среда, 20 февраля 2019 г.

Standing Stones II, Watercolour and Ink Sketch, February 2019.This is a variation on my...


Standing Stones II, Watercolour and Ink Sketch, February 2019.


This is a variation on my first sketch; not sure which one I prefer…


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2019 February 20 Doomed Star Eta Carinae Image Credit: NASA,…


2019 February 20


Doomed Star Eta Carinae
Image Credit: NASA, ESA, Hubble; Processing & License: Judy Schmidt


Explanation: Eta Carinae may be about to explode. But no one knows when – it may be next year, it may be one million years from now. Eta Carinae’s mass – about 100 times greater than our Sun – makes it an excellent candidate for a full blown supernova. Historical records do show that about 170 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This featured image brings out details in the unusual nebula that surrounds this rogue star. Diffraction spikes, caused by the telescope, are visible as bright multi-colored streaks emanating from Eta Carinae’s center. Two distinct lobes of the Homunculus Nebula encompass the hot central region, while some strange radial streaks are visible in red extending toward the image right. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks, however, remain unexplained.


∞ Source: apod.nasa.gov/apod/ap190220.html


Kinord Iron Age Hut Circle Complex Photoset 1, Dinnet, The Highlands, 20.2.19.











Kinord Iron Age Hut Circle Complex Photoset 1, Dinnet, The Highlands, 20.2.19.


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NASA Set to Demonstrate X-ray Communications in Space


NASA – SCaN Mission patch.


Feb. 19, 2019


A new experimental type of deep space communications technology is scheduled to be demonstrated on the International Space Station this spring.


Currently, NASA relies on radio waves to send information between spacecraft and Earth. Emerging laser communications technology offers higher data rates that let spacecraft transmit more data at a time. This demonstration involves X-ray communications, or XCOM, which offers even more advantages.


X-rays have much shorter wavelengths than both infrared and radio. This means that, in principle, XCOM can send more data for the same amount of transmission power. The X-rays can broadcast in tighter beams, thus using less energy when communicating over vast distances.



Image above: This image shows the Modulated X-ray Source, a key component in NASA’s first-ever demonstration of X-ray communication in space. Image Credits: NASA/W. Hrybyk.


If successful, the experiment could increase interest in the communications technology, which could permit more efficient gigabits-per-second data rates for deep space missions. Gigabits per second is a data transfer rate equivalent to one billion bits, or simple binary units, per second. These extremely high-speed rates of data transfer are not currently common, but new research projects have pushed computing capability toward this range for some technologies.


“We’ve waited a long time to demonstrate this capability,” said Jason Mitchell, an engineer at NASA’s Goddard Spaceflight Center in Greenbelt, Maryland, who helped develop the technology demonstration, which relies on a device called the Modulated X-ray Source, or MXS.


“For some missions, XCOM may be an enabling technology due to the extreme distances where they must operate,” Mitchell said.


Perhaps more dramatically, at least as far as human spaceflight is concerned, X-rays can pierce the hot plasma sheath that builds up as spacecraft hurdle through Earth’s atmosphere at hypersonic speeds. The plasma acts as a shield, cutting off radio frequency communications with anything outside the vehicle for several seconds — a nail-biting period of time dramatically portrayed in the movie, Apollo 13. No one has ever used X-rays in a communications system, though, so other applications not yet conceived could emerge, Mitchell said.


“Our goal for the immediate future is finding interested partners to help further develop this technology,” Mitchell said.


Encoding Digital Bits


To demonstrate this new communications technology, NASA will use the MXS to generate rapid-fire X-ray pulses. Operated by another Goddard-developed computing and navigation technology called NavCube, MXS will turn on and off many times per second while encoding digital bits for transmission.


From the experimental payload, the MXS device will then send the encoded data via the modulated X-rays to detectors on the Neutron-star Interior Composition Explorer, or NICER, which is located 165 feet away — about the width of a football field — on the space station. In this way, NICER becomes the receiver of a one-way X-ray signal.


Although the first XCOM test will involve the transmission of GPS-like signals, Mitchell said the team may attempt to transmit something more complicated after the initial attempt.


“It’s important is that we transmit a known code we can identify to make sure NICER receives the signal precisely the way we sent it,” Mitchell said.



Image above: NASA’s first-ever demonstration of X-ray communication will occur on the International Space Station. This image shows the locations of the Modulated X-ray Source and the Neutron star Interior Composition Explorer, or NICER, which are critical to the demonstration. Image Credit: NASA.


Although primarily built to gather data about the densest objects in the universe — neutron stars and their pulsating next-of-kin, known as pulsars — NICER was also designed to demonstrate advanced technology. In addition to the XCOM demonstration, the mission proved the effectiveness of X-ray navigation in space, showing in 2017 that pulsars could be used as timing sources for navigational purposes.


During that two-day demonstration, which the NICER team carried out with an experiment called Station Explorer for X-ray Timing and Navigation Technology, or SEXTANT, the mission gathered 78 measurements from four millisecond pulsars. The team fed that data into onboard algorithms to autonomously stitch together a navigational solution that revealed the location of NICER in its orbit around Earth as a space station payload. Within eight hours of starting the experiment, the system converged on a location within the targeted 6.2 miles and remained well below that threshold for the rest of the experiment.


NICER’s ability to carry out science and demonstrate emerging, revolutionary technologies has captured the attention of those planning NASA’s next era of human spaceflight. Missions that perform multiple functions are now considered a model, said Jake Bleacher, lead exploration scientist responsible for identifying areas where Goddard scientists can support human exploration of the Moon and Mars.


Technology Heritage


The idea to use X-rays to communicate and navigate originated more than a decade ago when NICER Principal Investigator Keith Gendreau began work on enabling technologies for a proposed black hole imager aimed at directly imaging the event horizon of a supermassive black hole or the point of no return where nothing — neither particles nor photons — can escape.


The idea was to establish a constellation of precisely aligned spacecraft that would in essence create an X-ray interferometer, an instrument used to measure displacements in objects. He conceived the idea of using X-ray sources as beacons to enable highly precise relative navigation. Using research and development funding, he developed the MXS.


Gendreau then reasoned that if he could modulate X-rays through a modulator, he could also communicate, thus giving birth to the NICER three-in-one mission concept.


The XCOM demonstration is managed by NASA’s Space Communications and Navigation program within the Human Exploration and Operations Mission Directorate. NICER is an Astrophysics Mission of Opportunity within the Explorers program. The Space Technology Mission Directorate supports the SEXTANT component of the mission, demonstrating pulsar-based spacecraft navigation.


