PR's Tumblrdome
Aqua Utopia｜海の底で記憶を紡ぐ
Sade Olutola
ojovivo
Jules of Nature
Game of Thrones Daily
2025 on Tumblr: Trends That Defined the Year
Origami Around
One Nice Bug Per Day
he wasn't even looking at me and he found me
todays bird
Today's Document
izzy's playlists!
Discoholic 🪩
sheepfilms
⁂
$LAYYYTER
@theartofmadeline
Claire Keane
I'd rather be in outer space 🛸
seen from United States
seen from United States
seen from United States
seen from United States
seen from United States
seen from United States
seen from United States
seen from Germany
seen from Tunisia
seen from United States
seen from Bangladesh
seen from Brazil
seen from United States
seen from Vietnam
seen from United Kingdom
seen from Malaysia
seen from Türkiye
seen from Malaysia
seen from Saudi Arabia
seen from United Kingdom
@hateyellowlovegems
looking for non-indifferent native speakers
hi, im Merk,sorry for disturbing,i just wanted to ask for some help or advice. Well, i want to help my friend with study of irish language, especially with native speakers, but neither i nor my friend know where to start looking them or groups where could we find feedback or some help.She (my friend) loves this language very much and ready to devote time to it. sorry for my bad english
saw your post on wanting to learn Irish, there's an Irish TV channel called TG4 and they dubbed SpongeBob into Irish (they have other shows too ), you can watch it on their website, idk if you need a vpn if you're outside Ireland or not
omg thanks you very very much for you reply from me and from my friend *-* bless you (!)
What Is an Atomic Clock?
The clock is ticking: A technology demonstration that could transform the way humans explore space is nearing its target launch date of June 24, 2019. Developed by NASA’s Jet Propulsion Laboratory in Pasadena, California, the Deep Space Atomic Clock is a serious upgrade to the satellite-based atomic clocks that, for example, enable the GPS on your phone.
Ultimately, this new technology could make spacecraft navigation to distant locations like Mars more autonomous. But what is an atomic clock? How are they used in space navigation, and what makes the Deep Space Atomic Clock different? Read on to get all the answers.
Why do we use clocks to navigate in space?
To determine a spacecraft’s distance from Earth, navigators send a signal to the spacecraft, which then returns it to Earth. The time the signal requires to make that two-way journey reveals the spacecraft’s distance from Earth, because the signal travels at a known speed (the speed of light).
While it may sound complicated, most of us use this concept every day. The grocery store might be a 30-minute walk from your house. If you know you can walk about a mile in 20 minutes, then you can calculate the distance to the store.
By sending multiple signals and taking many measurements over time, navigators can calculate a spacecraft’s trajectory: where it is and where it’s headed.
Most modern clocks, from wristwatches to those used on satellites, keep time using a quartz crystal oscillator. These devices take advantage of the fact that quartz crystals vibrate at a precise frequency when voltage is applied to them. The vibrations of the crystal act like the pendulum of a grandfather clock, ticking off how much time has passed.
To know the spacecraft’s position within a meter, navigators need clocks with precision time resolution - clocks that can measure billionths of a second.
Navigators also need clocks that are extremely stable. “Stability” refers to how consistently a clock measures a unit of time; its measurement of the length of a second, for example, needs to be the same (to better than a billionth of a second) over days and weeks.
What do atoms have to do with clocks?
By space navigation standards, quartz crystal clocks aren’t very stable. After only an hour, even the best-performing quartz oscillators can be off by a nanosecond (one billionth of a second). After six weeks, they may be off by a full millisecond (one thousandth of a second), or a distance error of 185 miles (300 kilometers). That would have a huge impact on measuring the position of a fast-moving spacecraft.
Atomic clocks combine a quartz crystal oscillator with an ensemble of atoms to achieve greater stability. NASA’s Deep Space Atomic Clock will be off by less than a nanosecond after four days and less than a microsecond (one millionth of a second) after 10 years. This is equivalent to being off by only one second every 10 million years.
Atoms are composed of a nucleus (consisting of protons and neutrons) surrounded by electrons. Each element on the periodic table represents an atom with a certain number of protons in its nucleus. The number of electrons swarming around the nucleus can vary, but they must occupy discreet energy levels, or orbits.
A jolt of energy - in the form of microwaves - can cause an electron to rise to a higher orbit around the nucleus. The electron must receive exactly the right amount of energy - meaning the microwaves must have a very specific frequency - in order to make this jump.
The energy required to make electrons change orbits is unique in each element and consistent throughout the universe for all atoms of a given element. For instance, the frequency necessary to make electrons in a carbon atom change energy levels is the same for every carbon atom in the universe. The Deep Space Atomic Clock uses mercury atoms; a different frequency is necessary to make those electrons change levels, and that frequency will be consistent for all mercury atoms.
