пятница, 5 октября 2018 г.

A new take on the 19th-century skull collection of Samuel Morton

In the 1830s and 1840s, American craniologist Samuel Morton collected and measured hundreds of human skulls in what he described as an attempt to compare the brain size of five human racial groups. At nearly the same time, across the world, German anatomist Friedrich Tiedemann was conducting similar research.











A new take on the 19th-century skull collection of Samuel Morton
The Morton skull collection at the University of Pennsylvania
[Credit: Paul Wolff Mitchell]

The scientists produced nearly equivalent results, but what they inferred from those findings differed drastically: Tiedemann used his to fight for equality and the abolition of slavery, and against the idea that different races were created separately. Morton’s research was used to maintain the status quo in the United States, which, at that time, meant racial division, hierarchy, and slavery.


Though the work happened almost 180 years ago, it still elicits debate, particularly over the concept of scientific racism and bias. A paper published in PLOS Biology from University of Pennsylvania doctoral candidate Paul Wolff Mitchell adds to the conversation, through analysis of never-before analyzed, handwritten cranial measurements he unearthed in Morton’s archives.


Mitchell determined that while Morton’s data-collection methods produced accurate numbers and were likely not intentionally biased, the scientist’s conclusions — that Caucasians had the largest skull size and therefore, the highest intelligence and that Africans had the smallest skull size and lowest intelligence — blatantly were. They also point to the importance of scientific interpretation.


“Morton and Tiedemann both thought the bigger and more complex the brain, the more superior the individual or species,” Mitchell says. It was a belief held by many scientists at the time, although one that modern science has disproven. “Beyond that, more than just the data were informing their scientific positions,” he adds. “Political and ethical considerations were, too.”


“It’s a complex story,” Mitchell says, one that requires walking through Morton’s process and what followed to fully grasp its intricacy.


Morton’s scientific path


Morton, a native Philadelphian, physician, and naturalist, recognized as the first physical anthropologist, began collecting human skulls in the early 1800s. Though he didn’t travel much himself, his role as president of the Academy of Natural Sciences afforded him the opportunity to correspond with scientists around the world to secure samples.











A new take on the 19th-century skull collection of Samuel Morton
Skulls from the collection of Samuel Morton, housed at the Penn Museum. Initially, Morton kept his collection at
the Academy of Natural Sciences, where he was then-president. The skulls moved to the Penn Museum in 1966
[Credit: Paul Wolff Mitchell]

He aimed to gather sufficient numbers from each of the five racial groups he recognized: Ethiopian (or African), Native American, Caucasian, Malay, and Mongolian. In total, he amassed around 900 skulls, the largest academic collection at the time, and one that remained so for half a century after his death. Today, the Morton Collection is stored and curated in the Physical Anthropology Section of the Penn Museum.


Initially, Morton measured the size of 256 skulls by pouring white pepper seed into each cavity, then gauging in cubic inches the volume of seed needed to fill a sample. From that work, he published Crania America in 1839, which reported statistics from every Native American skull and averages for the other groups. The next year, he published the first of three skull catalogues, and then a book called Crania Aegpytiaca and the second catalogue came in 1844.


In trying to replicate his seed measurements, Morton had difficulty so he switched to lead shot and went through the measurement process again, now with 672 skulls. “He came to basically the same conclusion as before,” Mitchell explains, “with Caucasians having the biggest brain size and Africans the smallest.” In 1849, Morton published a third and final catalogue with cranial data based on the lead-shot measurements of every individual skull.


He died just two years later, at the time considered a preeminent expert in his field. Until, that is, Charles Darwin published On the Origin of Species and the United States fought the Civil War.


Seeing something new


For more than a century following those two events, Morton’s science fell into obscurity, his methods modernized and surpassed, his theories debunked. Then in 1978, American scientist Stephen Jay Gould wrote several texts about scientific racism, the idea that scientific findings might justify continued discrimination and intolerance. He used Morton’s skull studies as a prime example.











A new take on the 19th-century skull collection of Samuel Morton
A skull from the collection of Samuel Morton, housed at the Penn Museum
[Credit: Paul Wolff Mitchell]

“Gould notices that the average for the Africans between the seed measurements and shot measurements increases a lot, but the average for the measurements of the Caucasians only increases a little, about the same amount that the measures for the Native Americans do,” Mitchell says. “This leads Gould to conclude that Morton was unconsciously underestimating brain size for the Africans.”


Because of the seeds’ compressible nature, Gould suggested skulls could be inadvertently overstuffed or lightly packed, producing inaccurate numbers. Morton had unconsciously done so, Gould surmised, packing seeds into Caucasian skulls and only lightly filling African skulls, leading to systematic underestimations of African cranial capacity.


Unbeknownst to Gould, however, he didn’t have all the facts, namely the full seed data Morton never published — data that Mitchell rediscovered in the scientist’s archives at the Academy of Natural Sciences.


“I was looking through Morton’s old catalogue of skulls. He had printed three copies throughout his life to advertise to other scientists and collectors what he had in his collection,” says Mitchell. “He also kept personal copies, which he signed and dated. The first copy was from 1840.”











A new take on the 19th-century skull collection of Samuel Morton
A skull from the collection of Samuel Morton, housed at the Penn Museum. In his day, Morton used measurements
he took to conclude that of five racial categories he recognized, Caucasians had the largest skull size
and therefore, the highest intelligence [Credit: Paul Wolff Mitchell]

That first edition didn’t include printed brain size like the latter two did, but in Morton’s personal copy, Mitchell noticed handwritten measurements accompanying many entries, some scratched out and rewritten. He also realized that the brain measurements from the 1840 and 1849 catalogues differed, leading him to conclude that those jotted down represented previously unseen seed measurements.


Having worked with the Morton skulls since 2010, under the tutelage of Janet Monge, curator in charge of the Penn Museum’s Physical Anthropology section and a Penn adjunct professor of anthropology, Mitchell had an intimate relationship with the collection. “I know those skulls well,” he says. “When I looked at what Morton had written down, I said, ‘Something’s not right here. That’s not the measurement he gives later.’ It was due to a great deal of familiarity with the skulls that I could see something new in these documents.”


What does it all mean?


For Mitchell, viewing the entries for the original seed measurements rather than the averages for four out of the five of Morton’s racial classifications shifts the conversation about these skulls. Mitchell’s analysis confirmed that Morton’s measurements were accurate; the seed and shot measurement averages differed because of different overall sample sizes. But, he points out, that finding almost doesn’t matter.