For more Goddard technology news, go to: https://www.nasa.gov/sites/default/files/atoms/files/winter_2019_final_web_version.pdf


For more on SCaN’s advanced communications and navigation technology program, go to: http://www.nasa.gov/scan


NavCube: https://www.nasa.gov/feature/goddard/2016/nasa-s-navcube-could-support-an-x-ray-communications-demonstration-in-space-a-nasa-first


Space Technology Mission Directorate: https://www.nasa.gov/directorates/spacetech/home/index.html


Neutron-star Interior Composition Explorer (NICER): https://www.nasa.gov/nicer


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


Images (mentioned), Text, Credits: NASA/Lynn Jenner/Goddard Spaceflight Center, by Lori Keesey.


Greetings, Orbiter.chArchive link


Experimental Fuel Hardware, Astrophysics and Life Science Fill Crew Day


ISS – Expedition 58 Mission patch.


February 19, 2019


The International Space Station is hosting a robotic experiment that may help enable and refuel future missions to the moon and Mars. The Expedition 58 crew installed that hardware today then worked on a variety of life science, astrophysics and combustion science gear.


The Robotic Refueling Mission-3 (RRM3) experiment will demonstrate transferring and storing fuels and coolants such as liquid methane and a cryogenic fluid in space. Astronauts Anne McClain and David Saint-Jacques installed the RRM3 hardware today inside Japan’s Kibo lab module airlock. The gear will be deployed outside Kibo then transferred to an external logistics carrier. Once there, the Dextre “robotic hand” will begin operations demonstrating fluid transfers with a set of specialized tools.



Image above: Expedition 58 Flight Engineer Anne McClain of NASA is pictured in the cupola holding biomedical gear for the Marrow experiment. Image Credit: NASA.


The two astronauts also split their time conducting maintenance on a pair of space incubators. McClain worked on a mouse habitat replacing filters inside Kibo’s Cell Biology Experiment Facility. Saint-Jacques swapped a carbon dioxide controller in the Space Automated Bioproduct Lab (SABL). SABL supports research into microorganisms, small animals, animal cells, tissue cultures and small plants.


McClain also replaced a laptop computer hard drive dedicated to the Alpha Magnetic Spectrometer-2 experiment. The experiment is housed on the on the station’s truss structure and searches for antimatter, dark matter and measures cosmic rays. She later cleaned up gear supporting gaseous flame studies inside the Combustion Integrated Rack.



International Space Station (ISS). Animation Credit: NASA

Back on Earth, three Expedition 59 crew members are a month away from joining the three orbital residents aboard the space station. Commander Alexey Ovchinin and Flight Engineers Nick Hague and Christina Koch are in Star City, Russia in final training before their March 14 launch to the orbital lab.


Related links:


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


Robotic Refueling Mission-3 (RRM3): https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1787


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


Cell Biology Experiment Facility: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=333


Space Automated Bioproduct Lab (SABL): https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=1148


Alpha Magnetic Spectrometer-2: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=729


Truss structure: https://www.nasa.gov/mission_pages/station/structure/elements/truss-structure


Gaseous flame studies: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1651


Combustion Integrated Rack: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=317


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


Greetings, Orbiter.chArchive link


First evidence discovered of a gigantic remnant around an exploding star

A San Diego State University astrophysicist has helped discover evidence of a gigantic remnant surrounding an exploding star–a shell of material so huge, it must have been erupting on a regular basis for millions of years.











First evidence discovered of a gigantic remnant around an exploding star
Crosshairs indicate the location of the nova studied. Remnant can be seen as a partial arc
to the right of the nova [Credit: San Diego State University]

When a white dwarf, the core of a dead star, is in a close orbit with another star, it pulls gas from the other star. The gas becomes heated and compressed, eventually exploding to create a nova. This explosion causes the star to brighten by a millionfold and eject material at thousands of miles per second. The ejected material forms a remnant or shell surrounding the nova.


Allen Shafter and former SDSU postdoc. Martin Henze, along with a team of astrophysicists led by Matthew Darnley at Liverpool John Moores University in England, have been studying a nova in the nearby Andromeda galaxy known as M31N 2008-12a. What makes the nova unusual is that it erupts far more frequently than any other known nova system.


“When we first discovered that M31N 2008-12a erupted every year, we were very surprised,” said Shafter. A more typical pattern is about every 10 years.


Shafter and his team believe M31N 2008-12a has been erupting regularly for millions of years. These frequent eruptions over time have resulted in a “super remnant” surrounding the nova measuring almost 400 light years across.


Using Hubble Space Telescope imaging along with ground-based telescopes, the team worked to determine the chemical composition of the super-remnant and confirm its association with M31N 2008-12a. These findings, published in an article in the journal Nature, open the door to the possibility that this nova and remnant are linked to something more crucial to the universe.


Type Ia supernovae are among the most powerful and luminous objects in the universe and are believed to occur when a white dwarf exceeds its maximum allowable mass. At that point, the entire white dwarf is blown apart instead of experiencing explosions on the surface as other novae do. These are relatively rare and unseen in our own galaxy since the early 1600s.


Theoretical models show that novae experiencing frequent explosions surrounded by large remnants must harbor massive white dwarfs that are nearing their limit. This means M31N 2008-12a is behaving precisely the way astronomers believe a nova does before it potentially explodes as a supernova.


The discovery of additional large remnants around other novae will help identify systems undergoing repeated eruptions and help astronomers determine how many type Ia supernovae are formed; how frequently they occur; and their potential association with novae like M31N 2008-12a. Type la supernova are a critical part of understanding how the entire universe expands and grows.


“They are, in effect, the measuring rods that allow us to map the visible universe,” said Shafter. “Despite their importance, we don’t fully understand where they come from.”


Shafter and his team are now working to understand if what they observed with M31N 2008-12a is rare, or if there is an unseen population of novae experiencing this as well.


Source: San Diego State University [February 15, 2019]




TANN



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A nearby river of stars

A recently published work by researchers from the University of Vienna, who have found a river of stars, a stellar stream in astronomical parlance, covering most of the southern sky. The stream is relatively nearby and contains at least 4000 stars that have been moving together in space since they formed, about 1 billion years ago. Due to its proximity to Earth, this stream is a perfect workbench on which to test the disruption of clusters, measure the gravitational field of the Milky Way, and learn about coeval extrasolar planet populations with upcoming planet-finding missions. For their search, the authors used data from the ESA Gaia satellite.











A nearby river of stars
Night sky centered on the south Galactic pole in a so-called stereographic projection. In this special projection, the
Milky Way curves around the entire image in an arc. The stars in the stream are displayed in red and cover
almost the entire southern Galactic hemisphere, thereby crossing many well-known constellations.
Background image: Gaia DR2 skyma [Credit: Astronomy & Astrophysics]

Our own host galaxy, the Milky Way, is home to star clusters of variable sizes and ages. We find many baby clusters within molecular clouds, fewer middle-age and old age clusters in the Galactic disk, and even fewer massive, old globular clusters in the halo. These clusters, regardless of their origin and age, are all subject to tidal forces along their orbits in the Galaxy. Given enough time, the Milky Way gravitational forces relentlessly pull them apart, dispersing their stars into the collection of stars we know as the Milky Way.


