среда, 10 апреля 2019 г.

NASA Demos CubeSat Laser Communications Capability


NASA logo.


April 10, 2019



Animation above: A brief laser flash at the center of the frame was part of an experiment conducted by two NASA CubeSats. In it, one small satellite used a laser to send information to the ISARA CubeSat, managed by JPL. Image Credit: The Aerospace Corporation.


Two NASA CubeSats teamed up on an impromptu optical, or laser, communications pointing experiment. The laser beam is seen as a brief flash of light close to the center of the focal plane, to the left of Earth’s horizon.


The light originated from the laser communications system onboard one of two Optical Communications and Sensor Demonstration (OCSD) spacecraft. The laser flash was recorded by a short-wavelength infrared camera, one of three cameras comprising the CubeSat Multispectral Observation System (CUMULOS) payload, onboard the Integrated Solar Array and Reflectarray Antenna (ISARA) spacecraft. At the time of the demonstration, the OCSD and ISARA spacecraft were both 280 miles (451 kilometers) above Earth and about 1,500 miles (2,414 kilometers) apart.



Image above: An exploded schematic view of an AeroCube-OCSD CubeSat. Image Credit: The Aerospace Corporation.


The optical communications beam was deliberately aimed at and swept across the ISARA camera. This demonstration shows that an optical crosslink between two CubeSats is feasible with proper pointing and alignment of the emitting and receiving spacecraft. Optimizing this capability could enable constellations of small satellites to transfer high volume data between one another in low-Earth orbit or even in orbit around the Moon.


Characteristics built into the design and operation of small spacecraft enable impromptu experiments such as this optical crosslink test. Their flexibility and responsiveness provide mission operators the ability to take advantage of opportunities to perform additional maneuvers and procedures not previously envisioned for a particular mission. Originally designed to be Earth facing, both the ISARA camera and OCSD laser were tipped onto their “sides” to point at one another to accomplish this additional crosslink achievement, an operation much more difficult for larger spacecraft.



AeroCube-7B and Aerocube-7C. Image Credit: Aerospace Corporation

Other features in this image include a star (R Doradus, one of the brightest infrared stars in the sky) that can be seen moving diagonally down toward the right side of the frame as the satellites orbit Earth, and Earth’s horizon as it meets space. Other subtle stationary points of white are “hot pixels” or digital noise from the camera.


CUMULOS is an Aerospace Corporation experimental three camera remote sensing payload hosted on NASA’s ISARA small spacecraft mission, which was deployed to low-Earth orbit in December 2017. The ISARA mission is managed by NASA’s Jet Propulsion Laboratory in Pasadena, California. The OCSD spacecraft were developed and are operated by The Aerospace Corporation. The OCSD and ISARA missions are funded by NASA’s Small Spacecraft Technology (SST) program within the agency’s Space Technology Mission Directorate.


Related links:


Aerospace Corporation: https://aerospace.org/?utm_source=gophotonics


NASA CubeSats: https://www.nasa.gov/mission_pages/cubesats/index.html


Optical Communications and Sensor Demonstration (OCSD): https://www.nasa.gov/directorates/spacetech/small_spacecraft/ocsd_project.html


Integrated Solar Array and Reflectarray Antenna (ISARA): https://www.nasa.gov/directorates/spacetech/small_spacecraft/isara_project.html


For more information on NASA space technology, please visit: https://www.nasa.gov/directorates/spacetech/home/index.html


Images (mentioned), Animation (mentioned), Text, Credits: NASA/Clare Skelly/JPL/Arielle Samuelson.


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Astronomers Capture First Image of a Black Hole


ESO – European Southern Observatory logo.


10 April 2019


ESO, ALMA, and APEX contribute to paradigm-shifting observations of the gargantuan black hole at the heart of the galaxy Messier 87



First Image of a Black Hole

The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. Today, in coordinated press conferences across the globe, EHT researchers reveal that they have succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.



Messier 87 Captured by ESO’s Very Large Telescope

This breakthrough was announced today in a series of six papers published in a special issue of  The Astrophysical Journal Letters. The image reveals the black hole at the centre of Messier 87 [1], a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5 billion times that of the Sun [2].