“The fact that the energy difference between these orbits is such a precise and stable value is really the key ingredient for atomic clocks,” said Eric Burt, an atomic clock physicist at JPL. “It’s the reason atomic clocks can reach a performance level beyond mechanical clocks.”
Being able to measure this unchangeable frequency in a particular atom offers science a universal, standardized measurement of time. (“Frequency” refers to the number of waves that pass a particular point in space in a given unit of time. So, by counting waves, it’s possible to measure time.) In fact, the official measurement of the length of a second is determined by the frequency needed to make electrons jump between two specific energy levels in a cesium atom.
In an atomic clock, the frequency of the quartz oscillator is transformed into a frequency that is applied to a collection of atoms. If the derived frequency is correct, it will cause many electrons in the atoms to change energy levels. If the frequency is incorrect, far fewer electrons will jump. This will determine if the quartz oscillator is off-frequency and by how much. A “correction” determined by the atoms can then be applied to the quartz oscillator to steer it back to the correct frequency. This type of correction is calculated and applied to the quartz oscillator every few seconds in the Deep Space Atomic Clock.
What’s unique about the Deep Space Atomic Clock?
Atomic clocks are used onboard GPS satellites that orbit the Earth, but even they must be sent updates two times per day to correct the clocks’ natural drift. Those updates come from more stable atomic clocks on the ground that are large (often the size of a refrigerator) and not designed to survive the physical demands of going to space.
Up to 50 times more stable than the atomic clocks on GPS satellites, NASA’s Deep Space Atomic Clock is intended to be the most stable atomic clock ever flown in space. It achieves this stability by using mercury ions.
Ions are atoms that have a net electric charge, rather than being electrically neutral. In any atomic clock, the atoms are contained in a vacuum chamber, and in some of those clocks, atoms interact with the vacuum chamber walls. Environmental changes such as temperature will then cause similar changes in the atoms and lead to frequency errors.
Many atomic clocks use neutral atoms, but because the mercury ions have an electric charge, they can be contained in an electromagnetic “trap” to prevent this interaction from happening, allowing the Deep Space Atomic Clock to achieve a new level of precision.
For missions going to distant destinations like Mars or other planets, such precision makes autonomous navigation possible with minimal communication to and from Earth - a huge improvement in how spacecraft are currently navigated.
The Deep Space Atomic Clock is hosted on a spacecraft provided by General Atomics Electromagnetic Systems of Englewood, Colorado.
debuted “Rocket Queen” at the Troubadour (1985)
Great white shark genome decoded
Huge genome reveals sequence adaptations in key wound healing and genome stability genes tied to cancer protection
The great white shark is one of the most recognized marine creatures on Earth, generating widespread public fascination and media attention, including spawning one of the most successful movies in Hollywood history. This shark possesses notable characteristics, including its massive size (up to 20 feet and 7,000 pounds) and diving to nearly 4,000 foot depths. Great whites are also a big conservation concern given their relatively low numbers in the world’s oceans.
In a major scientific step to understand the biology of this iconic apex predator and sharks in general, the entire genome of the white shark has now been decoded in detail.
A team led by scientists from Nova Southeastern University’s (NSU) Save Our Seas Foundation Shark Research Center and Guy Harvey Research Institute (GHRI), Cornell University College of Veterinary Medicine, and Monterey Bay Aquarium, completed the white shark genome and compared it to genomes from a variety of other vertebrates, including the giant whale shark and humans.
The findings are reported in the ‘Latest Articles’ section of the journal Proceedings of the National Academy of Sciences, USA.
Decoding the white shark’s genome revealed not only its huge size - one-and-a-half times the size of the human genome - but also a plethora of genetic changes that could be behind the evolutionary success of large-bodied and long-lived sharks.
The researchers found striking occurrences of specific DNA sequence changes indicating molecular adaptation (also known as positive selection) in numerous genes with important roles in maintaining genome stability ¬¬- the genetic defense mechanisms that counteract the accumulation of damage to a species’ DNA, thereby preserving the integrity of the genome.
These adaptive sequence changes were found in genes intimately tied to DNA repair, DNA damage response, and DNA damage tolerance, among other genes. The opposite phenomenon, genome instability, which results from accumulated DNA damage, is well known to predispose humans to numerous cancers and age-related diseases.
“Not only were there a surprisingly high number of genome stability genes that contained these adaptive changes, but there was also an enrichment of several of these genes, highlighting the importance of this genetic fine-tuning in the white shark,” said Mahmood Shivji, Ph.D., director of NSU’s Save Our Seas Foundation Shark Research Center and GHRI. Shivji co-led the study with Michael Stanhope, Ph.D., of Cornell University College of Veterinary Medicine.
Also notable was that the white shark genome contained a very high number of “jumping genes” or transposons, and in this case a specific type, known as LINEs. In fact this is one of the highest proportions of LINEs (nearly 30%) discovered in vertebrates so far.