“Most star clusters in the Galactic disk disperse rapidly after their birth as they do not contain enough stars to create a deep gravitational potential well, or in other words, they do not have enough glue to keep them together. Even in the immediate solar neighborhood, there are, however, a few clusters with sufficient stellar mass to remain bound for several hundred million years. So, in principle, similar, large, stream-like remnants of clusters or associations should also be part of the Milky Way disk.” says Stefan Meingast, lead author of the paper published in Astronomy & Astrophysics.


Thanks to the precision of the Gaia measurements, the authors could measure the 3D motion of stars in space. When carefully looking at the distribution of nearby stars moving together, one particular group of stars, as yet unknown and unstudied, immediately caught the eye of the researchers. It was a group of stars that showed precisely the expected characteristics of a cluster of stars born together but being pulled apart by the gravitational field of the Milky Way.


“Identifying nearby disk streams is like looking for the proverbial needle in a haystack. Astronomers have been looking at, and through, this new stream for a long time, as it covers most of the night sky, but only now realize it is there, and it is huge, and shockingly close to the Sun” says João Alves, second author of the paper. “Finding things close to home is very useful, it means they are not too faint nor too blurred for further detailed exploration, as astronomers dream.”


Due to sensitivity limitations of the Gaia observations, their selection only contained about 200 sources. An extrapolation beyond these limits suggests the stream should have at least 4000 stars, thereby making the structure more massive than most know clusters in the immediate solar neighborhood. The authors also determined the stream’s age to be around one billion years. As such, it already has completed four full orbits around the Galaxy, enough time to develop the stream-like structure as a consequence of gravitational interaction with the Milky Way disk.


“As soon as we investigated this particular group of stars in more detail, we knew that we had found what we were looking for: A coeval, stream-like structure, stretching for hundreds of parsecs across a third of the entire sky.” Says Verena Fürnkranz, co-author and Masters student at the University of Vienna. “It was so thrilling to be part of a new discovery” she adds.


This newly discovered nearby system can be used as a valuable gravity probe to measure the mass of the Galaxy. With follow-up work, this stream can tell us how galaxies get their stars, test the gravitational field of the Milky Way, and, because of its proximity, become a wonderful target for planet-finding missions. The authors hope to unravel even more such structures in the future with the help of the rich Gaia database.


Source: Astronomy & Astrophysics [February 15, 2019]




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Citizen Scientist Finds Ancient White Dwarf Star Encircled by Puzzling Rings







Citizen scientists working on Backyard Worlds: Planet 9 scrutinize “flipbooks” of images from NASA’s Wide-field Infrared Survey Explorer. This animation shows a flipbook containing the ring-bearing white dwarf LSPM J0207+3331 (circled). Credits: Backyard Worlds: Planet 9/NASA’s Goddard Space Flight Center


A volunteer working with the NASA-led Backyard Worlds: Planet 9 project has found the oldest and coldest known white dwarf — an Earth-sized remnant of a Sun-like star that has died — ringed by dust and debris. Astronomers suspect this could be the first known white dwarf with multiple dust rings.    


The star, LSPM J0207+3331 or J0207 for short, is forcing researchers to reconsider models of planetary systems and could help us learn about the distant future of our solar system.


“This white dwarf is so old that whatever process is feeding material into its rings must operate on billion-year timescales,” said John Debes, an astronomer at the Space Telescope Science Institute in Baltimore. “Most of the models scientists have created to explain rings around white dwarfs only work well up to around 100 million years, so this star is really challenging our assumptions of how planetary systems evolve.”


A paper detailing the findings, led by Debes, was published in the Feb. 19 issue of The Astrophysical Journal Letters and is now available online.


J0207 is located around 145 light-years away in the constellation Capricornus. White dwarfs slowly cool as they age, and Debes’ team calculated J0207 is about 3 billion years old based on a temperature just over 10,500 degrees Fahrenheit (5,800 degrees Celsius). A strong infrared signal picked up by NASA’s Wide-field Infrared Survey Explorer (WISE) mission — which mapped the entire sky in infrared light — suggested the presence of dust, making J0207 the oldest and coldest white dwarf with dust yet known. Previously, dust disks and rings had only been observed surrounding white dwarfs about one-third J0207’s age.


When a Sun-like star runs out of fuel, it swells into a red giant, ejects at least half of its mass, and leaves behind a very hot white dwarf. Over the course of the star’s giant phase, planets and asteroids close to the star become engulfed and incinerated. Planets and asteroids farther away survive, but move outward as their orbits expand. That’s because when the star loses mass, its gravitational influence on surrounding objects is greatly reduced.


This scenario describes the future of our solar system. 


Around 5 billion years from now, Mercury, then Venus and possibly Earth will be swallowed when the Sun grows into a red giant. Over hundreds of thousands to millions of years, the inner solar system will be scrubbed clean, and the remaining planets will drift outward.


Yet some white dwarfs — between 1 and 4 percent — show infrared emission indicating they’re surrounded by dusty disks or rings. Scientists think the dust may arise from distant asteroids and comets kicked closer to the star by gravitational interactions with displaced planets. As these small bodies approach the white dwarf, the star’s strong gravity tears them apart in a process called tidal disruption. The debris forms a ring of dust that will slowly spiral down onto the surface of the star.


J0207 was found through Backyard Worlds: Planet 9, a project led by Marc Kuchner, a co-author and astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, that asks volunteers to sort through WISE data for new discoveries.


Melina Thévenot, a co-author and citizen scientist in Germany working with the project, initially thought the infrared signal was bad data. She was searching through the ESA’s (European Space Agency’s) Gaia archives for brown dwarfs, objects too large to be planets and too small to be stars, when she noticed J0207. When she looked at the source in the WISE infrared data, it was too bright and too far away to be a brown dwarf. Thévenot passed her findings along to the Backyard Worlds: Planet 9 team. Debes and Kuchner contacted collaborator Adam Burgasser at the University of California, San Diego to obtain follow-up observations with the Keck II telescope at the W. M. Keck Observatory in Hawaii.


“That is a really motivating aspect of the search,” said Thévenot, one of more than 150,000 citizen scientists on the Backyard Worlds project. “The researchers will move their telescopes to look at worlds you have discovered. What I especially enjoy, though, is the interaction with the awesome research team. Everyone is very kind, and they are always trying to make the best out of our discoveries.”


The Keck observations helped confirm J0207’s record-setting properties. Now scientists are left to puzzle how it fits into their models.


