вторник, 23 апреля 2019 г.

Omega Centauri’s lost stars



The Milky Way, as seen by the Gaia satellite. Streams of co-moving stars are shown colored according to their motions as measured by Gaia. The “Fimbulthul” stream which is due to stars lost from the omega Centauri globular cluster (white box) has been highlighted. Credit R. Ibata. Hi-res image



A team of researchers from the Strasbourg Astronomical Observatory, Bologna Observatory and the University of Stockholm has identified a stream of stars that was torn off the globular cluster Omega Centauri. Searching through the 1.7 billion stars observed by the ESA Gaia mission, they have identified 309 stars that suggest that this globular cluster may actually be the remnant of a dwarf galaxy that is being torn apart by the gravitational forces of our Galaxy.


In 1677, Edmond Halley gave the name “Omega Centauri” (ω Cen) to what he thought was a star in the Centaurus constellation. Later in 1830 John Herschel realized that it was in fact a globular cluster that could be resolved into individual stars. We now know that Omega Centauri is the most massive globular cluster in the Milky Way: it is about 18,000 light years from us and contains several million stars that are about 12 billion years old. The nature of this object has been the subject of much debate: is it really a globular cluster, or could it be the heart of a dwarf galaxy whose periphery has been dispersed by the Milky Way?


This last hypothesis is based on the fact that ω Cen contains several stellar populations, with a large range of metallicities (i.e. heavy element content) that betray a formation over an extended period of time. An additional argument in favor of this hypothesis would be to find debris from the cluster scattered along its orbit in the Milky Way. Indeed, when a dwarf galaxy interacts with a massive galaxy like our own, stars are torn off by gravitational tidal forces, and these stars remain visible for a time as stellar streams, before becoming dispersed in the vast volumes of interstellar space surrounding the massive galaxy.


By analyzing the motions of stars measured by the Gaia satellite with an algorithm called STREAMFINDER developed by the team, the researchers identified several star streams. One of them, named “Fimbulthul” (after one of the rivers in Norse mythology that existed at the beginning of the world), contains 309 stars stretching over 18° in the sky. By modeling the trajectories of the stars, the team showed that the Fimbulthul structure is a stellar tidal stream torn off ω Cen, extending up to 28° from the cluster. Spectroscopic observations of 5 stars of this stream with the Canada-France Hawaii Telescope show that their velocities are very similar, and that they have metallicities comparable to the stars of ω Cen itself, which reinforces the idea that the tidal stream is linked to ω Cen.


“The stars that the team observed were quite faint for the instrument we were using,” says Dr. Nadine Manset, instrument scientist for Espadons and CFHT’s astronomy group manager. “It is great to see such challenging observations reinforce the Fimbulthul structure’s link to ω Cen.”


The researchers were then able to show that the stream is also present in the very crowded area of sky in the immediate vicinity of the cluster. Further modeling of the tidal stream will constrain the dynamical history of the dwarf galaxy that was the progenitor of ω Cen, and allow us to find even more stars lost by this system into the halo of the Milky Way.

The team’s paper appeared in the April 22nd edition of Nature.



Additional information:

Nature paper (Subscription required.)
arXiv preprint (no login required)




Contact Information:

 

Media contact:

Mary Beth Laychak, Outreach manager
Canada-France-Hawaii Telescope
 

laychak@cfht.hawaii.edu

Science contacts:  


Rodrigo Ibata, +33 3 68 85 23 91
Michele Bellazzini, +39 051 635 73 26 
Khyati Malhan, +46 72 085 22 05 
Nicolas Martin, +33 3 68 85 24 67 
Paolo Bianchini, +33 3 68 85 24 02





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New Life Science Begins; Next Dragon Cargo Mission Due This Week


ISS — Expedition 59 Mission patch.


April 22, 2019


The Expedition 59 crew has been unpacking Northrop Grumman’s Cygnus cargo craft over the weekend and began science operations on the newly delivered space research. The 17th SpaceX Dragon mission is now due to launch next week to replenish the International Space Station.


Three NASA astronauts and one Canadian Space Agency astronaut split the workday measuring the mass of 40 mice shipped to the station aboard Cygnus last week. Flight Engineers Anne McClain and Christina Koch started the first half of the day with Flight Engineers Nick Hague and David Saint-Jacques wrapping up the rodent research work in the afternoon. The quartet used the mass measurement device inside the Life Sciences Glovebox beginning the study to learn how microgravity impacts the immune system.



