суббота, 12 января 2019 г.

Screen for Genes In Parkinson’s disease accumulation of a…


Screen for Genes


In Parkinson’s disease accumulation of a toxic protein called alpha-synuclein (a-syn) causes problems with movement and mental abilities. Now researchers have developed a new way to identify genes that could be activated by drugs to reduce its levels. A-syn builds up over time to form damaging clumps and tangles inside brain cells. The team’s approach allowed them to screen the activity of over 7,500 genes to see if any affect the levels of a-syn. They identified 60 candidates and narrowed it down to six. They then tested whether altering the activity of these six genes could indirectly reduce a-syn levels in fruit flies, mice and human brain cells grown in the laboratory. Pictured here are the human cells labelled to show their centre (light-blue) and tube-like structures (microtubules – purple). The research suggests that treatments that target these genes may be able to halt a-syn build-up and slow disease progression.


Written by Deborah Oakley



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2019 January 12 Milky Way Falls Image Credit & Copyright: …


2019 January 12


Milky Way Falls
Image Credit & Copyright: Yuri Beletsky (Carnegie Las Campanas Observatory, TWAN)


Explanation: It can be the driest place on planet Earth, but water still flows in Chile’s Atacama desert, high in the mountains. After discovering this small creek with running water, the photographer returned to the site to watch the Milky Way rise in the dark southern skies, calculating the moment when Milky Way and precious flowing water would meet. In the panoramic night skyscape, stars and nebulae immersed in the glow along the Milky Way itself also shared that moment with the Milky Way’s satellite galaxies the Large and Small Magellanic clouds above the horizon at the right. Bright star Beta Centauri is poised at the very top of the waterfall. Above it lies the dark expanse of the Coalsack nebula and the stars of the Southern Cross.


∞ Source: apod.nasa.gov/apod/ap190112.html


2,000-year-old tomb sculptures discovered in east China

Chinese archaeologists have discovered more than 40 painted pottery items at a tomb dating back around 2,000 years in east China’s Shandong Province.











2,000-year-old tomb sculptures discovered in east China
Chinese archaeologists unearth 2,000-year-old pottery figurines dating back to Han dynasty (206 BC–9 AD)
from a tomb in Qingdao city, east China’s Shandong province [Credit: VCG]

The items, including figurines of people and horses as well as different kinds of pots, were found in Pingdu in the city of Qingdao after an excavation that started in June 2018.


“The figurines of attendants, chariots and horses indicate that the tomb owner may have been an official in the ancient state in Shandong during the Han Dynasty (206 BC- 220 AD),” said Lin Yuhai, head of the Qingdao institute of cultural relics preservation and archaeology.


All the heads of the horses were positioned towards the southeast, which was the direction of the ancient capital of Jimo in Shandong Peninsula around 2,000 years ago, according to archaeologists.


Excavation is ongoing on another site nearby, and archaeologists have found a total of 15 tombs that are estimated to date back to the mid-West Han Dynasty (206 BC- 8 AD) and belonging to two big families.


Source: Xinhua [January 05, 2019]



TANN



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Roman remains unearthed next to Colchester’s Mercury Theatre

Archaeologists have unearthed the mosaic-like floors of a number of Roman homes next to a theatre complex. The finds were part of an excavation next to the Mercury Theatre in Colchester, Essex.











Roman remains unearthed next to Colchester's Mercury Theatre
Excavations at the Mercury Theatre [Credit: Colchester Archaeological Trust]

As well as the Roman floors and home foundations, archaeologists have also found a number of items including a bone dice and a candle holder.
Archaeologist Philip Crummy said: “To find anything well-preserved in Colchester is exciting.”











Roman remains unearthed next to Colchester's Mercury Theatre
The tessellated flooring found at the site suggests the occupants were “well off”, say archaeologists [Credit: BBC]

The dig is part of an £8.9m extension and refurbishment of the Mercury Theatre, which sits next to the town’s Roman wall.


“This was clearly a fairly well-off part of Roman Colchester,” said Mr Crummy. “In Colchester of the 2nd Century, the homes often had tessellated or mosaic floors, under floor heating, piped water and painted walls – just like some of the houses you would find in the Mediterranean.











Roman remains unearthed next to Colchester's Mercury Theatre
The floors of the Roman houses are thought to be 2nd or 3rd Century AD [Credit: BBC]

“What we see here ranks near the middle standard of home. We have seen some lovely fragments of painted wall plaster. Its been very interesting and rewarding to be given the chance to investigate this.”
The Mercury extension will be built on piles which will be installed away from the most significant of the Roman flooring finds.











Roman remains unearthed next to Colchester's Mercury Theatre
Roman bone hair pin [Credit: Colchester Archaeological Trust]

“The floors we are looking at are typically second and third century,” said Mr Crummy. “What we can tell from what is on top of the floors is when it stopped being used and we can see from the remains lying on the floors there that these buildings were left derelict to stand.”


Finds include an iron object about 15in (38cm) in length and a coin dating to about AD360.











Roman remains unearthed next to Colchester's Mercury Theatre
Roman bone dice [Credit: Colchester Archaeological Trust]

It is thought to have been some kind of fitting and has been carefully packaged up and will be examined to see if there is some kind of mechanism.
“We’ve found a tiny little dice as small as a finger nail,” said Mr Crummy, “which suggests people were spending happy hours playing dice. There’s also a good looking counter, like a piece of tile which has been shaped, which we assume was used in games.”











Roman remains unearthed next to Colchester's Mercury Theatre
Building work is expected to start at the site once the dig is completed [Credit: BBC]

The theatre’s regeneration project has been awarded funding worth £7m from Arts Council England, Colchester Council and Essex County Council but has been seeking the remaining £1.9m needed from public donations.


Source: BBC News Website [January 06, 2019]



TANN



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Hubble’s First Frontier Field finds thousands of unseen, faraway galaxies

The first of a set of unprecedented, super-deep views of the universe from an ambitious collaborative program called The Frontier Fields is being released today at the 223rd meeting of the American Astronomical Society in Washington, D.C.