“These LINEs are known to cause genome instability by creating double stranded breaks in DNA,” said Stanhope. “It’s plausible that this proliferation of LINEs in the white shark genome could represent a strong selective agent for the evolution of efficient DNA repair mechanisms, and is reflected in the positive selection and enrichment of so many genome stability genes.”
The international research team, which also included scientists from California State University, Monterey Bay, Clemson University, University of Porto, Portugal, and the Theodosius Dobzhansky Center for Genome Bioinformatics, Russia, also found that many of the same genome stability genes in the white shark were also under positive selection and enriched in the huge-bodied, long-lived whale shark.
The discovery that the whale shark also had these key genome stability adaptations was significant because theoretically, the risk of developing cancer should increase with both the number of cells (large bodies) and an organism’s lifespan - there is statistical support for a positive relationship of body size and cancer risk within a species. Interestingly, this does not tend to hold up across species.
Contrary to expectations, very large-bodied animals do not get cancer more often than humans, suggesting they have evolved superior cancer-protective abilities. The genetic innovations discovered in genome stability genes in the white and whale shark could be adaptations facilitating the evolution of their large bodies and long lifespans.
“Decoding the white shark genome is providing science with a new set of keys to unlock lingering mysteries about these feared and misunderstood predators - why sharks have thrived for some 500 million years, longer than almost any vertebrate on earth” said Dr. Salvador Jorgensen, a Senior Research Scientist at the Monterey Bay Aquarium, who co-authored the study.
But the innovations did not end there.
The shark genomes revealed other intriguing evolutionary adaptations in genes linked to wound healing pathways. Sharks are known for their impressively rapid wound healing.
“We found positive selection and gene content enrichments involving several genes tied to some of the most fundamental pathways in wound healing, including in a key blood clotting gene,” said Stanhope. “These adaptations involving wound healing genes may underlie the vaunted ability of sharks to heal efficiently from even large wounds.”
The researchers say they have just explored the “tip of the iceberg” with respect to the white shark genome.
“Genome instability is a very important issue in many serious human diseases; now we find that nature has developed clever strategies to maintain the stability of genomes in these large-bodied, long-lived sharks,” said Shivji. “There’s still tons to be learned from these evolutionary marvels, including information that will potentially be useful to fight cancer and age-related diseases, and improve wound healing treatments in humans, as we uncover how these animals do it.”
Decoding the white shark genome will also assist with the conservation of this and related sharks, many of which have rapidly declining populations due to overfishing,“ said Steven O'Brien, a conservation geneticist at NSU, who co-conceived this study. "The genome data will be a great asset for understanding white shark population dynamics to better conserve this amazing species that has captured the imagination of so many.”
Images Courtesy of Byron Dilkes, Danah Divers
SpaceTime 20190220 Series 22 Episode 15 is now out
SpaceTime covers the latest news in astronomy & space sciences.
The show is available as a free twice weekly podcast through Apple Podcasts (itunes), Stitcher, Google Podcast, Pocketcasts, SoundCloud, Bitez.com, YouTube, Audio Boom, your favourite podcast download provider, and from www.spacetimewithstuartgary.com
SpaceTime is also broadcast coast to coast across the United States on Science360 Radio by the National Science Foundation in Washington D.C. and around the world on Tune-In Radio.
SpaceTime daily news blog: http://spacetimewithstuartgary.tumblr.com/ SpaceTime facebook: www.facebook.com/spacetimewithstuartgary SpaceTime Instagram @spacetimewithstuartgary SpaceTime twitter feed @stuartgary SpaceTime YouTube: https://www.youtube.com/c/SpaceTimewithStuartGary
Today’s stories…
Goodbye farewell and amen as mission end declared for the Opportunity rover One of the most successful and enduring feats of interplanetary exploration, NASA’s Mars Opportunity rover mission has finally been declared over after almost 15 years exploring the surface of the red planet.
Mining water on the moon The new Australian project to mine water on the Moon for conversion to rocket fuel.
Discovery of a stellar flare ten billion times more powerful than those on the Sun Astronomers has detected a massive stellar flare over ten billion times more powerful than the biggest solar flares produced by the Sun.
The Science Report Being pregnant in your teenage years may have a cascading effect down your bloodline. Greenland is melting faster than scientists previously thought. Native turtles in South Australia are facing extinction. The long-running clandestine hacking campaign being carried out by the United Arab Emirates. New near weightless material capable of both withstanding some of the most extreme temperatures. Young kids spending more time than ever staring at screens.
Last Saturday’s show….
A new fundamental constant of the Sun Astronomers have discovered that magnetic waves in the Sun’s corona - its outermost layer of atmosphere - react to sound waves escaping from the inside of the Sun.