A new take on the 19th-century skull collection of Samuel Morton
One of the skulls from Dr. Morton’s collection, showing the lead shot he used to measure cranial capacity
[Credit: Paul Wolff Mitchell]

“Just because Morton’s data were not biased doesn’t mean his science wasn’t,” Mitchell says. “He can measure skulls very accurately but also be a biased scientist.” Simply look at Tiedemann, he says. “The German scientist basically does the same thing Morton does but comes to a dramatically different conclusion.”


Through his work, Tiedemann noticed a range of skull sizes among all humans. Morton, on the other hand, focused on brain-size averages of different races. Although Morton’s numbers overlap across races, and although taking the averages of Tiedemann’s data — which he himself never did — reveal an almost perfect match to Morton’s, the interpretive differences of the two scientists supported their divergent conclusions.


With respect to today’s science, the biggest fault in Morton’s research may lie in that he didn’t collect data on body size, Mitchell says. Brain size correlates to body size, and brain and body size are well known adaptions to the climate in which people live. That means from an evolutionary perspective, there’s no reason to suppose a link between cranial size and intelligence.


“If you just collect heads from all over the globe and you don’t take body size into account, there is no meaningful way to compare your data,” Mitchell says. “People with bigger bodies have bigger brains.”











A new take on the 19th-century skull collection of Samuel Morton
Pages from Samuel Morton’s personal copy of his Catalogue of Skulls, 1840
[Credit: Paul Wolff Mitchell]

The other issue with Morton’s research, he notes, is that the racial categories he supposes have no biological basis. Which all leads Mitchell to question what, in the end, Morton’s data can really teach.


“When dealing with moral and political questions, interpretation is a key part of how the science gets done,” Mitchell concludes. “That will always have an element of bias. The only way to get around it is to have the open presentation of data, scrutiny of scientific work, and a diverse community of people working on and thinking about these issues.”


Paul Wolff Mitchell is a doctoral candidate in the Department of Anthropology in the School of Arts and Sciences. He also earned his bachelor’s and master’s degrees from the University of Pennsylvania.


Janet Monge is curator in charge of the Penn Museum’s Physical Anthropology section and an adjunct professor in the Department of Anthropology in the School of Arts and Sciences.


Source: University of Pennsylvania [October 04, 2018]



TANN



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Bronze Age and Roman pottery found near Cambridge during A14 upgrade

A Roman bowl and an intact Bronze Age urn are among “hugely significant” artefacts found during work to upgrade the A14.











Bronze Age and Roman pottery found near Cambridge during A14 upgrade
Samian ware decorated with lion fight scene [Credit: Highways England/
MOLA Headland Infrastructure]

A team of 250 archaeologists have been on site as part of Highways England’s £1.5bn scheme to improve the stretch between Cambridge and Huntingdon.
More than four tonnes of pottery fragments have been unearthed since work began two years ago. Experts said some of the pottery was of the “highest quality”.











Bronze Age and Roman pottery found near Cambridge during A14 upgrade
Complete Bronze Age collared urn [Credit: Highways England/
MOLA Headland Infrastructure]

Teams led by the Museum of London Archaeology have dug more than 40 separate excavation areas covering an area of 350 hectares (3.5 sq km). The entire area was the site of a medieval village and a Roman trade distribution centre, archaeologists found.
Among the pieces recovered are a Samianware Roman bowl, depicting a male figure fighting a lion, which would have been imported from France – giving an insight into the wealth, status and travels of the people who lived here.











Bronze Age and Roman pottery found near Cambridge during A14 upgrade
Iron Age coil-built fineware pot from near Fenstanton [Credit: Highways England/
MOLA Headland Infrastructure]

“We know there is quite dense archaeology in Cambridgeshire, but there is a particular concentration near Huntingdon where we are finding some of the highest quality pottery,” said Dr Sutton.
“The Roman bowl was the equivalent of their Sunday best china. It is a crazy assemblage in terms of size and quality.”











Bronze Age and Roman pottery found near Cambridge during A14 upgrade
Iron Age coil-built bowl from near Fenstanton [Credit: Highways England/
MOLA Headland Infrastructure]

He said it was not uncommon to find cemeteries, but the full Bronze Age collared urn – thought to be 3,000-4,000 years old – was especially important, and that “someone had put a lot of time and effort into making it”.


The items will be sorted and recorded by a 10-strong team of pottery specialists across the country over the next year.


Source: BBC News Website [October 04, 2018]



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Palmyra priest statue among haul of recovered Syrian relics

A stone image of an ancient priest is one of hundreds of stolen antiquities recovered by the Syrian government and put on display in Damascus this week, a reminder of the mass looting of Syria’s heritage during seven years of war.











Palmyra priest statue among haul of recovered Syrian relics
A funerary bust of a high priest dating to the Roman era (2nd century AD), on display at an exhibition titled “Syria’s
Recovered Treasures” showing artefacts recovered by the Syrian government from archaelogical sites affected by
fighting across the country, at the Damascus Opera House in the capital. The exhibition showcases about
500 pieces of antique ceramic pots, bronze statues, jewelry, and coins dating back to various periods
[Credit: Louai Beshara/AFP]

It was carved for Yalhi bin Yalhabouda, a high priest in Palmyra, upon his death in 120 AD, his status apparent from his tall hat and laurel wreath. It was illegally dug up during Islamic State’s occupation of the desert town.
“This civilization is not only for Syria, but we are the custodians of it and we preserve it for the world,” said Khalil Hariri, head of the Palmyra antiquities department.


Syria stood at the heart of the ancient Middle East, a crucible for some of the world’s earliest civilizations and was at times incorporated into Egyptian, Babylonian, Assyrian, Hittite, Persian, Greek and Roman empires.











Palmyra priest statue among haul of recovered Syrian relics
Restored sculptures are displayed in an exhibition at the Opera House in Damascus,
Syria, October 3, 2018 [Credit: Reuters/Omar Sanadiki]

After its descent into a messy, multi-sided civil war in 2011, when the country was fragmented into numerous enclaves, the warring parties began to plunder that inheritance, looting museums and excavating ancient sites.
Islamic State, which from its days as the al Qaeda branch in Iraq had long experience of selling stolen antiquities for profit, seized Palmyra and its extensive Roman-era ruins, a UNESCO world heritage site, in 2015.


As with other parts of Syria and Iraq which it turned into a short-lived “caliphate”, it made a public show of destroying many artefacts and ancient buildings as idolatrous, while secretly benefiting from the illicit trade in historical goods.