Artist’s impression of the Black Hole at the heart of M87

The EHT links telescopes around the globe to form an unprecedented Earth-sized virtual telescope [3]. The EHT offers scientists a new way to study the most extreme objects in the Universe predicted by Einstein’s general relativity during the centenary year of the historic experiment that first confirmed the theory [4].



ALMA

“We have taken the first picture of a black hole,” said EHT project director Sheperd S. Doeleman of the Center for Astrophysics | Harvard & Smithsonian. “This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”



APEX

Black holes are extraordinary cosmic objects with enormous masses but extremely compact sizes. The presence of these objects affects their environment in extreme ways, warping spacetime and superheating any surrounding material.



Simulation of a Supermassive Black Hole

“If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow — something predicted by Einstein’s general relativity that we’ve never seen before,” explained chair of the EHT Science Council Heino Falcke of Radboud University, the Netherlands. “This shadow, caused by the gravitational bending and capture of light by the event horizon, reveals a lot about the nature of these fascinating objects and has allowed us to measure the enormous mass of M87’s black hole.”



Simulation of a Supermassive Black Hole

Multiple calibration and imaging methods have revealed a ring-like structure with a dark central region — the black hole’s shadow — that persisted over multiple independent EHT observations.



Anatomy of a Black Hole

“Once we were sure we had imaged the shadow, we could compare our observations to extensive computer models that include the physics of warped space, superheated matter and strong magnetic fields. Many of the features of the observed image match our theoretical understanding surprisingly well,” remarks Paul T.P. Ho, EHT Board member and Director of the East Asian Observatory [5]. “This makes us confident about the interpretation of our observations, including our estimation of the black hole’s mass.”



Simulated Image of an Accreting Black Hole

“The confrontation of theory with observations is always a dramatic moment for a theorist. It was a relief and a source of pride to realise that the observations matched our predictions so well,” elaborated EHT Board member Luciano Rezzolla of Goethe Universität, Germany.



The EHT, a Planet-Scale Array

Creating the EHT was a formidable challenge which required upgrading and connecting a worldwide network of eight pre-existing telescopes deployed at a variety of challenging high-altitude sites. These locations included volcanoes in Hawai`i and Mexico, mountains in Arizona and the Spanish Sierra Nevada, the Chilean Atacama Desert, and Antarctica.



Messier 87 in the Constellation of Virgo

The EHT observations use a technique called very-long-baseline interferometry (VLBI) which synchronises telescope facilities around the world and exploits the rotation of our planet to form one huge, Earth-size telescope observing at a wavelength of 1.3mm. VLBI allows the EHT to achieve an angular resolution of 20 micro-arcseconds — enough to read a newspaper in New York from a café in Paris [6].



The Halo of Galaxy Messier 87

The telescopes contributing to this result were ALMA, APEX, the IRAM 30-meter telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope [7]. Petabytes of raw data from the telescopes were combined by highly specialised supercomputers hosted by the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory.



Artist’s Impression of a Black Hole Environment

European facilities and funding played a crucial role in this worldwide effort, with the participation of advanced European telescopes and the support from the European Research Council — particularly a €14 million grant for the BlackHoleCam project [8]. Support from ESO, IRAM and the Max Planck Society was also key. “This result builds on decades of European expertise in millimetre astronomy”, commented Karl Schuster, Director of IRAM and member of the EHT Board.



Photon Paths around a Black Hole

The construction of the EHT and the observations announced today represent the culmination of decades of observational, technical, and theoretical work. This example of global teamwork required close collaboration by researchers from around the world. Thirteen partner institutions worked together to create the EHT, using both pre-existing infrastructure and support from a variety of agencies. Key funding was provided by the US National Science Foundation (NSF), the EU’s European Research Council (ERC), and funding agencies in East Asia.



Key Concepts in Interferometry

“ESO is delighted to have significantly contributed to this result through its European leadership and pivotal role in two of the EHT’s component telescopes, located in Chile — ALMA and APEX,” commented ESO Director General Xavier Barcons. “ALMA is the most sensitive facility in the EHT, and its 66 high-precision antennas were critical in making the EHT a success.”



Locations of the EHT Telescopes

“We have achieved something presumed to be impossible just a generation ago,” concluded Doeleman. “Breakthroughs in technology, connections between the world’s best radio observatories, and innovative algorithms all came together to open an entirely new window on black holes and the event horizon.”