Hubble's First Frontier Field finds thousands of unseen, faraway galaxies
This long-exposure Hubble Space Telescope image of massive galaxy cluster Abell 2744 is the deepest ever made of any
cluster of galaxies. It shows some of the faintest and youngest galaxies ever detected in space. Abell 2744, located in the
constellation Sculptor, appears in the foreground of this image. It contains several hundred galaxies as they looked 3.5
 billion years ago. The immense gravity in Abell 2744 acts as a gravitational lens to warp space and brighten and magnify
images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did longer than 12 billion
years ago, not long after the big bang. This image is part of an unprecedented long-distance view of the universe from an
 ambitious collaborative project among the NASA Great Observatories called The Frontier Fields. Over the next several
years select patches of the sky will be photographed for the purpose of better understanding galaxy evolution. This
visible-light and near-infrared composite image was taken with the Wide Field Camera 3 [Credit: NASA, ESA,
and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)]

The long-exposure image taken with NASA’s Hubble Space Telescope is the deepest-ever picture taken of a cluster of galaxies, and also contains images of some of the intrinsically faintest and youngest galaxies ever detected.


The target is the massive cluster Abell 2744, which contains several hundred galaxies as they looked 3.5 billion years ago. The immense gravity in this foreground cluster is being used as a “gravitational lens,” which warps space to brighten and magnify images of far more-distant background galaxies as they looked over 12 billion years ago, not long after the big bang.


“The Frontier Fields is an experiment; can we use Hubble’s exquisite image quality and Einstein’s theory of General Relativity to search for the first galaxies?,” said Space Telescope Science Institute Director Matt Mountain. “With the other Great Observatories, we are undertaking an ambitious joint program to use galaxy clusters to explore the first billion years of the universe’s history.”


Simultaneous observations of this field are being done with NASA’s two other Great Observatories, the Spitzer Space Telescope and the Chandra X-ray Observatory. The assembly of all this multispectral information is expected to provide new insights into the origin and evolution of galaxies and their accompanying black holes.


The Hubble exposure reveals nearly 3,000 of these background galaxies interleaved with images of hundreds of foreground galaxies in the cluster. The many background galaxies would otherwise be invisible without the boost from gravitational lensing. Their images not only appear brighter, but also smeared, stretched, and duplicated across the field.


Thanks to the gravitational lensing phenomenon, the background galaxies are magnified to appear up to 10 to 20 times larger than they would normally appear. What’s more, the faintest of these highly magnified objects have intrinsic brightnesses roughly 10 to 20 times fainter than any galaxies ever previously observed.


The Hubble data are immediately being made available to the worldwide astronomy community where teams of researchers will do a detailed study of the visual crazy quilt of intermingled background and cluster galaxies to better understand the stages of galaxy development.


Though the foreground cluster Abell 2744 has been intensively studied as one of the most massive clusters in the universe, the Frontier Fields exposure reveals new details of the cluster population. Hubble sees dwarf galaxies in the cluster as small as 1/1,000th the mass of the Milky Way. At the other end of the size spectrum, Hubble detects the extended light from several monster central cluster galaxies that are as much as 100 times more massive than our Milky Way. Also visible is faint intra-cluster light from stars inside the cluster that have been stripped out of galaxies by gravitational interactions. These new deep images will also help astronomers map out the dark matter in the cluster with unprecedented detail, by charting its distorting effects on background light. An unseen form of matter, dark matter makes up the bulk of the mass of the cluster.


As the Abell cluster was being photographed with Hubble’s Wide Field Camera 3, the telescope’s Advanced Camera for Surveys was trained on a nearby parallel field that is 6 arc minutes away from the cluster. In this field, Hubble resolves roughly 10,000 galaxies seen in visible light, most of which are randomly scattered galaxies. The blue galaxies are distant star-forming galaxies seen from up to 8 billion years ago; the handful of larger, red galaxies are in the outskirts of the Abell 2744 cluster.


Hubble will again view these two Frontier Fields in May 2014, but Hubble’s visible-light and infrared camera will switch targets. This will allow for both fields to be observed over a full range of colors, from ultraviolet light to near-infrared.


With each new camera installed on Hubble, the space telescope has been used to make successively deeper, groundbreaking views of the universe. To get a better assessment of whether doing more deep field observations was scientifically compelling or urgent, the Space Telescope Science Institute or STScI in Baltimore, Md. chartered a “Hubble Deep Field Initiative” working group. The Hubble Frontier Fields initiative grew out of the working group’s high-level discussions at STScI concerning what important, forward-looking science Hubble should be doing in upcoming years. Despite several deep field surveys, astronomers realized that a lot was still to be learned about the far universe. Such knowledge would help in planning the observing strategy for the upcoming James Webb Space Telescope.


The astronomers also considered synergies with other observatories, such as Spitzer, Chandra, and the new Atacama Large Millimeter/submillimeter Array or ALMA. Over the coming years five more pairs of fields will be imaged. The next scheduled target is the massive cluster MACSJ 0416.1-2403, for which observations are starting this week.


Source: Space Telescope Science Institute (STScI) [January 07, 2019]




TANN



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NASA’s Hubble Helps Astronomers Uncover the Brightest Quasar in the Early Universe


J043947.08+163415.7

Credits: NASA, ESA, and X. Fan (University of Arizona)




Astronomers have discovered the brightest object ever seen at a time when the universe was less than one billion years old, with the help of NASA’s Hubble Space Telescope. The brilliant beacon is a quasar, the core of a galaxy with a black hole ravenously eating material surrounding it.


Though the quasar is very far away — 12.8 billion light-years — astronomers can detect it because a galaxy closer to Earth acts as a lens and makes the quasar look extra bright. The gravitational field of the closer galaxy warps space itself, bending and amplifying the distant quasar’s light. This effect is called gravitational lensing.


Though researchers have searched for these very remote quasars for over 20 years, a rare and fortuitous celestial alignment made this one visible to them. “We don’t expect to find many quasars brighter than that in the whole observable universe,” said lead investigator Xiaohui Fan of the University of Arizona, in Tucson

.

The super-bright quasar, cataloged as J043947.08+163415.7, could hold the record of being the brightest in the early universe for some time, making it a unique object for follow-up studies.

Shining with light equivalent to 600 trillion Suns, the quasar is fueled by a supermassive black hole at the heart of a young galaxy in the process of forming. An immense amount of energy is emitted as the black hole consumes material around it. The detection provides a rare opportunity to study a zoomed-in image of how such black holes accompanied star formation in the very early universe and influenced the assembly of galaxies. 


Besides being bright in visible and infrared wavelengths, the lensed quasar is also bright in submillimeter wavelengths, where it was observed with the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. This is due to hot dust heated by intense star formation in the galaxy hosting the lensed quasar. The formation rate is estimated to be up to 10,000 stars per year (by comparison, our Milky Way galaxy makes one star per year). 


