пятница, 10 января 2020 г.

NASA planet hunter finds its first Earth-size habitable-zone world


NASA's Transiting Exoplanet Survey Satellite (TESS) has discovered its first Earth-size planet in its star's habitable zone, the range of distances where conditions may be just right to allow the presence of liquid water on the surface. Scientists confirmed the find, called TOI 700 d, using NASA's Spitzer Space Telescope and have modeled the planet's potential environments to help inform future observations.

NASA planet hunter finds its first Earth-size habitable-zone world
This illustration of TOI 700 d is based on several simulated environments for an ocean-covered 
version of the planet [Credit: NASA's Goddard Space Flight Center]
TOI 700 d is one of only a few Earth-size planets discovered in a star's habitable zone so far. Others include several planets in the TRAPPIST-1 system and other worlds discovered by NASA's Kepler Space Telescope.

"TESS was designed and launched specifically to find Earth-sized planets orbiting nearby stars," said Paul Hertz, astrophysics division director at NASA Headquarters in Washington. "Planets around nearby stars are easiest to follow-up with larger telescopes in space and on Earth. Discovering TOI 700 d is a key science finding for TESS. Confirming the planet's size and habitable zone status with Spitzer is another win for Spitzer as it approaches the end of science operations this January."

TESS monitors large swaths of the sky, called sectors, for 27 days at a time. This long stare allows the satellite to track changes in stellar brightness caused by an orbiting planet crossing in front of its star from our perspective, an event called a transit.


TOI 700 is a small, cool M dwarf star located just over 100 light-years away in the southern constellation Dorado. It's roughly 40% of the Sun's mass and size and about half its surface temperature. The star appears in 11 of the 13 sectors TESS observed during the mission's first year, and scientists caught multiple transits by its three planets.

The star was originally misclassified in the TESS database as being more similar to our Sun, which meant the planets appeared larger and hotter than they really are. Several researchers, including Alton Spencer, a high school student working with members of the TESS team, identified the error.

"When we corrected the star's parameters, the sizes of its planets dropped, and we realized the outermost one was about the size of Earth and in the habitable zone," said Emily Gilbert, a graduate student at the University of Chicago. "Additionally, in 11 months of data we saw no flares from the star, which improves the chances TOI 700 d is habitable and makes it easier to model its atmospheric and surface conditions."

NASA planet hunter finds its first Earth-size habitable-zone world
TOI 700, a planetary system 100 light-years away in the constellation Dorado, is home to TOI 700 d, the first 
Earth-size habitable-zone planet discovered by NASA's Transiting Exoplanet Survey Satellite 
[Credit: NASA's Goddard Space Flight Center]
Gilbert and other researchers presented the findings at the 235th meeting of the American Astronomical Society in Honolulu, and three papers -- one of which Gilbert led -- have been submitted to scientific journals.

The innermost planet, called TOI 700 b, is almost exactly Earth-size, is probably rocky and completes an orbit every 10 days. The middle planet, TOI 700 c, is 2.6 times larger than Earth -- between the sizes of Earth and Neptune -- orbits every 16 days and is likely a gas-dominated world. TOI 700 d, the outermost known planet in the system and the only one in the habitable zone, measures 20% larger than Earth, orbits every 37 days and receives from its star 86% of the energy that the Sun provides to Earth. All of the planets are thought to be tidally locked to their star, which means they rotate once per orbit so that one side is constantly bathed in daylight.

A team of scientists led by Joseph Rodriguez, an astronomer at the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts, requested follow-up observations with Spitzer to confirm TOI 700 d.


"Given the impact of this discovery -- that it is TESS's first habitable-zone Earth-size planet -- we really wanted our understanding of this system to be as concrete as possible," Rodriguez said. "Spitzer saw TOI 700 d transit exactly when we expected it to. It's a great addition to the legacy of a mission that helped confirm two of the TRAPPIST-1 planets and identify five more."

The Spitzer data increased scientists' confidence that TOI 700 d is a real planet and sharpened their measurements of its orbital period by 56% and its size by 38%. It also ruled out other possible astrophysical causes of the transit signal, such as the presence of a smaller, dimmer companion star in the system.

Rodriguez and his colleagues also used follow-up observations from a 1-meter ground-based telescope in the global Las Cumbres Observatory network to improve scientists' confidence in the orbital period and size of TOI 700 c by 30% and 36%, respectively.


Because TOI 700 is bright, nearby, and shows no sign of stellar flares, the system is a prime candidate for precise mass measurements by current ground-based observatories. These measurements could confirm scientists' estimates that the inner and outer planets are rocky and the middle planet is made of gas.

Future missions may be able to identify whether the planets have atmospheres and, if so, even determine their compositions.

While the exact conditions on TOI 700 d are unknown, scientists can use current information, like the planet's size and the type of star it orbits, to generate computer models and make predictions. Researchers at NASA's Goddard Space Flight Center in Greenbelt, Maryland, modeled 20 potential environments of TOI 700 d to gauge if any version would result in surface temperatures and pressures suitable for habitability.


Their 3D climate models examined a variety of surface types and atmospheric compositions typically associated with what scientists regard to be potentially habitable worlds. Because TOI 700 d is tidally locked to its star, the planet's cloud formations and wind patterns may be strikingly different from Earth's.

