vendredi 31 mars 2017

Silicon sandwiches feed LHC’s upgraded collision appetite












CERN - European Organization for Nuclear Research logo.

March 31, 2017


Image above: The scientist carefully places the sensors in the probe station and tests them by applying a high voltage using a needle. The team must wear protective equipment to keep the sensor safe from dust and scratches (Image: Ulysse Fichet/CERN).

In a special, dust-free, clean laboratory, straddling the Swiss-French border, a group of physicists spend their time probing hand-sized hexagons of silicon. These hexagons are a fraction of a millimetre thick and are made up of over a hundred smaller hexagons, individual sensors each roughly one centimeter across. Together with layers of metal, the sensors will form a new subdetector to replace part of the end-cap calorimeters in CERN’s CMS experiment.

A calorimeter measures the energy a particle loses as it passes through. It is usually designed to stop entirely or “absorb” most of the particles coming from a collision. The new calorimeter sensors will be used to measure the energy and arrival time and to trace the path of individual particles that fly out in the form of debris from the collision point in the centre of the experiment. Once in place, this will be the first time that this type of silicon sensor has ever been used in the calorimeter of a particle detector on such a large scale.


Image above: Eva Sicking works on the probe station. She explains: “Currently we use individual probe needles to contact the cell we want to test and all of its direct neighbours, but we’re also developing a probe card with many pins below it so we can lower the card and connect all the pins and test all the sensors cells in one go, so we won’t need to place each of the eight needles individually.” (Image: Ulysse Fichet/CERN).

The sensors are part of a wider upgrade project to make sure that the experiments are able to cope with a larger number of particle collisions as a result of the High-Luminosity LHC (HL-LHC) upgrade in 2025, and the increased potential for discovery that comes with it. The current technology is based on long, clear lead-tungstate crystals designed to cope with the radiation in the detectors Although they will operate fine for the LHC era, until 2025, the amount of radiation expected during HL-LHC will darken the crystals until they become blind to particles passing through them.


Image above: The sensors constitute the core part of the new subdetector, which will replace the current end-cap at CMS, pictured (Image: David Barney/CERN).

“The lead-tungstate crystals we use now are designed to operate at comparably low collision rates and in a low-radiation environment.  With the HL-LHC, we’ll have hundreds of collisions at one time, so we needed something that could withstand the increased radiation and resolve showers from particles very close to each other in space and time,” explains Eva Sicking, the applied physicist leading this silicon sensor project. “We want to be able to distinguish the different particles that we see, and also know which ones came from which collisions.”

“These sensors not only provide a system that’s more radiation-hard; at the same time they also provide more information on where exactly the particles passed through. They also give us very good timing information, so we can determine exactly when this particle arrived, and thanks to the small cells it can do that for many collisions at the same time,” continues Andreas Maier, who is also working on the project.

Metal Sandwiches

To make sure the sensors are able to do this, instead of long crystals, the team are moving away from long crystals and instead building sandwiches – layers of the sensor alternating with layers of a heavy metal, such as lead.


Image above: A team of CMS researchers have already tested the first sandwich calorimeter prototype with single particles, but in the upgraded HL-LHC multiple particle collisions will occur at once and hundreds of debris particles will pass through the sensors at the same time. The prototype is based on silicon and dense metals – the image shows the alternating layers of metal and the silicon sensor. The particle beam will run from the left of the image through to the right. (Image: David Barney/CERN).

To test each sensor in the sandwich, the team is using a special probe station, with eight needles sitting above a vacuum plate. The plate holds the delicate, and expensive, silicon sensors firmly in place so that the needles can be manoeuvred and lowered to connect with contact pads marked on each sensor. They then apply a high voltage to the sensor to record the data that will be used to assess the sensor’s quality.


Image above: Using the probe station, the physicists test how much voltage can be applied to each sensor – the more voltage the sensors can withstand, the better any radiation damage can be mitigated. Impurities in the crystal or damages can cause high leakage current in the sensor. Such a cell will draw a large current which would make the full sensor difficult or even impossible to operate (Image: Ulysse Fichet/CERN).

