вторник, 28 августа 2018 г.

Experienced Cells It can be frustrating seeing a friend pick…


Experienced Cells


It can be frustrating seeing a friend pick up a new sport or musical instrument quicker than you. However, their previous experiences may have given them an advantage. Scientists have recently shown that memories of our experiences shape how cells in the hippocampus (in purple), the brain’s memory centre, learn and adapt to new situations. The team found that mice previously exposed to discomforting environments were warier of new potentially harmful surroundings, compared to mice that had been brought up in warm and safe conditions. Interestingly, these more experienced mice formed memories of the new environment differently from the naïve mice, relying on neurons in their existing hippocampal memory networks (shown in blue/green). This phenomenon, called metaplasticity, helps us to better understand how our brain uses memories and prior history to inform how we learn.


Written by Gaëlle Coullon



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2,500-year-old human remains found in Mallorca’s necropolis of Son Real

Archaeologists and anthropologists currently working in the necropolis of Son Real (municipality of Santa Margalida, Balearic Islands) have unearthed human remains some 2,500-year-old in the area of Punta dels Fenicis.











2,500-year-old human remains found in Mallorca’s necropolis of Son Real
Credit: Pep Córcoles/Diario de Mallorca

The importance of this discovery lies in the fact that this site continues to give surprises of this calibre since the modern phase of excavations began 20 years ago, in 1998.


In the 1960s, when the site was first discovered, a total of 106 tombs were documented and excavated. The work then lasted five years.


2,500-year-old human remains found in Mallorca’s necropolis of Son Real










2,500-year-old human remains found in Mallorca’s necropolis of Son Real
Credit: Pep Córcoles/Diario de Mallorca

In the last 20 years, it has hosted a total of 16 campaigns of about fifteen days each and the result has been 33 excavated tombs, and which continue to appear.
Jordi Hernández, who is directing the excavations said he was very satisfied with the result of the campaign. He also explained that in addition to the excavated tomb there are two more that have been located and whose excavation will begin shortly.


2,500-year-old human remains found in Mallorca’s necropolis of Son Real










2,500-year-old human remains found in Mallorca’s necropolis of Son Real
Credit: Pep Córcoles/Diario de Mallorca

The remains that have been found in the recently excavated tomb belong to a male adult, according to the anthropologist Francisca Cardona. The specialist explained that they were in the right lateral decubitus (fetal) position.
At the time of burial the man’s body was wrapped in a shroud. Some metal fragments have even found, in very poor condition, which are believed to be some kind of pin or brooch (fibula) that held the shroud.


2,500-year-old human remains found in Mallorca’s necropolis of Son Real










2,500-year-old human remains found in Mallorca’s necropolis of Son Real
Credit: Pep Córcoles/Diario de Mallorca

This burial site and the other two that will be excavated are located at the tip of the site’s northern sector. “This is the last area with real potential to yield more remains,” says Hernández.


The earliest indications of the necropolis stretch back to the 7th century BC, when the Talayotic culture had been underway for several centuries and the use of iron was spreading.


What at first was a cemetery for the ruling classes appears to have evolved and continued to be used in Roman Times. This longstanding activity is reflected in the changes in the burial rites.


“This site is unique in the entire western Mediterranean”, Hernández explains. “There is no other comparable necropolis from the same period in history, since other settlements either buried their dead in natural caves or in burrows, but not in a cemetery with the external monumentality of this necropolis”.


Source: Diario de Mallorca [August 24, 2018]



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Ancient tomb clusters discovered in Beijing

Ancient tomb clusters consisting of about 300 tombs have been found near the Beijing Olympic Sports Center in Beijing, China.











Ancient tomb clusters discovered in Beijing
Credit: VCG

The 300 tombs, discovered at a construction site, were presumably built around the Qing Dynasty (1644-1911). They are divided into east and west groups.


Ancient tomb clusters discovered in Beijing


Ancient tomb clusters discovered in Beijing










Ancient tomb clusters discovered in Beijing
Credit: VCG

The archaeology team has been excavating them for more than a month and it will take at least another month to finish the job.


Source: ECNS [August 25, 2018]



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Fireballs over Canada, UK, and France!