One simulation included an ocean-covered TOI 700 d with a dense, carbon-dioxide-dominated atmosphere similar to what scientists suspect surrounded Mars when it was young. The model atmosphere contains a deep layer of clouds on the star-facing side. Another model depicts TOI 700 d as a cloudless, all-land version of modern Earth, where winds flow away from the night side of the planet and converge on the point directly facing the star.

When starlight passes through a planet's atmosphere, it interacts with molecules like carbon dioxide and nitrogen to produce distinct signals, called spectral lines. The modeling team, led by Gabrielle Engelmann-Suissa, a Universities Space Research Association visiting research assistant at Goddard, produced simulated spectra for the 20 modeled versions of TOI 700 d.

"Someday, when we have real spectra from TOI 700 d, we can backtrack, match them to the closest simulated spectrum, and then match that to a model," Engelmann-Suissa said. "It's exciting because no matter what we find out about the planet, it's going to look completely different from what we have here on Earth."

Author: Jeanette Kazmierczak | Source: NASA/Jet Propulsion Laboratory [January 07, 2020]



* This article was originally published here

Ghost worms mostly unchanged since the age of dinosaurs


It is well known that the size, shape and structure of organisms can evolve at different speeds, ranging from fast-evolving adaptive radiations to living fossils such as cichlids or coelacanths, respectively.

Ghost worms mostly unchanged since the age of dinosaurs
Upper specimen: Stygocapitella josemariobrancoi from a beach close to Plymouth, UK: Lower specimen: Stygocapitella
furcata from the 4th of July beach on San Juan island, WA, USA [Credit: Jose Cerca, Christian Meyer,
Gunter Purschke, Torsten H. Struck]
A team led by biologists at the Natural History Museum (University of Oslo) has uncovered a group of species in which change in appearance seems to have been brought to a complete halt. The tiny annelid worms belonging to the genus Stygocapitella live in sandy beaches around the world. In their 275-million-year history, the worms have evolved 10 distinct species.

But what makes the group stand out is the presence of only four morphotypes. Such absence of morphological change has lately proven to be a common feature of many so-called cryptic species complexes, for example, in mammals, snails, crustaceans and jellyfish.


"Cryptic species are species which have already been distinct species for a substantial amount of time, but have accumulated very little or no morphological differences. Such species can help us understand how evolution proceeds in the absence of morphological evolution, and which factors might be important in these cases," explains Professor Torsten Struck at the Natural History Museum (University of Oslo)

Two of the Stygocapitella species that were investigated split apart at the time when stegosaurus and brachiosaurus lived. But despite 140 million years of evolution, these ghost worms today look almost exactly the same. However, looks may be deceiving. Molecular investigations reveal that they are highly genetically distinct, and considered reproductively isolated species.

Ghost worms mostly unchanged since the age of dinosaurs
Meiofauna field collection in Sommaoya (Tromso),
Northern Norway [Credit: Jose Cerca]
In comparison to other cryptic species complexes separated by a maximum of a couple million years, the time span in this complex is 10 times longer, which makes the lack of change in ghost worms extreme.

"These species can also be studied to understand how species respond to extreme ecological changes in the long run. Some of these morphotypes have experienced the much warmer conditions of the Cretaceous as well as the changing intervals of the ice ages," says Struck.


What makes the case of Stygocapitella particularly puzzling is that closely related taxa seem to be evolving morphotypes significantly faster. The findings therefore highlight that evolutionary change in appearance should be viewed as a continuum, ranging from accelerated to decelerated, and where the investigated worms stand out as one of the more extreme cases of the latter. The study also points out that species formation is not necessarily accompanied by morphological changes.

The researchers suggest that lack of morphological change may be linked to the worms having adapted to an environment that has changed little over time.

"Beaches have always been around and had the same composition then as now. We suspect these worms have remained in the same environment for millions and millions of years and they are well adapted. We suspect they have become good in moving around, but not having changed much," explains first author of the study Ph.D. Fellow Jose Cerca. "Alternatively, it has been suggested that populations regularly crash to only a few surviving individuals, and newly evolved characters get eliminated in the course of these events. Finally, besides or instead of the environment, their development may constrain their evolution."

However, the reasons for the slow rate of morphological change are still inconclusive in the current study, and remain to be explored by the group in the future.

The study is published in the journal Evolution.

Source: University of Oslo [January 06, 2020]



* This article was originally published here

Head cones seen in ancient Egyptian art really existed


In ancient Egyptian art, people often can be seen sporting cones on their heads. Now, for the first time, archaeologists have revealed evidence that they actually existed outside of artwork.

Head cones seen in ancient Egyptian art really existed
In 2010, researchers excavating this young woman's grave discovered a waxy cone atop her head
[Credit: Amarna Project, as published in Stevens et al. 2019]
Two head cones made of wax and fabric have been uncovered in graves in Amarna, a city built by the pharaoh Akhenaten and inhabited for some 15 years ending in 1332 BC, according to findings published in the journal Antiquity. The city is home to thousands of graves, including those of ordinary people.

The discovery sheds some light on why Egyptians wore the cones on their heads, and researchers' conclusions differ from a long-held theory that the cones were made from animal fat. Meanwhile, some experts have held that the head cones were merely artistic additions, like the symbolic halos in Christian iconography, rather than real headgear.

"The excavation of two cones confirms that three-dimensional wax-based head cones were sometimes worn by the dead in ancient Egypt, and that access to these objects was not restricted to the upper elite," the researchers said.