Sensitive instruments tell the team what the electrical current generated in the sensor is, as well as a measure called capacitance. If either of these run above a set level, the sensor cannot be used, as it will create noise that interferes with the data from any particle tracks. If the noise is too high, the researchers can assess if there is a problem at production level. If a problem is found, they go back to the manufacturers to make sure it’s ironed out before the real sensors go into production. All the sensors eventually used will go through this process, either at CERN or at other institutes.

Optimising power

Measuring current is particularly important because it can have an impact on how much power and energy is required when the machine is running.


Image above: The software shows the current running through each sensor, and the tile made of multiple smaller sensors is shown on the bottom right (Image: Andreas Maier/CERN).

“In an ideal world, the sensor would not show any leakage current, but in reality, impurities are introduced during the production of these sensors. Therefore, the current we measure is an indicator of the production quality,” Florian Pitters, another member of the group, explains.

Leakage current is acceptable below a certain level, but it is amplified as you add more sensors together and the power supply and cooling system has to deal with a larger amount of power and dissipated heat.

“Approximately 25% of the final electricity bill will be due only to leakage current. So if we can suppress it, that’s good.” Andreas.

If there’s any problem in the final sensors, it could cause the entire tile to short, rendering it useless. So these tests are vital to ensuring that the whole detector system runs at its best and that these components don’t create barriers to future discovery.

“There have been mistakes with things that people just couldn’t have known, until we tested them. We’ve discovered a few times that ways we intended to go just had to be abandoned, so we chose a new path. That’s how research goes,” says Andreas.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related links:

CERN’s CMS experiment: http://home.cern/about/experiments/cms

High-Luminosity LHC (HL-LHC): http://home.cern/topics/high-luminosity-lhc

For more information about European Organization for Nuclear Research (CERN), Visit: http://home.cern/

Images (mentioned), Text, Credits: CERN/Harriet Jarlett.

Best regards, Orbiter.ch

NASA’s CYGNSS Satellite Constellation Enters Science Operations Phase











NASA - Cyclone Global Navigation Satellite System (CYGNSS) logo.

March 31, 2017

NASA’s Cyclone Global Navigation Satellite System (CYGNSS) -- a constellation of eight microsatellites that will take detailed measurement of windspeeds inside hurricanes -- successfully completed the development and on-orbit commissioning phases of its mission on March 23 and moved into the science operations phase. The spacecraft have now begun their science instrument calibration and validation and are on track to deliver the first science data in May, just in time for the start of the 2017 Atlantic hurricane season.


Image above: This map shows the coverage of ocean surface wind measurements made by one of the eight spacecraft that make up the CYGNSS constellation over the course of 4 orbits (approximately 6 hours) on February 14, 2017. The blue values indicate relatively low wind speeds, while the yellow, orange, and red values indicate increasingly higher wind speeds. The highest wind speeds in this image (orange and red) are associated with a powerful extratropical cyclone that moved off the East Coast of North America. Image Credits: NOAA/NASA/University of Michigan.

The CYGNSS spacecraft, launched into low-inclination, low-Earth orbit over the tropics on December 15, will make frequent measurements of ocean surface winds in and near a hurricane’s inner core, an area that up until now has proven impossible to probe accurately from space. CYGNSS is able to measure the surface winds using GPS signals reflected by the ocean surface, which are able to penetrate through the intense rain in a storm’s eye wall.

"All spacecraft have completed their on-orbit engineering tests and are performing to specification," said SwRI’s Randy Rose, CYGNSS Project Systems Engineer at the Southwest Research Institute (SwRI) in San Antonio, which designed and built the spacecraft. "It is very gratifying to be seeing how well everything is working.  The scientists are going to get everything they'd hoped for, plus some."

Over the past several decades, forecasters have improved hurricane path prediction significantly, but their ability to predict the intensity of storms has lagged behind. With data from CYGNSS, forecasters hope to improve hurricane intensity forecasts by better understanding how storms rapidly intensify.