Debes compared the population of asteroid belt analogs in white dwarf systems to the grains of sand in an hourglass. Initially, there’s a steady stream of material. The planets fling asteroids inward towards the white dwarf to be torn apart, maintaining a dusty disk. But over time, the asteroid belts become depleted, just like grains of sand in the hourglass. Eventually, all the material in the disk falls down onto the surface of the white dwarf, so older white dwarfs like J0207 should be less likely to have disks or rings.


J0207’s ring may even be multiple rings. Debes and his colleagues suggest there could be two distinct components, one thin ring just at the point where the star’s tides break up the asteroids and a wider ring closer to the white dwarf. Follow-up with future missions like NASA’s James Webb Space Telescope may help astronomers tease apart the ring’s constituent parts.


“We built Backyard Worlds: Planet 9 mostly to search for brown dwarfs and new planets in the solar system,” Kuchner said. “But working with citizen scientists always leads to surprises. They are voracious — the project just celebrated its second birthday, and they’ve already discovered more than 1,000 likely brown dwarfs. Now that we’ve rebooted the website with double the amount of WISE data, we’re looking forward to even more exciting discoveries.”  


Backyard Worlds: Planet 9 is a collaboration between NASA, the American Museum of Natural History in New York, Arizona State University, National Optical Astronomy Observatory, the Space Telescope Science Institute in Baltimore, the University of California San Diego, Bucknell University, the University of Oklahoma, and Zooniverse, a collaboration of scientists, software developers and educators who collectively develop and manage citizen science projects on the internet.


NASA’s Jet Propulsion Laboratory in Pasadena, California, manages and operates WISE for NASA’s Science Mission Directorate. The WISE mission was selected competitively under NASA’s Explorers Program managed by the agency’s Goddard Space Flight Center. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah. The spacecraft was built by Ball Aerospace & Technologies Corp. in Boulder, Colorado. Placed in hibernation in 2011, the spacecraft was reactivated in 2013 and renamed NEOWISE. Science operations and data processing take place at the Infrared Processing and Analysis Center at Caltech, which manages JPL for NASA.



For more information about Backyard Worlds: Planet 9, visit: http://backyardworlds.org


For more information about NASA’s WISE mission, visit: http://www.nasa.gov/wise





Editor: Rob Garner


Source: NASA/Stars



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Marsupial lived among Arctic dinosaurs…


Marsupial lived among Arctic dinosaurs http://www.geologypage.com/2019/02/marsupial-lived-among-arctic-dinosaurs.html


Meteorite source in asteroid belt not a single debris field

A new study published online in Meteoritics and Planetary Science finds that our most common meteorites, those known as L chondrites, come from at least two different debris fields in the asteroid belt. The belt contains many debris fields created from former dwarf planets, or dwarf planets in the making, that collided long ago. These fragments, called asteroids, continue to collide, producing the meteorites that fall to Earth today.











Meteorite source in asteroid belt not a single debris field
Creston meteorite fall taken from the pier in Goleta near Santa Barbara, California
[Credit: SETI Institute/Christian M. Rodriguez]

“When meteorites fell near Creston, California on October 24, 2015, they initially seemed to be from the same debris field as those that fell 3 years earlier in Novato, 200 miles to the North,” says lead author and meteor astronomer Peter Jenniskens a SETI Institute researcher at NASA’s Ames Research Center in Silicon Valley, California. “Both meteorites were classified as L chondrites of type L6 and shock stage S3.”


An international consortium of 33 scientists compared the meteorites and found that the meteorite that fell in Creston managed to avoid collisions for a much longer period of time than those that previously fell in Novato.


“Before it fell to Earth, Creston had been in space for about 45 million years, while the Novato meteorites came from a much more recent collision, about 9 million years ago,” says cosmochemist Kees Welten of UC Berkeley.


Scientists are keen to find out where in the asteroid belt those collisions occurred, hoping to identify the asteroid family that spawns our most common meteorites. When the rock, the size of a large grapefruit, entered Earth’s atmosphere near Creston, traveling at a speed of 16 kilometers per second, the blinding light of the fireball was photographed by an all sky camera in Sunnyvale.


“To track which direction and from what distance meteorites approach Earth, we operate automated all sky cameras in California,” says Jenniskens. “The project is now part of a larger Global Fireball Observatory in collaboration with Curtin University in Australia. This was the first meteorite fall photographed by the new project at a time when we were still testing the cameras.”


The meteor was also captured, serendipitously, from the pier in Goleta, California by photographer Christian M. Rodriguez of nearby Santa Barbara, providing its track from a different perspective. Triangulation of the two tracks revealed that both the Creston and Novato meteorites approached on shallow inclined orbits relative to the plane of the planets, but Novato took 3 years to circle the Sun and Creston only 1.5 years. That suggests Novato was delivered by a resonance further from the Sun and deeper into the asteroid belt. As soon as orbits resonate with that of Jupiter or Saturn, they can rapidly change into orbits that meet Earth.



Movie revealing the shock veins inside the fifth Creston meteorite found, using X-ray 


Computed Tomography [Credit: UC Davis/Douglas Rowland]


“It was a once in a life time photograph,” says Rodriguez, who posted the photo on a social media website. “I’m glad it helped to find its whereabouts.”


L chondrites are the most common type of meteorites, but they come in two varieties: meteorites like Novato that long ago, at the dawn of the solar system, experienced shocks so massive they are now dark in part, and those like Creston that just have some dark veins.


Then, about 470 million years ago, many of the dark meteorites experienced another giant collision that may have created an asteroid family. The dark Novato meteorite did as well, losing most of its noble, or inert, gasses, such as Argon, through the heat of the collision.


“No Argon was lost from Creston’s minerals during the last 4.3 billion years,” says geochemist Matthias Meier from ETH Zurich in Switzerland. “That likely means the asteroid from which Creston originated did not experience the collision 470 million years ago that affected Novato.”


So far two other L chondrite falls like Creston (near Jesenice and Innisfree) were photographed by camera networks worldwide, and they both came in on short orbits like Creston. Two other L-chondrite falls like Novato (Villalbeto de la Pena and Park Forest) came in on wider orbits.


“If the meteorites that experienced the collision 470 million years ago come to us on wider orbits, that likely means that Creston and Novato did not come from the same asteroid family,” says Jenniskens.


Even though they come from different collisions in different parts of the asteroid belt, Creston and Novato have much in common and appear to be related to each other. It appears that they became solid matter on the same parent body.


“Probing the isotopes of lead showed that Creston and Novato both experienced a giant collision about 70 million years after the formation of the solar system,” says Qing-zhu Yin of UC Davis.


The authors speculate that the L chondrite parent body may have broken at that time and different parts ended up at different places in the asteroid belt.