Zooming in to the Heart of Messier 87



Artist’s impression of the Black Hole at the heart of M87

Notes:


[1] The shadow of a black hole is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole’s boundary — the event horizon from which the EHT takes its name — is around 2.5 times smaller than the shadow it casts and measures just under 40 billion km across.


[2] Supermassive black holes are relatively tiny astronomical objects — which has made them impossible to directly observe until now. As the size of a black hole’s event horizon is proportional to its mass, the more massive a black hole, the larger the shadow. Thanks to its enormous mass and relative proximity, M87’s black hole was predicted to be one of the largest viewable from Earth — making it a perfect target for the EHT.


[3] Although the telescopes are not physically connected, they are able to synchronize their recorded data with atomic clocks — hydrogen masers — which precisely time their observations. These observations were collected at a wavelength of 1.3 mm during a 2017 global campaign. Each telescope of the EHT produced enormous amounts of data – roughly 350 terabytes per day – which was stored on high-performance helium-filled hard drives. These data were flown to highly specialised supercomputers — known as correlators — at the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory to be combined. They were then painstakingly converted into an image using novel computational tools developed by the collaboration.


[4] 100 years ago, two expeditions set out for Principe Island off the coast of Africa and Sobral in Brazil to observe the 1919 solar eclipse, with the goal of testing general relativity by seeing if starlight would be bent around the limb of the sun, as predicted by Einstein. In an echo of those observations, the EHT has sent team members to some of the world’s highest and most isolated radio facilities to once again test our understanding of gravity.


[5] The East Asian Observatory (EAO) partner on the EHT project represents the participation of many regions in Asia, including China, Japan, Korea, Taiwan, Vietnam, Thailand, Malaysia, India and Indonesia.


[6] Future EHT observations will see substantially increased sensitivity with the participation of the IRAM NOEMA Observatory, the Greenland Telescope and the Kitt Peak Telescope.


[7] ALMA is a partnership of the European Southern Observatory (ESO; Europe, representing its member states), the U.S. National Science Foundation (NSF), and the National Institutes of Natural Sciences(NINS) of Japan, together with the National Research Council (Canada), the Ministry of Science and Technology (MOST; Taiwan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA; Taiwan), and Korea Astronomy and Space Science Institute (KASI; Republic of Korea), in cooperation with the Republic of Chile. APEX is operated by ESO, the 30-meter telescope is operated by IRAM (the IRAM Partner Organizations are MPG (Germany), CNRS (France) and IGN (Spain)), the James Clerk Maxwell Telescope is operated by the EAO, the Large Millimeter Telescope Alfonso Serrano is operated by INAOE and UMass, the Submillimeter Array is operated by SAO and ASIAA and the Submillimeter Telescope is operated by the Arizona Radio Observatory (ARO). The South Pole Telescope is operated by the University of Chicago with specialized EHT instrumentation provided by the University of Arizona.


[8] BlackHoleCam is an EU-funded project to image, measure and understand astrophysical black holes. The main goal of BlackHoleCam and the Event Horizon Telescope (EHT) is to make the first ever images of the billion solar masses black hole in the nearby galaxy M87 and of its smaller cousin, Sagittarius A*, the supermassive black hole at the centre of our Milky Way. This allows the determination of the deformation of spacetime caused by a black hole with extreme precision.


More information:


This research was presented in a series of six papers published today in a special issue of The Astrophysical Journal Letters.


The EHT collaboration involves more than 200 researchers from Africa, Asia, Europe, North and South America. The international collaboration is working to capture the most detailed black hole images ever by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.


The individual telescopes involved are; ALMA, APEX, the IRAM 30-meter Telescope, the IRAM NOEMA Observatory, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope (LMT), the Submillimeter Array (SMA), the Submillimeter Telescope (SMT), the South Pole Telescope (SPT), the Kitt Peak Telescope, and the Greenland Telescope (GLT).


The EHT consortium consists of 13 stakeholder institutes; the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory. 


ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.