“With CYGNSS, we’re doing important, breakthrough science with a constellation of satellites that are literally small enough to sit on your desk,” said John Scherrer, a program director in SwRI’s Space Science and Engineering Division who oversaw satellite construction. “While these satellites might be small, they provide big returns with data that we expect to one day help weather forecasters make important weather-related forecasts such as storm related damage projections and reliable evacuation orders.”

SwRI’s office in Boulder, Colorado, hosts the mission operations center, which commands the spacecraft, collects the telemetry, and transmits the data to the science operations center, based at the University of Michigan in Ann Arbor.

Cyclone Global Navigation Satellite System (CYGNSS). Image Credit: NASA

CYGNSS recently demonstrated its ability to observe surface winds in major storms during its flyover of Tropical Cyclone Enawo, on March 6, just hours before the storm made landfall over Madagascar.

“Enawo had maximum sustained winds estimated at 125 mph by the Joint Typhoon Warning Center around the time of the CYGNSS overpass,“ said Chris Ruf, Professor of Atmospheric Science at the University of Michigan and CYGNSS Principal Investigator. “The satellites’ measurements responded as expected to changes in the wind speed as they approached and passed over the storm center, showing strong and reliable sensitivity throughout. We are looking forward to the completion of our calibration and validation activities and the beginning of well-calibrated science observations.”

The CYGNSS mission is led by the University of Michigan. SwRI led the engineering development and manages the operation of the constellation. The University of Michigan Climate and Space Sciences and Engineering department leads the science investigation, and the Earth Science Division of NASA’s Science Mission Directorate oversees the mission.

For more information about CYGNSS, visit: http://www.nasa.gov/cygnss/

Images (mentioned), Text, Credits: NASA/Joe Atkinson.

Greetings, Orbiter.ch

Comet That Took a Century to Confirm Passes by Earth












NASA Goddard Space Flight Center logo.

March 31, 2017

On April 1, 2017, comet 41P will pass closer than it normally does to Earth, giving observers with binoculars or a telescope a special viewing opportunity. Comet hunters in the Northern Hemisphere should look for it near the constellations Draco and Ursa Major, which the Big Dipper is part of.

Whether a comet will put on a good show for observers is notoriously difficult to predict, but 41P has a history of outbursts, and put on quite a display in 1973. If the comet experiences similar outbursts this time, there’s a chance it could become bright enough to see with the naked eye. The comet is expected to reach perihelion, or its closest approach to the sun, on April 12.


Image above: In this image taken March 24, 2017, comet 41P/Tuttle-Giacobini-Kresák is shown moving through a field of faint galaxies in the bowl of the Big Dipper. On April 1, the comet will pass by Earth at a distance of about 13 million miles (0.14 astronomical units), or 55 times the distance from Earth to the moon; that is a much closer approach than usual for this Jupiter-family comet. Image Credits: image copyright Chris Schur, used with permission.

Officially named 41P/Tuttle-Giacobini-Kresák to honor its three discoverers, the comet is being playfully called the April Fool’s Day comet on this pass. Discovery credit goes first to Horace Tuttle, who spotted the comet in 1858. According to the Cometography website, 41P was recognized at the time as a periodic comet — one that orbits the sun — but astronomers initially were uncertain how long the comet needed to make the trip. The comet was rediscovered in 1907 by Michael Giacobini but not immediately linked to the object seen in 1858.

Later, the astronomer Andrew Crommelin determined that the two observations had been of the same object and predicted that the comet would return in 1928 and 1934, according to the Cometography entry for the comet. However, the object was not seen then and was considered lost. In 1951, L’ubor Kresák discovered it again and tied it to the earlier observations.

A member of the Jupiter family of comets, 41P makes a trip around the sun every 5.4 years, coming relatively close to Earth on some of those trips. On this approach, the comet will pass our planet at a distance of about 13 million miles (0.14 astronomical units), or about 55 times the distance from Earth to the moon. This is the comet’s closest approach to Earth in more than 50 years and perhaps more than a century.

For scientists, 41P’s visit is an opportunity to fill in details about the comet’s composition, coma and nucleus.


Image above: An artist’s illustration of a group of comet enthusiasts. Image Credits: NASA's Goddard Space Flight Center.