Source: SETI Institute [February 17, 2019]



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Predicting climate change

Thomas Crowther identifies long-disappeared forests available for restoration across the world. He will describe how there is room for an additional 1.2 trillion new trees around the world that could absorb more carbon than human emissions each year. Crowther also describes data from thousands of soil samples collected by local scientists that reveal the world’s Arctic and sub-Arctic regions store most of the world’s carbon. But the warming of these ecosystems is causing the release of this soil carbon, a process that could accelerate climate change by 17%. This research is revealing that the restoration of vegetation and soil carbon is by far our best weapon in the fight against climate change.











Predicting climate change
Data enables understanding of carbon cycle feedbacks to predict climate change at a large scale
[Credit: Andrew Coelho, Unsplash Photography]

The living parts of the planet make it unique from all other parts of the solar system, and they drive every aspect of biogeochemical cycling. It is essential that we represent these living processes into our understanding of current and future biogeochemical cycles in order to understand and predict climate change.
In their research, the Crowther Lab uses the largest global dataset of forest inventory data (the Global Forest Biodiversity Initiative), measured by people on the ground in over 1.2 million locations around the world combined with satellite observations, to get a mechanistic understanding of the global forest system. The lab also uses an equivalent database for below-ground ecology – the Global Soil Biodiversity Initiative. This initiative, with tens of thousands of soil samples that describe the global patterns in the biomass and the diversity of the global soil microbiome, paired with satellite data generates a first glimpse at the billions of below-ground species that determine soil fertility, atmospheric composition and the climate.











Predicting climate change
Thomas Crowther, Assistant Professor Environmental Systems Science, ETH Zurich, Switzerland
[Credit: Crowther Lab/ETH Zurich]

Using this combination of above ground and below ground data the research team can identify regions of high priority for biodiversity conservation. Additionally, they can finally start to understand the feedbacks that determine atmospheric carbon concentrations over the rest of the century. They now understand that, as the soil warms, carbon emissions from the soil will increase, particularly in the high-latitude arctic and sub-arctic regions.
Under a business-as-usual climate scenario the Crowther lab model suggests that warming would drive the loss of ~55 gigatons of carbon from the upper soil horizons by 2050. This value is around 12-17 per cent of the expected anthropogenic emissions over this period. These are the ‘climate change feed-backs’ that Crowther discusses in his session, and understanding these processes is critical to effectively managing natural systems in order to combat climate change.


Source: ETH Zurich [February 17, 2019]



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Indigenous hunters have positive impacts on food webs in desert Australia

Australia has the highest rate of mammal extinction in the world. Resettlement of indigenous communities resulted in the spread of invasive species, the absence of human-set fires, and a general cascade in the interconnected food web that led to the largest mammalian extinction event ever recorded. In this case, the absence of direct human activity on the landscape may be the cause of the extinctions, according to a Penn State anthropologist.











Indigenous hunters have positive impacts on food webs in desert Australia
Drawing of a Rufous Bettong from ‘Mammals of Australia’, John Gould, 1845-63
[Credit: Public Domain]

“I was motivated by the mystery that has occurred in the last 50 years in Australia,” said Rebecca Bliege Bird, professor of anthropology, Penn State. “The extinction of small-bodied mammals does not follow the same pattern we usually see with people changing the landscape and animals disappearing.”


Australia’s Western Desert, where Bird and her team work, is the homeland of the Martu, the traditional owners of a large region of the Little and Great Sandy Desert. During the mid-20th century, many Martu groups were first contacted in the process of establishing a missile testing range and resettled in missions and pastoral stations beyond their desert home. During their hiatus from the land, many native animals went extinct.


In the 1980s, many families returned to the desert to reestablish their land rights. They returned to livelihoods centered around hunting and gathering. Today, in a hybrid economy of commercial and customary resources, many Martu continue their traditional subsistence and burning practices in support of cultural commitments to their country.


Twenty-eight Australian endemic land mammal species have become extinct since European settlement. Local extinctions of mammals include the burrowing bettong and the banded hare wallaby, both of which were ubiquitous in the desert before the indigenous exodus, Bird told attendees at the 2019 annual meeting of the American Association for the Advancement of Science today (Feb. 17) in Washington, D.C.


“During the pre-1950, pre-contact period, Martu had more generalized diets than any animal species in the region,” said Bird. “When people returned, they were still the most generalized, but many plant and animal species were dropped from the diet.”











Indigenous hunters have positive impacts on food webs in desert Australia
Drawing of Banded-hare wallabies from John Gould Mammals of Australia, 1845-63
[Credit: Public Domain]

She also notes that prior to European settlement, the dingo, a native Australian dog, was part of Martu life. The patchy landscape created by Martu hunting fires may have been important for dingo survival. Without people, the dingo did not flourish and could not exclude populations of smaller invasive predators — cats and foxes– that threatened to consume all the native wildlife.


Bird and her team looked at the food webs — interactions of who eats what and who feeds whom, including humans — for the pre-contact and for the post-evacuation years. Comparisons of these webs show that the absence of indigenous hunters in the web makes it easier for invasive species to infiltrate the area and for some native animals to become endangered or extinct. This is most likely linked to the importance of traditional landscape burning practices, said Bird.


Indigenous Australians in the arid center of the continent often use fire to facilitate their hunting success. Much of Australia’s arid center is dominated by a hummock grass called spinifex.


In areas where Martu hunt more actively, hunting fires increase the patchiness of vegetation at different stages of regrowth, and buffer the spread of wildfires. Spinifex grasslands where Martu do not often hunt, exhibit a fire regime with much larger fires. Under an indigenous fire regime, the patchiness of the landscape boosts populations of native species such as dingo, monitor lizard and kangaroo, even after accounting for mortality due to hunting.


“The absence of humans creates big holes in the network,” said Bird. “Invading becomes easier for invasive species and it becomes easier for them to cause extinctions.” The National Science Foundation and the Max Planck Institute for Evolutionary Anthropology supported this work.


Source: Penn State University [February 17, 2019]



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New Sky Map detects hundreds of thousands of unknown galaxies

An international team of more than 200 astronomers from 18 countries has published the first phase of a major new radio sky survey at unprecedented sensitivity using the Low Frequency Array (LOFAR) telescope. The survey reveals hundreds of thousands of previously undetected galaxies, shedding new light on many research areas including the physics of black holes and how clusters of galaxies evolve. A special issue of the scientific journal Astronomy & Astrophysics is dedicated to the first twenty-six research papers describing the survey and its first results.