Palmyra priest statue among haul of recovered Syrian relics
Restored sculptures are displayed in an exhibition at the Opera House in Damascus,
Syria, October 3, 2018 [Credit: Reuters/Omar Sanadiki]

The group blew up Palmyra’s monumental arch and beheaded its 82-year-old antiquities chief, hanging his body from an ancient column. After changing hands more than once, it was retaken by the Syrian army last year.
The life-sized image of Yalhi bin Yalhabouda, standing out in relief from a stone tombstone, was excavated from Palmyra’s ancient tombs, said the city’s new antiquities chief Hariri, and found in a house in the modern town.


It is inscribed with his name and year of death and shows him carrying a cup of sacred oil and a bowl of cereal, such as would have been ritually distributed after his demise.











Palmyra priest statue among haul of recovered Syrian relics
A restored sculpture is displayed in an exhibition at the Opera House in Damascus,
Syria, October 3, 2018 [Credit: Reuters/Omar Sanadiki]

Iconoclast jihadists had smashed part of the sculpture’s cheek and hat, but it was restored. As with all other stolen Palmyra relics seized by the government, it will be returned to the city, Hariri said.
But while thousands of stolen objects have been recovered, tens of thousands more are missing – many of them likely outside Syria and in the hands of specialist dealers ready to wait decades before selling them to private collectors.


The 500 objects displayed in Damascus this week were from eras ranging from 10,000 BC to the Islamic period and were found in captured areas by the army, said Mahmoud Hammoud, head of Syria’s antiquities department.


Author: Angus McDowall | Source: Reuters [October 04, 2018]



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Unplundered Mycenaean tomb discovered in Nemea

The third excavation campaign of a five-year research project conducted by the Ephorate of Antiquities of Korinthia at the Mycenaean cemetery at Aidonia in Nemea, has been completed.











Unplundered Mycenaean tomb discovered in Nemea
Aerial view of the Mycenaean cemetery in Aidonia
[Credit: Greek Ministry of Culture]

The Mycenaean cemetery of Aidonia was discovered about four decades ago after it had been extensively looted. The site became more widely known in the 1990s after a collection of Mycenaean jewellery originating from the Aidonia cemetery was recovered while being sold abroad and subsequently exhibited in the Nemea Museum. The excavations by the Archaeological Service, which commenced soon after the repatriation of these artefacts, have brought to light a cluster of 16 rock-carved chamber tombs each with a dromos,  entrance and burial chamber.
In recent years, the Mycenaean cemetery of Aidonia has been the focus of new excavations conducted by the Ephorate of Antiquities of Corinth under the direction of Dr. Konstantinos Kissas, former Head of the Office and Assistant Professor at the University of Graz and his associate Dr. Kim Shelton, Professor of the University of California at Berkeley and Director of the Centre for Classical Archaeology in Nemea.











Unplundered Mycenaean tomb discovered in Nemea
The ‘dromos’ and entrance of the monumental chamber tomb [Credit: Greek Ministry of Culture]










Unplundered Mycenaean tomb discovered in Nemea
The four burial pits found in the tomb chamber, c.1600/1500-1250/1200 BC
[Credit: Greek Ministry of Culture]

The 2018 campaign saw the completion of the excavation of an unlooted chamber tomb of the Early Mycenaean period (c.1650-1400 BC), one of the largest found in the Aidonia necropolis.
The newly revealed tomb is distinguished by the short, but very wide, dromos and the circular-ellipsoid floor of the burial chamber, the dimensions of which exceed six metres in parts. Both the dromos and the chamber exhibit morphological features typical other mid-sized vaulted tombs of the early Mycenaean period.











Unplundered Mycenaean tomb discovered in Nemea
‘Palace-style’ pithamphora decorated of papyri and reeds, c.1600/1500 BC
[Credit: Greek Ministry of Culture]










Unplundered Mycenaean tomb discovered in Nemea
Clay cups with ring-shaped handles, c1600/1500 BC [Credit: Greek Ministry of Culture]

On the floor of the burial chamber were four large pits, covered with megalithic slabs, another element which recalls early Mycenaean vaulted tombs. These pits contained earlier burials which were accompanied by ceramic tableware and storage vases, some of which were monumental, like the ‘palace-style’ pithanmphora with symbolic decoration inspired by the plant and marine worlds.
Copper knives, daggers and swords were also found in the pits, as well as numerous arrow heads of copper, obsidian, and pyrite. Jewellery, necklace beads of various raw materials, fibulae and other prestigious items, such as sealstones, were also collected.











Unplundered Mycenaean tomb discovered in Nemea
Bronze short sword, c.1600/1500 BC [Credit: Greek Ministry of Culture]










Unplundered Mycenaean tomb discovered in Nemea
Necklace with amethyst and gold beads, c.1600/1500 BC [Credit: Greek Ministry of Culture]

The use of the monument continued during the Late Mycenaean period (c.1400-1200 BC), to which the burials found on the tomb’s floor date, though the grave goods are more frugal than those of the previous period.


The excavation also found evidence suggesting that part of the tomb’s tholos had collapsed shortly after it had ceased to be used.


The intensive use of the site both in the Archaic/Early Classical period and Roman Imperial times, as well as during the transition from the Middle to the Late Byzantine period contributed to the accumulation of thick deposits which essentially preserved the Mycenaean monument.


It is hoped that with the discovery of this unplundered tomb in Aidonia, like the interdisciplinary study of burial groups, will shed new light on the nature of the local ruling class of the Early Mycenaean period.


Source: Greek Ministry of Culture [October 04, 2018]



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Broad genetic variation on the Pontic-Caspian Steppe

The genetic variation within the Scythian nomad group is so broad that it must be explained with the group assimilating people it came in contact with. This is shown in a new study on Bronze and Iron Age genetics of the Pontic-Caspian Steppe, situated in the Black Sea region. The article is published in the scientific journal Science Advances.











Broad genetic variation on the Pontic-Caspian Steppe
This is an excavation of a Kazburun burial ground in Southern Urals
[Credit: Iia Shuteleva and Nikolai Shcherbakov]

“There is so much genetic variation among the Scythians, it seems that you didn’t have to be born a Scyth to be a part of their community,” says Anders Götherström, Professor at the Department of Archaeology and Classical Studies, Stockholm University.
This is likely the strategy needed for the group to have been able to grow as fast, expand as vast and to remain established for as long as they did. The findings emphasize the importance of assimilation to maintain Scythian dominance around the Black Sea region.


“It also sheds light on their attitude towards conquered people. Scythians are often thought of as an extremely aggressive group, but their gradual genetic expansion show us that they were also a group prepared to interact with and take in new people. For example, in one burial ground we found individuals of different genetic background buried according to Scythian tradition. This tells us that Scythians seem to have incorporated people from other groups into their families and their community,” says Maja Krzewińska, researcher at the Department of Archaeology and Classical Studies, Stockholm University.