On Saturday evening there were two bright fireballs observed, over the UK and only some hours later over Canada! A couple of days before, on Tuesday, another bright fireball was spotted over France and even caught on video.



If you witnessed one of these event and/or if you have a video or a photo of this event, please

Submit an Official Fireball Report

(available in 36 languages)


If you want to learn more about Fireballs: read our Fireball FAQ.



Fireball Over France on July 10th


The IMO has received 28 reports so far about a fireball seen from France, the Netherlands and Germany on Tue 10 July 2018 around 21:25 UTC. The french meteor network BOAM caught 4.4 seconds of the fireball from a camera station located in Chaligny (East of France). For this event, we also received a photo taken by M. Rebbe from Oberwolfach, Germany.





IMO Event#2379-2018 caught by the french meteor network BOAM



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IMO Event#2379-2018 caught by M.Rebbe – Oberwolfach, Germany



Fireball Over Northern England on July 14th


A couple of days later, 14 July 2018 at 21:47 UTC, a fireball was spotted over Northern England. So far, there are more than 50 reports, one even from the Netherlands.


UK-trajectory
IMO Event#2379-2018 – Witness Locations and Estimated ground trajectory

Fireball Over Ontario and Quebec (Canada) on July 14th


On 14 July 2018 at 01:05 UTC (21:05 LT) another fireball was observed over Quebec, reported by more than 77 observers from different states like Pennsylvania, Quebec, New York Vermont, Maine, New Hampshire, Massachusetts, and Connecticut.


This post was created as part of the NEMO collaboration.


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Meteor Activity Outlook for 18-24 August 2018

Meteor near San Diego, CA – © slworking2, August 13th, 2017

Canon EOS 6D, 15mm, ƒ/2.8, 15s, ISO3200)

During this period the moon will reach its first quarter phase on Saturday August 18th. At that time the moon will lie 90 degrees east of the sun in the sky and will set near midnight local summer time (LST) as seen from mid-northern latitudes. As the week progresses the waxing gibbous moon will encroach upon the morning hours, limiting the time observers have to view under moonless conditions. The estimated total hourly meteor rates for evening observers this week is near 4 as seen from mid-northern latitudes and also 3 for those viewing from subtropical southern latitudes (25S). For morning observers the estimated total hourly rates should be near 23 for those viewing from mid-northern latitudes and also 15 for those viewing from subtropical southern latitudes (25S). 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 during this period due to 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 August 18/19. 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 22:00 LST


Radiant Positions at 22:00

Local Summer Time






Radiant Positions at 01:00 LST


Radiant Positions at 0100

Local Summer Time






Radiant Positions at 4:00 LST


Radiant Positions at 04:00

Local Summer Time





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


The August Draconids (AUD) were discovered by Zdenek Sekanina in his study of meteor streams using radio methods. This stream is active from August 13-19 with maximum activity occurring on the 16th. The radiant is currently located at 18:12 (273) +59, which places it in southern Draco, 8 degrees northeast of the 2nd magnitude star known as Eltanin (gamma Draconis). This radiant is best placed near 2200 local summer time (LST), when it lies on the meridian and is located highest in the sky. With an entry velocity of 21 km/sec., the average August Draconid meteor would be of slow velocity. Rates this week are expected to be less than 1 per hour no matter your location


The last of the kappa Cygnids (KCG) are expected this weekend from a radiant located near 19:16 (289) +55. This area of the sky lies in northwestern Cygnus, 1 degree north of the 4th magnitude star known as kappa Cygni. This radiant is best placed near 2300 LST, when it lies on the meridian and is located highest in the sky. Rates should be less than 1 per hour no matter your location. Unfortunately these meteors are not well seen from the southern hemisphere due to their low radiant altitude. With an entry velocity of 21 km/sec., the average meteor from this source would be of slow velocity.


The center of the large Anthelion (ANT) radiant is currently located at 22:36 (339) -09. This position lies in central Aquarius, 4 degrees southeast of the 4th magnitude star known as Ancha (theta Aquarii). Due to the large size of this radiant, Anthelion activity may also appear from eastern Capricornus and western Pisces, as well as Aquarius. This radiant is best placed near 0200 LST, when it lies on the meridian and is located highest in the sky. Hourly rates at this time should be near 2 no matter your location. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of medium-slow velocity.