“Clearly, this black hole is not only accreting gas, but has a lot of star formation around it,” said team member Jinyi Yang at the University of Arizona. “However, because of the boosting effect of gravitational lensing, the actual rate of star formation could be much lower than the observed brightness suggests,” she added. 


The quasar existed at a transitional period in the universe’s evolution, called reionization, where light from young galaxies and quasars reheated the obscuring hydrogen that cooled off not long after the big bang.


The quasar would have gone undetected if not for the power of gravitational lensing, which boosted its brightness by a factor of 50. 


However, because very distant quasars are identified by their red color (due to absorption by diffuse gas in intergalactic space), sometimes their light is “contaminated,” and looks bluer because of the starlight of an intervening galaxy. As a result, they may be overlooked in quasar searches because their color is diluted to resemble that of a normal galaxy. Fan proposes that many other remote quasars have been missed due to this light contamination. 


His team got lucky with finding J043947.08+163415.7, because the quasar is so bright it drowns out the starlight from the especially faint foreground lensing galaxy. “Without this high level of magnification, it would make it impossible for us to see the galaxy,” said team member Feige Wang of the University of California, Santa Barbara. “We can even look for gas around the black hole and what the black hole may be influencing in the galaxy.” 


The object was selected by its color by combining photometric data from the United Kingdom Infrared Telescope Hemisphere Survey, the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1) at optical wavelengths, and NASA’s Wide-field Infrared Survey Explorer archive in the mid-infrared.


Follow-up spectroscopic observations were conducted by the University of Arizona’s Multi-Mirror Telescope, the Gemini Observatory and the Keck Observatory. These observations revealed the signature of a very faint foreground galaxy directly between the quasar and Earth that is magnifying the quasar image. However, because the source looks fuzzy in the ground-based observations (and so could be mistaken for only a galaxy), the researchers used Hubble’s exquisite imaging capabilities to confirm it is a lensed quasar. 


“It’s a hard system to photograph because it turns out to be so compact, which requires the sharpest view from Hubble,” Fan said.


The quasar is ripe for future scrutiny. Fan’s team is analyzing a detailed 20-hour spectrum from the European Southern Observatory’s Very Large Telescope, which would show gas absorption features to identify chemical composition and temperatures of intergalactic gas in the early universe. 


Astronomers also will use the Atacama Large Millimeter/submillimeter Array, and eventually NASA’s James Webb Space Telescope, to look within 150 light-years of the black hole to directly detect the influence of the black hole’s gravity on gas motion and star formation in its vicinity.


Fan will present the team’s results at a press conference Jan. 9, 2019, at the 233rd meeting of the American Astronomical Society in Seattle, Washington. The team’s science paper is available online in The Astrophysical Journal Letters.


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.



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Contact

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


Xiaohui Fan
University of Arizona, Tucson, Arizona
520-360-0956 (cell)
520-626-7558 (office)
fan@as.arizona.edu





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Meteor Activity Outlook for January 12-18, 2019

This is Michel Deconinck’s impression of the 2019 Quadrantids as seen from Artignosc Provence, France on the night of January 3/4. Michel was situated perfectly to witness this shower at maximum activity as other visual reports in this area of the world can testify.

During this period the moon will reach its first quarter phase on Monday January 14th. At this time the moon will be located 90 degrees east of the sun and will set near midnight local standard time (LST) as seen from mid-northern latitudes. As the week progresses the waxing gibbous moon will set later in the morning, encroaching on the more active morning hours. Hourly meteor rates for evening observers this week is near 3 as seen from mid-northern latitudes (45N) and 2 as seen from tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 12 as seen from mid-northern latitudes and 10 from the southern tropics. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Evening rates are reduced due to interfering moonlight. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brighter meteors will be visible from such locations.


The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning January 12/13. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies near the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located far below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.






Radiant Positions at 7:00pm Local Standard Time







Radiant Positions at 12:00am Local Standard Time







Radiant Positions at 5:00am Local Standard Time





These sources of meteoric activity are expected to be active this week.


Now that the activity from particles produced by comet 2P/Encke have ceased encountering the Earth, the Taurid showers are over and we resume reporting activity from the Anthelion (ANT) radiant. This is not a true radiant but rather activity caused by the Earth’s motion through space. As the Earth revolves around the sun it encounters particles orbiting in a pro-grade motion that are approaching their perihelion point. They all appear to be radiating from an area near the opposition point of the sun, hence the name Anthelion. These were once recorded as separate showers throughout the year but it is now suggested to bin them into their category separate from true showers and sporadics. There are several lists that have the delta Cancrids currently active, but we include them with the Anthelions as the celestial positions overlap. This radiant is a very large oval some thirty degrees wide by fifteen degrees high. Activity from this radiant can appear from more than one constellation. The position listed here is for the center of the radiant which is currently located at 08:20 (125) +20. This position lies in western Cancer, 6 degrees northwest of the 4th magnitude star known as Asellus Australis (delta Cancri). Since the radiant is so large, Anthelion activity may also appear from eastern Gemini as well as Cancer. This radiant is best placed near 01:00 LST when it lies on the meridian and is highest in the sky. Rates at this time should be near 2 per hour as seen from the northern hemisphere and 1 per hour as seen from south of the equator. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.


The alpha Hydrids (AHY) were discovered by Dr. Peter Brown and are mentioned in his article “A meteoroid stream survey using the Canadian Meteor Orbit Radar”. This shower is active from December 17 through January 17 with maximum activity occurring on January 3rd. The radiant is currently located at 09:02 (136) -11. This position lies in southwestern Hydra, 5 degrees southwest of the 2nd magnitude star known as Alphard (alpha Hydrae). These meteors are best seen near 0200 LST when the radiant lies highest above the horizon. At 43 km/sec. the alpha Hydrids produce meteors of medium velocity. Expected rates this week are less than 1 per hour no matter your location.


The January xi Ursae Majorids (XUM) is a shower discovered by Japanese observers of SonotoCo based on video observations in 2007-2008. This shower is active from January 15-22, with maximum activity occurring on the 18th. At maximum the radiant is located at 11:15 (169) +33, which lies in southwestern Ursa Major, just west of the 3rd magnitude star known as Alula Borealis (xi Ursae Majoris).  These meteors are best seen near 04:00 LST when the radiant lies highest above the horizon. Hourly rates should be near 1 as seen from the northern hemisphere and less than 1 as seen south of the equator. These meteors encounter the atmosphere at 41 km/sec., which would produce meteors of average velocity.