Links:


ESO EHT web page: https://www.eso.org/public/science/event-horizon/


Invitation for media to the press conference: https://www.eso.org/public/announcements/ann19018/


EHT Website & Press Release: https://eventhorizontelescope.org/


ESOBlog on the EHT Project: https://www.eso.org/public/blog/photographing-a-black-hole/


Images of ALMA: https://www.eso.org/public/images/archive/category/alma/


Images of APEX: https://www.eso.org/public/images/archive/category/apex/


EHT comic by NAOJ (PDF format, 39,1 MB): https://www.eso.org/public/archives/releases/pdf/eso1907a.pdf


Papers:


Paper I: The Shadow of the Supermassive Black Hole:
https://doi.org/110.3847/2041-8213/ab0ec7


Paper II: Array and Instrumentation:
https://doi.org/110.3847/2041-8213/ab0c96


Paper III: Data processing and Calibration:
https://doi.org/110.3847/2041-8213/ab0c57


Paper IV: Imaging the Central Supermassive Black Hole:
http://doi.org/10.3847/2041-8213/ab0e85


Paper V: Physical Origin of the Asymmetric Ring:
https://doi.org/10.3847/2041-8213/ab0f43


Paper VI: The Shadow and Mass of the Central Black Hole:
https://doi.org/10.3847/2041-8213/ab1141


Images, Text, Credits: ESO/Calum Turner/L. Calçada/M. Kornmesser/Jordy Davelaar et al./Radboud University/BlackHoleCam/Bronzwaer/Davelaar/Moscibrodzka/Falcke/Radboud University/ IAU and Sky & Telescope/Chris Mihos (Case Western Reserve University)/ESO/Nicolle R. Fuller/NSF/NRAO/AUI/NSF; S. Dagnello/EHT/Eduardo Ros/Luciano Rezzolla/Heino Falcke/Videos: ESO/L. Calçada, Digitized Sky Survey 2, ESA/Hubble, RadioAstron, De Gasperin et al., Kim et al., EHT Collaboration. Music: Niklas Falcke/ESO/M. Kornmesser.


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historyarchaeologyartefacts: The Throne Room at the heart of…


historyarchaeologyartefacts:



The Throne Room at the heart of the Bronze Age palace of Knossos, considered the oldest throne room in Europe. Crete, 15th century BC [1125×750]



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historyarchaeologyartefacts: Roman sculpture of Isis made with…


historyarchaeologyartefacts:



Roman sculpture of Isis made with black and white marble, 2nd century A.D., Wien Museum [1384×2962]



Source


historyarchaeologyartefacts: The Twelve Angle Stone, one of the…


historyarchaeologyartefacts:



The Twelve Angle Stone, one of the finest examples of Inca masonry. [1600×1082]



Source


Gazed Pottery Where our eyes linger says a lot about the…


Gazed Pottery


Where our eyes linger says a lot about the modern world, from a wandering gaze taking in a city skyline to repetitive back and forth glances at a smartphone. Just as society has evolved, how we investigate new objects – where we place our selective attention – has changed too. Here eye-tracking computers followed the gazes of 113 volunteers exploring pottery from different periods in history (three examples shown here) – 4000-3000 BCE on the left, through to 100 BCE on the right. As styles and shapes changed, so do the eyes’ attention patterns, lingering in warm colours in horizontal lines (lower left) but scanning later objects more vertically. Investigating the links between changing cultures and our attention, neuroarchaeology may have much to teach us about how we interact with the world today based on how we’ve changed for thousands of years, and even suggest ways to help those help those who process information differently as in, for example, autism and dementia.


Written by John Ankers



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‘Mare and Foal’ Standing Stones, Hadrian’s Wall, Haltwhistle,...





‘Mare and Foal’ Standing Stones, Hadrian’s Wall, Haltwhistle, Northumberland.


Source link


2019 April 10 Martian Moon Phobos Crosses the Sun Video Credit:…


2019 April 10


Martian Moon Phobos Crosses the Sun
Video Credit: NASA, JPL-Caltech, MSSS, Curiosity Rover


Explanation: What’s that passing in front of the Sun? It looks like a moon, but it can’t be Earth’s Moon, because it isn’t round. It’s the Martian moon Phobos. The featured video was taken from the surface of Mars late last month by the Curiosity rover. Phobos, at 11.5 kilometers across, is 150 times smaller than Luna (our moon) in diameter, but also 50 times closer to its parent planet. In fact, Phobos is so close to Mars that it is expected to break up and crash into Mars within the next 50 million years. In the near term, the low orbit of Phobos results in more rapid solar eclipses than seen from Earth. The featured video has been sped up – the actual transit took about 35 seconds. A similar video was taken of Mars’ smaller and most distant moon Diemos transiting the Sun. The videographer – the robotic rover Curiosity – continues to explore Gale crater, most recently an area with stunning vistas and unusual rocks dubbed Glen Torridon.