The Northern delta Aquariids (NDA) are active from July 23 through August 27. The radiant is currently located at 23:28 (352) +04. This position is located in western Pisces, 3 degrees south of the 4th magnitude star known as theta Piscium. Maximum activity was expected on August 14, so hourly rates should be near 1 per hour no matter your location. The radiant is best placed near 0300 LST, when it lies highest in the sky. With an entry velocity of 38 km/sec., these meteors would be of medium velocities. This shower seems to be a continuation of the Northern June Aquilids, which had been active since early June.


The last of the Southern delta Aquariids (SDA) are expected this week from a radiant located at 23:58 (359) -09. This position is located in western Cetus, 3 degrees west of the 4th magnitude star known as Deneb Kaitos Shemali (iota Ceti). Hourly rates are now less than 1 per hour no matter your location. The radiant is best placed near 0400 LST, when it lies highest in the sky. With an entry velocity of 41 km/sec., most activity from this radiant would be of average velocities.


The last of the beta Hydrusids (HDY) is expected this weekend. Activity from this stream is seen from August 15-19 with maximum activity occurring on the 17th. At maximum the radiant lies at 02:25 (036) -75, which places it in southern Hydrus between the bright stars known as beta and gamma Hydri. Due to the far southern location, these meteors are not visible from the northern hemisphere. For southern observers, this area of the sky is best seen during the last dark hour before dawn when the radiant lies highest in a dark sky. Current rates are expected to be less than 1 per hour during this period no matter your location. With an entry velocity of 23 km/sec., the average meteor from this source would be of slow velocity.


The eta Eridanids (ERI) were discovered by Japanese observers back in 2001. Activity from this stream is seen from July 23 though September 17 with maximum activity occurring on August 11. The radiant currently lies at 03:24 (051) -10, which places it in western Eridanus, 2 degrees west of the 4th magnitude star known as Ran (epsilon Eridani). This area of the sky is best seen during the last dark hour before dawn when the radiant lies highest in a dark sky. Current rates are expected to near 1 per hour as seen from the northern hemisphere and near 2 per hour as seen from south of the equator. With an entry velocity of 65 km/sec., the average meteor from this source would be of swift velocity. These meteors were noticeable during the recent Perseid maximum.


The Perseids (PER) are still active from a radiant located at 03:46 (057) +59. This position lies in southern Camelopardalis, 7 degrees northeast of the 3rd magnitude star known as gamma Persei. This area of the sky is best placed for viewing during the last dark hour before dawn when it lies highest in the sky. Rates from dark sky sites are expected to be near 5 per hour as seen from the northern hemisphere and 2 as seen from south of the equator. Unfortunately these meteors are not well seen from the southern hemisphere as the numbers decrease to zero from mid-southern latitudes (S45). With an entry velocity of 59 km/sec., the average meteor from this source would be of swift velocity.


New evidence from video cameras suggest that the Aurigids (AUR) are active as early as August 18. If so, the radiant would be currently located at 04:54 (074) +39. This area of the sky is located on the Perseus/Auriga border, 3 degrees southwest of the 3rd magnitude star known as Haedus (eta Auriga). This area of the sky is best placed for viewing during the last dark hour before dawn when it lies highest in the sky. Rates are expected to be less than 1 no matter your location. With an entry velocity of 66 km/sec., the average meteor from this source would be of swift velocity.


As seen from the mid-northern hemisphere (45N) one would expect to see approximately 14 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 3 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 8 per hour as seen from rural observing sites and 2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Rates are reduced during the evening hours due to moonlight.