The December Leonis Minorids (DLM) are a shower of long duration active from December 6th through January 18th. Maximum occurs near December 21st when rates may reach 3 an hour. Current rates are likely less than 1 per hour no matter your location. The radiant is currently located at 12:03 (181) +21. This position lies in western Coma Berenices, 7 degrees northeast of the 2nd magnitude star known as Denebola (beta Leonis). These meteors are best seen near 0400 LST when the radiant lies highest above the horizon. At 63 km/sec. the December Leonis Minorids produce mostly swift meteors.


The eta Corvids (ECV) were recently discovered by Sirko Molau and the IMO Video Meteor Network Team. This stream is active from January 16-29, with maximum activity occurring on the 22nd. The current position of the radiant is 12:16 (184) -14, which places the radiant in northern Corvus, 4 degrees northwest of the 3rd magnitude star known as Algorab (delta Corvi). These meteors are best seen near 0400 LST when the radiant lies highest above the horizon. Current hourly rates would be less than 1 per hour no matter your location. At 68 km/sec. these meteors would be fast.


The lambda Bootids (LBO) were discovered by Dr. Peter Brown and his team at the University of Western Ontario, London, Ontario, Canada. They were using radio means to discover new streams. These meteors are active from December 31 through January 17 with maximum activity occurring on the 16th. The radiant currently lies at 14:34 (218) +45. This position lies in northwestern Bootes, 4 degrees southeast of the 4th magnitude star known as Xuange (lambda Bootis). Current rates are expected to be near 1 per hour as seen from the northern hemisphere. Rates would be less than 1 per hour for observers located in the southern hemisphere. At 41 km/sec. these meteors are of medium velocity.


The gamma Ursae Minorids (GUM) were also discovered by Dr. Peter Brown and associates. These meteors are active from January 09-20, with maximum occurring on the 18th. The radiant is currently located at 15:08 (228) +71, which places it southern Ursa Minor, 2 degrees south of the 3rd magnitude star known as Pherkad (gamma Ursae Minoris). These meteors are best seen during the last few hours before dawn, when the radiant lies highest in a dark sky. Expected rates are less than 1 per hour during this period no matter your location. These meteors encounter the atmosphere at 30 km/sec., which would produce meteors of medium-slow velocity.


As seen from the mid-northern hemisphere (45N) one would expect to see approximately 9 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 2 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 9 per hour as seen from rural observing sites and 2 per hour during the evening hours.


The list below offers the information from above in tabular form. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.






















































































SHOWER DATE OF MAXIMUM ACTIVITY CELESTIAL POSITION ENTRY VELOCITY CULMINATION HOURLY RATE CLASS
RA (RA in Deg.) DEC Km/Sec Local Standard Time North-South
Anthelion (ANT) 08:20 (125) +20 30 01:00 2 – 1 II
alpha Hydrids (AHY) Jan 03 09:02 (136) -11 43 02:00 <1 – <1 IV
January xi Ursae Majorids (XUM) Jan 18 11:15 (169) +33 41 04:00 1 – <1 IV
December Leonis Minorids (DLM) Dec 21 12:03 (181) +21 63 05:00 <1 – <1 II
eta Corvids (ECV) Jan 22 12:16 (184) -14 68 05:00 <1 – <1 IV
lambda Bootids (LBO) Jan 16 14:34 (218) +45 41 07:00 <1 – <1 IV
gamma Ursae Minorids (GUM) Jan 18 15:08 (228) +71 30 08:00 <1 – <1 IV

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Station, SpaceX Managers Set Dragon Release For Sunday Afternoon


ISS – Expedition 58 Mission patch.


January 11, 2019


To take advantage of calmer sea states in a different location in the Pacific Ocean, SpaceX and the International Space Station Program agreed to move the departure of the SpaceX-CRS-16 Dragon cargo craft from the station from early Sunday morning to late Sunday afternoon, setting up the first night splashdown and recovery of a Dragon vehicle.


Dragon’s hatch will be closed Sunday morning, and the spacecraft will be detached from the Harmony module around 3 p.m. EST Sunday.



Image above: The SpaceX Dragon cargo craft is pictured attached to the International Space Station’s Harmony module as the orbital complex flew 258 miles above the Indian Ocean off the eastern coast of South Africa. Image Credit: NASA.


Ground controllers will now release Dragon from the Canadarm2 robotic arm at 6:30 p.m. Sunday. NASA TV coverage of the operation without commentary will begin at 6:15 p.m. NASA Flight Engineer Anne McClain will monitor the release from the station’s cupola.


Dragon’s deorbit burn to begin its descent back to Earth is now scheduled at approximately 11:19 p.m. with splashdown scheduled at around 12:10 a.m. Monday (9:10 p.m. Pacific time) just west of Baja California.


Related links:


Expedition 58: https://www.nasa.gov/mission_pages/station/expeditions/expedition58/index.html


SpaceX Dragon: https://www.nasa.gov/mission_pages/station/structure/launch/spacex.html


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


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


NASA TV: https://www.nasa.gov/nasatv


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


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


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


Best regards, Orbiter.chArchive link


Hungarian Yamnaya > Bell Beakers?

Ever since the publication of the Olalde et al. Beaker paper (see here), there’s been a lot of talk online about Hungarian Yamnaya as the most likely source of the Yamnaya-related, R1b-P312-rich northern Bell Beakers who went on to dominate much of Central and Western Europe during the Bronze Age.
Certainly, this is still possible, and we might find out soon if it’s true because several Hungarian Yamnaya samples are apparently about to be published. But I wouldn’t bet the proverbial farm on it just yet.
The most Yamnaya-like Beaker in the Olalde et al. dataset and ancient DNA record to date is from the Szigetszentmiklós burial site, which is indeed in present-day Hungary. But this individual, labeled I2787, is dated to just 2457–2201 calBCE, which isn’t an early date for a Beaker and probably a couple hundred years past the proto-Beaker time frame.
Moreover, he belongs to Y-haplogroup R1b-Z2103, a paternal marker most closely associated in the ancient DNA record with eastern Yamnaya groups. And he doesn’t exactly look like a classic northern Beaker, because he doesn’t have a brachycephalic head with an exceedingly flat occiput (like this).
So I’d say that this is either an acculturated Beaker of recent Yamnaya origin, or perhaps the son of a Yamnaya father and Beaker mother. Below are several qpAdm mixture models that I ran to explore the latter possibility. They look very solid.