Archaeologists excavating some 700 graves found the first head cone in 2010 in the grave of a woman in her twenties. A second was found in 2015 in the grave of someone 15 to 20 years old that had been disturbed by looting.

The cone found atop the woman's head was sitting on her well-preserved hair, the study says. The dome was in six pieces, suggesting a side and a base. Its cream color showed some dark patches and felt "silky" but brittle.

The researchers found evidence of where insects had tunneled through the material, and they found impressions where fabric may have once been on the cone.

Head cones seen in ancient Egyptian art really existed
Plan of excavation of a young woman with a head cone buried at Amarna, Egypt
[Credit: Amarna Project, as published in Stevens et al. 2019]
The second cone was also fragmented -- into one large piece and two smaller ones. It was also largely damaged by insects and had the same dark spots on it. The largest piece of that cone was wax that had shaped itself around organic material, including the hardened remains of soft tissue and body fluids.

Given that the second grave had been disturbed, researchers surmised that as the body degraded, the tissue became incorporated with the wax, according to the findings.

The tradition of cone-shaped headpieces endured in ancient Egyptian art for 1,500 years. The cones could be seen on figures attending banquets, religious events and after their death. Some scenes appear to associate them with sensuality or fertility. They appeared in a variety of colors and were marked with decorations. And the cones could be seen on males and females.


Given the lack of head cones in the archeological record, some researchers believed they were made out of materials that would have long since degraded over time. A prevailing theory is that the cones were perfumed pieces of animal fat or wax called unguent. As the wax melted, the scent of the perfume -- likely myrrh -- would be released, possibly cleansing hair and body. Some Egyptian texts refer to this as a purification process for the person wearing it.

Egyptians buried in the Amarna graves were also found with tweezers, combs, mirrors, eye paints and jewelry.

"All may have, in part, conveyed a sense of desiring to 'look one's best' in the afterlife -- a function the cones too could have served," the researchers said in the study.

Head cones seen in ancient Egyptian art really existed
Two figures wear head cones in a wall painting from the archaeological site of Amarna, Egypt, dating
to around 3,300 years ago [Credit: Amarna Project, as published in Stevens et al. 2019]
Both of the cones were revealed to be largely made of wax derived from plants and animals. The researchers believe that this wax shell was initially shaped around fabric. And given that the wax itself didn't melt, the researchers wondered about the purpose of the cones. It's still possible that the wax was perfumed, but it would have long since evaporated, so they can't know for sure.


The discovery of the cone buried with the woman could suggest the cones are a symbol of rebirth. The cones also may only have been included in some burials under specific circumstances.

"The Armana discovery supports the idea that head cones were also worn by the living, although it remains difficult to ascertain how often and why," the researchers wrote in the study.

"In the case of ancient Akhetaten, we can probably interpret head cones as part of a suite of personal accoutrements deemed appropriate for use in a range of celebrations and rituals for, and involving, the living, the dead, the (sun god) Aten and other deities."

Author: Ashley Strickland | Source: CNN [December 21, 2019]



* This article was originally published here

Mynydd Rhiw Bronze Age Cairn 2, Rhiw, Llyn Peninsula, North Wales, 5.1.20.

Mynydd Rhiw Bronze Age Cairn 2, Rhiw, Llyn Peninsula, North Wales, 5.1.20.



* This article was originally published here

Netherlands returns 1,500 historical artifacts to Indonesia


The Dutch government has returned 1,500 historical artifacts to Indonesia, four years after an agreement was made with the Education and Culture Ministry.

Netherlands returns 1,500 historical artifacts to Indonesia
Credit: National Museum Jakarta
“Basically, there are 1,500 [objects] that used to be held in the Nusantara Museum in Delft, Netherlands, which were returned to Indonesia through the national museum,” Education and Culture Ministry culture director-general Hilman Farid said at a press conference at the National Museum in Central Jakarta as quoted by tempo.co.


The 100-year-old Nusantara Museum was the only museum in the Netherlands dedicated specifically to art and cultural objects from Indonesia, a former Dutch colony, and it closed its doors in 2013 due to financial difficulties.

The museum had initially offered to hand over around 12,000 artifacts to Indonesia, but the culture director-general opted to accept a selection of 1,500 objects instead.

The repatriation process symbolically started in November 2016, when Netherlands Prime Minister Mark Rutte presented President Joko “Jokowi” Widodo with a Bugis keris from the collection.

Netherlands returns 1,500 historical artifacts to Indonesia
Credit: National Museum Jakarta
“This is the first time in the history of Indonesia that Indonesian cultural objects or artifacts that were taken [to the Netherlands] are returned,” Hilman said. “This is very historic and we want to share it with the public. Hopefully, this paves the way for the return of objects in other European museums.”

National Museum head Siswanto said the museum would present the artifacts to the public in an exhibition scheduled for June 2020.


He added that the returned artifacts would not just be limited to the National Museum.

“Other museums will also have the opportunity to get back their cultural objects. This offer might encourage regional museums to improve the quality of their collection.”

Netherlands returns 1,500 historical artifacts to Indonesia
Credit: National Museum Jakarta
Golkar lawmaker Adrianus Asia Sidot of the House Commission X, which oversees art and culture, said he appreciated the Dutch government’s decision to return the artifacts.

“The return [of the artifacts] is a very meaningful New Year’s gift,” Adrianus said in a statement on the official House of Representatives website.