The Pontic-Caspian Steppe — a dynamic place


The vast area of the Pontic-Caspian Steppe region has worked as a motor for demographic events throughout Eurasia, especially in the western part of the meta-continent. Crucial events in European history and prehistory can be traced back to people of the Steppe. Including the invention of horseback riding, chariots, a new type of warfare and the spread of Indo-European languages.


“The Central Eurasian Steppe seems to have been a very dynamic place. An important geographical region which acted both as a melting-pot and a nursery of people, as well as communicative and technological innovations. This is where people met, shared ideas and genes. From this ‘pit-stop’ genes and ideas were spread from the East to the West,” says Gülşah Merve Kılınç, researcher at the Department of Archaeology and Classical Studies, Stockholm University.


A gradual genetic mix


An international research team, led from Stockholm University, have investigated genomic data from 35 individuals, spanning 2,200 years. The material mainly consists of human remains from the southern Urals and central Eurasian Steppe. The researchers have analyzed DNA from four different nomadic groups; Cimmerians, Scythians, Sarmatians and Bronze Age Srubanya individuals.


Even though a couple of the groups had an early history somewhere else all the groups share genetic background and follow each other chronologically. The Cimmerians were displaced by the Scythians and those in return were followed by the Sarmatians.


“It’s not one group completely displacing another. The expansion process seems to have been more gradual. First from Altai to southern Urals, and thereafter further west. It suggests that the Pontic-Caspian Steppe served as a natural transition point and the source of western nomads, despite their cultural roots stretching further east,” says Maja Krzewińska.


Source: Stockholm University [October 04, 2018]



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Neanderthal bones found in Polish cave

Polish archaeologists have announced they have unearthed what is now believed to be the oldest surviving human remains in Poland.











Neanderthal bones found in Polish cave
Credit: PAP/Jacek Bednarczyk

The Neanderthal bones, found in a cave in southern Poland, are about 115,000 years old – more than 50,000 years older than the previous most ancient fragments found on Polish soil.


The tiny bone fragments known as phalanges (bones forming part of the finger structure), believed to have belonged to a child, have most likely been consumed and partially digested by a large bird, as evidenced by the porous bone surface. This is the first time ever that a specimen dating back to the Ice Age has been found in this condition, researchers say.


The previous oldest osseous remains ever discovered in Poland until the announcement was made had been the Neanderthal teeth found in another cave, their estimated age being between 42,000 and 52,000 years.


The 115,000-year-old bone fragments have been unearthed deep inside a prehistoric cavern, beneath a few metres of earth and soil. Since the remains are both tiny and very poorly preserved, researchers say that no DNA analysis is possible, although their Neanderthal lineage is beyond doubt considering both the layer of soil where they were found and the presence of typical stone tools customarily used by the Neanderthals. The bones were positively identified as belonging to a Neanderthal by two anthropologists, one of whom works for the Jagiellonian University in Kraków, while the other is employed at the Washington University in St Louis.











Neanderthal bones found in Polish cave
Credit: PAP/Jacek Bednarczyk

“It is a unique find,” says professor Paweł Valde-Nowak from the Jagiellonian University, adding that there have been very few instances where fragments of bones belonging to the distant relatives of the modern man have been unearthed on Polish soil.


“Neanderthal remains found in Poland can literally be counted on the fingers of one hand,” the researcher says, adding that the Neanderthals have first appeared in this part of the continent about 300,000 years ago, with the oldest stone tools discovered here being 200,000 years old.


Unlike bone fragments, these findings were quite numerous, even though nearly all of them have been located in southern parts of the country as the north had been covered by the ice sheet at the time.


The European Neanderthals became mostly extinct about 35,000 years ago, although recent findings suggest some may have survived even 10,000 years beyond that time. Unlike in Western Europe, there is no evidence that the Neanderthal and the modern man coexisted in this part of the continent. “We are still debating on how long did the Neanderthal inhabit the European continent, including Poland.” professor Valde-Nowak says. “Unfortunately, so far we haven’t been able to come up with convincing evidence.”


Source: Poland in English [October 05, 2018]



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World Teacher Appreciation Day!

On #WorldTeachersDay, we are recognizing our two current astronauts who are former classroom teachers, Joe Acaba and Ricky Arnold, as well as honoring teachers everywhere. What better way to celebrate than by learning from teachers who are literally out-of-this-world!


During the past Year of Education on Station, astronauts connected with more than 175,000 students and 40,000 teachers during live Q & A sessions. 


Let’s take a look at some of the questions those students asked:


The view from space is supposed to be amazing. Is it really that great and could you explain? 



Taking a look at our home planet from the International Space Station is one of the most fascinating things to see! The views and vistas are unforgettable, and you want to take everyone you know to the Cupola (window) to experience this. Want to see what the view is like? Check out earthkam to learn more.


What kind of experiments do you do in space?



There are several experiments that take place on a continuous basis aboard the orbiting laboratory – anything from combustion to life sciences to horticulture. Several organizations around the world have had the opportunity to test their experiments 250 miles off the surface of the Earth. 


What is the most overlooked attribute of an astronaut?



If you are a good listener and follower, you can be successful on the space station. As you work with your team, you can rely on each other’s strengths to achieve a common goal. Each astronaut needs to have expeditionary skills to be successful. Check out some of those skills here. 


Are you able to grow any plants on the International Space Station?



Nothing excites Serena Auñón-Chancellor more than seeing a living, green plant on the International Space Station. She can’t wait to use some of the lettuce harvest to top her next burger! Learn more about the plants that Serena sees on station here. 


What food are you growing on the ISS and which tastes the best? 



While aboard the International Space Station, taste buds may not react the same way as they do on earth but the astronauts have access to a variety of snacks and meals. They have also grown 12 variants of lettuce that they have had the opportunity to taste.


Learn more about Joe Acaba, Ricky Arnold, and the Year of Education on Station.


Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.


Explosive Beginnings Seen down a high-powered microscope, these…


Explosive Beginnings


Seen down a high-powered microscope, these red shapes are endothelial cells – normally found making up the lining of blood vessels – growing on a tiny bead. This enthusiastic ‘sprouting’ is the first step in the formation of new blood vessels, which are essential for a foetus growing in the womb or during wound healing, but highly dangerous if they start to feed a growing tumour. By taking such a detailed look at the very earliest stages of blood vessel growth in a three-dimensional system, researchers are hoping to understand more about how the environment around endothelial cells encourages them to sprout. In the future, this knowledge could point towards new ways to repair or reconnect damaged blood vessels, such as after a heart attack. It could also lead to novel cancer treatments designed to halt the spread of unwanted blood vessels into tumours, cutting off the supply of oxygen and nutrients.