Image above: The Canadarm2 robotic arm is positioned to grapple the Northrop Grumman Cygnus cargo craft as it approaches its capture point with the International Space Station orbiting 255 miles above the Atlantic Ocean. Highlighting the foreground is the Soyuz MS-12 crew ship docked to the Rassvet module. Image Credit: NASA.


The SpaceX Dragon cargo craft is due to join the five other spacecraft parked at the station after it launches from Florida April 30. Dragon is scheduled to arrive May 2 and Saint-Jacques will command the Canadarm2 robotic arm to reach out and capture the cargo vessel. Dragon will deliver over 5,000 pounds of new science, supplies and hardware to the orbital lab.



International Space Station (ISS). Animation Credit: NASA

Cosmonauts Oleg Kononenko and Alexey Ovchinin stayed focused on the Russian side of the station with their complement of orbital science and lab maintenance. Commander Kononenko updated communications gear, cleaned fans and filters and explored enzyme behaviors. Flight Engineer Ovchinin offloaded cargo from the new Progress 72 resupply ship and studied radiation exposure.


Related links:


Expedition 59: https://www.nasa.gov/mission_pages/station/expeditions/expedition59/index.html


Northrop Grumman’s Cygnus: https://www.nasa.gov/northropgrumman


Rodent research: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7868


Mass measurement device: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=7343


Life Sciences Glovebox: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=7676


SpaceX Dragon: https://www.nasa.gov/spacex


Canadarm2: https://www.nasa.gov/mission_pages/station/structure/elements/mobile-servicing-system.html


Enzyme behaviors: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1324


Progress 72: https://go.nasa.gov/2IaDAKd


Radiation exposure: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1367


Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html


International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html


Image (mentioned), Animation (mentioned), Text, Credits: NASA/Mark Garcia.


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Human Research, Materials Science and Robotics on Tuesday’s Schedule


ISS — Expedition 59 Mission patch.


April 23, 2019


The Expedition 59 crew spent the majority of Tuesday conducting space experiments and setting up research hardware. The International Space Station residents are also continuing to unpack a pair of recently arrived cargo ships while training for the next U.S. cargo mission.


The weightless conditions of microgravity pull fluids towards an astronaut’s head causing a common space phenomenon sometimes called “puffy-face.” Flight Engineer Nick Hague of NASA spent the morning collecting and stowing his blood, urine and saliva samples for the long-running Fluid Shifts study. The research observes and seeks to reverse the upward flow of fluids causing increased head and eye pressure that concerns flight surgeons.



Image above: The moon is photographed in its waning gibbous phase just above the Earth’s limb as the International Space Station orbited 258 miles above the North Atlantic Ocean just off the Canadian-American coast. Image Credit: NASA.


NASA astronaut Christina Koch set up hardware in the Destiny lab module to begin researching the feasibility of manufacturing fiber optic cable in space. The Space Fibers study takes place inside the Microgravity Science Glovebox and will explore a blend of materials more transparent than silica-based glass.


A new materials exposure experiment is ready for deployment outside Japan’s Kibo lab module. NASA astronaut Anne McClain installed the MISSE-FF gear inside Kibo’s airlock before depressurizing the unit. Robotics controllers will deploy the exposed sample trays outside the airlock. The study will help scientists understand how radiation, the vacuum of space and micrometeoroids affect a variety of materials.



International Space Station (ISS). Image Credit: NASA

Canadian Space Agency astronaut David Saint-Jacques is training for his role to capture the next SpaceX Dragon cargo craft. Hague joined him today for the robotics training and will back him up in the cupola. Dragon is scheduled to launch April 30 from Florida and take a two-day trip to the station where it will be grappled with the Canadarm2 robotic arm and installed to the Harmony module.


Commander Oleg Kononenko helped attach sensors to Flight Engineer Alexey Ovchinin as the duo researched cardiovascular activity during exercise in space. Kononenko went on to replace smoke detectors as Ovchinin worked on life support maintenance.


