среда, 16 октября 2019 г.

The Leekfrith Iron Age Torcs, The Potteries Museum and Gallery, Stoke on Trent, 5.10.19.

The Leekfrith Iron Age Torcs, The Potteries Museum and Gallery, Stoke on Trent, 5.10.19.

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The Battle Axe people came from the steppe (Malmstrom et al. 2019)

It’s been obvious for a while now that the Corded Ware culture (CWC) and its Scandinavian variant, the Battle Axe culture (BAC), originated on the Pontic-Caspian steppe. However, Malmstrom et al. drive the point home in a new open access paper at Proceedings B [LINK]. From the paper, emphasis is mine:

The Neolithic period is characterized by major cultural transformations and human migrations, with lasting effects across Europe. To understand the population dynamics in Neolithic Scandinavia and the Baltic Sea area, we investigate the genomes of individuals associated with the Battle Axe Culture (BAC), a Middle Neolithic complex in Scandinavia resembling the continental Corded Ware Culture (CWC). We sequenced 11 individuals (dated to 3330–1665 calibrated before common era (cal BCE)) from modern-day Sweden, Estonia, and Poland to 0.26–3.24× coverage. Three of the individuals were from CWC contexts and two from the central-Swedish BAC burial ‘Bergsgraven’. By analysing these genomes together with the previously published data, we show that the BAC represents a group different from other Neolithic populations in Scandinavia, revealing stratification among cultural groups. Similar to continental CWC, the BAC-associated individuals display ancestry from the Pontic–Caspian steppe herders, as well as smaller components originating from hunter–gatherers and Early Neolithic farmers. Thus, the steppe ancestry seen in these Scandinavian BAC individuals can be explained only by migration into Scandinavia. Furthermore, we highlight the reuse of megalithic tombs of the earlier Funnel Beaker Culture (FBC) by people related to BAC. The BAC groups likely mixed with resident middle Neolithic farmers (e.g. FBC) without substantial contributions from Neolithic foragers.

By contrast, the CWC individuals from Obłaczkowo in Poland (poz44 and poz81) show an extremely high proportion of steppe ancestry (greater than 90%), which is different from the later CWC-associated individuals excavated in Pikutkowo (Poland) [23], but similar to some other CWC-associated individuals from Germany, Lithuania, and Latvia [2,8,31]. Interestingly, these individuals with a large fraction of steppe ancestry have typically been dated to more than 2600 BCE, making them among the earliest CWC individuals genetically investigated. This observation, i.e. early CWC individuals resembled (genetically) Yamnaya-associated individuals, while later CWC groups show higher levels of European Neolithic farmer ancestry (Pearson’s correlation coefficient: −0.51, p = 0.006) (figure 2), suggests an initial dispersal that occurred rapidly.

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HiPOD 14 October 2019:A Martian Game Board   It’s spring in the…

HiPOD 14 October 2019:A Martian Game Board

   It’s spring in the Northern Hemisphere of Mars, and the polar region is still blanketed by seasonal carbon dioxide frost (dry ice). This image shows an area near the sand sea (called an “erg”) that is surrounding the water ice-rich layered deposits.

The many bumps are sand dunes less than 100 meters across that are mostly covered by seasonal frost, appearing in a manner that looks artificial but is a natural consequence of the wind patterns in this region. The smaller, darker spots are places where the seasonal frost has sublimed away, exposing the dark surface below. The combination of these features makes for an unearthly scene!

NASA/JPL/University of Arizona

HiPOD 16 October 2019: Pristine Dust Deposits in Syria Planum …

HiPOD 16 October 2019: Pristine Dust Deposits in Syria Planum

   Wind-blown deposits known as transverse aeolian ridges (TARs) are frequently visible in images of the Martian tropics. They are bright ripples with heights of 2.6 meters and spacing that averages 47 meters. The TARs generally appear inactive and eroded, sometimes cratered or littered with boulders from nearby impacts and avalanches.