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 Summer Time North-South
August Draconids (AUD) Aug 16 18:12 (273) +59 21 22:00 <1 – <1 IV
kappa Cygnids (KCG) Aug 13 19:16 (289) +55 21 23:00 <1 – <1 II
Anthelions (ANT) 22:36 (339) -09 30 02:00 2 – 2 II
Northern delta Aquariids (NDA) Aug 14 23:28 (352) +04 38 03:00 1 – 1 IV
Southern delta Aquariids (SDA) Jul 30 23:58 (359) -09 41 04:00 <1 – <1 I
beta Hydrusids (HDY) Aug 17 02:25 (036) -75 23 06:00 0 – <1 III
eta Eridanids (ERI) Aug 11 03:24 (051) -10 65 07:00 1 – 2 IV
Perseids (PER) Aug 13 03:46 (057) +59 59 07:00 5 – 2 I
Aurigids (AUR) Sep 01 04:54 (074) +39 66 08:00 <1 – <1 II

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Оса без головы


Всадник без головы Оса ищет оторванную голову и улетает с ней
 Decapitated wasp grabs its head before flying away
 keyztolope Опубликовал  17 янв. 2014 г.
 (For licensing or usage, contact licensing@viralhog.com) Оса ищет оторванную голову и улетает с ней Оса ищет оторванную голову и улетает с ней Оса ищет оторванную голову и улетает с ней Оса ищет оторванную голову и улетает с ней  

Geminid Meteor Shower 2017

On the night of December 13-14, 2017, the annual Geminid meteor shower peaks this month to grace the winter night sky with ‘shooting stars’. This shower is easily one of the best of the year to observe producing bright meteors and average rates of up to 120 meteors per hour during the peak.


The meteors are not your traditional remnants of a comet, they originate from asteroid 3200 Phaethon. It is thought that the asteroid collided with another object many years ago to cause a stream of dust and rock around its orbit. For this reason, this particular shower has been known to produce occasional bright fireballs. The Earth passes through the orbital plane of this 5 kilometer space rock during December causing some of these tiny pieces of rock and dust to enter the Earth’s upper atmosphere and burn up causing the meteor shower. 


Observing opportunities


This year, the Moon will rise as a slender crescent not until the early hours making for good meteor viewing for most of the night (weather permitting). The Geminids begin their streak across the sky from the constellation of Gemini as shown in the illustration above, however please read on to find out the best way to observe the light show. Gemini is not the place in the sky to look!


The best time to view the Geminids


The constellation of Gemini is located to the left of Orion and rises in the North East just as the sun is setting. This means that the Geminids can be observed during convenient hours as soon as the sky is completely dark. Any time after 8pm local time would suffice wherever your location in the northern hemisphere but the later you observe, the higher Gemini will be in the sky increasing the rates of visible meteors. 


How to observe the Geminids


As the meteors are visible to the naked eye, no special equipment is needed other than your eyes! A common mistake is to find the direction of the constellation of Gemini and concentrate on that area on the north-eastern sky. This is not the best way to observe them. The meteors start there journey from here but then streak across a large part of the sky so you are actually more likely to catch them in other parts of the sky as they suddenly brighten. The best method is to get a reclining chair and lie down flat so you can see as much of the sky as possible. Keep plenty of layers on and wear a hat. December nights can quickly become bitterly cold after sunset, especially when not moving around much!


 


The post Geminid Meteor Shower 2017 appeared first on Comet Watch.


Gemini Confirms the Most Distant Radio Galaxy



Top: Two-dimensional GMOS spectrum of the strong emission line observed in the radio galaxy TGSS J1530+1049. The size of the emission region is a bit less than one arcsec. Bottom: One-dimensional profile of the observed emission line. The asymmetry indicates that the line is Lyman-α at redshift of z = 5.72, making TGSS J1530+1049 the most distant radio galaxy known to date.


Using the Gemini North telescope in Hawai`i, an international team of astronomers from Brazil, Italy, the Netherlands, and the UK has discovered the most distant radio galaxy to date, at 12.5 billion light years, when the Universe was just 7% of its current age.


The team used spectroscopic data from the Gemini Multi-Object Spectrograph (GMOS-N) to measure a redshift of z = 5.72 for the radio galaxy identified as TGSS J1530+1049. This is the largest redshift of any known radio galaxy. The redshift of a galaxy tells astronomers its distance because galaxies at greater distances move away from us at higher speeds, and this motion causes the galaxy’s light to shift farther into the red. Because light has a finite speed and takes time to reach us, more distant galaxies are also seen at earlier times in the history of the Universe.