“An important aspect of Jupiter-family comets is that fewer of them have been studied, especially in terms of the composition of ices in their nuclei, compared with comets from the Oort cloud,” said Michael DiSanti of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. He and his team will be observing 41P on April 1 using NASA’s Infrared Telescope Facility in Hawaii.

Astronomers will try to determine characteristics such as how quickly 41P’s nucleus rotates, which provides clues about how structurally sound the nucleus is, and whether any changes can be documented in the coma and tail. Observers also will look for outbursts, which are an indication of how active a comet is.

By cataloging the subtle, and sometimes not-so-subtle, differences among comets, researchers can construct a family tree and trace the history of how and where these objects formed as the solar system was taking shape.

“Comets are remnants from the early solar system,” said DiSanti. “Each comet that comes into the neighborhood of Earth gives us a chance to add to our understanding of the events that led to the formation of our own planet.”

Related links:

Comets: http://www.nasa.gov/comets

Goddard Space Flight Center: https://www.nasa.gov/centers/goddard/home/index.html

Images (mentioned), Text, Credits: NASA's Goddard Space Flight Center, by Elizabeth Zubritsky/Rob Garner.

Greetings, Orbiter.ch

Space Station Crew Cultivates Crystals for Drug Development












ISS - International Space Station logo.

March 31, 2017

Crew members aboard the International Space Station will begin conducting research this week to improve the way we grow crystals on Earth. The information gained from the experiments could speed up the process for drug development, benefiting humans around the world.

Proteins serve an important role within the human body. Without them, the body wouldn’t be able to regulate, repair or protect itself. Many proteins are too small to be studied even under a microscope, and must be crystallized in order to determine their 3-D structures. These structures tell researchers how a single protein functions and its involvement in the development of disease. Once modeled, drug developers can use the structure to develop a specific drug to interact with the protein, a process called structure-based drug design.


Image above: Crystal formation within a 50 millimeter loop, taken on Expedition 6. Crystal growth investigations have been occurring on the station since before humans lived there because of the unique environment microgravity provides. Image Credit: NASA.

Two investigations, The Effect of Macromolecular Transport on Microgravity Protein Crystallization (LMM Biophysics 1) and Growth Rate Dispersion as a Predictive Indicator for Biological Crystal Samples Where Quality Can be Improved with Microgravity Growth (LMM Biophysics 3), will study the formation of these crystals, looking at why microgravity-grown crystals often are of higher quality than Earth-grown, and which crystals may benefit from being grown in space.

Rate of Growth – LMM Biophysics 1

Researchers know that crystals grown in space often contain fewer imperfections than those grown on Earth, but the reasoning behind that phenomenon isn’t crystal clear. A widely accepted theory in the crystallography community is that the crystals are of higher quality because they grow slower in microgravity due to a lack of buoyancy-induced convection. The only way these protein molecules move in microgravity is by random diffusion, a process that is much slower than movement on Earth.

Another less-explored theory is that a higher level of purification can be achieved in microgravity. A pure crystal may contain thousands of copies of a single protein. Once crystals are returned to Earth and exposed to an X-Ray beam, the X-ray diffraction pattern can be used to mathematically map a protein’s structure.

“When you purify proteins to grow crystals, the protein molecules tend to stick to each other in a random fashion,” said Lawrence DeLucas, LMM Biophysics 1 primary investigator. “These protein aggregates can then incorporate into the growing crystals causing defects, disturbing the protein alignment, which then reduces the crystal’s X-ray diffraction quality.”


Image above: European Space Agency astronaut Paolo Nespoli works within the Light Microscopy Module during Expedition 26. Experiments from each of the investigations will take place within the LMM. The LMM is a highly flexible, state-of-the-art light imaging microscope and is used in the research of microscopic phenomena in microgravity. Image Credit: NASA.

The theory states that in microgravity, a dimer, or two proteins stuck together, will move much slower than a monomer, or a single protein, giving aggregates less opportunity to incorporate into the crystal.

“You’re selecting out for predominantly monomer growth, and minimizing the amount of aggregates that are incorporated into the crystal because they move so much more slowly,” said DeLucas.