New Sky Map detects hundreds of thousands of unknown galaxies
This image shows how the LOFAR radio telescope opens a new view of the universe. The image shows galaxy cluster Abell
1314. In shades of grey, a piece of the sky can be seen as we know it in visible light. The orange hues show the radio
emitting radiation in the same part of the sky. The radio image looks completely different and changes our assumptions
about how galaxies arise and develop. These objects are located at a distance of approximately 460 million light
 years from earth.In the middle of every galaxy there is a black hole. When matter falls into it, an unbelievable
 amount of energy is released and electrons are ejected like a fountain. These accelerated electrons produce
radio emission that can extend over gigantic distances and is not visible at optical wavelengths
[Credit: Rafaël Mostert/LOFAR Surveys Team/Sloan Digital Sky Survey DR13]

Radio astronomy reveals processes in the Universe that we cannot see with optical instruments. In this first part of the sky survey, LOFAR observed a quarter of the northern hemisphere at low radio frequencies. At this point, approximately ten percent of that data is now made public. It maps three hundred thousand sources, almost all of which are galaxies in the distant Universe; their radio signals have travelled billions of light years before reaching Earth.
Black holes


Huub Röttgering, Leiden University (The Netherlands): “If we take a radio telescope and we look up at the sky, we see mainly emission from the immediate environment of massive black holes. With LOFAR we hope to answer the fascinating question: where do those black holes come from?” What we do know is that black holes are pretty messy eaters. When gas falls onto them they emit jets of material that can be seen at radio wavelengths.



Credit: ASTRON


Philip Best, University of Edinburgh (UK), adds: “LOFAR has a remarkable sensitivity and that allows us to see that these jets are present in all of the most massive galaxies, which means that their black holes never stop eating.”


Clusters of galaxies


Clusters of galaxies are ensembles of hundreds to thousands of galaxies and it has been known for decades that when two clusters of galaxies merge, they can produce radio emission spanning millions of light years. This emission is thought to come from particles that are accelerated during the merger process. Amanda Wilber, University of Hamburg (Germany), elaborates: “With radio observations we can detect radiation from the tenuous medium that exists between galaxies. This radiation is generated by energetic shocks and turbulence. LOFAR allows us to detect many more of these sources and understand what is powering them.”


Annalisa Bonafede, University of Bologna and INAF (Italy), adds: “What we are beginning to see with LOFAR is that, in some cases, clusters of galaxies that are not merging can also show this emission, albeit at a very low level that was previously undetectable. This discovery tells us that, besides merger events, there are other phenomena that can trigger particle acceleration over huge scales.”


Magnetic fields


“Magnetic fields pervade the cosmos, and we want to understand how this happened. Measuring magnetic fields in intergalactic space can be difficult, because they are very weak. However, the unprecedented accuracy of the LOFAR measurements has allowed us to measure the effect of cosmic magnetic fields on radio waves from a giant radio galaxy that is 11 million light years in size. This work shows how we can use LOFAR to help us understand the origin of cosmic magnetic fields”, explains Shane O’Sullivan, University of Hamburg.



Credit: Robert Schulz (ASTRON)


High-quality images


Creating low-frequency radio sky maps takes both significant telescope and computational time and requires large teams to analyse the data. “LOFAR produces enormous amounts of data – we have to process the equivalent of ten million DVDs of data. The LOFAR surveys were recently made possible by a mathematical breakthrough in the way we understand interferometry”, says Cyril Tasse, Observatoire de Paris – Station de radioastronomie à Nançay (France).


“We have been working together with SURF in the Netherlands to efficiently transform the massive amounts of data into high-quality images. These images are now public and will allow astronomers to study the evolution of galaxies in unprecedented detail”, says Timothy Shimwell, Netherlands Institute for Radio Astronomy (ASTRON) and Leiden University.


SURF’s compute and data centre located at SURFsara in Amsterdam runs on 100 percent renewable energy and hosts over 20 petabytes of LOFAR data. “This is more than half of all data collected by the LOFAR telescope to date. It is the largest astronomical data collection in the world. Processing the enormous data sets is a huge challenge for scientists. What normally would have taken centuries on a regular computer was processed in less than one year using the high throughput compute cluster (Grid) and expertise”, says Raymond Oonk (SURFsara).



Credit: Rafaël Mostert (Leiden University & ASTRON)


LOFAR


The LOFAR telescope, the Low Frequency Array, is unique in its capabilities to map the sky in fine detail at metre wavelengths. LOFAR is operated by ASTRON in The Netherlands and is considered to be the world’s leading telescope of its type. “This sky map will be a wonderful scientific legacy for the future. It is a testimony to the designers of LOFAR that this telescope performs so well”, says Carole Jackson, Director General of ASTRON.


The next step


The 26 research papers in the special issue of Astronomy & Astrophysics were done with only the first two percent of the sky survey. The team aims to make sensitive high-resolution images of the whole northern sky, which will reveal 15 million radio sources in total. “Just imagine some of the discoveries we may make along the way. I certainly look forward to it”, says Jackson. “And among these there will be the first massive black holes that formed when the Universe was only a ‘baby’, with an age a few percent of its present age”, adds Röttgering.


Source: Netherlands Institute for Radio Astronomy (ASTRON) [February 18, 2019]




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Great white shark genome decoded

The great white shark is one of the most recognized marine creatures on Earth, generating widespread public fascination and media attention, including spawning one of the most successful movies in Hollywood history. This shark possesses notable characteristics, including its massive size (up to 20 feet and 7,000 pounds) and diving to nearly 4,000 foot depths. Great whites are also a big conservation concern given their relatively low numbers in the world’s oceans.











Great white shark genome decoded
In a major scientific step to understand the biology of this iconic apex predator and sharks in general, the entire genome
of the white shark has now been decoded in detail [Credit: Byron Dilkes, Danah Divers]

In a major scientific step to understand the biology of this iconic apex predator and sharks in general, the entire genome of the white shark has now been decoded in detail.


A team led by scientists from Nova Southeastern University’s (NSU) Save Our Seas Foundation Shark Research Center and Guy Harvey Research Institute (GHRI), Cornell University College of Veterinary Medicine, and Monterey Bay Aquarium, completed the white shark genome and compared it to genomes from a variety of other vertebrates, including the giant whale shark and humans.


Decoding the white shark’s genome revealed not only its huge size – one-and-a-half times the size of the human genome – but also a plethora of genetic changes that could be behind the evolutionary success of large-bodied and long-lived sharks.


The researchers found striking occurrences of specific DNA sequence changes indicating molecular adaptation (also known as positive selection) in numerous genes with important roles in maintaining genome stability ¬¬- the genetic defense mechanisms that counteract the accumulation of damage to a species’ DNA, thereby preserving the integrity of the genome.


These adaptive sequence changes were found in genes intimately tied to DNA repair, DNA damage response, and DNA damage tolerance, among other genes. The opposite phenomenon, genome instability, which results from accumulated DNA damage, is well known to predispose humans to numerous cancers and age-related diseases.


