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Blazars occupy an intriguing spot in the cosmic zoo. They’re bright active galactic nuclei (AGN) that blast out cosmic rays, are bright in radio emission, and sport huge jets of material traveling in our direction at nearly the speed of light. For some blazars, their jets look curvy and snaky and astronomers have questions.

Does a blazar’s central black hole’s appetite affect the jets? Is there some internal activity in the accretion disk that causes the variability in brightness? Or, is something else at work here? According to Silke Britzen of the Max Planck Institute for Radio Astronomy in Germany, it might be more interesting than one black hole (or its accretion disk) doing its thing.

“We present evidence and discuss the possibility that it is in fact the precession of the jet source, either caused by a supermassive binary black hole at the footpoint of the jet or – less likely – by a warped accretion disk around a single black hole, that is responsible for the observed variability,” said Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany.

The Galaxy with Two Black Holes

The idea of a precessing warped accretion disk around one supermassive black hole is interesting because that motion could affect the jets. It also plays a role in those periodic changes in brightness. That effect shows up in some other galaxies, too. But, what else could cause the precession? Britzen and the team investigated an object called OJ 287 to see if it could give some clues. It appears to have two black holes—essentially a black hole binary—at its core. Studies of this galaxy and 12 other AGNS led to the conclusion that jet curvature may provide a smoking gun clue to the existence of binary black holes in galaxy cores.

How would that work? It’s complex, but essentially, you have two black holes doing an orbital dance in the center of the galaxy. One black hole is emitting the jet and the other one’s gravitational influence affects the appearance and behavior of the jet. According to Michal Zajacek, who is a co-author of the study with Britzen, it helps explain the jet’s appearance. “Physics of accretion disks and jets is rather complex but their bulk kinematics can be compared to simple gyroscopes,” he said. “If you exert an external torque on an accretion disk, for instance by an orbiting secondary black hole, it will precess and nutate, and along with it the jet as well, similar to the Earth’s rotation axis that is affected by the Moon and the Sun.”

 A magnetized radio jet (yellow), precessing due to a pair of supermassive black holes. The larger one is shown in black at the center of the accretion disk. It contains warmer (blue) and cooler (red) gas. The white arrow indicates the spin of the larger black hole. The second black hole orbits (orange) around the central supermassive black hole and the orange arrow shows the orientation of its orbital angular momentum. Due to misalignment, torque from the secondary drives the precession of the accretion disk as well as the launched jet (green circle and arrows).  Radio emission is indicated with white curved lines. These show how the jet swirls around and produces variations in radio emission. Courtesy: Michal Zaja?ek/UTFA MUNI
A magnetized radio jet (yellow), precessing due to a pair of supermassive black holes. The larger one is (black) at the center of the accretion disk. It contains warmer (blue) and cooler (red) gas. The white arrow indicates the spin of the larger black hole. The second black hole orbits (orange) around the central supermassive black hole and the orange arrow shows the orientation of its orbital angular momentum. Due to misalignment, torque from the secondary drives the precession of the accretion disk as well as the launched jet (green circle and arrows). White curved lines indicate radio emission. Courtesy: Michal Zaja?ek/UTFA MUNI

Searching for the Black Hole Binaries

If this is the case for other blazars, the meandering jet and brightness variability may well be the clue astronomers need to probe for other binary black holes. It’s not an easy task to find the black holes, even though the AGNS themselves are bright, according to Britzen. “We still lack the sufficient resolution to probe
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An Astronaut Might Need Kidney Dialysis on the Way Home from Mars

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Long term space exploration comes with many challenges. Not least is how much toilet paper to take but more worryingly is the impact on human physiology. We have not evolved in a weightless environment, we are not used to floating around for months on end nor are we able to cope with increased levels of radiation. It is likely that organs like the kidneys will become damaged but it make take time for signs to appear. Researchers are developing ways to detect organ issues in the early stages and develop ways to protect them during long duration flights. 