Written by Kat Arney



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Tracing the Universe: X-ray survey supports standard cosmological model


ESA – XMM-Newton Mission patch.


05 October 2018


Scanning the sky for X-ray sources, ESA’s XMM-Newton X-ray observatory has been busy with the XXL Survey, its largest observational programme to date. The second batch of data from the survey has just been released, including information on 365 galaxy clusters, which trace the large-scale structure of the Universe and its evolution through time, and on 26 000 active galactic nuclei (AGN).



Image above: The 365 galaxy clusters of the XXL Survey – X-ray view. Image Credits: ESA/XMM-Newton/XXL Survey.


By examining two large regions of the sky at great sensitivity, this is the first X-ray survey to detect enough galaxy clusters and AGN in contiguous volumes of space to make it possible for scientists to map the distribution of these objects out to the distant Universe in unprecedented detail. The results are compatible with expectations from the currently-accepted cosmological model.


X-rays are produced in some of the most energetic processes in the Universe, but because they are blocked by Earth’s atmosphere, they can only be observed from space. When X-ray telescopes observe the extragalactic Universe, they basically see two sources: the hot gas pervading clusters of galaxies, and Active Galactic Nuclei (AGN) – bright, compact regions at the centres of some galaxies where a supermassive black hole is accreting the surrounding matter.


ESA’s XMM-Newton is one of the most powerful X-ray telescopes ever placed in orbit. Over the last eight years, it has spent 2000 hours measuring X-ray radiation as part of the XXL Survey, which searched for galaxy clusters and AGN by scanning two areas of seemingly-empty sky each measuring 25 square degrees (as a reference, the full moon measures about half a degree across).


The first set of XXL data was released in 2015; it included 100 of the brightest galaxy clusters and 1000 AGN. This month, a new data catalogue was published containing an astonishing 365 clusters and 26 000 AGN. The first results using this data are published in a special issue of Astronomy & Astrophysics: https://www.aanda.org/component/toc/?task=topic&id=927


The survey mapped X-ray clusters so distant that the light left them when the Universe was just half of its present age, and AGN that are even further away. Some of the observed sources are so far-flung that XMM-Newton received no more than 50 X-ray photons from them, making it challenging to tell whether they are clusters or AGN.



Image above: Multi-wavelength view of galaxy cluster XLSSC006. Image Credits: ESA/XMM-Newton (X-rays); CFHT (optical); XXL Survey.


“It was relatively easy to find galaxy clusters and AGN, because they are the only extragalactic objects visible in X-ray light,” explains Marguerite Pierre from CEA Saclay, France.


“But we had to use several other telescopes collecting light at many different wavelengths, as well as extensive computing facilities, to gather more information about each source, including pinning down their nature and distance.”


Matter in the Universe is not evenly distributed but forms a cosmic web of filaments shaped by gravity, with galaxy clusters found at their intersections. Galaxy clusters are the largest bound entities in the Universe – they trace the highest density peaks in its large-scale structure, making them a powerful tool for answering questions about cosmology.


The structure and evolution of the Universe is described by a set of cosmological parameters, which include the density of its various components and the rate that it is expanding. Currently, we know the value of many of these parameters fairly well, but large samples of cosmic tracers at a variety of distances are required to more accurately describe the underlying structure of the Universe. The ultimate goal of the XXL Survey is to provide an extensive, well-characterised catalogue of clusters that can be used to constrain the cosmological parameters.


ESA’s Planck satellite determined values for cosmological parameters by studying the cosmic microwave background, which is information from the very early Universe. After estimating these parameters using the latest data from the XXL Survey – which is based on information from the more recent Universe – scientists compared their findings against the Planck values.



XMM-Newton. Image Credit: ESA

“Although we didn’t find as many galaxy clusters as predicted by the Planck cosmological model, we obtained a distribution of clusters and AGN that is compatible with the currently favoured cosmological model, which resorts to Einstein’s cosmological constant as an explanation for the accelerated expansion of the Universe, rather than invoking even more exotic possibilities,” explains Marguerite Pierre.


“We can already improve on the Planck estimate for the cosmological constant, even though our analysis has only been carried out on half of the XXL cluster sample; we will spend the next couple of years analysing the rest of the data with the aim of refining the cosmological constraints.”


It is more difficult to estimate values for the cosmological parameters using AGN, as their properties are affected by many external influences. Scientists have instead been using the AGN data from the XXL Survey to understand more about how black holes form and evolve.


Thanks to XXL, this is the first time that scientists have been able to measure the three-dimensional clustering effect of distant X-ray clusters and AGN on very large scales. They can now finally see where the AGN are located within the large-scale structure of the Universe indicated by the galaxy clusters.


The results confirm that XMM-Newton is a powerful survey machine. They also pave the way for the final cosmological analysis of this survey, which will provide independent constraints on the cosmological parameters to unravel more mysteries of the Universe.



Image above: The 365 galaxy clusters of the XXL Survey – Optical view. Image Credits: CFHT Legacy Survey/CTIO/XXL Survey.


The cosmic web will be probed further by ESA’s future Euclid satellite, which will observe light emitted up to 10 billion years ago. Euclid will see a huge number of sources, as it will detect optical and infrared light; with its large surveyed area and rich multi-wavelength coverage, the XXL data will serve as a reference for these observations.


Observations by XMM-Newton have also raised new questions about the physics of galaxy clusters, which will be investigated in greater detail by ESA’s next X-ray mission, Athena. Due to launch in 2031, Athena will be far more sensitive than its predecessor. While XMM-Newton can observe clusters at a variety of distances from us, probing different epochs in the Universe’s history, Athena will observe clusters so distant that their light left them as they were forming, telling us even more about the way these gigantic structures take shape and evolve.


In the meantime, scientists in the XXL collaboration plan to process the remaining observations and review data using improved processing techniques. The final XXL data release containing even more X-ray sources, as well as the complete cosmological analysis, is foreseen for 2021.


“It is very exciting that data from this space telescope is contributing to our understanding of the evolution of the Universe,” concludes Norbert Schartel, XMM-Newton Project Scientist at ESA. “This was made possible thanks to the collaboration between a huge number of institutions across many different countries.”