Beaker_Hungary_I2787
Beaker_Central_Europe 0.445±0.045
Yamnaya_Samara 0.555±0.045
chisq 9.199
tail prob 0.68586
Full output
Beaker_Hungary_I2787
Beaker_Britain 0.551±0.057
Yamnaya_Samara 0.449±0.057
chisq 10.972
tail prob 0.531339
Full output
Beaker_Hungary_I2787
Beaker_The_Netherlands 0.576±0.062
Yamnaya_Samara 0.424±0.062
chisq 11.469
tail prob 0.489238
Full output



The idea that I2787 is a Beaker with recent Yamnaya ancestry isn’t an original one. It was put forth very eloquently and convincingly months ago by the Bell Beaker Blogger himself:



Szigetszentmiklós Cemetery (Santa’s Six Foot Elves)



I2786 is another Beaker male from the Szigetszentmiklós site who shows an excess of Yamnaya-related ancestry compared to most other Beakers. Again, it’s likely that this individual harbors recent Yamnaya ancestry, because his Y-halogroup is I2a-M223, which has been recorded in eastern Yamnaya alongside R1b-Z2103.
So my gut feeling for now is that Hungarian Yamnaya samples will mostly belong to Y-haplogroups R1b-Z2103 and I2a-M223, rather than R1b-P312, and thus they won’t fit the bill in any obvious way as the population that may have given rise to northern Beakers.
One of the oldest individuals in the ancient DNA record belonging to R1b-P312 is I5748, a Beaker dated to 2579–2233 calBCE from the Oostwoud-Tuithoorn burial site in what is now West Frisia, The Netherlands.
Interestingly, this part of Northwestern Europe was home to the Single Grave population shortly before I5748 was alive. And the Single Grave culture is a variant of the Corded Ware culture. So can anyone tell me if there’s any evidence that I5748 and his kind were relative newcomers to West Frisia, from, say, somewhere in the direction of the Carpathian Basin? If not, then what are the chances that northern Beakers are by and large the descendants of the Single Grave people?
In fact, there’s not much difference in terms of genome-wide genetic structure between the Beakers from the Oostwoud-Tuithoorn site and Corded Ware people from what is now Germany. The Principal Component Analysis (PCA) below illustrates this well. But, you might say, Corded Ware males by and large belong to Y-haplogroup R1a-M417. Yep, but this doesn’t mean that R1b-P312 wasn’t common in some Single Grave clans.



At this stage, I don’t have a clue where the northern Beakers may have come from exactly, and unfortunately I don’t have any inside information about the Y-haplogroups of Hungarian Yamnaya. I don’t even know if any Single Grave samples are being analyzed. But I’ll leave you with this map from a recent paper by French archeologist and Beaker expert Olivier Lemercier (see here). To me it suggests rather strongly that northern Beakers developed from the synthesis of Corded Ware newcomers to Western Europe and indigenous Western Europeans. As far as I can tell, that’s what the paper basically argues as well.



See also…
Late PIE ground zero now obvious; location of PIE homeland still uncertain, but…

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Nature’s magnifying glass reveals unexpected intermediate mass exoplanets

Astronomers have found a new exoplanet that could alter the standing theory of planet formation. With a mass that’s between that of Neptune and Saturn, and its location beyond the “snow line” of its host star, an alien world of this scale was supposed to be rare.











Nature's magnifying glass reveals unexpected intermediate mass exoplanets
Planet OGLE-2012-BLG-0950Lb was detected through gravitational microlensing, a phenomenon that acts
as nature’s magnifying glass [Credit: LCO/D. Bennett]

Aparna Bhattacharya, a postdoctoral researcher from the University of Maryland and NASA’s Goddard Space Flight Center (GSFC), led the team that made the discovery, which was announced today during a press conference at the 233rd Meeting of the American Astronomical Society in Seattle.


Using the Near-Infrared Camera, second generation (NIRC2) instrument on the 10-meter Keck II telescope of the W. M. Keck Observatory on Maunakea, Hawaii and the Wide Field Camera 3 (WFC3) instrument on the Hubble Space Telescope, the researchers took simultaneous high-resolution images of the exoplanet, named OGLE-2012-BLG-0950Lb, allowing them to determine its mass.


“We were surprised to see the mass come out right in the middle of the predicted intermediate giant planet mass gap,” said Bhattacharya. “It’s like finding an oasis in the middle of the exoplanet desert!”


“I was very pleased with how quickly Aparna completed the analysis,” said co-author David Bennett, a senior research scientist at the University of Maryland and GSFC. “She had to develop some new methods to analyze this data — a type of analysis that had never been done before.”


In an uncanny timing of events, another team of astronomers (which included Bhattacharya and Bennett) published a statistical analysis at almost the same time showing that such sub-Saturn mass planets are not rare after all.


“We were just finishing up the analysis when the mass measurements of OGLE-2012- BLG-0950Lb came in,” said lead author Daisuke Suzuki of Japan’s Institute of Space and Astronautical Science. “This planet confirmed our interpretation of the statistical study.”


The teams’ results on OGLE-2012-BLG-0950Lb are published in the December issue of The Astronomical Journal and the statistical study was published in the December 20th issue of the Astrophysical Journal Letters.


OGLE-2012-BLG-0950Lb was among the sub-Saturn planets in the statistical study; all were detected through microlensing, the only method currently sensitive enough to detect planets with less than Saturn’s mass in Jupiter-like orbits.


Microlensing leverages a consequence of Einstein’s theory of general relativity: the bending and magnification of light near a massive object like a star, producing a natural lens on the sky. In the case of OGLE-2012-BLG-0950Lb, the light from a distant background star was magnified by OGLE-2012-BLG-0950L (the exoplanet’s host star) over the course of two months as it passed close to perfect alignment in the sky with the background star.


By carefully analyzing the light during the alignment, an unexpected dimming with a duration of about a day was observed, revealing the presence of OGLE-2012-BLG-0950Lb via its own influence on the lensing.