The study was led by graduate students Aayush Saxena (Leiden Observatory, Netherlands) and Murilo Marinello (Observatório Nacional, Brazil), and the observations were obtained through Brazil’s participation in Gemini. “In the Gemini spectrum of TGSS J1530+1049, we found a single emission line of hydrogen, known as the Lyman alpha. The observed shift of this line allowed us to estimate the galaxy’s distance,” explains Marinello.


The relatively small size of the radio emission region in TGSS J1530+1049 indicates that it is quite young, as expected at such early times. Thus, the galaxy is still in the process of assembling. The radio emission in this kind of galaxy is powered by a supermassive black hole that is sucking in material from the surrounding environment. This discovery of the most distant radio galaxy confirms that black holes can grow to enormous masses very quickly in the early Universe.


The measured redshift of TGSS J1530+1049 places it near the end of the Epoch of Reionization, when the majority of the neutral hydrogen in the Universe was ionized by high-energy photons from young stars and other sources of radiation. “The Epoch of Reionization is very important in cosmology, but it is still not well understood,” said Roderik Overzier, also of Brazil’s Observatorio Nacional, and the Principal Investigator of the Gemini program. “Distant radio galaxies can be used as tools to find out more about this period.”


The research has been published by Monthly Notices of the Royal Astronomical Society. A preprint of the paper is available at astro-ph.





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2018 August 28 Sea and Sky Glows over the Oregon Coast Image…


2018 August 28


Sea and Sky Glows over the Oregon Coast
Image Credit & Copyright: Rudy Montoya


Explanation: Every step caused the sand to light up blue. That glow was bioluminescence – a blue radiance that also lights the surf in this surreal scene captured last month at Meyer’s Creek Beach in Oregon, USA. Volcanic stacks dot the foreground sea, while a thin fog layer scatters light on the horizon. The rays of light spreading from the left horizon were created by car headlights on the Oregon Coast Highway (US 101), while the orange light on the right horizon emanates from a fishing boat. Visible far in the distance is the band of our Milky Way Galaxy, appearing to rise from a dark rocky outcrop. Sixteen images were added together to bring up the background Milky Way and to reduce noise.


∞ Source: apod.nasa.gov/apod/ap180828.html


The growth crisis of Jupiter explained


Astronomy – Astrophysics logo.


August 27, 2018


For two million years, the largest planet in our system has grown slowly. We know today the cause.



The growth of Jupiter has gone through several distinct phases

Image above: This true color mosaic of Jupiter was constructed from images taken by the narrow angle camera onboard NASA’s Cassini spacecraft on December 29, 2000, during its closest approach to the giant planet at a distance of approximately 10 million kilometers (6.2 million miles). Image Credits: NASA/JPL/Space Science Institute.


Jupiter is the largest planet in our solar system, but for a while it has had growth problems. Swiss researchers have clarified this mystery, announced Monday the University of Bern in a statement.


For two million years, Jupiter grew slowly, according to studies on meteorites. A phenomenon that astronomers from the Universities of Berne and Zurich and ETH Zurich have tried to understand. Using a new model, they traced the origin of the gas giant and solved the mystery.



Animation above: Time-lapse sequence from the approach of Voyager 1, showing the motion of atmospheric bands and circulation of the Great Red Spot. Recorded over 32 days with one photograph taken every 10 hours (once per Jovian day). Animation Credit: NASA.


“We were able to show that Jupiter has grown through different phases,” says Julia Venturini from the University of Zurich, which summarizes the results she and her colleagues have published in the journal Nature Astronomy. During these phases, the mass of Jupiter did not develop uniformly.


Less growth, more energy


In the beginning, the planet embryo collected small pebbles of only a few centimeters and rapidly formed a planetary nucleus during the first million years, explains the University of Bern. In the second phase, during the next two million years, the growth of the planet has progressed more slowly.


Collisions with one-kilometer diameter blocks then only slowly added more mass, but provided a lot of energy, which was even more important.