In Syria Planum, unusual bright deposits might be accumulations of dust blown from higher to lower elevations by nighttime slope winds, reaching speeds of up to 50 meters per second. These dust deposits resemble TARs in height and spacing but with a distinct shape from other TARs. A close up view shows that the deposits form pyramidal features with steep faces on the upwind sides (wind is blowing from the top of the picture) and tapered slopes in the downwind direction. Ridges form where the “pyramids” line up together, and the spacing of the ridges appears to be controlled by the length of the “pyramids.”

These observations suggest that TARs elsewhere on Mars may have formed in a similar fashion, perhaps millions of years ago when the atmosphere was more active. They also may be forming in Syria Planum today.

NASA/JPL/University of Arizona

HiPOD 16 October 2019: Down in Chukhung Crater   Chukhung is a…

HiPOD 16 October 2019: Down in Chukhung Crater

   Chukhung is a 45 kilometer-diameter, central pit crater in Tempe Terra, having likely formed 3 billion years ago. The southern portion of the crater floor hosts a large viscous flow feature that is hypothesized to be a glacier.

There are sinuous ridges that emanate from the margin of the flow feature toward the center of the crater. These ridges could be evidence of glacial meltwater preserved in the form of eskers, inverted channels formed when the softer sediments surrounding the channel deposits are eroded away. It is unclear whether the conditions for wet-based glaciation ever existed on Mars, but these ridges could be evidence that it once did.

NASA/JPL/University of Arizona

Triple Threat Any fight is easier to face with backup. And…

Triple Threat

Any fight is easier to face with backup. And there are few more formidable foes than cancer. For some time, doctors have tackled lung cancers caused by a mutation in a particular gene, KRAS, with drugs that inhibit that gene’s impact. However, although these treatments can knock back the threat, it often bounces back, making these cases of lung cancer particularly dangerous. A new approach tried providing those inhibitors with backup, attacking not just that aspect of the cancer, but two other mechanisms as well. On tests in mice, the three-pronged approach successfully shrank lung tumours (right after treatment, with each colour representing a different tumour), and kept them small, while tumours in mice that received just the KRAS inhibitors tended to return. The study found similarly promising results in tests with human cells, suggesting this approach may help stack the odds against this deadly form of lung cancer.

Written by Anthony Lewis

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2019 October 16 BHB2007: A Baby Binary Star in Formation Image…

2019 October 16

BHB2007: A Baby Binary Star in Formation
Image Credit: ALMA (ESO/NAOJ/NRAO), F. O. Alves et al.

Explanation: How do binary stars form? To help find out, ESO’s Atacama Large Millimeter Array (ALMA) recently captured one of the highest resolution images yet taken of a binary star system in formation. Most stars are not alone – they typically form as part of a multiple star systems where star each orbits a common center of gravity. The two bright spots in the featured image are small disks that surround the forming proto-stars in [BHB2007] 11, while the surrounding pretzel-shaped filaments are gas and dust that have been gravitationally pulled from a larger disk. The circumstellar filaments span roughly the radius of the orbit of Neptune. The BHB2007 system is a small part of the Pipe Nebula (also known as Barnard 59), a photogenic network of dust and gas that protrudes from Milky Way’s spiral disk in the constellation of Ophiuchus. The binary star formation process should be complete within a few million years.

∞ Source: apod.nasa.gov/apod/ap191016.html

Astronomers use giant galaxy cluster to magnify X-ray emissions of an early-forming...

False color and X-ray images of the giant arc in SPT-CLJ2344-4243. The X-ray emitting giant arc is shown relative to the center of the foreground lensing galaxy cluster in a false color image at optical wavelengths. The inset shows Chandra X-ray 0.5–7 keV (left) and Hubble optical (right) images of the giant arc at a scale 1.5 times larger.

A team of astronomers, including Professor Keren Sharon from the University of Michigan, have utilized a massive cluster of galaxies in order to look back in time to the first generation of galaxies. The work of Sharon and her coauthors, led by Matthew Bayliss, a research scientist in MIT’s Kavli Institute for Astrophysics and Space Research, was published recently in Nature Astronomy.

An experiment of gravitational lensing

In previous studies, strong gravitational lensing by galaxy clusters was leveraged to observe faint galaxies at optical and infrared wavelengths. However, this is the first time gravitational lensing has been used to peer into distant star formation in the X-ray.