Image above: Lysozyme Crystal formation as seen under a light microscope. Crystals grown in microgravity typically reflect fewer imperfections, making them more ideal for drug development and other research. Image Credits: Lawrence DeLucas.

The LMM Biophysics 1 investigation will put these two theories to the test, to try to understand the reason(s) microgravity-grown crystals are often of superior quality and size compared to their Earth-grown counterparts. Improved X-ray diffraction data results in a more precise protein structure and thereby enhancing our understanding of the protein’s biological function and future drug discovery.

Crystal Types – LMM Biophysics 3

As LMM Biophysics 1 studies why space-grown crystals are of higher quality than Earth-grown crystals, LMM Biophysics 3 will take a look at which crystals may benefit from crystallization in space. Research has found that only some proteins crystallized in space benefit from microgravity growth. The shape and surface of the protein that makes up a crystal defines its potential for success in microgravity.

“Some proteins are like building blocks,” said Edward Snell, LMM Biophysics 3 primary investigator. “It’s very easy to stack them. Those are the ones that won’t benefit from microgravity. Others are like jelly beans. When you try and build a nice array of them on the ground, they want to roll away and not be ordered. Those are the ones that benefit from microgravity. What we’re trying to do is distinguish the blocks from the jelly beans.”

video
International Space Station Protein Crystal Growth

Video above: This animation explains how protein crystal growth investigations performed in the microgravity environment of the International Space Station enable more perfectly grown crystals, which help researchers to better understand the nature of the proteins through their detailed structures. Video Credits: NASA/Johnson.

Understanding how different proteins crystallize in microgravity will give researchers a deeper view into how these proteins function, and help to determine which crystals should be transported to the space station for growth.

“We’re maximizing the use of a scarce resource, and making sure that every crystal we put up there benefits the scientists on the ground,” said Snell.

These crystals could be used in drug development and disease research around the world. Follow @ISS_Research for more information about the science happening on the space station.

Related links:

LMM Biophysics 1: https://www.nasa.gov/mission_pages/station/research/experiments/2191.html

LMM Biophysics 3: https://www.nasa.gov/mission_pages/station/research/experiments/1970.html

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

Images (mentioned), Video (mentioned), Text, Credits: NASA/Kristine Rainey/JSC/International Space Station Program Science Office/Jenny Howard.

Best regards, Orbiter.ch

Hubble's Double Galaxy Gaze: Leda and NGC 4424












NASA - Hubble Space Telescope patch.

March 31, 2017


Some astronomical objects have endearing or quirky nicknames, inspired by mythology or their own appearance. Take, for example, the constellation of Orion (The Hunter), the Sombrero Galaxy, the Horsehead Nebula, or even the Milky Way. However, the vast majority of cosmic objects appear in astronomical catalogs and are given rather less poetic names based on the order of their discovery.

Two galaxies are clearly visible in this Hubble image, the larger of which is NGC 4424. This galaxy is cataloged in the New General Catalog of Nebulae and Clusters of Stars (NGC), which was compiled in 1888. The NGC is one of the largest astronomical catalogs, which is why so many Hubble Pictures of the Week feature NGC objects. In total there are 7,840 entries in the catalog and they are also generally the larger, brighter, and more eye-catching objects in the night sky, and hence the ones more easily spotted by early stargazers.

The smaller, flatter, bright galaxy sitting just below NGC 4424 is named LEDA 213994. The Lyon-Meudon Extragalactic Database (LEDA) is far more modern than the NGC and contains millions of objects.

Many NGC objects still go by their initial names simply because they were christened within the NGC first. However, since astronomers can't resist a good acronym and “Leda” is more appealing than “the LMED,” the smaller galaxy is called "Leda." Leda was a princess in Ancient Greek mythology.

Hubble Space Telescope

For images and more information about Hubble, visit:

http://hubblesite.org/
http://www.nasa.gov/hubble
http://www.spacetelescope.org/

Text credits: European Space Agency/NASA/Karl Hille/Image, animation, credits: ESA/Hubble & NASA.