“Going forward, we have the responsibility to safeguard, secure and take care of these valuable historical relics. If other nations value Indonesia’s culture, we should value it even more.”

Source: The Jakarta Post [January 07, 2020]



* This article was originally published here

Castell Bryn Gwyn Prehistoric Earthworks, Anglesey, North Wales, 3.1.20.

Castell Bryn Gwyn Prehistoric Earthworks, Anglesey, North Wales, 3.1.20.



* This article was originally published here

2020 January 10 Nacreous Clouds over Sweden Image Credit &...



2020 January 10

Nacreous Clouds over Sweden
Image Credit & Copyright: P-M Hedén (Clear Skies, TWAN)

Explanation: Vivid and lustrous, wafting iridescent waves of color filled this mountain and skyscape near Tanndalen, Sweden on January 3. Known as nacreous clouds or mother-of-pearl clouds, they are rare. This northern winter season they have been making unforgettable appearances at high latitudes, though. A type of polar stratospheric cloud, they form when unusually cold temperatures in the usually cloudless lower stratosphere form ice crystals. Still sunlit at altitudes of around 15 to 25 kilometers the clouds can diffract sunlight after sunset and before the dawn.

∞ Source: apod.nasa.gov/apod/ap200110.html



* This article was originally published here

The conservation of cultural heritage in the face of climate catastrophe


Cultural heritage can be destroyed. It can decay. Once it is gone, it is gone forever, sadly. Writing in the International Journal of Global Warming, Portuguese researchers discuss the potential impact of climate change on cultural heritage and how we might lose artifacts as extreme weather has a worsening impact on our world.

The conservation of cultural heritage in the face of climate catastrophe
Roman Temple of Évora, Portugal [Credit: WikiCommons]
Guilherme Coelho, Hugo Entradas Silva, and Fernando Henriques of the Universidade NOVA de Lisboa explain that museum pieces are subject to deterioration depending on the conditions in which they are stored, whether or not they are being exhibited or archived.

The indoor climate is obviously more controllable than the outdoor, but nevertheless the increasing cost of air-conditioning, (de)humidification, and temperature control, are all likely to affect in a detrimental way how conservators look after their charges. In addition, sometimes the building themselves are the cultural heritage.


The team has now modelled various climate change scenarios to see how weather conditions might affect a building such as Lisbon's historic church of Saint Christopher. They modelled conditions in Lisbon, but also applied likely conditions associated with Seville (Mediterranean climate), Prague and Oslo (Continental climate), as well as London (Oceanic climate).

They not only consider the integrity of artifacts within but also visitor comfort. After all, what is the purpose of conserving cultural heritage without allowing people to appreciate it? Ultimately, climate change is unlikely to be of benefit to house artifacts in buildings that are themselves cultural artifacts.

Author: David Bradley | Source: Inderscience [January 07, 2020]



* This article was originally published here

Hubble Detects Smallest Known Dark Matter Clumps

Quasars' Multiple Images Shed Light on Tiny Dark Matter Clumps
Credits: NASA, ESA, A. Nierenberg (JPL) and T. Treu (UCLA)

Illustration of Strong Gravitational Lensing
Credits: NASA, ESA, and D. Player (STScI
Release Images



Using NASA's Hubble Space Telescope and a new observing technique, astronomers have found that dark matter forms much smaller clumps than previously known. This result confirms one of the fundamental predictions of the widely accepted "cold dark matter" theory.

All galaxies, according to this theory, form and are embedded within clouds of dark matter. Dark matter itself consists of slow-moving, or “cold,” particles that come together to form structures ranging from hundreds of thousands of times the mass of the Milky Way galaxy to clumps no more massive than the heft of a commercial airplane. (In this context, "cold" refers to the particles' speed.)
The Hubble observation yields new insights into the nature of dark matter and how it behaves. "We made a very compelling observational test for the cold dark matter model and it passes with flying colors," said Tommaso Treu of the University of California, Los Angeles (UCLA), a member of the observing team.

Dark matter is an invisible form of matter that makes up the bulk of the universe's mass and creates the scaffolding upon which galaxies are built. Although astronomers cannot see dark matter, they can detect its presence indirectly by measuring how its gravity affects stars and galaxies. Detecting the smallest dark matter formations by looking for embedded stars can be difficult or impossible, because they contain very few stars.

While dark matter concentrations have been detected around large- and medium-sized galaxies, much smaller clumps of dark matter have not been found until now. In the absence of observational evidence for such small-scale clumps, some researchers have developed alternative theories, including "warm dark matter." This idea suggests that dark matter particles are fast moving, zipping along too quickly to merge and form smaller concentrations. The new observations do not support this scenario, finding that dark matter is "colder" than it would have to be in the warm dark matter alternative theory.

"Dark matter is colder than we knew at smaller scales," said Anna Nierenberg of NASA's Jet Propulsion Laboratory in Pasadena, California, leader of the Hubble survey. "Astronomers have carried out other observational tests of dark matter theories before, but ours provides the strongest evidence yet for the presence of small clumps of cold dark matter. By combining the latest theoretical predictions, statistical tools, and new Hubble observations, we now have a much more robust result than was previously possible."