∞ Source: apod.nasa.gov/apod/ap190410.html


historyarchaeologyartefacts: “The Shaft of the Dead Man” cave…


historyarchaeologyartefacts:



“The Shaft of the Dead Man” cave painting in Lascaux cave, France. Featuring a disemboweled bison and a man with a bird-shaped head having an erection. 17,000 years old. [1522 x 1191]



Source


religions-of-the-world:Seals of the goddess Inanna


religions-of-the-world:



Seals of the goddess Inanna



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via-appia: Mosaic from the impluvium of the House of Gometric…


via-appia:



Mosaic from the impluvium of the House of Gometric Mosaics, Pompeii


Roman, 1st century AD



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Burials of Africans slaves found at old rubbish dump in Portugal

In a bid to discover more about the slave trade, archaeologists are still working day in and out on several projects. Most recently, archaeologists discovered more than 150 skeletons of enslaved Africans at the site of an old rubbish dump in Portugal.











Burials of Africans slaves found at old rubbish dump in Portugal
Remains of an African slave found in Lagos, Portugal
[Credit: Dryas Arqueologia LDA]

The skeletons were found at the site of Valle da Gafaria, located outside the Medieval walls of the port city of Lagos along the southwest coast of Portugal. The archaeologists found several of them tied or in positions that suggest they were not buried in the conventional style.
According to the research conducted by the archaeologists, the rubbish dump was used as a burial site between the 15th and 17th century when slavery was very rampant in Portugal.











Burials of Africans slaves found at old rubbish dump in Portugal
Adult female from Valle da Gafaria whose positioning suggests she may have been tied up for burial
[Credit: M.T. Santos Ferreira via Forbes]

Confirmation of their ancestry was revealed through genetic analysis of the bones and dental formation that suggested the people were from southern Africa specifically of Bantu origin.
Aside from the bones found, remains of imported ceramics, butchered animal bones, and a few African style ornaments were also found.











Burials of Africans slaves found at old rubbish dump in Portugal
Santos Ferreira, with one of the human remains of Lagos
[Credit: Dryas Arqueologia LDA]

The latest discovery brings to mind that slavery was just as rampant in Europe at the time as it was in the Americas despite much spotlight given to the latter.
Research conducted by Maria Teresa Ferreira, Catarina Coelho, and Sofia Wasterlain of the University of Coimbra and published in the International Journal of Osteoarchaeology probed further into why the enslaved Africans were buried in a rubbish dump instead of a rather fitting cemetery.











Burials of Africans slaves found at old rubbish dump in Portugal
The excavation site [Credit: Dryas Arqueologia LDA]

The site is one of the few designated burial grounds for enslaved Africans and it’s the oldest sample to be discovered and studied in the world.


Author: Elisabeth Ofosuah Johnson | Source: Face2Face Africa [April 05, 2019]



TANN



Archive


Air temperatures in the Arctic are driving system change

A new paper shows that air temperature is the “smoking gun” behind climate change in the Arctic, according to John Walsh, chief scientist for the UAF International Arctic Research Center.











Air temperatures in the Arctic are driving system change
Peaks of the southern Brooks Range along a stretch of the Dalton Highway, about 250 miles north of Fairbanks
[Credit: Todd Paris/UAF]

“The Arctic system is trending away from its 20th century state and into an unprecedented state, with implications not only within but beyond the Arctic,” according to lead author Jason Box of the Geological Survey of Denmark and Greenland in Copenhagen.


Several University of Alaska Fairbanks researchers are co-authors on the paper, which says that “increasing air temperatures and precipitation are drivers of major changes in various components of the Arctic system.”


The study is the first to combine observations of physical climate indicators, such as snow cover, with biological impacts, such as a mismatch in the timing of flowers blooming and pollinators working.