Ultima Thule more like a walnut pancake than a snow man New images of the distant Kuiper Belt object Ultima Thule show that its far stranger than previously thought.
Black Hole mergers could reveal new particles A new study suggests gravitational-wave signals could contain signatures of extremely low-mass particles that might be a component of dark matter.
The Science Report A a gigantic cavity - two-thirds the area of Manhattan – discovered growing under Thwaites Glacier. When it comes to weight loss - breakfast may not be the most important meal of the day. Fears of another major Chinese data theft uncovered by computer experts. Teens who don’t get enough sleep are more likely to take part in dangerous behaviours. The growing business of fortune telling and psychics.
SpaceTime Background SpaceTime is Australia’s most respected astronomy and space science news program. The show reports on the latest stories and discoveries making news in astronomy, astrophysics, cosmology, planetary science, galactic and stellar evolution, physics, spaceflight, and general science. SpaceTime features interviews with leading Australian scientists about their latest research. The show is broadcast coast to coast across the United States by the National Science Foundation on Science360 Radio and around the world on Tune in Radio. SpaceTime is available in Australia as a twice weekly podcast which averages around three million downloads annually. It’s hosted on line through Bitez.com on all major podcast platforms. SpaceTime began life in 1995 as ‘StarStuff’ on ABC NewsRadio. Stuart Gary created the show while he was NewsRadio’s Science Editor, evening presenter, and news anchor (a position he held for more than 17 years). Gary wrote, produced and hosted StarStuff, consistently achieving 9 percent of the Australian radio audience share - according to Neilsen ratings survey figures for the five major Australian metro markets (Sydney, Melbourne, Brisbane, Adelaide, & Perth). The StarStuff podcast was hosted by ABC Science on line achieving over 1.3 million downloads annually. Sadly, the popular program was axed in 2015 during ABC budget cuts. Rather than remain with the ABC, Gary resigned to continue producing the show independently and rebranding it as SpaceTime. The first episode of SpaceTime was broadcast on February 8th 2016 and the show has been in continuous production ever since. SpaceTime now reaches an audience almost three times greater that it achieved as StarStuff and continues to grow.
So sometimes my sisters and I watch music videos and commentate the whole thing. This just happens to be the outcome.
Guns ‘N’ Roses | “Patience” (1989)
5 THINGS TO KNOW ABOUT JANUARY’S TOTAL LUNAR ECLIPSE
This month’s rare total eclipse will be the last one visible from the United States until 2022.
Walter Freeman is an assistant teaching professor in the Physics Department at Syracuse University. Freeman answers five questions about the upcoming eclipse.
Freeman says:
What should those in the viewing area of the Jan. 20-21 total lunar eclipse expect to see?
“Viewers will see a normal full Moon at first starting at around 10:35 p.m. Eastern time. At that time, the Earth’s shadow will begin to pass in front of the Moon, blocking almost all of the Sun’s light from reaching it. Observers will see the Moon appear to be progressively ‘swallowed up’ starting from the lower left. This process will end at 11:40 p.m., when the Earth’s shadow covers the whole of the Moon’s surface; this is the beginning of 'totality.’ This will last until around 12:40 a.m., when the motion of the Earth’s shadow will carry it past the Moon, and the Moon will gradually again be lit by the Sun. At 1:45 a.m., the Moon will be fully visible again.
How often does this sort of eclipse happen?
"There is a little less than one total lunar eclipse per year on average. A lunar eclipse can only happen during a full Moon when the Moon is on the opposite side of the Earth from the Sun. But the Moon’s orbit is tilted a little bit compared to the Earth’s, so usually when the Moon is full, the Earth’s shadow passes a little bit above or a little bit below it. This is why we don’t have a lunar eclipse every month.”
What’s the difference between a total lunar eclipse and a “blood Moon” …or are they the same thing?
“The Moon won’t be completely invisible during the period of totality when the Earth’s shadow completely covers it! A little bit of sunlight is refracted by the Earth’s atmosphere and reaches the Moon, bending around the edges of the Earth. This small amount of red light still illuminates the Moon enough for us to see it. Instead of being bright and white, the Moon will be very dim and red, ten thousand or so times dimmer than usual; people call this a 'blood Moon.’
"Since the Moon doesn’t shine on its own, but only reflects the Sun’s light, any lunar eclipse happens when the Earth is exactly between the Sun and the Moon.”
Is there anything that those on the ground should be aware of when they’re looking up at a total lunar eclipse?
“There are no precautions you need to take when observing a lunar eclipse since the Moon is never bright enough to hurt our eyes like the Sun is. A blood Moon is one of the few opportunities we have to see both the Moon and the stars in the sky at the same time, since the Moon is usually too bright!”
When will the next one happen that can be viewed from parts of North America?