We have known for some years that space flight causes health problems. Reduced muscle and bone density are the more well known but since the 1970’s we have also seen a weakening of the heart, eyesight issues and kidney stone development. The main cause of the problem is thought to be increased exposure to radiation from space. It’s not just the radiation from the Sun but Galactic Cosmic Radiation from deep space also plays a part. Fortunately for us here on Earth, the magnetic field protects us and those in low Earth orbit to a degree too. Those who travel further afield; to the Moon and other planets will be far more at risk. 

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ESA astronaut Alexander Gerst gets a workout on the Advanced Resistive Exercise Device (ARED). Credit: NASA

To date, no-one has attempted to study what might be happening inside our organs as a result of long duration space flight, until now. A new study, published in Nature Communications, reports upon the analysis of kidney health in space flight. The study was funded by Wellcome, St Peters Trust and Kidney Research UK and was undertaken by a team of researchers from over 40 groups.

The research team collected samples from over 40 low Earth orbit missions from humans and mice chiefly from the International Space Station. Using these samples they conducted biomolecular, physiological and anatomical assessments. Using mice, they were able to simulate Galactic Cosmic Radiation doses equivalent to a 1.5 year to 2.5 year Mars mission. 

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NASA Image: ISS020E049908 – NASA astronaut Nicole Stott, Expedition 20/21 flight engineer, is pictured near the Mice Drawer System (MDS) in the Kibo laboratory of the International Space Station.

Indications from the study showed that the kidney from both animal and human experienced changes. Parts of the kidney, known as tubules, are responsible for tweaking the calcium and salt balances and these showed signs of shrinkage after less than a month in space. The researchers believe though that this is more likely the result of weightlessness rather than radiation doses. The team did suggest however that further research is appropriate to see if the combination of increased doses of radiation coupled with microgravity had an increasing effect.

Another finding of the study was the way in which salt is processed by the kidneys. It is now thought that fundamental changes to how this is handled leads to the formation of kidney stones whilst it was originally assumed to be the result solely of microgravity.

Perhaps the most shocking finding of the study though was that anyone venturing beyond the confines fo the Earth’s protective magnetic field for 2.5 years is likely to experience permanent kidney damage and loss of function. This was demonstrated in the mice samples that had experienced a simulated Galactic Cosmic Radiation dose

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Moon Lander Detects Technosignatures Coming from Earth

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The search for life has to be one of the most talked about questions in science. The question is, what do you look for? The Odysseus lunar lander has recently detected signs of a technologically advanced civilisation…on Earth! The lander is equipped with an instrument called ROLSES which has probed the radio emissions from Earth as if it was an exoplanet to se if it could detect signs of life! 

Odysseus was launched on 15 February, it was the Intuitive Machines lunar lander and it touched down in the solar polar region of the Moon seven days later. Since then it has been collecting valuable data from the area as a prelude for future human exploration. It was part of the Commercial Lunar Payload Services program which have all been built by private companies. Despite the hiccup of a landing where Odysseus tipped onto its side it has still been performing well.

There have been other challenges along the way. The laser guided navigation system which was supposed to aid the landing over the rocky surface failed. In a nod to Armstrong landing Apollo 11 manually in the last few minutes, the ground crew had to land using the optical camera system alone.  Even the journey to the Moon was not without incident. One of the antennae of the ROLSES system overheated and became dislodged from its housing.  On landing, an image showed the antenna sticking out. 

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Neil Armstrong and Buzz Aldrin plant the US flag on the Lunar Surface during 1st human moonwalk in history 45 years ago on July 20, 1969 during Apollo 1l mission. Credit: NASA

On board Odysseus is the Radio wave Observations at the Lunar Surface of the photo Electron Sheath or ROLSES for short. It is a radio experiment designed to explore properties of the Earth’s atmosphere from the surface of the Moon. It was a unique opportunity to observe Earth in a completely different way and, to see if our approach for hunting for technologically capable alien civilisations are correct.