Animation above: Asteroid Impact on Jupiter on March 17, 2016 by amateur Austrian astronomer. This is not the first time we’ve seen Jupiter get struck by an object. Back in 1994 it was hit by cometary fragments from Shoemaker-Levy 9, and again in 2010 and 2012.


Collisions with these blocks released heat. This heat warmed the gaseous atmosphere of the young planet, preventing rapid cooling, contraction and further enrichment of the gas. This explains the relatively long time that Jupiter spent in the mass phase from 15 to 50 times that of the Earth, as the researchers explain.


It was not until the third phase that the gases finally accumulated and made Jupiter a gaseous giant about 300 times the mass of the earth and about 143’000 kilometers in diameter.


Jupiter as a barrier


The study was inspired by new data on meteorites, says the University of Bern. These showed that the young solar system, while still a disk of dust and gas, was divided into two regions. Jupiter then served as a barrier of separation between the two.



Animation above: How Jupiter protects Earth from asteroids. Animation Credit: Petr Scheirich.


For two million years, when Jupiter went from 20 to 50 times the mass of earth, she apparently disrupted the dust disk and had to create a seal. Materials outside its orbit could not mix with those inside its orbit. This separation lasted until Jupiter reached a mass sufficient to deflect the rock and disperse it into the inner regions of the solar system.


University of Bern: http://www.unibe.ch/index_eng.html


University of Bern release: http://www.unibe.ch/news/media_news/media_relations_e/media_releases/2018/medienmitteilungen_2018/jupiter_had_growth_disorders/index_eng.html


Image (mentioned), Animations (mentioned), Text, Credits: ATS/University of Bern/University of Zurich/ETHZ/Orbiter.ch Aerospace/Roland Berga.


Best regards, Orbiter.chArchive link


Gravity, Hazard of Alteration

A

human journey to Mars, at first

glance, offers an inexhaustible amount of complexities. To bring a mission to

the Red Planet from fiction to fact, NASA’s Human Research Program has organized some of the hazards

astronauts will encounter on a continual basis into five classifications.


image

The variance of gravity fields that

astronauts will encounter on a mission to Mars is the fourth hazard.


image

On Mars, astronauts would need to

live and work in three-eighths of Earth’s gravitational pull for up to two

years. Additionally, on the six-month trek between the planets, explorers will

experience total weightlessness. 


image

Besides Mars and deep space there

is a third gravity field that must be considered. When astronauts finally

return home they will need to readapt many of the systems in their bodies to

Earth’s gravity.


image

To further complicate the problem,

when astronauts transition from one gravity field to another, it’s usually

quite an intense experience. Blasting off from the surface of a planet or a

hurdling descent through an atmosphere is many times the force of gravity.


image

Research is being conducted to

ensure that astronauts stay healthy before, during and after their mission.

Specifically researchers study astronauts’

vision, fine motor skills, fluid distribution, exercise protocols and response to

pharmaceuticals.


image

Exploration to the Moon and Mars will expose astronauts to five

known hazards of spaceflight, including gravity. To learn more, and find out

what NASA’s Human Research Program is doing to protect humans in

space, check out the “Hazards of Human Spaceflight" website.

Or, check out this week’s episode of “Houston

We Have a Podcast
,” in which host Gary Jordan

further dives into the threat of gravity with Peter

Norsk,

Senior Research Director/ Element Scientist at

the Johnson Space Center.


image


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


Pictish Symbol Stones Photoset 1, Meigle Pictish Museum, Meigle, Scotland, 20.8.18.










Pictish Symbol Stones Photoset 1, Meigle Pictish Museum, Meigle, Scotland, 20.8.18.


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How Scientists Predicted Corona’s Appearance During Aug. 21, 2017, Total Solar Eclipse


NASA – Solar Dynamics Observatory (SD0) patch.


Aug. 27, 2018


It was Aug. 14, 2017, just one week before the Moon would cross paths with the Sun and Earth, casting its shadow across the United States. The entire country buzzed with anticipation for the fleeting chance to see the corona, the Sun’s tenuous outer atmosphere.