Related links:


Expedition 59: https://www.nasa.gov/mission_pages/station/expeditions/expedition59/index.html


Fluid Shifts: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1126


Destiny lab module: https://www.nasa.gov/mission_pages/station/structure/elements/us-destiny-laboratory


Space Fibers: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7375


Microgravity Science Glovebox: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=341


Kibo lab module: https://www.nasa.gov/mission_pages/station/structure/elements/japan-kibo-laboratory


MISSE-FF: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=7515


SpaceX Dragon: https://www.nasa.gov/spacex


Canadarm2: https://www.nasa.gov/mission_pages/station/structure/elements/mobile-servicing-system.html


Harmony module: https://www.nasa.gov/mission_pages/station/structure/elements/harmony


Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html


International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html


Images (mentioned), Text, Credits: NASA/Mark Garcia.


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Sweat Sensors Aedes aegypti mosquitoes, which can transmit…


Sweat Sensors


Aedes aegypti mosquitoes, which can transmit diseases such as Zika, are especially attracted to humans, and this could be because of the unique smell of our sweat. Compared to other vertebrates, human sweat contains more lactic acid, potentially a useful clue for mosquitoes seeking a good meal. Based on previous work in flies, researchers hypothesised that mosquitoes would detect lactic acid using a specific type of olfactory [smell] receptor in their antennae. To test this, they disrupted the gene encoding one of these receptors, Ir8a, adding a fluorescent gene so that transformed mosquitoes could be identified by a red glow (pictured, left). Those mosquitoes couldn’t detect lactic acid and were less keen to land on human skin than untreated mosquitoes (right), suggesting both that Ir8a is indeed required for them to sense lactic acid, and that this is a key component of their attraction to us.


Written by Emmanuelle Briolat



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Tourmaline on Cleavelandite | #Geology #GeologyPage…


Tourmaline on Cleavelandite | #Geology #GeologyPage #Mineral


Locality: Paprok, Nuristan Province, Afghanistan


Size: 13.8 x 10.6 x 10.3 cm


Photo Copyright © Saphira Minerals


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2019 April 23 Meteors, Comet, and Big Dipper over La Palma…


2019 April 23


Meteors, Comet, and Big Dipper over La Palma
Image Credit & Copyright: Vincent Duparc


Explanation: Meteor showers are caused by streams of solid particles, dust size and larger, moving as a group through space. In most cases, the orbits of these meteor streams can be identified with dust expelled from a comet. When the Earth passes through a stream, the particles leave brilliant trails through the night sky as they disintegrate in Earth’s atmosphere. The meteor paths are all parallel to each other, but, like train tracks, the effect of perspective causes them to appear to originate from a radiant point in the distance. The featured image composite was taken during January’s Quadrantid meteor shower from La Palma, one of Spain’s Canary Islands, off the northwest coast of Africa. The Quadrantids radiant is visible just below the handle of the Big Dipper. A careful eye will also discern the faint green coma of Comet Wirtanen. Tonight is the peak of the modest Lyrid meteor shower, with several meteors per hour visible from dark locations with clear skies.


∞ Source: apod.nasa.gov/apod/ap190423.html


Sunstone : What is Sunstone? Where to find Sunstone?…


Sunstone : What is Sunstone? Where to find Sunstone? http://www.geologypage.com/2019/04/sunstone.html


‘The Whispering Knights’ Willow Sculpture, ‘The Rollright Stones’...

‘The Whispering Knights’ Willow Sculpture, ‘The Rollright Stones’ Prehistoric Complex, Oxfordshire, 22.4.19.












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Liquid blood found inside 42,000 year old foal boosts hopes of bringing extinct species...

Semyon Grigoryev, head of the Mammoth Museum in Yakutsk, said today: ‘The autopsy shows beautifully preserved internal organs.











Liquid blood found inside 42,000 year old foal boosts hopes of bringing extinct species back to life
Credit: North-Eastern Federal University

‘Samples of liquid blood were taken from heart vessels — it was preserved in the liquid state for 42,000 years thanks to favourable burial conditions and permafrost.


‘The muscle tissues preserved their natural reddish colour. We can now claim that this is the best preserved Ice Age animal ever found in the world.’


Dr Grigoryev revealed in an interview with TASS that the foal is in an exceptional condition without any visible damage.