Nature's magnifying glass reveals unexpected intermediate mass exoplanets
Comparison of Saturn and Neptune to an artist’s conception of planet OGLE-2012-BLG-0950Lb
[Credit: NASA/JPL/GODDARD/F. Reddy/C. Ranc]

Methodology


OGLE-2012-BLG-0950Lb was first detected by the microlensing survey telescopes of the Optical Gravitational Lensing Experiment (OGLE) and the Microlensing Observations in Astrophysics (MOA) collaborations.


Bhattacharya’s team then conducted follow-up observations using Keck Observatory’s powerful adaptive optics system in combination with NIRC2.


“The Keck observations allowed us to determine that the sub-Saturn or super-Neptune size planet has a mass of 39 times that of the Earth, and that its host star is 0.58 times the mass of the Sun,” said Bennett. “They measured the separation of the foreground planetary system from the background star. This allowed us to work out the complete geometry of the microlensing event. Without this data, we only knew the star-planet mass ratio, not the individual masses.”


For the statistical study, Suzuki’s team and MOA analyzed the properties of 30 sub-Saturn planets found by microlensing and compared them to predictions from the core accretion theory.


Challenging the Theory


What is unique about the microlensing method is its sensitivity to sub-Saturn planets like OGLE-2012-BLG-0950Lb that orbit beyond the “snow line” of their host stars.


The snow line, or frost line, is the distance in a young solar system, (a.k.a. a protoplanetary disk) at which it is cold enough for water to condense into ice. At and beyond the snow line there is a dramatic increase in the amount of solid material needed for planet formation. According to the core accretion theory, the solids are thought to build up into planetary cores first through chemical and then gravitational processes.


“A key process of the core accretion theory is called “runaway gas accretion,” said Bennett. “Giant planets are thought to start their formation process by collecting a core mass of about 10 times the Earth mass in rock and ice. At this stage, a slow accretion of hydrogen and helium gas begins until the mass has doubled. Then, the accretion of hydrogen and helium is expected to speed up exponentially in this runaway gas accretion process. This process stops when the supply is exhausted. If the supply of gas is stopped before runaway accretion stops, we get “failed Jupiter” planets with masses of 10-20 Earth-masses (like Neptune).”


The runaway gas accretion scenario of the core accretion theory predicts that planets like OGLE-2012- BLG-0950Lb are expected to be rare. At 39 times the mass of the Earth, planets this size are thought to be continuing through a stage of rapid growth, ending in a much more massive planet. This new result suggests that the runaway growth scenario may need revision.


Suzuki’s team compared the distribution of planet-star mass ratios found by microlensing to distributions predicted by the core accretion theory.


They found that the core accretion theory’s runaway gas accretion process predicts about 10 times fewer intermediate mass giant planets like OGLE-2012- BLG-0950Lb than are seen in the microlensing results.


This discrepancy implies that gas giant formation may involve processes that have been overlooked by existing core accretion models, or that the planet forming environment varies considerably as a function of host star mass.


Next Steps


This discovery has not only called into question an established theory, it was made using a new technique that will be a key part of NASA’s next big planet finding mission, the Wide Field Infra-Red Survey Telescope (WFIRST), which is scheduled to launch into orbit in the mid-2020s.


“This is exactly the method that WFIRST will use to measure the masses of the planets that it discovers with its exoplanet microlensing survey. Until WFIRST comes online, we need to develop this method with observations from our Keck Key Strategic Mission Support (KSMS) program as well as observations from Hubble,” said Bennett.


“It’s very exciting to see Keck and Hubble combine forces to provide this surprising new result,” said Keck Observatory Chief Scientist John O’Meara. “And it’s equally exciting to know that we can make these kind of advances today to help facilitate the best science from WFIRST and Keck’s partnership in the future.”


The NASA Keck KSMS program will continue to make follow-up observations of microlensing events detected by telescopes on the ground and in space.


Source: W. M. Keck Observatory [January 08, 2019]




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Ancient gene duplication gave grasses multiple ways to wait out winter

If you’ve ever grown carrots in your garden and puzzled over never once seeing them flower, don’t blame your lack of a green thumb.











Ancient gene duplication gave grasses multiple ways to wait out winter
New research provides valuable insight into how winter-adapted grasses gain the ability to flower in spring, which could
be helpful for improving crops, like winter wheat (above), that rely on this process [Credit: Pixabay]

Carrots, beets and many other plants won’t flower until they’ve gone through winter. The extended cold gives them the signal to flower quickly once spring arrives, providing the plants an edge in the race to produce seeds.


But cold isn’t always required. In the 1930s, two English scientists discovered that some crops in the grass family, like rye or wheat, can use short days instead of cold to tell them when winter has come.


“But nothing was known about how it works,” says Rick Amasino, a professor of biochemistry and genetics at the University of Wisconsin-Madison.


Now, more than 80 years later, Daniel Woods and others in Amasino’s group have finally discovered how grasses count the short days of winter to prepare for flowering. In most plants, a protein called florigen induces flowering during the lengthening days of spring and summer. Grasses have multiple copies of the florigen gene, thanks to an ancient duplication in their genomes. One of those copies has been repurposed to be expressed during the short days of winter, giving some grasses a new way to prepare for spring.


The work is published in the journal eLife. The new research provides valuable insight into how winter-adapted grasses gain the ability to flower in spring, which could be helpful for improving crops, like winter wheat, that rely on this process.


Vernalization, the requirement for a period of cold before flowering can take place, evolved multiple times in diverse plant families. Scientists believe that vernalization allows plants to fill a new niche, one where they store up energy one year and flower quickly the next spring before they get shaded out or outcompeted by other plants. In the past, Amasino and his group have identified genes regulating vernalization in a member of the cabbage family known as Arabidopsis.


To get at the use of daylength as a winter signal, Amasino’s group turned to Brachypodium, a grass used in the lab that is related to crops like corn, rice and wheat. They found that, out of 51 varieties of Brachypodium, 40 could sense short days as a sign of winter, showing there was variation for this trait among the varieties.


“If you have variation, you can do genetics,” says Amasino, who is a member of the Great Lakes Bioenergy Research Center, a U.S. Department of Energy-funded institute headquartered at UW-Madison.


The researchers pinpointed the cause of that variation to a single letter change in a single gene that is one of 14 duplicates of the florigen gene.


The team found that the duplicate, named FTL9, has evolved to act as a sort of inverse of its parent gene florigen. Where florigen builds up in leaves during long days to cause flowering, FTL9 accumulates during the short days of winter. While enough florigen makes flowering inevitable, FTL9 only makes flowering possible by releasing the brakes on florigen once spring arrives.