“Partial solar eclipses (where the Earth’s shadow doesn’t completely cover the Moon, and only takes a bite out of the side of it) are more common. But the next total solar eclipse visible from the United States will be on November 8, 2022 – visible as the Moon sets in the West just before sunrise.”
@darlingfreddie
AAS NOVA
Mixing up a Batch of Stars
By Astrobites
“Star Light, [Supernova] Bright”
Though the Big Bang and the birth of the universe as we know it — or, at least, *think* we know it — all happened way before any of us were born, we can still piece together the universe’s history from the starlight we observe today.
Scientists believe that the very first stars in our universe were born a long, long, long, long, long time ago, when the universe was “just” a few hundred million years old (much younger than the universe’s current age of nearly 14 billion years).
These first stars were huge — scientists believe they might have been a hundred or so times more massive than the Sun.
They were born of gas containing only hydrogen, helium, and tiny traces of lithium — the only three elements that were even around after the Big Bang.
All elements heavier than hydrogen and helium in the universe, which astronomers refer to collectively as “metals”, were forged later, after these first stars exploded into brilliantly-bright supernovae and expelled the first heavier elements out into space.
These first metals can be traced in the “second-generation” stars, which are the extremely metal-poor stars that were born after the first stars went supernovae.
Scientists study second-generation stars in our Milky Way to learn more about how they formed and how the first stars led to their birth.
In today’s astrobite, we consider the story told by a special class of second-generation star: the carbon-enhanced, metal-poor (CEMP) stars.
CEMP stars are metal-poor but have relatively high carbonicity, which means they have enhanced amounts of carbon compared to their iron content.
Specifically, we look at CEMP-no stars, which are CEMP stars that also have relatively little barium with respect to iron.
These CEMP-no stars are believed to directly represent the chemical composition of the environment they formed in.
At this time, however, we’re still not sure how these carbon-enhanced stars formed.
One theory says that CEMP-no stars were born after faint supernovae.
Since faint supernovae are known to expel relatively less iron than more “normal” supernovae, and since CEMP-no stars have carbon that’s enhanced relative to their iron content, it’s possible that CEMP-no stars show carbon enhancements because they were born after faint supernovae.
However, it’s not clear what percentage of the universe’s first stars may have exploded as faint supernovae.
It’s also not clear if that percentage was enough to explain all of the CEMP-no stars we expect there to be in the universe.
Today’s authors consider a different perspective.
They question if the carbon enhancements observed for these CEMP-no stars might be explained in part by inhomogeneous metal mixing, an uneven distribution of metals in the environment where they formed.
So far, not much research has been done on the effects of inhomogeneous mixing of elements in the early universe.
So today’s authors used theory and modeling to test their scenario, in which inhomogeneous metal mixing leads to the formation of a CEMP-no star.
To Mix and Make a Star
We can break down the authors’ proposed scenario for forming a CEMP-no star into four crucial steps, which are illustrated in the CENTRE IMAGE.
1. One of the universe’s first stars explodes into a supernova.
2. The explosion eventually leads to overdensities in the surrounding gas, such that some parts of the gas are ‘clumpier’ than others.
Due to inhomogeneous mixing after the explosion, these clumps have differing elemental abundances from each other.
3. A clump with higher carbonicity relative to another nearby clump collapses and forms stars.
4. The newly-formed stars send out energetic photons.
These photons pierce the other nearby clump, break apart the molecules contained in that nearby clump, and thus stop that clump from collapsing and making its own stars as well.
The authors used oodles of theory to build and test a model of this scenario.
Here are just a few of the many aspects of the scenario that they explored in detail:
• How quickly the clump with higher carbonicity would need to collapse
• How various cooling methods for the surrounding gas would affect the clump’s timescale of collapse
• How long it would take the newly formed stars to send out energetic photons
The authors’ work culminated in an analytical, closed set of equations that related the carbonicity of the clump to the difference in carbonicity (and thus the level of inhomogeneity) between that clump and its neighboring clump.
They found that this relationship depended most strongly on the difference in carbonicity and the physical distance between the two clumps.
The LOWER IMAGE predicts how well this scenario could explain the formation of 64 CEMP-no stars that have been observed.
The authors find that for their standard model, with a clump distance of 30 pc and a difference in carbonicity of about 1 unit, about 11% of observed CEMP-no stars can be explained by this scenario.
They stress how they’re not saying that all CEMP-no stars in the universe formed through this inhomogeneous pathway.
They’re merely proposing that this is how a certain proportion of the CEMP-no stars we observe today may have formed.
They look to future 3D simulations to dive deeper into inhomogeneous mixing, and investigate how efficiently the process might have occurred in the early universe.
But in the meantime, if we couple this inhomogeneous pathway with the faint-supernova pathway we discussed at the beginning of this astrobite, then we may not need so many faint supernovae after all to tell the story of how these CEMP-no stars came to be.