But the wait was uniquely nerve-wracking for a group of scientists at Predictive Science Inc., a private research company in San Diego: They had just published a prediction of what the corona would look like on Aug. 21, the day of the total solar eclipse. How would their prediction — the result of a complex numerical model and tens of hours of computing — compare to the real thing?


“Waiting for totality, you know exactly what you’ve predicted and what you’re expecting,” Predictive Science researcher Zoran Mikić said. “Because you work with the model so much and see the prediction so many times, it’s burned into your brain. There’s a lot of anxiety because if you’re totally wrong, it’s a bit embarrassing.”




Images above: Predictive Science Inc. developed a numerical model that simulated what the corona would look like during the Aug. 21, 2017, total solar eclipse. Click and drag the slider to compare a composite image generated from photographs taken on the day of the total eclipse (above) to the model’s predictions (bellow). Images Credits: Predictive Science Inc./Miloslav Druckmüller, Peter Aniol, Shadia Habbal/NASA Goddard, Joy Ng.


The Predictive Science researchers used data from NASA’s Solar Dynamics Observatory, or SDO, to develop a model that simulates the corona. Their model uses measurements of magnetic fields on the Sun’s surface to predict how the magnetic field shapes the corona. Their work was supported by NASA, the National Science Foundation and the Air Force Office of Scientific Research. Mikić is the lead author of a paper summarizing their work and published in Nature Astronomy on Aug. 27, 2018.


Coronal science is deeply rooted in the history of total eclipses; even with state-of-the-art technology, it’s only during a total eclipse that scientists can resolve the lowest region of the corona, just above the Sun’s surface. This dynamic part of the solar atmosphere is threaded with complex magnetic fields that supply the energy for tremendous eruptions like flares and coronal mass ejections.


As particles and radiation from solar explosions travel out from the Sun, they can manifest as disturbances in near-Earth space, known as space weather. Just as variable as the weather we experience on Earth, space weather can disrupt communications signals, astronauts and satellites in orbit, or even power grids.


The ability to forecast and predict space weather — much like we do terrestrial weather — is critical to mitigating these impacts, and models such as Predictive Science’s are key tools in the effort.


Eclipses offer a unique opportunity for researchers to test their models. By comparing the model’s corona prediction to observations during the eclipse itself, they could assess and improve the performance of their models.


The model the Predictive Science team used for the August 2017 eclipse was their most complex yet in two decades of eclipse-predicting.


Greater complexity demands more computing hours, and each simulation required thousands of processers and took about two days of real time to complete. The research group ran their model on several supercomputers including facilities at the University of Texas at Austin’s Texas Advanced Computer Center; the San Diego Supercomputer Center at the University of California San Diego; and the Pleiades supercomputer at the NASA Advanced Supercomputing facility at NASA’s Ames Research Center in Silicon Valley, California.


In addition to SDO’s maps of the Sun’s magnetic field, the model used SDO observations of prominences — snakelike structures made of cool, dense solar material that protrude from the Sun’s surface. Prominences form in stressed parts of the magnetic field, where it’s twisted into a rope and capable of erupting if overwound.


The researchers also included new calculations for coronal heating. We don’t yet understand how the corona blazes upwards of 2 million degrees Fahrenheit, while just 1,000 miles below, the underlying surface simmers at a balmy 10,000 F. One theory proposes electromagnetic waves — called Alfvén waves — launched from the Sun’s churning surface rush out into the corona, heating particles as they propagate outwards, a bit like how ocean waves push and accelerate surfers toward the shore.


By accounting for prominences and these tiny — but numerous — waves, the scientists hoped to paint an increasingly detailed portrait of the corona’s complex behavior.



Animation above: This visualization shows the Sun’s three-dimensional magnetic field during one full solar rotation. The Predictive Science researchers modeled magnetic field lines in order to calculate the presence of complex structures in the corona. Image Credits: Predictive Science Inc./NASA Goddard, Joy Ng.


After the eclipse, the group found their prediction bore a striking resemblance to the Aug. 21, 2017, corona, although the model lacks many finer structures. Both the prediction and photos from the ground taken on the day of the eclipse show three helmet streamers — immense, petal-shaped structures that form over a network of magnetic loops. The strength of the comparison supports advances in the new model.