‘This is extremely rare for paleontological finds, because some of them are either incomplete, fragmented, with serious body deformations or strongly mummified,’ said the expert.


Liquid blood found inside 42,000 year old foal boosts hopes of bringing extinct species back to life










Liquid blood found inside 42,000 year old foal boosts hopes of bringing extinct species back to life
Credit: North-Eastern Federal University

‘The foal’s hair is intact on its head, legs and part of its body. Its tail and mane are black, the rest of the foal’s body is bay. Having preserved hair is another scientific sensation as all previous ancient horses were found without hair.’


This is the second month of intense joint work of the Yakutian university team and scientists from South Korean Sooam Biotech Research Foundation.


‘Our studies showed that at the moment of death the foal was from one to two weeks old, so he was just recently born,’ said the scientist.


‘As in previous cases of really well-preserved remains of prehistoric animals, the cause of death was drowning in mud which froze and turned into permafrost. A lot of mud and silt which the foal gulped during the last seconds of its life were found inside its gastrointestinal tract.’


Liquid blood found inside 42,000 year old foal boosts hopes of bringing extinct species back to life










Liquid blood found inside 42,000 year old foal boosts hopes of bringing extinct species back to life
Credit: North-Eastern Federal University

Scientists have already indicated  that they are ‘confident of success’ in extracting cells from this foal in order to clone its species — the extinct Lenskaya breed — back to life, as previously reported by The Siberian Times.


Work is so advanced that the team is reportedly choosing a mother for the historic role of giving birth to the comeback species.


Michil Yakovlev, editor of the university’s corporate media, said: “Hopefully, the world will soon meet the clone of the ancient foal who lived 42,000 years ago.”


The foal was found in the Batagai depression in Yakutia. An attempt to restore the species to life is seen as paving the way for a similar effort to restore to life the giant woolly mammoth. The same scientists are working on both projects.











Liquid blood found inside 42,000 year old foal boosts hopes of bringing extinct species back to life
Credit: North-Eastern Federal University

The unique foal will become one of the key exhibits of one year long The Mammoth exhibition in Japan, starting in June this year.


‘More than 30 exhibits from Yakutia will travel to the exhibition,’ said Dr Grigoryev.


‘For the first time we’ll show the world’s only frozen woolly mammoth trunk, as well as the carcass of the Yukagir bison, an ancient partridge and the Batagai horse.’


Source: The Siberian Times [April 18, 2019]



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US returns looted fragment of Mayan stela to Mexico

The National Museum of Anthropology received from the United States a fragment of Stela 2 from the Mayan site La Mar, in Chiapas, which corresponds to the upper right corner of the stela and its approximate measurements are 45 cm wide by 74 cm long, and 7 cm thick.











US returns looted fragment of Mayan stela to Mexico
Credit: INAH

The repatriated part of the Late Classic period (800-850 AD) lost its original thickness since it was cut to subtract and move the piece out of Mexico. According to authorities at Yale University, since 1966 the piece was in the possession of a US citizen, religious missionary and amateur collector based in Indiana, who gave it to the university to be returned to Mexico.
Between 1895 and 1900, Teobert Maler mapped, photographed and described a significant number of ancient Mayan settlements distributed on the west bank of the Usumacinta. This registration made by the Austrian-German expeditionary has allowed the United States to return a fragment of Stela 2 from the La Mar archaeological site in Chiapas, from which it was stolen decades ago.

The act of delivery-reception of this cultural property, now under the custody of the National Institute of Anthropology and History (INAH), took place at the headquarters of the Ministry of Foreign Affairs (SRE), in Mexico City.











US returns looted fragment of Mayan stela to Mexico
Credit: INAH

Archaeologist Alejandro Bautista explained that it was in October 2018 when the Institute for the Preservation of the Cultural Heritage of Yale University informed the Consulate General of Mexico in New York, its desire to return to Mexico an archaeological asset identified in that institute as a fragment of Stela 2 of La Mar.
Bautista noted that the work was published by Teobert Maler in «Investigations in the central portion of the Usumatsíntla Valley» (sic). In a photograph captured by the explorer in 1900, the monument is fragmented into five parts, and together they appear five Mayan characters of high rank and a series of hieroglyphic cartridges.