Editor’s note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.
Title: Formation of carbon-enhanced metal-poor stars as a consequence of inhomogeneous metal mixing
Author: Tilman Hartwig and Naoki Yoshida First Author’s Institution: The University of Tokyo, Japan Status: Submitted to ApJL
About the author, Jamila Pegues:
Hi there! I’m a 3rd-year grad student at Harvard. I focus on the evolution of protoplanetary disks and extra-solar systems. I like using chemical/structural modeling and theory to explain what we see in observations. I’m also interested in artificial intelligence; I like trying to model processes of decision-making and utility with equations and algorithms. Outside of research, I enjoy running, cooking, reading stuff, and playing board/video games with friends. Fun Fact: I write trashy sci-fi novels! Stay tuned — maybe I’ll actually publish one someday!
TOP IMAGE….An image of the supernova remnant Cassiopeia A from NASA’s Chandra X-ray Observatory. [NASA/CXC/SAO]
CENTRE IMAGE….A graphic illustrating the authors’ scenario. In the first panel on the left, a first star explodes into a supernova that has a typical carbon abundance. In the second panel we see how, due to inhomogeneous mixing, the supernova leads to a clump of gas that has higher carbonicity (along the top row) and a clump that has less carbonicity (along the bottom row). Then in the third and fourth panels, we see that the clump with higher carbonicity produces CEMP stars. These stars send out energetic photons that prevent the clump with less carbonicity from producing stars as well. [Hartwig & Yoshida 2019]
LOWER IMAGE….Predictions of how well the authors’ inhomogeneous metal mixing scenario explains the formation of 64 CEMP-no stars that have been observed. The x-axis shows the distance between the two clumps in parsecs (pc). The y-axis represents the minimum difference in carbonicity between the two clumps (where higher numbers mean a larger difference) that would allow this scenario to produce a CEMP-no star. The black line is the 50% line. So for example, if we pick a spot along the black line, then 50% of the observed CEMP-no stars in the survey could be explained by the corresponding distance and difference-in-carbonicity values, while another 50% would require a larger difference in carbonicity. The red and green areas explain 0% and 100% of the observed CEMP-no stars, respectively. So if all of the clumps resulting from the first stars’ supernovae fell into the green region, then this scenario would explain 100% of the CEMP-no stars observed in the survey. [Hartwig & Yoshida 2019]
How Lunar craters reveal Earths impact history
Using images and thermal data collected by NASA’s Lunar Reconnaissance Orbiter (LRO), Southwest Research Institute scientists and their collaborators have calculated the ages of large lunar craters across the Moon to be less than 1 billion years. By comparing the impact history of the Moon with Earth’s craters over this interval, they discovered that the rate of sizable asteroid collisions has increased by a factor of two to three on both bodies over the last 290 million years.
For decades, scientists have tried to understand the rate that asteroids hit Earth by carefully studying impact craters and by using radiometric dating of the rocks around them. Earth has fewer older craters than expected compared to other bodies in the solar system, making it difficult to find an accurate impact rate and to determine if it has changed over time. Many experts assumed that the earliest Earth craters may have been worn away by wind, storms and geologic processes, mechanisms not present on the Moon.
“What this research uncovered is that the Earth has fewer older craters on stable terrains not because of erosion, but because the impact rate was lower prior to 290 million years ago,” said SwRI’s William Bottke, an asteroid expert who coauthored a paper outlining the research published January 18 in the journal Science. “The Moon is like a time capsule, helping us understand the Earth. We found that the Moon shared a similar bombardment history, which meant the answer to Earth’s impact rate was staring everyone right in the face.”
Though large impacts are rare, Earth and the Moon are hit in the same proportions over time. Lunar craters experience little erosion over billions of years, but scientists could not pinpoint their ages until the Lunar Reconnaissance Orbiter (LRO) started circling the Moon a decade ago, studying its surface.
LRO’s thermal radiometer, called Diviner, measures the heat radiating off the Moon’s surface. By looking at these data during the lunar night, scientists measured how much of the surface is covered by large, warm rocks, versus cooler, fine-grained lunar soil. Large impact craters formed in the last billion years are littered with boulders and rocks, while older craters are smoother. Using a relatively new technique to calculate how long it takes to reduce lunar stones into soil, the paper’s first author Sara Mazrouei and coauthor Rebecca Ghent at the University of Toronto calculated the ages of all lunar craters to be younger than about a billion years.
The work paid off, returning several unexpected findings. First, the team discovered that the rate of large crater formation on the Moon was about two to three times higher over the last 290 million years than over the previous 700 million years. The reason for this jump in the impact rate is unknown. It might be related to large collisions taking place more than 300 million years ago in the main asteroid belt between the orbits of Mars and Jupiter. Such events can create debris that ultimately penetrates the inner solar system.