Notes for Editors:


The results are presented in a series of 20 papers by the XXL Survey collaboration, published in a special issue of Astronomy & Astrophysics: https://www.aanda.org/component/toc/?task=topic&id=927


The European Space Agency’s X-ray Multi-Mirror Mission, XMM-Newton, was launched in December 1999. The largest scientific satellite to have been built in Europe, it is also one of the most sensitive X-ray observatories ever flown. More than 170 wafer-thin, cylindrical mirrors direct incoming radiation into three high-throughput X-ray telescopes. XMM-Newton’s orbit takes it almost a third of the way to the Moon, allowing for long, uninterrupted views of celestial objects.


XXL is an international project based around an XMM Very Large Programme surveying two 25 square degree extragalactic fields at a depth of about 5 × 10-15 erg cm-2 s-1 in the 0.5-2 keV band for point-like sources. Multi-band information and spectroscopic follow-up of the X-ray sources are obtained through a number of survey programmes.


Besides XMM-Newton, the study is based on data from the following telescopes and astronomical facilities: the European Southern Observatory (ESO) in Chile; the Canada-France-Hawaii Telescope in Hawaii, USA; the William Herschel Telescope on La Palma, Canary Islands, Spain; the Anglo-Australian Telescope at the Siding Spring Observatory, Australia; the Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile; the Giant Metrewave Radio Telescope near Pune, India; the Australia Telescope Compact Array at the Paul Wild Observatory, Australia; and NASA’s Spitzer Space Telescope.


The study also relies on extensive calculations performed at the computing centres of IN2P3/CNRS, France, of the University of Geneva, Switzerland, of the Laboratoire d’Astrophysique de Marseille, France, and of the INAF-IASF in Milan, Italy.


Related links:


ESA’s Planck satellite: http://sci.esa.int/planck


ESA’s future Euclid satellite: http://sci.esa.int/euclid


ESA’s next X-ray mission, Athena: http://sci.esa.int/athena


ESA’s XMM-Newton: http://sci.esa.int/xmm-newton/


Images (mentioned), Text, Credit: ESA.


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Fluorite | #Geology #GeologyPage #Mineral Locality: Shangbao,…


Fluorite | #Geology #GeologyPage #Mineral


Locality: Shangbao, Leiyang Co., Hengyang Prefecture, Hunan Province, China


Size: 7.5 x 6 x 4 cm


Photo Copyright © Anton Watzl Minerals


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Wave Rock | #Geology #GeologyPage #Australia Wave Rock is a…


Wave Rock | #Geology #GeologyPage #Australia


Wave Rock is a natural rock formation that is shaped like a tall breaking ocean wave. The “wave” is about 14 m (46 ft) high and around 110 m (360 ft) long. It forms the north side of a solitary hill, which is known as “Hyden Rock”. This hill, which is a granite inselberg, lies about 3 km (2 mi) east of the small town of Hyden and 296 km (184 mi) east-southeast of Perth, Western Australia. Wave Rock and Hyden Rock are part of a 160 ha (395-acre) nature reserve, Hyden Wildlife Park.


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Fluorite on Barite | #Geology #GeologyPage #Mineral Locality:…


Fluorite on Barite | #Geology #GeologyPage #Mineral


Locality: Berbes Mining area, Ribadesella, Asturias, Spain


Size: 5.4 x 4.3 x 4


Photo Copyright © Saphira Minerals


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Topaz | #Geology #GeologyPage #Mineral Locality:…


Topaz | #Geology #GeologyPage #Mineral


Locality: Maynard’s Claim, Thomas Range, Juab Co., Utah, USA


Size: 4.5 x 3 x 3


Photo Copyright © Saphira Minerals


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Tourmaline | #Geology #GeologyPage #Mineral Locality: Oceanview…


Tourmaline | #Geology #GeologyPage #Mineral


Locality: Oceanview Mine, Pala, San Diego Co., California, USA

Size: 7.2 x 4.8 x 4 cm


Photo Copyright © Anton Watzl Minerals


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2018 October 5 The Last Days of Venus as the Evening Star …


2018 October 5


The Last Days of Venus as the Evening Star
Image Credit & Copyright: Radu-Mihai Anghel


Explanation: That’s not a young crescent Moon poised above the hills along the western horizon at sunset. It’s Venus in a crescent phase. About 54 million kilometers away and less than 20 percent illuminated, it was captured by telescope and camera on September 30 near Bacau, Romania. The bright celestial beacon is now languishing in the evening twilight, its days as the Evening Star in 2018 coming to a close. But it also grows larger in apparent size and becomes an ever thinner crescent in telescopic views. Heading toward an inferior conjunction (non-judgmental), the inner planet will be positioned between Earth and Sun on October 26 and lost from view in the solar glare. At month’s end a crescent Venus will reappear in the east though, rising just before the Sun as the brilliant Morning Star.


∞ Source: apod.nasa.gov/apod/ap181005.html


Curiosity Rover to Temporarily Switch ‘Brains’


NASA – Mars Science Laboratory (MSL) patch.


Oct. 4, 2018



Image above: A self-portrait of NASA’s Curiosity rover taken on Sol 2082 (June 15, 2018). A Martian dust storm has reduced sunlight and visibility at the rover’s location in Gale Crater. Image Credits: NASA/JPL-Caltech.


Engineers at NASA’s Jet Propulsion Laboratory in Pasadena, California, this week commanded the agency’s Curiosity rover to switch to its second computer. The switch will enable engineers to do a detailed diagnosis of a technical issue that has prevented the rover’s active computer from storing science and some key engineering data since Sept. 15.


Like many NASA spacecraft, Curiosity was designed with two, redundant computers — in this case, referred to as a Side-A and a Side-B computer — so that it can continue operations if one experiences a glitch. After reviewing several options, JPL engineers recommended that the rover switch from Side B to Side A, the computer the rover used initially after landing.


The rover continues to send limited engineering data stored in short-term memory when it connects to a relay orbiter. It is otherwise healthy and receiving commands. But whatever is preventing Curiosity from storing science data in long-term memory is also preventing the storage of the rover’s event records, a journal of all its actions that engineers need in order to make a diagnosis. The computer swap will allow data and event records to be stored on the Side-A computer.


Side A experienced hardware and software issues over five years ago on sol 200 of the mission, leaving the rover uncommandable and running down its battery. At that time, the team successfully switched to Side B. Engineers have since diagnosed and quarantined the part of Side A’s memory that was affected so that computer is again available to support the mission.


“At this point, we’re confident we’ll be getting back to full operations, but it’s too early to say how soon,” said Steven Lee of JPL, Curiosity’s deputy project manager. “We are operating on Side A starting today, but it could take us time to fully understand the root cause of the issue and devise workarounds for the memory on Side B.