The archeologist Omar Silis, of the Direction of Public Registry of Monuments and Archaeological Zones of the INAH, described that in the scene visible in the fragment, the upper part of the portrait of a possible ruler appears, which wears a headdress, as well as ornaments such as earmuffs, breastplate, bracelets and necklaces.











US returns looted fragment of Mayan stela to Mexico
Credit: INAH

Both experts agreed that the geopolitical importance of La Mar is revealed by the central square, the twin buildings, the ball game and at least three stelae described by Maler in which scenes of La Mar’s interaction with other centers were captured. regional offices such as Palenque and Piedras Negras.
Alejandro Bautista pointed out that Stela 1 of La Mar is located in the Regional Museum of Chiapas, in Tuxtla Gutiérrez; so it would be appropriate that the fragment of Stela 2 also be exhibited in that space, after conservation tasks in the National Museum of Anthropology, where it was received by its director, the historian Antonio Saborit, and after its registration in the Registry Public as a good that is part of the collections in INAH custody.


Source: Mexicanist [April 19, 2019]



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Greek team digitizing ancient Christian manuscripts at Sinai monastery

A team from Greece are photographing thousands of fragile manuscripts, including some of the earliest copies of the Christian gospels, using a complex process that includes taking images in red, green and blue light and merging them with computer software to create a single high-quality color picture. There is a tangible sense of urgency to the mission.











Greek team digitizing ancient Christian manuscripts at Sinai monastery
‘Codex Syriacus’, an ancient copy of the Gospels in Syriac, is seen on display in St. Catherine’s Monastery
in South Sinai, Egypt [Credit: Mohamed Abd El Ghany/Reuters]

Although the monastery has survived centuries of warfare, it lies in a region where Islamist militants have destroyed countless cultural artifacts and documents in Syria and Iraq. Egypt’s Christian churches have also been targeted by an Islamist insurgency in the rugged and thinly populated northern Sinai.
‘The Holy Monastery of the God-Trodden Mount Sinai’ — which is part of the Eastern Orthodox church — lies in the safer southern half of the Sinai Peninsula. But in 2017, Islamic State claimed responsibility for an attack on a nearby Egyptian police checkpoint, in which one officer was killed.











Greek team digitizing ancient Christian manuscripts at Sinai monastery
Librarian Father Justin of Sinai walks inside the library of St. Catherine’s Monastery in South Sinai, Egypt
[Credit: Mohamed Abd El Ghany/Reuters]

“The upheaval of our times requires a rapid completion of this project,” Archbishop Damianos of Sinai, Faran and Raitho, and Abbot of St. Catherine’s Monastery, told Reuters by email.


The aim is to create the first digital archive of all 4,500 manuscripts in the library, starting with around 1,100 in the Syriac and Arabic languages, which are particularly rare.











Greek team digitizing ancient Christian manuscripts at Sinai monastery
Librarian Father Justin of Sinai turns the pages of an ancient manuscript from the library of St. Catherine’s Monastery
in South Sinai, Egypt [Credit: Mohamed Abd El Ghany/Reuters]

The task could take more than a decade, using digital cameras and computer arrays alongside sophisticated cradles designed to support the more fragile manuscripts.
The project began last year and is being undertaken by the non-profit research organization Early Manuscripts Electronic Library (EMEL), in collaboration with the monastery and the Library of the University of California, Los Angeles. UCLA Library said it will start publishing the manuscripts online, in full color, from the fall of 2019.











Greek team digitizing ancient Christian manuscripts at Sinai monastery
Gold lettering is seen on an ancient manuscript from the library of St. Catherine’s Monastery in South Sinai, Egypt
[Credit: Mohamed Abd El Ghany/Reuters]

“This library is an archive of the history of Christianity and its neighbors in the Mediterranean world, and therefore is of interest to communities all over the world who find their history here,” Michael Phelps, Director of the Early Manuscripts Electronic Library, told Reuters.


The monastery lies at the foot of Mount Sinai, by tradition the site where Moses received the Ten Commandments.











Greek team digitizing ancient Christian manuscripts at Sinai monastery
The ancient mosaic of the Transfiguration is seen inside St. Catherine’s Monastery in South Sinai, Egypt
[Credit: Mohamed Abd El Ghany/Reuters]

UNESCO has listed the area as a World Heritage site, citing its sacred status in Christianity, Islam and Judaism. It says St. Catherine’s was founded in the 6th century, and is the oldest Christian monastery still in use for its original function.
The most famous manuscript in the library is the 4th century ‘Codex Sinaiticus’ — a Greek manuscript of the Bible which contains the oldest surviving complete New Testament. Its pages are divided between several institutions.