The second surprise came from comparing the ages of large craters on the Moon to those on Earth. Their similar size and age distributions challenge the theory that Earth had lost so many craters through erosion on stable terrains back to 650 million years ago.
Scientists confirmed this deduction by studying kimberlite pipes – long-extinct volcanoes that stretch, in a carrot shape, a couple of kilometers below the surface. Scientists know a lot about the ages and rate of erosion of kimberlite pipes because they are widely mined for diamonds. They also are located on some of the least eroded regions of Earth, the same places where we find preserved impact craters. Tom Gernon, a coauthor and Earth scientist based at the University of Southampton in England, showed that kimberlite pipes formed in the last 650 million years on stable terrains had not experienced much erosion, indicating that the large impact craters younger than this in the same regions must also be intact. “So that’s how we know those craters represent a near-complete record,” Ghent said.
“We can now apply this technique to study the surfaces of other planets to find out if they might also show more impacts,” Bottke said. “Our findings also have implications for the history of life, which is punctuated by extinction events and rapid evolution of new species. Though the forces driving these events are complicated, asteroid impacts have surely played a role in this ongoing saga.”
The research for the paper, titled “Earth and Moon impact flux increased at the end of the Paleozoic,” was funded in part by NASA’s Solar System Exploration Research Virtual Institute (SSERVI). SwRI researchers serve on 13 teams within SSERVI, which is based and managed at NASA’s Ames Research Center in California’s Silicon Valley. SSERVI is funded by the Science Mission Directorate and Human Exploration and Operations Mission Directorate at NASA Headquarters in Washington, D.C. For more about SSERVI, visit sservi.nasa.gov.
IMAGES….SwRI was part of a team that used Lunar Reconnaissance Orbiter data to study the Moon’s craters, scaled by size and color-coded by age here, to understand the impact history of the Earth. The lunar surface is dominated by blue craters younger than 290 million years old, which is consistent with those on Earth, indicating that bombardments on both bodies has increased since that time. Image Courtesy of NASA/LRO/USGS/University of Toronto
everything.
SPACE INTERNET TO ENHANCE EARTH OBSERVATION
Every day satellites collect a wealth of information about Earth, but they must send it down to the ground before we can make use of it.
Sometimes this data can be lost, damaged, or delayed, but our access to it could be improved using Delay Tolerant Networks (DTNs) – a new way of communicating with spacecraft.
Imagine the inconvenience of only being able to send a message to a friend when your phones are directly facing each other with a perfect connection. Fortunately, the internet allows us to circumnavigate this problem by passing data to in-between nodes, and if your friend’s phone isn’t connected to the internet, the data is stored until it can be transferred to them.
Currently communication with Earth observation satellites does not benefit from this internet-like transmission and storage of information through in-between nodes. Earth observation satellites only send data down to Earth when they are directly overhead a ground station. When a satellite isn’t facing a ground station, data starts queuing up. There is no system that automatically sort the queue to prioritise the sending of urgent data – information captured about natural disasters, perhaps – from the ordinary.
Delay Tolerant Networks offer a solution in the form of using relay spacecraft and other ground stations. These would act as intermediate nodes that would be able to hold on to data and pass it on as soon as the next ‘hop’ is available, ensuring its safe delivery by relaying it up to a spacecraft or down to a ground station at just the right time. DTNs provide a new way of transmitting information, creating the foundation for a 'space internet’.
So far, DTNs have mostly been explored in the context of deep space – when distant planetary orbiters and rovers need to use intermediary nodes to communicate with Earth. But a team of researchers supported by ESA’s Discovery and Preparation Programme recently investigated the possible benefits of Delay Tolerant Networking for Earth observation.
The team, made up of representatives from GMV INSYEN, German Aerospace Center (DLR), Solenix Deutschland and the University of Bologna analysed how DTNs could improve our communication with Earth observation spacecraft.
Sebastian Martin, responsible for the project from ESA’s side, explains further, “DTNs allow information to be sent through a network that does not have a direct route from the starting point to the final receiver of information. In-between 'nodes’ receive information and store it until they can send it on to a neighbour. In addition, DTNs can automatically schedule when to store information and when to forward it over different possible routes.”
The team began by investigating how one of the existing Copernicus Sentinel missions could benefit from DTN technology. They then modelled a futuristic scenario with a full system of DTN-enabled Earth observation satellites, ground stations and control centres. In both scenarios, they found that the data automatically reached their destination via optimal routes and that the network correctly handled data with different priorities.
They also looked into a second benefit of DTNs. When existing Earth observation satellites pass over ground stations on their orbits around Earth, a short amount of time at the beginning and the end of its pass is not used to transfer information. This is because there is a risk of data getting lost when the satellite is low over the horizon with a poor connection with the ground station. Using DTNs, it is possible to automatically check for lost data and get it resent. This means it is safer for satellites to attempt to send information as soon as the ground station is in sight, possibly resulting in more data being transferred during each pass of the satellite.