Climate indicators are key pieces of information that capture the essence of a system, according to Walsh. An example would be September sea ice extent, which summarizes the effects of things like temperature, winds, ocean heat and other variables.











Air temperatures in the Arctic are driving system change
The Yukon River winds through western interior Alaska in early April
[Credit: Todd Paris/UAF]

“I didn’t expect the tie-in with temperature to be as strong as it was,” Walsh said. “All the variables are connected with temperature. All components of the Arctic system are involved in this change.”


“Never have so many Arctic indicators been brought together in a single paper,” he said.


The authors correlated records of observations from 1971 to 2017 of nine key indicators: air temperature, permafrost, hydroclimatology, snow cover, sea ice, land ice, wildfires, tundra and terrestrial ecosystems, and carbon cycling. All the indicators correlate with rising temperatures, pointing to a warming climate and a fundamental change in the Arctic.


“The Arctic system is trending away from its 20th century state and into an unprecedented state, with implications not only within but beyond the Arctic,” according to lead author Jason Box of the Geological Survey of Denmark and Greenland in Copenhagen.



“Because the Arctic atmosphere is warming faster than the rest of the world, weather patterns across Europe, North America and Asia are becoming more persistent, leading to extreme weather conditions. Another example is the disruption of the ocean circulation that can further destabilize climate: for example, cooling across northwestern Europe and strengthening of storms,” said Box.
The paper is the flagship piece in a special issue on Arctic climate change indicators published by the journal Environmental Research Letters. IARC’s Igor Polyakov is lead editor for this special issue, which has other papers co-authored by UAF scientists. In addition to Walsh, the authors include the Geophysical Institute’s Uma Bhatt and Vladimir Romanovsky, and Eugénie Euskirchen of the Institute of Arctic Biology, along with many international colleagues.


The authors of the study hope that these indicator-based observations provide a foundation for a more integrated understanding of the Arctic and its role in the dynamics of the Earth’s biogeophysical systems.


Source: University of Alaska Fairbanks [April 07, 2019]



TANN



Archive


Revolutionary camera allows scientists to predict evolution of ancient stars

For the first time scientists have been able to prove a decades old theory on stars thanks to a revolutionary high-speed camera.











Revolutionary camera allows scientists to predict evolution of ancient stars
First light with HiPERCAM – the spiral galaxy NGC 4800, which lies at a distance of 80 million light years
[Credit: University of Sheffield]

Scientists at the University of Sheffield have been working with HiPERCAM, a high-speed, multicolour camera, which is capable of taking more than 1,000 images per second, allowing experts to measure both the mass and the radius of a cool subdwarf star for the first time.


The findings published in Nature Astronomy have allowed researchers to verify the commonly used stellar structure model – which describes the internal structure of a star in detail – and make detailed predictions about the brightness, the colour and its future evolution.


Scientists know that old stars have fewer metals than young stars, but the effects of this on the structure of stars was, until now, untested. Old stars (often referred to as cool subdwarf stars) are faint and there are few in the solar neighbourhood.


Up until now scientists have not had a camera powerful enough to be able to get precise measurements of their stellar parameters such as the mass and the radius.


HiPERCAM can take one picture every millisecond as opposed to a normal camera on a large telescope which usually captures only one picture every few minutes. This has given scientists the ability to measure the star accurately for the first time.











Revolutionary camera allows scientists to predict evolution of ancient stars
Artist’s impression of a binary star [Credit: Mark Garlick]

Professor Vik Dhillon, Dr Steven Parsons and Dr Stuart Littlefair, from the Department of Physics and Astronomy at the University of Sheffield, led the HiPERCAM project in partnership with the Science and Technology Facilities Council’s Astronomy Technology Centre (ATC) and the Instituto de Astrofisica de Canarias, along with researchers from the University of Warwick and Durham University.


Professor Dhillon said: “Now we have been able to measure the size of the star we can see it is in line with stellar structure theory. These results would not have been possible with any other telescope.


“This not only proves stellar structure theory, but has also verified the potential of HiPERCAM.”


The paper is the first to be published using HiPERCAM data, which is mounted on the Gran Telescopio Canarias (GTC) – the world’s largest optical telescope, with a 10.4 metre mirror diameter.