“Not only were there a surprisingly high number of genome stability genes that contained these adaptive changes, but there was also an enrichment of several of these genes, highlighting the importance of this genetic fine-tuning in the white shark,” said Mahmood Shivji, Ph.D., director of NSU’s Save Our Seas Foundation Shark Research Center and GHRI. Shivji co-led the study with Michael Stanhope, Ph.D., of Cornell University College of Veterinary Medicine.


Also notable was that the white shark genome contained a very high number of “jumping genes” or transposons, and in this case a specific type, known as LINEs. In fact this is one of the highest proportions of LINEs (nearly 30%) discovered in vertebrates so far.


“These LINEs are known to cause genome instability by creating double stranded breaks in DNA,” said Stanhope. “It’s plausible that this proliferation of LINEs in the white shark genome could represent a strong selective agent for the evolution of efficient DNA repair mechanisms, and is reflected in the positive selection and enrichment of so many genome stability genes.”











Great white shark genome decoded
Great white shark [Credit: Byron Dilkes, Danah Divers]

The international research team, which also included scientists from California State University, Monterey Bay, Clemson University, University of Porto, Portugal, and the Theodosius Dobzhansky Center for Genome Bioinformatics, Russia, also found that many of the same genome stability genes in the white shark were also under positive selection and enriched in the huge-bodied, long-lived whale shark.


The discovery that the whale shark also had these key genome stability adaptations was significant because theoretically, the risk of developing cancer should increase with both the number of cells (large bodies) and an organism’s lifespan – there is statistical support for a positive relationship of body size and cancer risk within a species. Interestingly, this does not tend to hold up across species.


Contrary to expectations, very large-bodied animals do not get cancer more often than humans, suggesting they have evolved superior cancer-protective abilities. The genetic innovations discovered in genome stability genes in the white and whale shark could be adaptations facilitating the evolution of their large bodies and long lifespans.


“Decoding the white shark genome is providing science with a new set of keys to unlock lingering mysteries about these feared and misunderstood predators – why sharks have thrived for some 500 million years, longer than almost any vertebrate on earth” said Dr. Salvador Jorgensen, a Senior Research Scientist at the Monterey Bay Aquarium, who co-authored the study.


But the innovations did not end there.


The shark genomes revealed other intriguing evolutionary adaptations in genes linked to wound healing pathways. Sharks are known for their impressively rapid wound healing.


“We found positive selection and gene content enrichments involving several genes tied to some of the most fundamental pathways in wound healing, including in a key blood clotting gene,” said Stanhope. “These adaptations involving wound healing genes may underlie the vaunted ability of sharks to heal efficiently from even large wounds.”


The researchers say they have just explored the “tip of the iceberg” with respect to the white shark genome.


“Genome instability is a very important issue in many serious human diseases; now we find that nature has developed clever strategies to maintain the stability of genomes in these large-bodied, long-lived sharks,” said Shivji. “There’s still tons to be learned from these evolutionary marvels, including information that will potentially be useful to fight cancer and age-related diseases, and improve wound healing treatments in humans, as we uncover how these animals do it.”


Decoding the white shark genome will also assist with the conservation of this and related sharks, many of which have rapidly declining populations due to overfishing,” said Steven O’Brien, a conservation geneticist at NSU, who co-conceived this study. “The genome data will be a great asset for understanding white shark population dynamics to better conserve this amazing species that has captured the imagination of so many.”


The findings are reported in the journal Proceedings of the National Academy of Sciences.


Source: Nova Southeastern University [February 18, 2019]



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Newly discovered marsupial lived among Arctic dinosaurs

A research team has discovered a previously unknown species of marsupial that lived in Alaska’s Arctic during the era of dinosaurs, adding a vivid new detail to a complex ancient landscape.











Newly discovered marsupial lived among Arctic dinosaurs
This portrait of northern Alaska’s landscape and animals about 70 million years ago features a small mammal.
The creature, though not necessarily Unnuakomys hutchisoni, illustrates scientists’ conclusion
that mammals lived among the dinosaurs [Credit: James Havens]

The thumb-sized animal, named Unnuakomys hutchisoni, lived in the Arctic about 69 million years ago during the late Cretaceous Period. Its discovery, led by scientists from the University of Colorado and University of Alaska Fairbanks, is outlined in an article published in the Journal of Systematic Palaeontology.
The discovery adds to the picture of an environment that scientists say was surprisingly diverse. The tiny animal, which is the northernmost marsupial ever discovered, lived among a unique variety of dinosaurs, plants and other animals.


Alaska’s North Slope, which was at about 80 degrees north latitude when U. hutchisoni lived there, was once thought to be a barren environment during the late Cretaceous. That perception has gradually changed since dinosaurs were discovered along the Colville River in the 1980s, with new evidence showing the region was home to a diverse collection of unique species that didn’t exist anywhere else.



A 3D rendering shows fossilized teeth and jaws belonging to Unnuakomys hutchisoni, a newly discovered marsupial 


that lived on Alaska’s North Slope 69 million years ago. Scientists found its tiny teeth, which are about the size 


of a grain of sand, at a site along the Colville River [Credit: University of Colorado at Boulder]


Finding a new marsupial species in the far north adds a new layer to that evolving view, said Patrick Druckenmiller, the director of the University of Alaska Museum of the North.
“Northern Alaska was not only inhabited by a wide variety of dinosaurs, but in fact we’re finding there were also new species of mammals that helped to fill out the ecology,” said Druckenmiller, who has studied dinosaurs in the region for more than a decade. “With every new species, we paint a new picture of this ancient polar landscape.”


Marsupials are a type of mammal that carries underdeveloped offspring in a pouch. Kangaroos and koalas are the best-known modern marsupials. Ancient relatives were much smaller during the late Cretaceous, Druckenmiller said. Unnuakomys hutchisoni was probably more like a tiny opossum, feeding on insects and plants while surviving in darkness for as many as four months each winter.











Newly discovered marsupial lived among Arctic dinosaurs
Scientists excavate a dinosaur bone bed along the Colville River
[Credit: Patrick Druckenmiller]

The research team, whose project was funded with a National Science Foundation grant, identified the new marsupial using a painstaking process. With the help of numerous graduate and undergraduate students, they collected, washed and screened ancient river sediment collected on the North Slope and then carefully inspected it under a microscope. Over many years, they were able to locate numerous fossilized teeth roughly the size of a grain of sand.
“I liken it to searching for proverbial needles in haystacks — more rocks than fossils,” said Florida State University paleobiologist Gregory Erickson, who contributed to the paper.