Greetings, Orbiter.ch

NASA Observations Reshape Basic Plasma Wave Physics












NASA - Magnetospheric Multiscale (MMS) patch.

March 31, 2017

When NASA’s Magnetospheric Multiscale — or MMS — mission was launched, the scientists knew it would answer questions fundamental to the nature of our universe — and MMS hasn’t disappointed. A new finding, presented in a paper in Nature Communications, provides observational proof of a 50-year-old theory and reshapes the basic understanding of a type of wave in space known as a kinetic Alfvén wave. The results, which reveal unexpected, small-scale complexities in the wave, are also applicable to nuclear fusion techniques, which rely on minimizing the existence of such waves inside the equipment to trap heat efficiently.

video
Observations Reshape Basic Plasma Wave Physics

Video Credits: NASA's Goddard Space Flight Center/Genna Duberstein.

Kinetic Alfvén waves have long been suspected to be energy transporters in plasmas — a fundamental state of matter composed of charged particles — throughout the universe. But it wasn’t until now, with the help of MMS, that scientists have been able to take a closer look at the microphysics of the waves on the relatively small scales where the energy transfer actually happens.

“This is the first time we’ve been able to see this energy transfer directly,” said Dan Gershman, lead author and MMS scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland in College Park. “We’re seeing a more detailed picture of Alfvén waves than anyone’s been able to get before.”

The waves could be studied on a small scale for the first time because of the unique design of the MMS spacecraft. MMS’s four spacecraft fly in a compact 3-D pyramid formation, with just four miles between them — closer than ever achieved before and small enough to fit between two wave peaks. Having multiple spacecraft allowed the scientists to measure precise details about the wave, such as how fast it moved and in what direction it travelled.

video
Typical Alfvén Waves

Video above: n a typical Alfvén wave, the particles (yellow) move freely along the magnetic field lines (blue). Video Credits: NASA Goddard's Scientific Visualization Studio/Tom Bridgman, data visualizer.

Previous multi-spacecraft missions flew at much larger separations, which didn’t allow them to see the small scales — much like trying to measure the thickness of a piece of paper with a yardstick. MMS’s tight flying formation, however, allowed the spacecraft to investigate the shorter wavelengths of kinetic Alfvén waves, instead of glossing over the small-scale effects.

“It’s only at these small scales that the waves are able to transfer energy, which is why it’s so important to study them,” Gershman said.

As kinetic Alfvén waves move through a plasma, electrons traveling at the right speed get trapped in the weak spots of the wave’s magnetic field. Because the field is stronger on either side of such spots, the electrons bounce back and forth as if bordered by two walls, in what is known as a magnetic mirror in the wave. As a result, the electrons aren't distributed evenly throughout: Some areas have a higher density of electrons, and other pockets are left with fewer electrons. Other electrons, which travel too fast or too slow to ride the wave, end up passing energy back and forth with the wave as they jockey to keep up.

video
Kinetic Alfvén Waves

Video above: In a kinetic Alfvén wave, some particles become trapped in the weak spots of the wave’s magnetic field and ride along with the wave as it moves through space. Video Credits: NASA Goddard's Scientific Visualization Studio/Tom Bridgman, data visualizer.

The wave’s ability to trap particles was predicted more than 50 years ago but hadn’t been directly captured with such comprehensive measurements until now. The new results also showed a much higher rate of trapping than expected.

This method of trapping particles also has applications in nuclear fusion technology. Nuclear reactors use magnetic fields to confine plasma in order to extract energy. Current methods are highly inefficient as they require large amounts of energy to power the magnetic field and keep the plasma hot. The new results may offer a better understanding of one process that transports energy through a plasma.

“We can produce, with some effort, these waves in the laboratory to study, but the wave is much smaller than it is in space,” said Stewart Prager, plasma scientist at the Princeton Plasma Physics Laboratory in Princeton, New Jersey. “In space, they can measure finer properties that are hard to measure in the laboratory.”

