunar Dust is Still One of The Biggest Challenges Facing Moon Exploration

Lead Image:
Turbidity samples of some of the dissolved regolith.
Credit – Freer, Pesch, & Zabel

The post Moon Dust Could Contaminate Lunar Explorers’ Water Supply appeared first on Universe Today.

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Gaia Hit by a Micrometeoroid AND Caught in a Solar Storm

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For over ten years, the ESA’s Gaia Observatory has monitored the proper motion, luminosity, temperature, and composition of over a billion stars throughout our Milky Way galaxy and beyond. This data will be used to construct the largest and most precise 3D map of the cosmos ever made and provide insight into the origins, structure, and evolutionary history of our galaxy. Unfortunately, this sophisticated astrometry telescope is positioned at the Sun-Earth L2 Lagrange Point, far beyond the protection of Earth’s atmosphere and magnetosphere.

As a result, Gaia has experienced two major hazards in recent months that could endanger the mission. These included a micrometeoroid impact in April that disrupted some of Gaia‘s very sensitive sensors. This was followed by a solar storm in May—the strongest in 20 years—that caused electrical problems for the mission. These two incidents could threaten Gaia‘s ability to continue mapping stars, planets, comets, asteroids, quasars, and other objects in the Universe until its planned completion date of 2025.

Micrometeroids are a common problem at the L2 Lagrange Point, roughly 1.5 million km (932,057 mi) from Earth, so engineers designed Gaia with a protective cover. Unfortunately, the particle was traveling at a very high velocity and struck the cover at precisely the wrong angle, causing a breach. This has allowed stray sunlight to interfere with Gaia’s ability to simultaneously collect light from so many distant stars. Gaia‘s engineering team was addressing this issue the moment the solar storm hit, adding electrical issues to their list of problems.

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Gaia’s all-sky view of our Milky Way Galaxy and neighboring galaxies, based on measurements of nearly 1.7 billion stars. Credit: ESA

Mission controllers first noticed signs of disruption in May when Gaia began registering thousands of false detections. They soon realized that this may have been due to the solar storm that began on May 11th, which could have caused one of the spacecraft’s charge-coupled devices (CCDs) to fail, which converts light gathered by Gaia’s billion-pixel camera into electronic signals. The observatory relies on 106 CCDs, each playing a different role. The affected sensor was vital for Gaia’s ability to confirm the detection of stars and validate its observations.

While the spacecraft was built to withstand radiation, it has been operating in space for almost twice as long as originally planned (6 years) and may have been pushed to its limits. As Edmund Serpell, Gaia spacecraft operations engineer at ESOC, explained in an ESA press release:

“Gaia typically sends over 25 gigabytes of data to Earth every day, but this amount would be much, much higher if the spacecraft’s onboard software didn’t eliminate false star detections first. Both recent incidents disrupted this process. As a result, the spacecraft began generating a huge number of false detections that overwhelmed our systems. We cannot physically repair the spacecraft from 1.5 million km away. However, by carefully modifying the threshold at which Gaia’s software identifies a faint point of light as a star, we have been able to dramatically reduce the number of false detections generated by both the straylight and CCD issues.”

Meanwhile, the Gaia teams at ESA’s European Space Operations Centre (ESOC), the European Space Research and Technology Centre (ESTEC), and the European Space Astronomy Center (ESAC) have spent the past few months investigating these problems. They have also worked closely with engineers from Airbus Defence and Space (the spacecraft’s manufacturer) and payload experts at the Data Processing and Analysis Consortium. Thanks to their efforts, the GaiaObservatory recently returned to regular operations.

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Mountain Lakes of the Wind River Range—A Photo Gallery

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By Michael Lanza

We followed the Doubletop Mountain Trail as it rolled over open plateau country above 10,000 feet in the Wind River Range, crossing one gorgeous lake basin after another where wildflowers still carpeted the ground in the week before Labor Day. In the distance, peaks along the Continental Divide soared to over 13,000 feet, jabbing at the underbellies of clouds. Turning onto the Highline Trail, we reached an unnamed tarn in late afternoon and walked beyond it to a flat, broad bench overlooking a meadow and lake below a pair of huge towers, 12,119-foot Sky Pilot Peak and 12,224-foot Mount Oeneis. It was a serendipitous find to make our home for the night.

But the real magic arrived the next morning, when nature served up a perfect stew of conditions—calm air, dappled light, still water, and a stunning backdrop—to create a scene that validates carrying all the weight on your back for days (and makes for a pretty good photo, above).

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Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-books to classic backpacking trips. Click here to learn how I can help you plan your next trip.

Washakie Lake in the Wind River Range, Wyoming.
” data-image-caption=”Sunset light over Washakie Lake in the Wind River Range, Wyoming.
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/05/01072631/Wind9-45-Washakie-Lake-in-the-Wind-River-Range-WY.jpg?fit=300%2C200&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/05/01072631/Wind9-45-Washakie-Lake-in-the-Wind-River-Range-WY.jpg?fit=900%2C600&ssl=1″ tabindex=”0″ role=”button” src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/05/01072631/Wind9-45-Washakie-Lake-in-the-Wind-River-Range-WY-1024×683.jpg?resize=900%2C600&ssl=1″ alt=”Washakie Lake in the Wind River Range, Wyoming.” class=”wp-image-63052″ srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/05/01072631/Wind9-45-Washakie-Lake-in-the-Wind-River-Range-WY.jpg 1024w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/05/01072631/Wind9-45-Washakie-Lake-in-the-Wind-River-Range-WY.jpg 300w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/05/01072631/Wind9-45-Washakie-Lake-in-the-Wind-River-Range-WY.jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/05/01072631/Wind9-45-Washakie-Lake-in-the-Wind-River-Range-WY.jpg 150w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/05/01072631/Wind9-45-Washakie-Lake-in-the-Wind-River-Range-WY.jpg 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />Sunset light over Washakie Lake in the Wind River Range, Wyoming.

I first began exploring Wyoming’s Wind River Range about 30 years ago and have returned many times since, drawn back again and again by its almost bottomless well of adventure potential. In that time, I’ve learned about the many reasons to walk for days through the Winds, which exist in the deep shadow of Grand Teton and Yellowstone national parks just a couple of hours to the north—a state of relative anonymity that many backpackers celebrate. Its lack of national park status and sheer vastness enable a high degree of solitude for backpackers willing to make the considerable effort (and take the time) to explore more deeply into the range, which extends for nearly 100 miles north to south.

And few mountain ranges match the grandiosity of the Wind River Range. The Colorado Rockies and High Sierra reach greater heights and I would include both among the handful of
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