Hunting for dark matter concentrations devoid of stars has proved challenging. The Hubble research team, however, used a technique in which they did not need to look for the gravitational influence of stars as tracers of dark matter. The team targeted eight powerful and distant cosmic "streetlights," called quasars (regions around active black holes that emit enormous amounts of light). The astronomers measured how the light emitted by oxygen and neon gas orbiting each of the quasars' black holes is warped by the gravity of a massive foreground galaxy, which is acting as a magnifying lens.

Using this method, the team uncovered dark matter clumps along the telescope's line of sight to the quasars, as well as in and around the intervening lensing galaxies. The dark matter concentrations detected by Hubble are 1/10,000th to 1/100,000th times the mass of the Milky Way's dark matter halo. Many of these tiny groupings most likely do not contain even small galaxies, and therefore would have been impossible to detect by the traditional method of looking for embedded stars.

The eight quasars and galaxies were aligned so precisely that the warping effect, called gravitational lensing, produced four distorted images of each quasar. The effect is like looking at a funhouse mirror. Such quadruple images of quasars are rare because of the nearly exact alignment needed between the foreground galaxy and background quasar. However, the researchers needed the multiple images to conduct a more detailed analysis.

The presence of the dark matter clumps alters the apparent brightness and position of each distorted quasar image. Astronomers compared these measurements with predictions of how the quasar images would look without the influence of the dark matter. The researchers used the measurements to calculate the masses of the tiny dark matter concentrations. To analyze the data, the researchers also developed elaborate computing programs and intensive reconstruction techniques.

"Imagine that each one of these eight galaxies is a giant magnifying glass," explained team member Daniel Gilman of UCLA. "Small dark matter clumps act as small cracks on the magnifying glass, altering the brightness and position of the four quasar images compared to what you would expect to see if the glass were smooth."

The researchers used Hubble’s Wide Field Camera 3 to capture the near-infrared light from each quasar and disperse it into its component colors for study with spectroscopy. Unique emissions from the background quasars are best seen in infrared light. "Hubble's observations from space allow us to make these measurements in galaxy systems that would not be accessible with the lower resolution of ground-based telescopes—and Earth's atmosphere is opaque to the infrared light we needed to observe," explained team member Simon Birrer of UCLA.

Treu added: "It's incredible that after nearly 30 years of operation, Hubble is enabling cutting-edge views into fundamental physics and the nature of the universe that we didn't even dream of when the telescope was launched."

The gravitational lenses were discovered by sifting through ground-based surveys such as the Sloan Digital Sky Survey and Dark Energy Survey, which provide the most detailed three-dimensional maps of the universe ever made. The quasars are located roughly 10 billion light-years from Earth; the foreground galaxies, about 2 billion light-years.

The number of small structures detected in the study offers more clues about dark matter's nature. "The particle properties of dark matter affect how many clumps form," Nierenberg explained. "That means you can learn about the particle physics of dark matter by counting the number of small clumps."

However, the type of particle that makes up dark matter is still a mystery. "At present, there's no direct evidence in the lab that dark matter particles exist," Birrer said. "Particle physicists would not even talk about dark matter if the cosmologists didn’t say it's there, based on observations of its effects. When we cosmologists talk about dark matter, we're asking 'how does it govern the appearance of the universe, and on what scales?'"

Astronomers will be able to conduct follow-up studies of dark matter using future NASA space telescopes such as the James Webb Space Telescope and the Wide Field Infrared Survey Telescope (WFIRST), both infrared observatories. Webb will be capable of efficiently obtaining these measurements for all known quadruply lensed quasars. WFIRST's sharpness and large field of view will help astronomers make observations of the entire region of space affected by the immense gravitational field of massive galaxies and galaxy clusters. This will help researchers uncover many more of these rare systems.

The team will present its results at the 235th meeting of the American Astronomical Society in Honolulu, Hawaii.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.




Contact:  

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4493 / 410-338-4514

dweaver@stsci.edu / villard@stsci.edu

Anna Nierenberg
Jet Propulsion Laboratory, Pasadena, California
818-393-5095

anna.m.nierenberg@jpl.nasa.gov

Tommaso Treu / Daniel Gilman
University of California, Los Angeles, California
310-206-5617 (office) / 757-814-5869 (cell)
tt@astro.ucla.edu / gilmana@ucla.edu



Related Links:




* This article was originally published here

Mynydd Rhiw Bronze Age Cairn 3, Rhiw, Llyn Peninsula, North Wales, 5.1.20.

Mynydd Rhiw Bronze Age Cairn 3, Rhiw, Llyn Peninsula, North Wales, 5.1.20.



* This article was originally published here

If trees could talk: Using historic log structures to map migration of Europeans, Native Americans


Log cabins in West Virginia's Appalachian Mountains have a story to tell: when people leave, the forest takes over.

If trees could talk: Using historic log structures to map migration of Europeans, Native Americans
Preparing to collect tree-ring samples from The Pitsenbarger Barn in Pendleton County. The barn was later
determined to have an inferred construction date of 1840 [Credit: Kristen de Graauw]
Researchers at West Virginia University are using tree-ring dating to determine not only when trees were cut down to build historic log buildings in the region but also what the forests were like before European immigrants arrived. This could help researchers shed light on when Native Americans abandoned the area and how their absence altered the landscape.

Geography graduate student Kristen de Graauw and her mentor, Professor Amy Hessl, uncovered evidence of the significant growth of trees in what may have been a previously cleared area. That growth in the late 17th century coincided with the estimated timing of Native American population decreases following the arrival of European immigrants. This corroborated the hypothesis that a change in the land's use caused forests to regrow, they explained.