Amasino ventures that whether plants have evolved to track winter via cold or short days depends on where they take root. In warmer climates, the sun may be a better signal of winter than temperature is. But in colder regions, it might be best to wait for the very last danger of frost to pass before investing in fragile flowers. In support of this idea, the Brachypodium adapted to follow short days were mostly collected from the balmy Mediterranean.


Better understanding how plants have evolved systems to mark the end of winter may help scientists keep crops productive, especially in a warming climate. Because as growing regions heat up, crops that follow the sun will always reliably track the seasons, even if winter’s chill falters.


Author: Eric Hamilton | Source: University of Wisconsin-Madison [January 08, 2019]



TANN



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Thin layers of sediment point to early arrival of life on land

New clues emerging from fossils found in the oldest soils on Earth suggest that multicellular, land-dwelling organisms possibly emerged much earlier than thought.











Thin layers of sediment point to early arrival of life on land
Part of a quilted Ediacaran fossil is partly covered by ancient wind-drift from Namibia
[Credit: Greg Retallack]

The evidence for such a conclusion emerged from fossil assemblages, previously considered to be ocean organisms, found in thin layers of silt and sand located between thicker sandstone beds in South Australia. The sediments date to between 542 million to 635 million years ago – during a geological period known as the Ediacaran.


“These Ediacaran organisms are one of the enduring mysteries of the fossil record,” said Greg Retallack, fossil collections director at the University of Oregon’s Museum of Natural and Cultural History. “Were they worms, sea jellies, sea pens, amoebae, algae? They are notoriously difficult to classify, but conventional wisdom has long held that they were marine organisms.”


Retallack’s new study, published online in the journal Sedimentary Geology, suggests otherwise based on a geochemical and microscopic re-examination of both the age and environmental associations in the thin, silty-to-sandy layers.


The sediments, known as interflag sandstone laminae, reveal telltale marks of ancient wind erosion—phenomena more closely associated with modern river banks than with oceans or seas. These thin, alternating layers, which are light in color and rich in fine grain sizes, appear similar to sheets of white paper between books bound in brown and red, Retallack noted.


“Such wind-drifted layers are widespread on river levees and sandbars today. They are present throughout the Flinders Ranges of South Australia and also in Ediacaran rocks of southern Namibia,” he said.


The emergence of multicellular life on land dates to about 565 million years ago, although there is debate on whether Ediacaran fossils of that age originated from organisms in the sea or on land, Retallack said.


If the sediments themselves were deposited on dry land, it would follow that the organisms fossilized there were land dwellers, said Retallack, who also is a professor in the UO’s Department of Earth Sciences. The organisms that left the fossils, he said, would have been from multicellular organisms visible with the naked eye. Such life would have preceded the emergence of green plant vegetation, which is believed to have started between 470 million and 583 million years ago.


Last November, Retallack and Nora Noffke of Old Dominion University had reported on traces of life left in 3.7 billion-year-old soils in a metamorphic rock formation in southwestern Greenland. In the journal Palaeogeography, Palaeoclimatology, Palaeoecology, they identified isotopic ratios of carbon potentially indicative of early land-dwelling microbes.


While the Ediacaran organisms remain enigmatic when it comes to biological classification, Retallack’s new study offers some important clues.


“The investigation points to a terrestrial habitat for some of these organisms, and combined with growing evidence from studies of fossil soils and biological soil crust features, it suggests that they may have been land creatures such as lichens,” Retallack said.


For the paper, Retallack also re-examined well-known interflag sandstone laminae at four southern Indiana locations, which date to the Pennsylvanian period, and a central Colorado site from the Eocene epoch. These locations and examination of modern rivers showed the same sedimentary processes seen in Ediacaran rocks of South Australia and Africa.


Author: Kristin Strommer | Source: University of Oregon [January 08, 2019]



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Drones increasingly used to protect Great Wall

Drones have been used for the first time to help protect the Great Wall in Yanqing District, Beijing.











Drones increasingly used to protect Great Wall
Aerial photo taken on Oct. 28, 2018 shows the autumn scenery of the Mutianyu Great Wall in Beijing,
capital of China [Credit: Xinhua/Chen Yehua]

Local authorities have put various drones into service for different purposes, work previously done only by human inspectors.


A multi-rotor unmanned aerial vehicle (UAV) is being used to collect data at centimetre level on core parts of the UNESCO world heritage site to establish a 3D model. A fixed-wing UAV is employed in long-distance inspection to maintain a close eye on potentially illegal construction near the Great Wall.


The use of drones helps human inspectors gain a precise understanding of the preservation of the Great Wall at delicate levels and reveals more information on areas difficult for people to access.


Yanqing has the most extensive Great Wall elements in the capital city as well as a complete preservation system.


Authorities said drones, satellite images and other new technologies will provide the most comprehensive, accurate data on the Great Wall to create a digital archive platform.


Source: ECNS [January 08, 2019]



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Berenike fortress on the Red Sea coast found

Archaeologists in Egypt have found the fortress that protected the Berenike port, on the coast of the Red Sea, which along with other ports on the coast also served as a passage of war elephants for the army of the Ptolemies.











Berenike fortress on the Red Sea coast found
Section of the northern defensive wall of Berenike, viewed from the west
[Credit: S.E. Sidebotham/Antiquity]

The construction of the fortress was made at the time of the Ptolemaic Dynasty. The fortifications are quite large, comprising a double line of walls which protected the western part of the fortress and a single line to the east and north. The corners and the parts where the walls were connected bear square towers.
 A complex measuring approximately 160 m long and 80 m wide is the largest and most fortified part of the Berenike fortress. It consists of three large courtyards and several structures forming an enclosed complex of workshops and stores.











Berenike fortress on the Red Sea coast found
The gatehouse of Hellenistic Berenike, viewed from the northeast
[Credit: S.E. Sidebotham/Antiquity]










Berenike fortress on the Red Sea coast found
Gate of Hellenistic Berenike, viewed from the north-west 
[Credit: S.E. Sidebotham/Antiquity]










Berenike fortress on the Red Sea coast found
Internal chamber of the Hellenistic gate, showing the entrances of four rock-cut niches
and the tunnel, viewed from the west [Credit: S.E. Sidebotham/Antiquity]

The architecture of the fortress, which is very impressive, has been greatly preserved as it was covered by sand.
A well cut on the rock and several drains and pools found within the gatehouse were used to collect and distribute water drawn from the ground or gathered from rain. Two of the pools, the largest ones, had a capacity of over 17,000 litres. This also indicates the climate at the site was very different than what is the case today.