“We spent the last week checking out Side A and preparing it for the swap,” Lee said. “It’s certainly possible to run the mission on the Side-A computer if we really need to. But our plan is to switch back to Side B as soon as we can fix the problem to utilize its larger memory size.”


For more about Curiosity, visit: https://mars.nasa.gov/msl/


For more about NASA’s Mars program, visit: https://mars.nasa.gov


Image (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Andrew Good.


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VLA Sky Survey Reveals First “Orphan” Gamma Ray Burst


Artist’s conception of a gamma ray burst. Jet of fast-moving material is propelled outward through spherical shell of ejected material from initial explosion of a massive star and its collapse into a black hole. Credit: Bill Saxton, NRAO/AUI/NSF. Hi-res image



Series of radio images of FIRST J1419+3940 from 1993 to 2017 show its slow fade.

Credit: Law et al., Bill Saxton, NRAO/AUI/NSF 




Animation of images from 1993 to 2017 shows radio emission from suspected “orphan” gamma ray burst fading with time.


Credit: Law et al., Bill Saxton, NRAO/AUI/NSF




Astronomers comparing data from an ongoing major survey of the sky using the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) to data from earlier surveys likely have made the first discovery of the afterglow of a powerful gamma ray burst that produced no gamma rays detectable at Earth. The unprecedented discovery of this “orphan” gamma ray burst (GRB) offers key clues to understanding the aftermath of these highly energetic events.


“GRBs emit their gamma rays in narrowly focused beams. In this case, we believe the beams were pointed away from Earth, so gamma ray telescopes did not see this event. What we found is the radio emission from the explosion’s aftermath, acting over time much as we expect for a GRB,” said Casey Law, of the University of California, Berkeley.


While searching through data from the first epoch of observing for the VLA Sky Survey (VLASS) in late 2017, the astronomers noted that an object that appeared in images from an earlier VLA survey in 1994 did not appear in the VLASS images. They then searched for additional data from the VLA and other radio telescopes. They found that observations of the object’s location in the sky dating back as far as 1975 had not detected it until it first appeared in a VLA image from 1993.


The object then appeared in several images made with the VLA and the Westerbork telescope in the Netherlands from 1993 through 2015. The object, dubbed FIRST J1419+3940, is in the outskirts of a galaxy more than 280 million light-years from Earth.


“This is a small galaxy with active star formation, similar to others in which we have seen the type of GRBs that result when a very massive star explodes,” Law said.


The strength of the radio emission from J1419+3940 and the fact that it slowly evolved over time support the idea that it is the afterglow of such a GRB, the scientists said. They suggested that the explosion and burst of gamma rays should have been seen sometime in 1992 or 1993.


However, after searching databases from gamma ray observatories, “We could find no convincing candidate for a detected GRB from this galaxy,” Law said.


While there are other possible explanations for the object’s behavior, the scientists said that a GRB is the most likely.


“This is exciting, and not just because it probably is the first ‘orphan’ GRB to be discovered. It also is the oldest well-localized GRB, and the long time period during which it has been observed means it can give us valuable new information about GRB afterglows,” Law said.


“Until now, we’ve never seen how the afterglows of GRBs behave at such late times,” noted Brian Metzger of Columbia University, co-author of the study. “If a neutron star is responsible for powering the GRB and is still active, this might give us an unprecedented opportunity to view this activity as the expanding ejecta from the supernova explosion finally becomes transparent.”


“I’m delighted to see this discovery, which I expect will be the first of many to come from the unique investment the National Radio Astronomy Observatory (NRAO) and the National Science Foundation are making in VLASS,” said NRAO Director Tony Beasley.


VLASS is the largest observing project in the history of the VLA. Begun in 2017, the survey will use 5,500 hours of observing time over seven years. The survey will make three complete scans of the sky visible from the VLA, roughly 80 percent of the sky. Initial images from the first round of observations now are available to astronomers.


VLASS follows two earlier sky surveys done with the VLA. The NRAO VLA Sky Survey (NVSS), like VLASS, was an all-sky survey done from 1993 to 1996, and the FIRST (Faint Images of the Radio Sky at Twenty centimeters) survey studied a smaller portion of the sky in more detail from 1993 to 2002. The astronomers discovered FIRST J1419+3940 by comparing a 1994 image from the FIRST survey to the VLASS 2017 data.


From 2001 to 2012, the VLA underwent a major upgrade, greatly increasing its sensitivity, or ability to image faint objects. The upgrade made possible a new, improved survey offering a rich scientific payoff. The earlier surveys have been cited more than 4,500 times in scientific papers, and scientists expect VLASS to be a valuable resource for research in the coming years.


Law and his colleagues are publishing their findings in the Astrophysical Journal Letters.


The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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Black holes ruled out as universe’s missing dark matter

For one brief shining moment after the 2015 detection of gravitational waves from colliding black holes, astronomers held out hope that the universe’s mysterious dark matter might consist of a plenitude of black holes sprinkled throughout the universe. University of California, Berkeley, physicists have dashed those hopes.











Black holes ruled out as universe's missing dark matter
A supernova (bright spot at lower left) and its host galaxy (upper center), as they would appear if gravitationally lensed
by an intervening black hole (center). The gravitational field of the black hole distorts and magnifies the image and makes
both the galaxy and the supernova shine brighter. Gravitationally magnified supernovas would occur rather frequently
 if black holes were the dominant form of matter in the universe. The lack of such findings can be used to set limits
on the mass and abundance of black holes [Credit: Miguel Zumalacarregui/UC Berkeley]

Based on a statistical analysis of 740 of the brightest supernovas discovered as of 2014, and the fact that none of them appear to be magnified or brightened by hidden black hole “gravitational lenses,” the researchers concluded that primordial black holes can make up no more than about 40 percent of the dark matter in the universe. Primordial black holes could only have been created within the first milliseconds of the Big Bang as regions of the universe with a concentrated mass tens or hundreds of times that of the sun collapsed into objects a hundred kilometers across.


The results suggest that none of the universe’s dark matter consists of heavy black holes, or any similar object, including massive compact halo objects, so-called MACHOs.


Dark matter is one of astronomy’s most embarrassing conundrums: despite comprising 84.5 percent of the matter in the universe, no one can find it. Proposed dark matter candidates span nearly 90 orders of magnitude in mass, from ultralight particles like axions to MACHOs.


Several theorists have proposed scenarios in which there are multiple types of dark matter. But if dark matter consists of several unrelated components, each would require a different explanation for its origin, which makes the models very complex.