Greek team digitizing ancient Christian manuscripts at Sinai monastery
Detail of the ancient mosaic of the Transfiguration is seen inside St. Catherine’s Monastery in South Sinai, Egypt
[Credit: Mohamed Abd El Ghany/Reuters]

Another is the Codex Syriacus, an ancient copy of the Gospels in Syriac. Other manuscripts cover science, medicine and the Greek classics.


The digitization of the first stage alone, the Syriac-Arabic manuscripts, will take around three years and cost a projected $2.75 million, said Phelps.











Greek team digitizing ancient Christian manuscripts at Sinai monastery
A general view of St. Catherine’s Monastery in South Sinai, Egypt
[Credit: Mohamed Abd El Ghany/Reuters]

“Throughout the centuries, monks have lived here in prayer, in dedication to spiritual goals, a witness to God’s revelation to mankind… in that sense especially, the Sinai Monastery is an ark, a spiritual ark in the wilderness,” said Father Justin of Sinai, the monastery’s librarian.


The project will provide a more complete record than partial microfilming carried out decades ago by the U.S Library of Congress, and also by the National Library of Israel. The two institutions are making their records available to the new digitization effort, the project organizers said.


Author: Mohamed Zaki | Source: Reuters [April 18, 2019]



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Earth vs. asteroids: humans strike back


ESA — Hera Mission.


22 April 2019


Incoming asteroids have been scarring our home planet for billions of years. This month humankind left our own mark on an asteroid for the first time: Japan’s Hayabusa2 spacecraft dropped a copper projectile at very high speed in an attempt to form a crater on asteroid Ryugu. A much bigger asteroid impact is planned for the coming decade, involving an international double-spacecraft mission.



SCI impactor on way to Ryugu asteroid

On 5 April, Hayabusa2 released an experiment called the ‘Small Carry-on Impactor’ or SCI for short, carrying a plastic explosive charge that shot a 2.5-kg copper projectile at the surface of the 900-m diameter Ryugu asteroid at a velocity of around 2 km per second. The objective is to uncover subsurface material to be brought back to Earth for detailed analysis.


“We are expecting it to form a distinctive crater,” comments Patrick Michel, CNRS Director of Research of France’s Côte d’Azur Observatory, serving as co-investigator and interdisciplinary scientist on the Japanese mission. “But we don’t know for sure yet, because Hayabusa2 was moved around to the other side of Ryugu, for maximum safety.


“The asteroid’s low gravity means it has an escape velocity of a few tens of centimetres per second, so most of the material ejected by the impact would have gone straight out to space. But at the same time it is possible that lower-velocity ejecta might have gone into orbit around Ryugu and might pose a danger to the Hayabusa2 spacecraft.



Plume from impact

“So the plan is to wait until this Thursday, 25 April, to go back and image the crater. We expect that very small fragments will meanwhile have their orbits disrupted by solar radiation pressure – the slow but persistent push of sunlight itself. In the meantime we’ve also been downloading images from a camera called DCAM3 that accompanied the SCI payload to see if it caught a glimpse of the crater and the early ejecta evolution.”


According to simulations, the crater is predicted to have a roughly 2 m diameter, although the modelling of impacts in such a low-gravity environment is extremely challenging. It should appear darker than the surrounding surface, based on a February touch-and-go sampling operation when Hayabusa2’s thrusters dislodged surface dust to expose blacker material underneath.



Hayabusa2

“For us this is an exciting first data point to compare with simulations,” adds Patrick, “but we have a much larger impact to look forward to in future, as part of the forthcoming double-spacecraft Asteroid Impact & Deflection Assessment (AIDA) mission.