"The historic logs showed evidence that a lot of trees began to grow at the same time across a fairly large area in West Virginia. This synchronous growth may indicate that trees began growing on cleared land that Native Americans had once inhabited and then abandoned following European contact," de Graauw said. "It's a small area, but we found compelling evidence that a major forest change occurred, and that change coincided with the estimated timing of depopulation in that particular region. However, there was also a sub-continental drought that may have led to broad-scale forest thinning and subsequent tree growth in the 1670s in eastern North America."


De Graauw used dendrochronology, or the science of tree-ring dating, to identify when trees grew and were cut down for construction. She sampled logs from buildings like houses, barns, forts, churches and smokehouses. The buildings are in Greenbrier, Hardy, Pendleton and Pocahontas counties in West Virginia and in Highland County, Virginia.

Their results suggest that the loss of Native American populations from the area may have led to forest regrowth through land abandonment. The evidence of forest regrowth may help local archaeologists better recount when Native Americans depopulated the region, which previously was not well understood.

The oldest log building they have sampled so far was built in 1784.

"We know through historical records that European immigrants moved into the study area around the 1740s to 1760s, yet I have not found a building that is from that time period. It could be that the buildings did not last on the landscape. Some people reused the logs; others may have burned, or logs of dilapidated buildings may have been used for fuel," de Graauw said. "We know that buildings were being constructed prior to the 1780s - we just haven't found them yet."

If trees could talk: Using historic log structures to map migration of Europeans, Native Americans
Kristen de Graauw removes oak core sample from the boring tool
[Credit: West Virginia University/Shawn Cockrell]
To sample the logs, the researchers used a hollowed drill bit to reach the center of each log.

"This method allows us to capture the rings of the tree all the way from its initiation to the very outer ring of the tree, which reflects when that log was cut down out of the forest," de Graauw said. "That very last ring is what tells us when the log was felled with the intention for construction. That allows us to know when it was built. By matching patterns of ring-width variability through time using live trees, dead trees and the logs in the buildings, we are able to assign calendar dates to the logs. We can then estimate when the tree began growing."

As they began their study, the researchers weren't confident that many building owners would allow the researchers to sample their logs. They were surprised by the hospitality they received.

"Most people were willing to help because they wanted to learn how old their buildings were," de Graauw said. "It was sort of a win-win - they got to find out how old their building is and tie that date to historical records, and we got to use the data within those logs to reconstruct past forests."


It is known that Native American populations declined following the arrival of Europeans in the Americas, but it is not well understood when the population decrease occurred in this region or if abandonment of Native American land management techniques would have led to forest regrowth, the researchers explained.

"Sometimes the tree ring record offers a new possibility for understanding history. It's a new line of evidence. The idea is that when people abandoned their cleared areas, forests regrew, but we don't even know what tribal groups were here," Hessl said. "The study needs to be replicated in more places before we can really confirm what we are seeing. But, de Graauw's idea of applying these data from historic buildings to this research question is novel. The fact that she has observed some potential legacies there is really exciting."

In the future, they hope to expand the study by adding other methods, including charcoal records and archaeological techniques, and taking samples in other locations to help disentangle whether trees established as a result of depopulation or the previously identified sub-continental drought event.

"There is so much to still learn about Native Americans at this point in history in eastern North America as far as the spread of epidemics and warfare and when depopulation occurred in different places. The idea is that depopulation wouldn't have all happened at the same time. It would have been spread out based on physical geography and the interactions of people," de Graauw said. "In other regions, I would expect that depopulation would not have necessarily happened at the same time that it did here. There's a difference in timing, which is why working with archaeologists is really important for us."

Dating log buildings has been a hobby of de Graauw's for more than 10 years. It has allowed her to blend her passions for American history and Appalachian folklore with her research interest in forest ecology.

"As I started graduate school, I was trying to find a way to merge my hobby with my academic interests," de Graauw said. "This project really came from that."

The study was published in the Journal of Biogeography.

Source: West Virginia University [January 07, 2020]



* This article was originally published here

Goldilocks Stars Are Best Places to Look for Life

Comparison of G, K, and M Stars for Habitability
Credits: NASA, ESA, and Z. Levy (STScI
Science: NASA , ESA , and E. Guinan (Villanova University)



Orange Dwarf Stars Most Likely to Host Planets

To date astronomers have discovered over 4,000 planets orbiting other stars. Statistically, there should be over 100 billion planets in our Milky Way galaxy. They come in a wide range of sizes and characteristics, largely unimagined before exoplanets were first discovered in the mid-1990s. The biggest motivation for perusing these worlds is to find "Genesis II," a planet where life has arisen and evolved beyond microbes. The ultimate payoff would be finding intelligent life off the Earth.

A major step in searching for habitable planets is finding suitable stars that could foster the emergence of complex organisms. Because our Sun has nurtured life on Earth for nearly 4 billion years, conventional wisdom would suggest that stars like it would be prime candidates. But stars like our Sun represent only about 10% of the Milky Way population. What's more, they are comparatively short-lived. Our Sun is halfway through its estimated 10 billion-year lifetime.