The instrument was built at NASA’s Goddard Space Flight Center in Maryland and included radio antennae and a device called a radio spectrometer. It’s purpose was to record a wide range of radio emissions from the ‘radio quiet’ locale of the Moon. It turned out to be a bit of a bonus though as the team were able to record radio waves coming from Earth for about an hour and a half. 

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NASA has selected three commercial Moon landing service providers that will deliver science and technology payloads under Commercial Lunar Payload Services (CLPS) as part of the Artemis program. Each commercial lander will carry NASA-provided payloads that will conduct science investigations and demonstrate advanced technologies on the lunar surface, paving the way for NASA astronauts to land on the lunar surface by 2024…The selections are:..• Astrobotic of Pittsburgh has been awarded $79.5 million and has proposed to fly as many as 14 payloads to Lacus Mortis, a large crater on the near side of the Moon, by July 2021…• Intuitive Machines of Houston has been awarded $77 million. The company has proposed to fly as many as five payloads to Oceanus Procellarum, a scientifically intriguing dark spot on the Moon, by July 2021…• Orbit Beyond of Edison,
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The Inner and Outer Milky Way Aren’t the Same Thickness, and that’s Surprising

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At first glance, the universe and night sky seem largely unchanging. The reality is very different, even now, a gas cloud is charging toward the Milky Way Galaxy and is expected to crash into us in 27 million years. A team of astronomers hoping to locate the exact position of the expected impact site have been unsuccessful but have accidentally measured the thickness of the Milky Way! Analysing radio data, they have been able to deduce the thickness of the inner and outer regions and discovered a dramatic difference between the two. 

The team of astronomers from the US National Science Foundation’s Green Bank Observatory were attempting to study the Smith Cloud. This high velocity cloud of hydrogen gas is located in the constellation Aquila at a distance of somewhere between 36,000 and 45,000 light years. Previous studies from the Green Bank Observatory have shown the cloud contains at least 1 million times the mass of the Sun and measures 9,800 light years long by 3,300 light years wide. 

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A false-color image of the Smith Cloud made with data from the Green Bank Telescope (GBT). New analysis indicates that it is wrapped in a dark matter halo. Credit: NRAO/AUI/NSF

The plan was simple enough, to observe the spot where the cloud is currently interacting with the Milky Way. The observation is tricky enough though as the cloud is on the far side of the Milky Way and there is a lot of stuff in the way! The team, led by Toney Minter used the 20m Green Bank Telescope to search for dust and emissions from hydroxyl molecules (composed of a hydrogen and oxygen molecule.)  What the team expected to see was a difference in composition in the region of the Milky Way interacted with the cloud which, should have very little dust and hydroxyl molecules. Clouds in the Milky Way tend to have both so a difference should be detectable. 

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The Robert C. Byrd Green Bank Telescope. Credit: Jay Young.

Minter was candidly open about the study joking ‘I knew there was a low probability that I’d find what I was looking for—and I didn’t,. But this is all part of the scientific process. You learn from what you DO and DON’T find.’

Disappointingly the team did not detect any differences in composition but what they did find was equally as interesting. The study revealed information about the Milky Way itself and the structure of its inner regions. Minter and his team had to look through the Milky Way’s inner regions for their study and what they were able to determine was the thickness of the layer of molecules in the inner Galaxy. The information enabled them to deduce the scale height of the clouds of molecular gas in the inner Milky Way. The results showed that the layer of molecules in the inner region measured 330 light years thick while those in the outer parts measured twice as much, around 660 light years.

The discovery still leaves questions unanswered. The observation certainly shows the difference in thickness between the inner and outer regions but it doesn’t give any clue as to what is driving the difference. Further observations are now required to follow up on this discovery to try and model the underlying process. Of course one other question remains unanswered and that is the nature and mechanics of the Smith Cloud and how it will impact our own Galaxy. Far from being disappointed though, Minter stated ‘That’s why astronomy is exciting, our knowledge is always evolving’

Source : While Aiming for
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