The camera can take high-speed images of objects in the universe, allowing their rapid brightness variations – due to phenomena such as eclipses and explosions – to be studied in unprecedented detail.


Data captured by the camera, taken in five different colours simultaneously, allow scientists to study the remnants of dead stars such as white dwarfs, neutron stars and black holes.


The GTC is based on the island of La Palma, situated 2,500 metres above sea level, which is one of the best places in the world to study the night sky.


Source: University of Sheffield [April 08, 2019]




TANN



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Physicists examine the antimatter puzzle

Why does the observable universe contain virtually no antimatter? Particles of antimatter have the same mass but opposite electrical charge of their matter counterparts. Very small amounts of antimatter can be created in the laboratory. However, hardly any antimatter is observed elsewhere in the universe.











Physicists examine the antimatter puzzle
Physicists theorize that a time-reversal violation is the key ingredient needed to unravel the cosmic mystery of missing
antimatter. Such time-reversal violating forces result in a property in particles called a permanent electric dipole
moment (EDM). The pear-shaped nucleus radium-225 (shown above) amplifies the observable EDM and improves
the sensitivity of EDM searches [Credit: Jaideep Taggart Singh, Facility for Rare Isotope Beams]

Physicists believe that there were equal amounts of matter and antimatter in the early history of the universe – so how did the antimatter vanish? A Michigan State University researcher is part of a team of researchers that examines these questions in an article recently published in Reviews of Modern Physics.


Jaideep Taggart Singh, MSU assistant professor of physics at the Facility for Rare Isotope Beams, or FRIB, studies atoms and molecules embedded in solids using lasers. Singh has a joint appointment in the MSU’s Department of Physics and Astronomy.


The answer could be rooted in the nature of forces between subatomic particles that are not the same when time is reversed. Physicists theorize that this time-reversal violation is the key ingredient needed to unravel the cosmic mystery of the missing antimatter. Such time-reversal violating forces result in a property in particles called a permanent electric dipole moment (EDM). For over 60 years, physicists have searched for EDMs with increasing precision, but they have never observed them. However, recent theories of particle physics predict measurable EDMs. This has led to a worldwide search for EDMs in systems such as neutrons, molecules, and atoms.


EDM searches often involve atomic clocks operating in a controlled magnetic field (uniform in space and stable in time). In an electric field, an ultra-stable atomic clock with a nonzero EDM will run slightly faster or slower. The success of such experiments depends on how well physicists can control the surrounding magnetic field and other environmental factors.











Physicists examine the antimatter puzzle
Jaideep Singh, assistant professor in MSU’s Facility for Rare Isotope Beams, works with a magnetic shield
in his lab [Credit: G.L. Kohuth/Michigan State University]

EDMs of atoms such as radium and mercury are primarily due to forces originating within the nuclear medium. The best limits on these types of forces are presently derived from the mercury-199 atom. Researchers at the University of Washington, Seattle, have found that their mercury-199 clock loses less than one second every 400 centuries. This experiment is impossible to improve upon unless one can build a clock less sensitive to environmental factors. A competing experiment that seeks to do just that is the search for the EDM of radium-225. It is a collaboration between Argonne National Laboratory, Michigan State University, and the University of Science and Technology of China.


The rare isotope radium-225 is an attractive alternative. Its “pear-shaped” nucleus (see figure) amplifies the observable EDM by orders of magnitude compared to the nearly spherical nucleus of mercury-199. In order to perform a competitive experiment, a radium-225 clock only needs to be stable to less than one second every two years. This is difficult but feasible. The sensitivity of this radium clock is currently limited only by the small number of atoms available (about 0.000005 milligrams per day). In the future, using an even more “pear-shaped” nuclei, such as the rare isotope protactinium-229, may improve the sensitivity of these EDM searches by another factor of a thousand. In other words, a competitive experiment with a protactinium clock would only need to be stable to less than one second every day.


“We, everything we see, and the rest of the observable universe exists because the antimatter vanished during birth of the universe,” Singh said. “Discovering a new source of time-reversal violation, perhaps using rare pear-shaped nuclei, would begin to explain how this happened.”