Scientists have always known the twisted magnetic fields underlying prominences are an important part of the Sun, but the team’s earlier models weren’t sophisticated enough to reflect it. The same is true for the waves heating the corona. “In some sense, the model’s performance tells us the new heating model is headed in the right direction,” Mikić said. “It’s certainly showing improved results. We should pursue and refine it further.”


In the business of eclipse predictions, it helps when the Sun is quiet, or less active. In August 2017, the Sun was in one such quiet phase, moving steadily toward a period of low solar activity in its approximately 11-year cycle.


The scientists fed their model with magnetic field data collected from the Sun’s Earth-facing side over the preceding 27 days — the time it takes the Sun to complete one full rotation — since they currently don’t have a way to observe the entire spherical solar surface all at once. With that approach, measurements taken at the beginning of the 27-day period — from parts of the Sun’s surface that have subsequently rotated toward the back where they can no longer be seen — are more likely to grow outdated than those taken at the end. But in times of diminished solar activity, the magnetic field isn’t quick to change, so even 27-day-old data is useful.


One discrepancy between the prediction and the observations is a skinnier feature, called a pseudostreamer, that jets out from the Sun’s upper-right. The researchers determined their model missed the pseudostreamer because the magnetic field changed in that specific region during the data collection. A different model’s prediction successfully captured this pseudostreamer, Mikić said, because it appears to have estimated the magnetic field more accurately there.


“The biggest thing I take away from this is they’ve got a sophisticated model that looks good, but they’re limited by their observations,” said Alex Young, a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who wasn’t involved with the study. “What the model misses is a matter of the Sun changing, and that’s something they can’t handle without enough observations from the right places.”



Animation above: Predictive Science Inc. developed a numerical model that simulated what the corona would look like during the Aug. 21, 2017, total solar eclipse. This animation compares a composite image generated from photographs taken on the day of the total eclipse (Aug. 21, 2017) to the model’s predictions. Animation Credits: Predictive Science Inc./Miloslav Druckmüller, Peter Aniol, Shadia Habbal/NASA Goddard, Joy Ng.


Testing a model like this so thoroughly supports the idea that, with more data and diverse vantage points, scientists can better calculate the Sun’s finer dynamics — and ultimately improve their ability to forecast space weather events that can interfere with technology and astronauts in space.


Just under a year after millions glimpsed the corona themselves during the total eclipse, on Aug. 12, 2018, NASA launched Parker Solar Probe on its way to actually fly through the corona, going closer to the Sun than any spacecraft before.


Parker Solar Probe will send back to Earth observations from inside the corona itself, which researchers can add to their models, filling crucial knowledge gaps in the corona’s complicated physics.


Mikić said models like theirs can complement the mission by contextualizing the spacecraft’s journey through the corona. Scientists have never worked with data collected so close to the Sun. By modeling the entire corona — the bigger picture — researchers will provide crucial perspective on Parker’s surroundings as it ventures into entirely unexplored territory.


“This is amazing science for Parker Solar Probe and from the eclipse, that shares one key purpose,” said Thomas Zurbuchen, associate administrator at NASA Headquarters in Washington. “Beyond the science, this is about really advancing our understanding of and ability to predict space weather, a major impact we can have at NASA.”


Related links:


Nature Astronomy: https://www.nature.com/articles/s41550-018-0562-5


NASA Advanced Supercomputing: http://www.nas.nasa.gov/


Parker Solar Probe and the Curious Case of the Hot Corona: https://www.nasa.gov/feature/goddard/2018/nasa-s-parker-solar-probe-and-the-curious-case-of-the-hot-corona


Eclipse 2017: Science from the Moon’s Shadow: https://www.nasa.gov/feature/goddard/2017/eclipse-2017-science-from-the-moon-s-shadow/


Eclipses and Transits: http://www.nasa.gov/topics/solarsystem/features/eclipse/index.html


SDO (Solar Dynamics Observatory): http://www.nasa.gov/mission_pages/sdo/main/index.html


Images (mentioned), Animations (mentioned), Text, Credits: NASA/Rob Garner/Goddard Space Flight Center, by Lina Tran.


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