Complex organisms arose on Earth only 500 million years ago. And, the modern form of humans has been here only for the blink of an eye on cosmological timescales: 200,000 years. The future of humanity is unknown. But what is for certain is that Earth will become uninhabitable for higher forms of life in a little over 1 billion years, as the Sun grows warmer and desiccates our planet.

Therefore, stars slightly cooler than our Sun — called orange dwarfs — are considered better hang-outs for advanced life. They can burn steadily for tens of billions of years. This opens up a vast timescape for biological evolution to pursue an infinity of experiments for yielding robust life forms. And, for every star like our Sun there are three times as many orange dwarfs in the Milky Way.

The only type of star that is more abundant are red dwarfs. But these are feisty little stars. They are so magnetically active they pump out 500 times as much radiation in the form of X-rays and ultraviolet light as our Sun does. Planets around these stars take a beating. They would be no place to call home for organisms like us.

An emerging idea, bolstered by stellar surveys performed by Hubble and other telescopes, is that the orange dwarfs are "Goldilocks stars" — not too hot, not too cool, and above all, not too violent to host life-friendly planets over a vast horizon of cosmic time.

In the search for life beyond Earth, astronomers look for planets in a star's "habitable zone" — sometimes nicknamed the "Goldilocks zone" — where temperatures are just right for liquid water to exist on a planet's surface to nurture life as we know it.

An emerging idea, bolstered by a three-decade-long set of stellar surveys, is that there are "Goldilocks stars" — not too hot, not too cool, and above all, not too violent to host life-friendly planets.

Because our Sun has nurtured life on Earth for nearly 4 billion years, conventional wisdom would suggest that stars like it would be prime candidates in the search for other potentially habitable worlds. In reality, stars slightly cooler and less luminous than our Sun, classified as K dwarfs, are the true "Goldilocks stars," said Edward Guinan of Villanova University, Villanova, Pennsylvania. "K-dwarf stars are in the 'sweet spot,' with properties intermediate between the rarer, more luminous, but shorter-lived solar-type stars (G stars) and the more numerous red dwarf stars (M stars). The K stars, especially the warmer ones, have the best of all worlds. If you are looking for planets with habitability, the abundance of K stars pump up your chances of finding life."

For starters, there are three times as many K dwarfs in our galaxy as stars like our Sun. Roughly 1,000 K stars lie within 100 light-years of our Sun as prime candidates for exploration. These so-called orange dwarfs live from 15 billion to 45 billion years. By contrast, our Sun, now already halfway through its lifetime, lasts for only 10 billion years. Its comparatively rapid rate of stellar evolution will leave the Earth largely uninhabitable in just another 1 or 2 billion years. "Solar-type stars limit how long a planet's atmosphere can remain stable," Guinan said. That's because a billion or so years from now, Earth will orbit inside the hotter (inner) edge of the Sun's habitable zone, which moves outward as the Sun grows warmer and brighter. As a result, the Earth will be desiccated as it loses its present atmosphere and oceans. By an age of 9 billion years the Sun will have swelled up to become a red giant that could engulf the Earth.

Despite their small size, the even more abundant red dwarf stars, also known as M dwarf stars, have even longer lifetimes and appear to be hostile to life as we know it. Planets that are located in a red dwarf's comparatively narrow habitable zone, which is very close to the star, are exposed to extreme levels of X-ray and ultraviolet (UV) radiation, which can be up to hundreds of thousands of times more intense than what Earth receives from the Sun. A relentless fireworks show of flares and coronal mass ejections bombard planets with a dragon's breath of seething plasma and showers of penetrating high-energy particles. Red dwarf habitable-zone planets can be baked bone dry and have their atmospheres stripped away very early in their lives. This could likely prohibit the planets from evolving to be more hospitable a few billion years after red dwarf outbursts have subsided. "We're not so optimistic anymore about the chances of finding advanced life around many M stars," Guinan said.

The K dwarfs do not have intensely active magnetic fields that power strong X-ray and UV emissions and energetic outbursts, and therefore they shoot off flares much less frequently, based on Guinan's research. Accompanying planets would get about 1/100th as much deadly X-ray radiation as those orbiting the close-in habitable zones of magnetically-active M stars.

In a program called the "GoldiloKs" Project, Guinan and his Villanova colleague Scott Engle, are working with undergraduate students to measure the age, rotation rate, and X-ray and far-ultraviolet radiation in a sampling of mostly cool G and K stars.They are using NASA's Hubble Space Telescope, Chandra X-ray Observatory, and the European Space Agency's XMM-Newton satellite for their observations. Hubble's sensitive ultraviolet-light observations of radiation from hydrogen were used to assess the radiation from a sample of about 20 orange dwarfs. "Hubble is the only telescope that can do this kind of observation," Guinan said.

Guinan and Engle found that the levels of radiation were much more benign to any accompanying planets than those found around red dwarfs. K stars also have longer lifetimes and therefore slower migration of the habitable zone. Therefore, K dwarfs seem like the ideal place to go looking for life, and these stars would allow time for highly evolved life to develop on planets. Over the Sun's entire lifetime — 10 billion years — K stars only increase their brightness by about 10-15%, giving biological evolution a much longer timespan to evolve advanced life forms than on Earth.

Guinan and Engle looked at some of the more interesting K stars hosting planets, including Kepler-442, Tau Ceti, and Epsilon Eridani. (The latter two were early targets of the late 1950s Project Ozma — the first attempt to detect radio transmissions from extraterrestrial civilizations.)