Jaelyn Eberle, curator of fossil vertebrates at the University of Colorado Museum of Natural History, led the effort to examine those teeth and a few tiny jawbones. Their analysis revealed a new species and genus of marsupial.











Newly discovered marsupial lived among Arctic dinosaurs
The Colville River flows across Alaska’s North Slope. The bluffs on the left bank are made of the 70-million-year-old
Prince Creek Formation and contain bones and teeth of dinosaurs and tiny mammals
[Credit: Patrick Druckenmiller]

Mammal teeth have unique cusps that differ from species to species, making them a bit like fingerprints for long-dead organisms, said Eberle, the lead author of the study.


“If I were to go down to the Denver Zoo and crank open the mouth of a lion and look in — which I don’t recommend — I could tell you its genus and probably its species based only on its cheek teeth,” Eberle said.


The name Unnuakomys hutchisoni combines the Iñupiaq word for “night” and the Greek word “mys” for mouse, a reference to the dark winters the animal endured, and a tribute to J. Howard Hutchison, a paleontologist who discovered the fossil-rich site where its teeth were eventually found.


Source: University of Alaska Fairbanks [February 18, 2019]



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Solar Tadpole-Like Jets Seen With NASA’S IRIS Add New Clue to Age-Old Mystery


NASA – IRIS Mission patch.


Feb. 19, 2019


Scientists have discovered tadpole-shaped jets coming out of regions with intense magnetic fields on the Sun. Unlike those living on Earth, these “tadpoles” — formally called pseudo-shocks — are made entirely of plasma, the electrically conducting material made of charged particles that account for an estimated 99 percent of the observable universe. The discovery adds a new clue to one of the longest-standing mysteries in astrophysics.



Animation above: Images from IRIS show the tadpole-shaped jets containing pseudo-shocks streaking out from the Sun. Animation Credits: Abhishek Srivastava IIT (BHU)/Joy Ng, NASA’s Goddard Space Flight Center.


For 150 years scientists have been trying to figure out why the wispy upper atmosphere of the Sun — the corona — is over 200 times hotter than the solar surface. This region, which extends millions of miles, somehow becomes superheated and continually releases highly charged particles, which race across the solar system at supersonic speeds.


When those particles encounter Earth, they have the potential to harm satellites and astronauts, disrupt telecommunications, and even interfere with power grids during particularly strong events. Understanding how the corona gets so hot can ultimately help us understand the fundamental physics behind what drives these disruptions.


In recent years, scientists have largely debated two possible explanations for coronal heating: nanoflares and electromagnetic waves. The nanoflare theory proposes bomb-like explosions, which release energy into the solar atmosphere. Siblings to the larger solar flares, they are expected to occur when magnetic field lines explosively reconnect, releasing a surge of hot, charged particles. An alternative theory suggests a type of electromagnetic wave called Alfvén waves might push charged particles into the atmosphere like an ocean wave pushing a surfer. Scientists now think the corona may be heated by a combination of phenomenon like these, instead of a single one alone.



Interface Region Imaging Spectrograph or IRIS spacecraft. Image Credits: NASA/GSFC

The new discovery of pseudo-shocks adds another player to that debate. Particularly, it may contribute heat to the corona during specific times, namely when the Sun is active, such as during solar maximums — the most active part of the Sun’s 11-year cycle marked by an increase in sunspots, solar flares and coronal mass ejections.


The discovery of the solar tadpoles was somewhat fortuitous. When recently analyzing data from NASA’s Interface Region Imaging Spectrograph, or IRIS, scientists noticed unique elongated jets emerging from sunspots ­— cool, magnetically-active regions on the Sun’s surface — and rising 3,000 miles up into the inner corona. The jets, with bulky heads and rarefied tails, looked to the scientists like tadpoles swimming up through the Sun’s layers.


“We were looking for waves and plasma ejecta, but instead, we noticed these dynamical pseudo-shocks, like disconnected plasma jets, that are not like real shocks but highly energetic to fulfill Sun’s radiative losses,” said Abhishek Srivastava, scientist at the Indian Institute of Technology (BHU) in Varanasi, India, and lead author on the new paper in Nature Astronomy.


Using computer simulations matching the events, they determined these pseudo-shocks could carry enough energy and plasma to heat the inner corona.



Animation above: A computer simulation shows how the pseudo-shock is ejected and becomes disconnected from the plasma below (green). Animation Credits: Abhishek Srivastava IIT (BHU)/Joy Ng, NASA’s Goddard Space Flight Center.


The scientists believe the pseudo-shocks are ejected by magnetic reconnection — an explosive tangling of magnetic field lines, which often occurs in and around sunspots. The pseudo-shocks have only been observed around the rims of sunspots so far, but scientists expect they’ll be found in other highly magnetized regions as well.



Image above: The tadpole-shaped pseudo-shocks, shown in dashed white box, are ejected from highly magnetized regions on the solar surface. Image Credits: Abhishek Srivastava IIT (BHU)/Joy Ng, NASA’s Goddard Space Flight Center.


Over the past five years, IRIS has kept an eye on the Sun in its 10,000-plus orbits around Earth. It’s one of several in NASA’s Sun-staring fleet that have continually observed the Sun over the past two decades. Together, they are working to resolve the debate over coronal heating and solve other mysteries the Sun keeps.


“From the beginning, the IRIS science investigation has focused on combining high-resolution observations of the solar atmosphere with numerical simulations that capture essential physical processes,” said Bart De Pontieu research scientist at Lockheed Martin Solar & Astrophysics Laboratory in Palo Alto, California. “This paper is a nice illustration of how such a coordinated approach can lead to new physical insights into what drives the dynamics of the solar atmosphere.”


The newest member in NASA’s heliophysics fleet, Parker Solar Probe, may be able to provide some additional clues to the coronal heating mystery. Launched in 2018, the spacecraft flies through the solar corona to trace how energy and heat move through the region and to explore what accelerates the solar wind as well as solar energetic particles. Looking at phenomena far above the region where pseudo-shocks are found, Parker Solar Probe’s investigation hopes to shed light on other heating mechanisms, like nanoflares and electromagnetic waves. This work will complement the research conducted with IRIS.


“This new heating mechanism could be compared to the investigations that Parker Solar Probe will be doing,” said Aleida Higginson, deputy project scientist for Parker Solar Probe at Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “Together they could provide a comprehensive picture of coronal heating.”


Related Links:


Nature Astronomy: https://www.nature.com/articles/s41550-018-0590-1


Learn more about NASA’s IRIS Mission: https://www.nasa.gov/iris


NASA’s 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


Learn more about NASA’s Parker Solar Probe: https://www.nasa.gov/content/goddard/parker-solar-probe


Animations (mentioned), Images (mentioned), Text, Credits: NASA/Rob Garner/Goddard Space Flight Center, by Mara Johnson-Groh.


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