FRIB will produce an abundance of pear-shaped nuclei such as radium-225 and, for the first time, protactinium-229. This will enable a search for an EDM with unprecedented sensitivity to answer the antimatter puzzle.


MSU is establishing FRIB as a new scientific user facility for the Office of Nuclear Physics in the U.S. Department of Energy Office of Science. Under construction on campus and operated by MSU, FRIB will enable scientists to make discoveries about the properties of rare isotopes in order to better understand the physics of nuclei, nuclear astrophysics, fundamental interactions, and applications for society, including in medicine, homeland security, and industry.


Authors: Jaideep Singh & Karen King | Source: Michigan State University [April 08, 2019]



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Iron volcanoes may have erupted on metal asteroids

Metallic asteroids are thought to have started out as blobs of molten iron floating in space. As if that’s not strange enough, scientists now think that as the metal cooled and solidified, volcanoes spewing liquid iron could have erupted through a solid iron crust onto the surface of the asteroid.











Iron volcanoes may have erupted on metal asteroids
As a metallic asteroid such as Psyche cooled and solidified, iron volcanoes
may have erupted onto its surface [Credit: Elena Hartley]

This scenario emerged from an analysis by planetary scientists at UC Santa Cruz whose investigation was prompted in part by NASA’s plans to launch a probe to Psyche, the largest metallic asteroid in the solar system. Francis Nimmo, professor of Earth and planetary sciences, said he was interested in the composition of metallic asteroids indicated by analyses of iron meteorites, so he had graduate student Jacob Abrahams work on some simple models of how the asteroids cooled and solidified.


“One day he turned to me and said, ‘I think these things are going to erupt,'” Nimmo said. “I’d never thought about it before, but it makes sense because you have a buoyant liquid beneath a dense crust, so the liquid wants to come up to the top.”


The researchers described their findings in a paper that has been accepted for publication in Geophysical Research Letters and is available online.


Metallic asteroids originated early in the history of the solar system when planets were beginning to form. A protoplanet or “planetesimal” involved in a catastrophic collision could be stripped of its rocky outer layers, exposing a molten, iron-rich core. In the cold of space, this blob of liquid metal would quickly begin to cool and solidify.


“In some cases it would crystallize from the center out and wouldn’t have volcanism, but some would crystallize from the top down, so you’d get a solid sheet of metal on the surface with liquid metal underneath,” Nimmo said.


As for what the iron volcanoes would look like, Abrahams said it depends on the composition of the melt. “If it’s mostly pure iron, then you would have eruptions of low-viscosity surface flows spreading out in thin sheets, so nothing like the thick, viscous lava flows you see on Hawaii,” he said. “At the other extreme, if there are light elements mixed in and gases that expand rapidly, you could have explosive volcanism that might leave pits in the surface.”


NASA’s Psyche mission is scheduled to launch in 2022 and reach the asteroid in 2026. Signs of past volcanism that researchers could look for include variations in the color or composition of material on the surface, and possibly features that look like volcanic vents. Large volcanic cones are probably unlikely, Abrahams said.


Unfortunately, because metallic asteroids would have solidified fairly quickly after their formation, there has been plenty of time (billions of years) for any surface features of volcanism to be degraded. “It’s not clear what they might look like now,” Abrahams said.


The best opportunity to find evidence of ferrovolcanism on metallic asteroids might actually come from studying iron meteorites already in collections on Earth, the researchers said.


“There are lots of these metallic meteorites, and now that we know what we’re looking for, we might find evidence of volcanism in them,” Nimmo said. “If material got erupted onto the surface, it would cool very fast, which would be reflected in the composition of the meteorite. And it might have holes in it left by escaping gas.”


When they presented their findings at a recent Lunar and Planetary Science Conference, Abrahams and Nimmo discovered that another research team had independently arrived at similar conclusions about the possibility of ferrovolcanism.


“It’s not a shocking idea, but we’d just never thought about iron volcanism before, so it’s something new and interesting to investigate,” Abrahams said.


Author: Tim Stephens | Source: University of California – Santa Cruz [April 08, 2019]




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Moel Ty Uchaf Prehistoric Stone Circle, Llandrillo, Wales, 9.4.19.

Moel Ty Uchaf Prehistoric Stone Circle, Llandrillo, Wales, 9.4.19.



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