"Kepler-442 is noteworthy in that this star (spectral classification, K5) hosts what is considered one of the best Goldilocks planets, Kepler-442b, a rocky planet that is a little more than twice Earth's mass. So the Kepler-442 system is a Goldilocks planet hosted by a Goldilocks star!" said Guinan.

Over the last 30 years Guinan and Engle and their students have observed a variety of stellar types. Based on their studies, the researchers have determined relationships among stellar age, rotation rate, X-ray-UV emissions and flare activity. These data have been utilized to investigate the effects of high-energy radiation on planet atmospheres and possible life.

The results are being presented at the 235th meeting of the American Astronomical Societyin Honolulu, Hawaii.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.




Contact:

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu

Edward Guinan
Villanova University, Villanova, Pennsylvania
edward.guinan@villanova.edu

Related Links: NASA's Hubble Portal




* This article was originally published here

Prehistoric Pottery Photoset 1, Oriel Ynys Mon, Llangefni, Anglesey, North Wales, 5.1.20.

Prehistoric Pottery Photoset 1, Oriel Ynys Mon, Llangefni, Anglesey, North Wales, 5.1.20.



* This article was originally published here

Undisturbed burials on school site shed light on Roman Somerset


Ancient burials unearthed at the site of a new school in the town are shedding significant new light on life and death in Roman Somerset.

Undisturbed burials on school site shed light on Roman Somerset
This older female was buried with a pillow supporting her head and a pottery vessel positioned alongside.
The small stone-built coffin-like box is known as a cist and is very unusual for Somerset.
The burial indicates high status [Credit: Wessex Archaeology]
Archaeologists working on the Somerset County Council-owned land have discovered around 50 burials dating from the Roman period (43-410 AD) on the plot for the new premises, which will replace the current King Ina junior and infants schools. The burials were of adults and children and included grave goods such as pottery and brooches.


The South West Heritage Trust has overseen the excavations, and archaeologist Steve Membery said: "This site is a significant discovery - the most comprehensive modern excavation of a Roman cemetery in Somerset.

Undisturbed burials on school site shed light on Roman Somerset
Almost all of the burials found on the site adopted the Roman tradition of placing a pot alongside the head
 in the grave. These objects were placed as offerings [Credit: Wessex Archaeology]
"The application of technology including aerial drones and techniques such as isotope and ancient DNA analysis offers major opportunities for insights into the lives of the Roman population of Somerton."

The form of the burials is unusual locally and sheds lights on the transition between Iron Age and Roman society.

Undisturbed burials on school site shed light on Roman Somerset
At the foot of this burial is a large cooking pot. During post excavation analysis
of the pot it was found to have a chicken wing in the bottom
[Credit: Wessex Archaeology]
"The individuals were evidently of some status in native society," added Mr Membery. "The burials also show early adoption of Roman burial practices, such as offerings, alongside traditionally Iron Age characteristics."


The graves were dug into the bedrock and lined with stone curbs to create a coffin structure. These were then sealed with flat lias slabs, while others have an uncommon tented roof.

Undisturbed burials on school site shed light on Roman Somerset
Aerial view of the site clearly showing the presence of Iron Age roundhouses
[Credit: Wessex Archaeology]
Traces of Iron Age roundhouses, field systems and of a Roman building are also evident.

Work on the new 420-pupil, 14-class school had to be delayed while experts from Wessex Archaeology dug the site and unearthed the fascinating discoveries.

Undisturbed burials on school site shed light on Roman Somerset
This reconstructed ceramic pot was placed in a grave as an offering
[Credit: Wessex Archaeology]
Now the field work has been completed, construction by BAM Construction is expected to start later this month.


Cllr Faye Purbrick, County Hall cabinet member for education and transformation, said: "The findings are both exciting and extraordinary, providing us with valuable insight into Somerset’s early history.

Undisturbed burials on school site shed light on Roman Somerset
An unusual lead weight that was probably part of a survey instrument (similar to a sextant)
called a groma [Credit: Wessex Archaeology]
"We will be able to understand so much more about the lives of Roman people in Somerton thanks to these discoveries.

"Our team have a great track record of delivering fantastic new schools and while we’d always prefer any delay to be avoided, I think that the students, parents and teachers will understand in this instance, given the scale and importance of the archaeological finds here.

Undisturbed burials on school site shed light on Roman Somerset
This coin of Emperor Vespasian 69-79 AD
[Credit: Wessex Archaeology]
"I am looking forward to seeing another new Somerset school reach the construction stage and would like to thank the school for its support throughout.


"The children have already had an opportunity to visit the site, hopefully inspiring some future archaeologists, and I’m sure they will be excited to continue to learn more about this very special site.

Undisturbed burials on school site shed light on Roman Somerset
A brooche [Credit: Wessex Archaeology]
"The site archaeology has been carefully gathered for further scientific analysis. A full report of the findings will be published in due course.

"It is hoped that the discoveries can be used to teach pupils about the history of the area, and that the archaeology of the roundhouses can be reflected in the site development."

Author: Phil Hill | Source: Somerset Country Gazette [January 07, 2020]



* This article was originally published here

Sculptured Stones at Nant Gwrtheyrn, Llyn Peninsula, North Wales, 3.1.20.

Sculptured Stones at Nant Gwrtheyrn, Llyn Peninsula, North Wales, 3.1.20.



* This article was originally published here

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