“In late 2022 the US Double Asteroid Redirect Test or DART spacecraft will crash into the smaller of the two Didymos asteroids. As with Hayabusa2’s SCI test it should form a very distinct crater and expose subsurface material in an even lower gravity environment, but its main purpose is to actually divert the orbit of the 160 m diameter ‘Didymoon’ asteroid in a measurable way.”
7



DART mission profile

The DART spacecraft will have a mass of 550 kg, and will strike Didymoon at 6 km/s. Striking an asteroid five times smaller with a spacecraft more than 200 times larger and moving three times faster should deliver sufficient impact energy to achieve the first ever asteroid deflection experiment for planetary defence.


A proposed ESA mission called Hera would then visit Didymos to survey the diverted asteroid, measure its mass and perform high-resolution mapping of the crater left by the DART impact.


“The actual relation between projectile size, speed and crater size in low gravity environments is still poorly understood,” adds Patrick, also serving as Hera’s lead scientist. “Having both SCI and Hera data on crater sizes in two different impact speed regimes will offer crucial insights.



Hera at Didymos

“These scaling laws are also crucial on a practical basis, because they underpin how our calculations estimating the efficiency of asteroid deflection are made, taking account the properties of the asteroid material as well as the impact velocity involved.


“This is why Hera is so important; not only will we have DART’s full-scale test of asteroid deflection in space, but also Hera’s detailed follow-up survey to discover Didymoon’s composition and structure. Hera will also record the precise shape of the DART crater, right down to centimetre scale.



Infrared imaging of the impact crater

“So, building on this Hayabusa2 impact experiment, DART and Hera between them will go on to close the gap in asteroid deflection techniques, bringing us to a point where such a method might be used for real.”


Didymoon will also be by far the smallest asteroid ever explored, so will offer insights into the cohesion of material in an environment whose gravity is more than a million times weaker than our own – an alien situation extremely challenging to simulate.



NASA’s Deep Impact hitting a comet

In 2004, NASA’s Deep Impact spacecraft launched an impactor into comet Tempel 1. The body was subsequently revisited, but the artificial crater was hard to pinpoint – largely because the comet had flown close to the Sun in the meantime, and its heating would have modified the surface.



Hera mission

Hera will visit Didymoon around four years after DART’s impact, but because it is an inactive asteroid in deep space, no such modification will occur. “The crater will still be ‘fresh’ for Hera,” Patrick concludes.


Related links:


Asteroid Impact & Deflection Assessment (AIDA): http://www.esa.int/Our_Activities/Operations/Space_Safety_Security/Hera/Asteroid_Impact_Deflection_Assessment_AIDA_mission


Hayabusa2: http://www.hayabusa2.jaxa.jp/en/


Hera: http://www.esa.int/Our_Activities/Operations/Space_Safety_Security/Hera/Hera


Images, Video, Text, Credits: ESA/ScienceOffice.org/JAXA/The University of Tokyo/Kochi University/Rikkyo University/Nagoya University/Chiba Institute of Technology/Meiji University/The University of Aizu/AIST/NASA.


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Restoration of early Byzantine church in central Turkey completed

Restoration works on the ancient Constantine-Helena Church [Andaval Church] located on the Christian holy pilgrimage path in central Turkey’s Niğde province, have been completed, the local governor’s office said Monday.











Restoration of early Byzantine church in central Turkey completed
Credit: Anadolu Agency

The church, which is one of the historical landmarks in the city, along with the ancient city of Tyana, a Roman-era water basin and the Byzantine-era Gümüşler cave monastery, was heavily damaged in an explosion in 1977 and had been going through restoration works since 1996.
Speaking at the opening ceremony of the church, Niğde Governor Yılmaz Şimşek said that the church has an important place in world history, adding that he hopes the ancient church and the archaeological site it is located in will boost the city’s tourism.


Restoration of early Byzantine church in central Turkey completed










Restoration of early Byzantine church in central Turkey completed
Credit: Anadolu Agency











Restoration of early Byzantine church in central Turkey completed
Credit: Anadolu Agency

Şimşek noted that the church is the earliest examples of its kind as a stone structure, adding that the paintings on its wall have survived till today.


The church was constructed under the name of the Roman Emperor Constantine the Great’s mother Helena in the sixth century and was located on the historic holy pilgrimage road that started from Bordeaux, France and ended at Jerusalem.


Source: Daily Sabah [April 18, 2019]



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Полет на параплане с обрыва на мысу Куяльницкого лимана, соленого озера. Экстремальный развлекательный полет проводится для любителей. ...

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