While conducting their research, the astronomers detected an infant galaxy, about 1/10,000 the size of the Milky Way, in its first high-energy stage of star formation. According to Sharon and her colleagues, the detection of this distant galaxy supports the idea that scientists can use galaxy clusters to observe phenomena dating back to the universe’s early history – in this case, nearly 9.4 billion years ago.

Galaxy clusters are the most massive objects in the universe. Because they are so large and composed of many galaxies all bound together by gravity, their gravitational pull is often so strong that it can bend space-time. When this happens, light may no longer move in straight lines as its path is warped by the gravitational pull of the cluster. As a result, the light from background objects is magnified. When this phenomena is used to astronomers’ advantage, it is called gravitational lensing.

Galaxy clusters are the most massive gravitationally bound objects in the Universe, composed of dark matter, hot gas, hundreds of galaxies. Because they are so massive, their gravity bends space-time, an effect predicted by Einstein’s general relativity. When this happens, light may no longer move in straight lines as its path follows the warped space-time. As a result, the image of background objects appears distorted and magnified. When this phenomena is used to astronomers’ advantage, it is called gravitational lensing.

“We have observed that the Phoenix cluster is causing lensing of several background sources, magnifying them and creating multiple images,” said Sharon. “I can take those observations and use them to solve for how much mass there is in this intervening object and determine the degree of magnification.”

Gravitational lensing essentially allows astronomers to use galaxy clusters as enormous magnifying glasses. If they are able to approximate the mass of a cluster, they can estimate the gravitational effects it may have on background light sources. For instance, the light from an object positioned behind the cluster would travel directly towards the cluster before bending around it and continuing towards the observer, appearing as distorted, magnified images of the object. This helps astronomers study galaxies that would otherwise be too faint for present-day telescopes.

Sourcing the X-rays

While studying gravitationally-lensed faint galaxies is now routine, faint X-ray sources behind galaxy clusters pose an additional challenge. The cores of galaxy clusters are filled with hot gas, which emits brightly in the X-ray. The X-ray light of the background source, although magnified, can be lost in the X-ray light of the foreground cluster.

While examining X-ray data of the Phoenix cluster, Dr. Bayliss realized that there was X-ray emission originating from one of the gravitationally-lensed background galaxies that appeared as a point source.

“This radiation is likely coming not from something that is very X-ray luminous, but from a stellar object or X-ray binary,” said Sharon. “This is very hard to see at such large distances and is only visible in this case because it is being magnified by the Phoenix cluster at a factor of 60. This is the farthest away it’s ever been seen.”

Isolating the background object

In order to achieve a better understanding of the identified X-ray emissions, the team tested whether they could isolate the fainter X-rays coming from the background object. Using data taken by NASA’s Chandra X-ray Observatory, the Hubble Space Telescope and the Magellan telescope in Chile, the team developed a model to precisely measure the X-ray emissions from the Phoenix cluster and subtract it from the data. What was left were the lensed emissions that they were able to trace back to a tiny dwarf galaxy, originating approximately 9.4 billion years ago.

The researchers further examined the the X-ray, optical, and infra-red emission coming from this galaxy and were able to measure its physical conditions, such as age, metallicity (the fraction of heavy elements), star formation rate, and mass. The gravitational lensing analysis, led by Sharon, enabled the team to convert the observed measurements to the intrinsic ones one would have measured without lensing magnification. Because this galaxy has low mass and low metallicity, and because X-rays are typically produced during extreme events, the researchers conclude that this galaxy may by similar to the first generation of galaxies formed in the very early universe, and responsible for ionizing it.

“The universe’s first stars and galaxies had enough energetic photons to create larger and larger spheres for ionized materials. After that epoch, light was free to travel through the universe,” said Sharon. “It’s interesting to find galaxies that are analogs of those first galaxies in an epoch where we can see them.”

by Nicholle Cardinal

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The Staffordshire Hoard, The Potteries Museum and Gallery, Stoke on Trent, 5.10.19.

The Staffordshire Hoard, The Potteries Museum and Gallery, Stoke on Trent, 5.10.19.

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