Data can also be lost for other reasons, like bad weather. Optical communications, for example, can be severely affected by cloud cover, so to avoid loss of data it is necessary to wait for clear skies to send information. DTN networks would support this data being sent at any time, as lost data would be automatically detected and resent. A third advantage of DTNs is that data can be automatically prioritised. Michael Staub, who managed the project from GMV INSYEN, explains, “The DTNs that we created successfully sorted data depending on its priority, meaning that important observations – for example those made during natural disasters – would be sent as quickly as possible, even if other data joined the queue first.”
This study is one step further in our understanding of how DTNs could revolutionise space communications. Next, experts will investigate how DTNs can be implemented technically, what data types would profit most, the potential impact on operations and operators, and where new markets and users could benefit from this technology.
One option being considered for testing DTNs is ESA’s OPS-SAT CubeSat.
The 30-centimetre high demonstrator will test out a large variety of technologies, including DTNs, to provide information useful for larger future missions. Eventually, the more spacecraft and ground stations using DTN technology, the more benefits the technology will bring.
“Through this study, we have shown that DTNs would be very beneficial for Earth observation scenarios,” concludes Staub. “The networks we propose will enable organisations and commercial entities to interoperate, including encouraging the sharing of each other’s facilities and resources.”
With space exploration becoming more complex, current communication networks become increasingly inadequate. DTNs would facilitate the next generation of space missions.
IMAGE 1….A new look at developing a space based internet system.
IMAGE 2….ESA’s Aeolus satellite sending data to a ground station in Sweden (artist’s impression)
IMAGE 3….Different types of Delay Tolerant Networks
IMAGE 4….Sentinel-2 carries an innovative high-resolution multispectral imager with 13 spectral bands for a new perspective of our land and vegetation. Once its data are acquired, they are sent to the core Sentinel ground stations in Italy, Spain and Norway. For continual data delivery, the satellite is also equipped with a laser terminal to transmit data to satellites in geostationary orbit carrying the European Data Relay System (EDRS). These satellites then transmit the Sentinel-2 data to the ground. Complementing the Sentinel ground-station network, EDRS ensures the timely availability of large volumes of data. Sentinel-1 carries the same laser terminal. Copyright ESA/ATG medialab
IMAGE 5….Artist’s impression of Ops-Sat Ops-Sat will be a catalyst for change in space operations. Copyright ESA
TESTING EINSTEIN: UA STUDENT SIMULATES THOUSANDS OF BLACK HOLES
Lia Medeiros, a doctoral student at the University of Arizona, is developing mathematical models that will allow researchers to pit Einstein’s general theory of relativity against the most powerful monsters of nature: supermassive black holes such as Sgr A*, which lurks at the center of the Milky Way.
Medeiros has developed a diagnostic tool that astronomers can use to compare upcoming observations of supermassive black holes by the Event Horizon Telescope to the predictions of mathematical models of these maelstroms of space and time.
“We want to test whether black holes we observe in space behave the way we expect,” says Medeiros, who will present her dissertation research (comprising three published papers and a fourth to be submitted to the Astrophysical Journal) in an oral session at the 233rd meeting of the American Astronomical Society at the Washington State Convention Center in Seattle. “If we detect a deviation from our expectations we may fundamentally change the way we think about black holes and gravity itself.”
Astronomers believe that the shape of the shadow is a property of the geometry of space time and does not depend on the accretion or astrophysical effects. Medeiros uses computer simulations of the black hole shadow, a diagnostic feature predicted by general relativity, to test Kerr’s metric, a solution to Einstein’s equations that is believed to describe the characteristics of black holes in space. She simulated a large number of black hole shadows that deviate from Kerr and developed a method of using the upcoming Event Horizon Telescope observations of the black hole shadow to place constraints on these deviations.
“If black holes fit our expectations, the method I have developed will also allow us to quantify how far from these expectations a theory could be and still fit the data. This will hopefully allow us to rule out many other theories,” Medeiros says.
“I’m developing tools so we can actually use EHT observations to test whether Sgr A* is described by the Kerr metric,” she added.
Medeiros’ work is part of the Event Horizon Telescope, or EHT, an international collaboration attempting to directly image the supermassive black hole at the center of our galaxy for the first time.
To help scientists analyze and synchronize the torrential amounts of data generated by the EHT, the National Science Foundation has awarded $6 million over five years under a Partnerships for International Research and Education, or PIRE, grant, with partnering institutions around the world providing an additional $3 million. Headquartered at the UA, PIRE is a project to develop new technologies that enable scientists to store, transfer and make sense of unprecedented amounts of data, such as those generated by the globe-spanning telescope.
led zeppelin
Crack baby crack