Berenike fortress on the Red Sea coast found
Complex of rock-cut foundation trenches of the north-western tower of a defensive/industrial building,
viewed from the south [Credit: S.E. Sidebotham/Antiquity]










Berenike fortress on the Red Sea coast found
Water in the fully excavated chamber of the Hellenistic gate. On the right, the shape of the first phase of the well,
viewed from the north [Credit: S.E. Sidebotham/Antiquity]










Berenike fortress on the Red Sea coast found
A view of the interior of a narrow, rock-cut tunnel, which connects to a water collection
and storage system within the gatehouse. View from the east, from a gate chamber
[Credit: S.E. Sidebotham/Antiquity]

In an ancient trash dump, at the south side of the north defensive wall, archaeologists unearthed terracotta figurines, coins and a piece of an elephant skull.
The fortifications were probably deemed unnecessary after a while by the city’s administrators, and some of them were dismantled soon after their construction. They were probably constructed in the first place because the Ptolemies were not sure how local people would react to their presence, a common practice of theirs. Archaeologists found no evidence of attack against the city.











Berenike fortress on the Red Sea coast found
Fragments of the skull of a young elephant found by bioarchaeologist Marta Osypińska in an ancient trash dump
located on the south side of the northern defensive wall [Credit: S.E. Sidebotham/Antiquity]










Berenike fortress on the Red Sea coast found
Inside one of the niches, the researchers discovered the remains of amphoras that were used for extracting water
 from a well in the gatehouse [Credit: S.E. Sidebotham/Antiquity]

Another interesting fact drawn from historical records is that Berenike was part of a chain of ports along the Red Sea coastline from where elephants were brought to Egypt in order to supply the army of the Ptolemies. The animals were probably imported from Eritrea in East Africa.
The town became a significant trade centre after Rome took over Egypt in 30 BC, with commercial relations stretching to Greece and Italy as well as South Arabia, India, the Malay Peninsula, Ethiopia and East Africa.











Berenike fortress on the Red Sea coast found
Hellenistic structures marked on the geomagnetic map: 1) the ‘fort’ with its three phases (blue: oldest; yellow: middle,
main phase, joined with the city’s fortifications; red: youngest); 2) northern defensive wall; 3) gate building
[Credit: T. Herbich/Antiquity/interpretation by M. Woźniak & J. Rądkowska]

The discovery was announced last month by a team of Polish-American archaeologists, and the results of the research were published in the journal Antiquity. The team was led by chief directors Steven Sidebotham, professor of ancient history and archaeology at the University of Delaware, and Iwona Zych, the deputy director of the Polish Centre of Mediterranean Archaeology at the University of Warsaw. Research at the site was carried out with the financial support of the Polish National Science Centre.


Source: Archaeology and Arts [January 08, 2019]



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The lonely giant: Milky Way-sized galaxy lacking galactic neighbours

Long ago in a galaxy far, far away, fewer galaxies were born than expected — and that could create new questions for galaxy physics, according to a new University of Michigan study.











The lonely giant: Milky Way-sized galaxy lacking galactic neighbours
Colour images of the two recently discovered satellite galaxies around M94. The images were taken with Hyper Suprime-
Cam on the Subaru telescope, located at nearly 14,000 ft above sea level on the summit of Mauna Kea in Hawaii
[Credit: Smercina et al. 2018]

The study examined the satellite galaxies of Messier 94, or M94, a galaxy similar in size to our Milky Way. Researchers have long known the Milky Way has about 10 smaller, satellite galaxies surrounding it, each with at least a million stars, and up to more than a billion, such as the Magellanic Clouds.


Now, with the powerful Subaru telescope, astronomers can peer at galaxies five or 10 times the distance from the Milky Way, such as M94. They then can use the physics of how satellite galaxies form around the Milky Way to predict how many satellite galaxies a similar-sized galaxy such as M94 may have.


When U-M astronomers examined M94, they expected to find a similar number of satellite galaxies. However, they detected just two galaxies near M94, with very few stars each. Their results, led by Adam Smercina, a National Science Foundation fellow in the U-M Department of Astronomy, are published in the journal Astrophysical Letters.


“More than just an observational oddity, we show that the current crop of galaxy formation models cannot produce such a satellite system,” Smercina said. “Our results indicate that Milky Way-like galaxies most likely host a much wider diversity of satellite populations than is predicted by any current model.”


Smercina also says their results have implications for the current understanding of how galaxies form — which is in much larger halos of dark matter.


These halos of dark matter surrounding galaxies have immense gravitational force, and can pull in gas from their immediate vicinity. Large galaxies like the Milky Way generally form in halos of about the same mass. But these smaller satellite galaxies, which form in smaller ‘subhalos,’ are not nearly so dependable.


The production rate of high-mass stars in these satellite galaxies actually modulates their growth. If, for example, the nascent satellite galaxy forms too many high-mass stars at one time, their eventual supernova explosions might expel all its gas and halt all further growth. But astronomers are unsure at what size halo this ‘scatter’ in galaxy formation becomes important.


Smercina says M94 indicates that galaxy formation in intermediate-sized dark halos may be much more uncertain than previously thought.


“We think that that scatter — the range of galaxies we expect to see — may be a lot higher than what people currently think for dark matter halos of a certain mass,” he said. “Nobody’s under any illusions as to there being this huge scatter at the very lowest halo masses, but it’s at these intermediate dark matter halos that the discussion is happening.”


To observe the number of satellite dwarf galaxies around M94, the researchers took a composite image of the large galaxy. The image covered about 12 square degrees of the night sky — the full moon, for comparison, appears as about one square degree. This kind of image includes layers and layers of “noise,” including cosmic rays and scattered light, which make faint dwarf galaxies difficult to detect.


To make sure they weren’t missing satellite galaxies, Smercina and his team engineered artificial galaxies back into the image and recovered them using the same methods as for real satellites. With this technique, the researchers confirmed that were no more than two galaxies around M94.


“The real kicker is whether or not the community expected this could be possible,” Smercina said. “That is the real curiosity of this finding — the result is something the simulations don’t predict. When you can discover something we didn’t really think we could find, you can make a contribution to our understanding of how our universe works, that’s really rewarding.”


Author: Morgan Sherburne | Source: University of Michigan [January 09, 2019]




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