“I can imagine it being two types of black holes, very heavy and very light ones, or black holes and new particles. But in that case one of the components is orders of magnitude heavier than the other, and they need to be produced in comparable abundance. We would be going from something astrophysical to something that is truly microscopic, perhaps even the lightest thing in the universe, and that would be very difficult to explain,” said lead author Miguel Zumalacárregui, a Marie Curie Global Fellow at the Berkeley Center for Cosmological Physics.


An as-yet unpublished reanalysis by the same team using an updated list of 1,048 supernovas cuts the limit in half, to a maximum of about 23 percent, further slamming the door on the dark matter-black hole proposal.


“We are back to the standard discussions. What is dark matter? Indeed, we are running out of good options,” said Uroš Seljak, a UC Berkeley professor of physics and astronomy and BCCP co-director. “This is a challenge for future generations.”


The analysis is detailed in a paper published this week in the journal Physical Review Letters.


Dark matter lensing


Their conclusions are based on the fact that an unseen population of primordial black holes, or any massive compact object, would gravitationally bend and magnify light from distant objects on its way to Earth. Therefore, gravitational lensing should affect the light from distant Type Ia supernovas. These are the exploding stars that scientists have used as standard brightness sources to measure cosmic distances and document the expansion of the universe.


Zumalacárregui conducted a complex statistical analysis of data on the brightness and distance supernovas catalogued in two compilations — 580 in the Union and 740 in the joint light-curve analysis (JLA) catalogs — and concluded that eight should be brighter by a few tenths of a percent than predicted based on observations of how these supernovas brighten and fade over time. No such brightening has been detected.


Other researchers have performed similar but simpler analyses that yielded inconclusive results. But Zumalacárregui incorporated the precise probability of seeing all magnifications, from small to huge, as well as uncertainties in brightness and distance of each supernova. Even for low-mass black holes — those 1 percent the mass of the sun — there should be some highly magnified distant supernovas, he said, but there are none.


“You cannot see this effect on one supernova, but when you put them all together and do a full Bayesian analysis you start putting very strong constraints on the dark matter, because each supernova counts and you have so many of them,” Zumalacárregui said. The more supernovas included in the analysis, and the farther away they are, the tighter the constraints. Data on 1,048 bright supernovas from the Pantheon catalog provided an even lower upper limit — 23 percent — than the newly published analysis.


Seljak published a paper proposing this type of analysis in the late 1990s, but when interest shifted from looking for big objects, MACHOs, to looking for fundamental particles, in particular weakly interacting massive particles, or WIMPs, follow-up plans fell by the wayside. By then, many experiments had excluded most masses and types of MACHOs, leaving little hope of discovering such objects.


At the time, too, only a small number of distant Type Ia supernovas had been discovered and their distances measured.


Only after the LIGO observations brought up the issue again did Seljak and Zumalacárregui embark on the complicated analysis to determine the limits on dark matter.


“What was intriguing is that the masses of the black holes in the LIGO event were right where black holes had not yet been excluded as dark matter,” Seljak said. “That was an interesting coincidence that got everyone excited. But it was a coincidence.”


Author: Robert Sanders | Source: University of California – Berkeley [October 03, 2018]



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Detailed look at white dwarf orbited by planetary fragments

A new study, led by Paula Izquierdo, a doctoral student at the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), has gone deeply into the analysis of this exceptional white dwarf, which shows periodic transits produced by fragments of a shredded planetesimal. The observations used for this research were obtained with the Gran Telescopio Canarias and with the Liverpool Telescope.











Detailed look at white dwarf orbited by planetary fragments
This artist’s rendering shows a disk of dust and planetary fragments around a star
[Credit: NASA/JPL-Caltech]

The article, published recently in the journal Monthly Notices of the Royal Astronomical Society (MNRAS), confirms the ongoing evolution of the transits produced by remnants of a planetesimal orbiting the white dwarf WD 1145+017. This “debris” passes in front of the star every 4.5 hours, blocking a fraction of the light from the star. Continuous interaction and fragmentation of these chunks of debris brings about major changes in the depth and the shape of the observed transits.


WD 1145+017 is a white dwarf, the remaining core of a star which has exhausted its nuclear fuel. Most white dwarfs have masses less than that of the Sun, and sizes similar to Earth. Many studies indicate that 95% of all the stars in the universe will end their lives as white dwarfs, among them our own Sun.


“Studying this system will give us information about the future of our Solar System,” explains Paula Izquierdo, the lead author of the paper. For that reason WD 1145+017 is special. It is the first white dwarf for which changes in brightness due to occultations (part of the light from the star is blocked by the fragments of a rocky body in a 4.5-hour orbit) have been detected and undergoing continuous collisions resulting ultimately in their disintegration.


Although this system was discovered only in 2015 it has already drawn the attention of a large number of research groups. This most recent study presents the first simultaneous spectroscopic data, obtained with the Gran Telescopio Canarias (10.4m) and photometric data from the Liverpool Telescope (2m), both of which at the Roque de los Muchachos Observatory (Garafía, La Palma).


“When the system is out of transit, we assume that we detect 100% of the flux, because nothing gets in the way of the light emitted by the white dwarf,” explains the researcher at the IAC/ULL. “But when the planetary debris orbiting the star crosses our sight line,” she adds, “which happens during a transit, the amount of light we receive is reduced. This reduction is as large as 50% in the deepest transit we have observed: large clouds of dust blowing off the planetesimal fragments are able to occult half the light from the white dwarf.”


The study also confirms that the transits in the visible range of light are “grey.” That is to say there is no relation between the depth of the transits and their colour, which causes the transits to be equally deep in the five wavebands studied. The authors discuss a new hypothesis in which the observed drop in the amount of light is due to an optically-thick structure, not to an optically-thin structure as previously proposed.


“The deepest transit shows a complex structure which we have been able to model using the superposition of different dust clouds, as if it was produced by six equally spaced fragments coming from the planetesimal,” explains Pablo Rodríguez-Gil, coauthor of the article, researcher at the IAC, and associate professor at the ULL.


Among the different findings, the team has observed a reduction in the quantity of absorption produced by iron during the deepest transit detected: “Part of this absorption,” states coauthor Boris Gänsicke, an astronomer at the University of Warwick (United Kingdom), “does not originate in the atmosphere of the white dwarf, but in a disc of gas also orbiting around it, so we have demonstrated that the disc of fragments and the gas disc must be spatially related.”


Finally, they used the distance at which WD 1145+017 is placed, obtained from the Gaia mission, to derive the mass, radius, temperature, and age of the system.


Source: Instituto de Astrofísica de Canarias (IAC) [October 03, 2018]




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