Magnetospheric Multiscale (MMS). Image Credit: NASA

This work may also teach us more about our sun.  Some scientists think kinetic Alfvén waves are key to how the solar wind — the constant outpouring of solar particles that sweeps out into space — is heated to extreme temperatures. The new results provide insight on how that process might work.

Throughout the universe, kinetic Alfvén waves are ubiquitous across magnetic environments, and are even expected to be in the extra-galactic jets of quasars. By studying our near-Earth environment, NASA missions like MMS can make use of a unique, nearby laboratory to understand the physics of magnetic fields across the universe.

Related Link:

Learn more about NASA’s MMS Mission: http://www.nasa.gov/mission_pages/mms/index.html

Image (mentioned), Videos (mentioned), Text, Credits: NASA’s Goddard Space Flight Center, by Mara Johnson-Groh/Rob Garner.

Greetings, Orbiter.ch

Mysterious Cosmic Explosion Puzzles Astronomers












NASA - Chandra X-ray Observatory patch.

March 31, 2017

A mysterious flash of X-rays has been discovered by NASA’s Chandra X-ray Observatory in the deepest X-ray image ever obtained. This source likely comes from some sort of destructive event, but may be of a variety that scientists have never seen before.

The X-ray source, located in a region of the sky known as the Chandra Deep Field-South (CDF-S), has remarkable properties. Prior to October 2014, this source was not detected in X-rays, but then it erupted and became at least a factor of 1,000 brighter in a few hours. After about a day, the source had faded completely below the sensitivity of Chandra.


Animation above: Animation of CDF-S Transient. Animation Credits: X-ray: NASA/CXC/Pontifical Catholic University/F. Bauer et al.

Thousands of hours of legacy data from the Hubble and Spitzer Space Telescopes helped determine that the event likely came from a faint, small galaxy about 10.7 billion light years from Earth. For a few minutes, the X-ray source produced a thousand times more energy than all the stars in this galaxy.

“Ever since discovering this source, we’ve been struggling to understand its origin,” said Franz Bauer of the Pontifical Catholic University of Chile in Santiago, Chile. “It’s like we have a jigsaw puzzle but we don’t have all of the pieces.”

Two of the three main possibilities to explain the X-ray source invoke gamma-ray burst (GRB) events. GRBs are jetted explosions triggered either by the collapse of a massive star or by the merger of a neutron star with another neutron star or a black hole. If the jet is pointing towards the Earth, a burst of gamma rays is detected. As the jet expands, it loses energy and produces weaker, more isotropic radiation at X-ray and other wavelengths.

Possible explanations for the CDF-S X-ray source, according to the researchers, are a GRB that is not pointed toward Earth, or a GRB that lies beyond the small galaxy. A third possibility is that a medium-sized black hole shredded a white dwarf star.


Image above: Still Image of CDF-S Transient. Image Credits: X-ray: NASA/CXC/Pontifical Catholic University/F. Bauer et al.

“None of these ideas fits the data perfectly,” said co-author Ezequiel Treister, also of the Pontifical Catholic University, “but then again, we’ve rarely if ever seen any of the proposed possibilities in actual data, so we don’t understand them well at all.”

The mysterious X-ray source was not seen at any other time during the two and a half months of exposure time Chandra has observed the CDF-S region, which has been spread out over the past 17 years. Moreover, no similar events have yet to be found in Chandra observations of other parts of the sky.

This X-ray source in the CDF-S has different properties from the as yet unexplained variable X-ray sources discovered in the elliptical galaxies NGC 5128 and NGC 4636 by Jimmy Irwin and collaborators. In particular, the CDF-S source is likely associated with the destruction of a neutron star, white dwarf, or massive star, and is roughly 100,000 times more luminous in X-rays. It is also located in a much smaller and younger host galaxy, and is only detected during a single, several-hour burst.

“We may have observed a completely new type of cataclysmic event,” said co-author Kevin Schawinski, of ETH Zurich in Switzerland. “Whatever it is, a lot more observations are needed to work out what we’re seeing.”

 Chandra X-ray Observatory. Image Credits: NASA/CXC

Additional highly targeted searches through the Chandra archive and those of ESA’s XMM-Newton and NASA’s Swift satellite may uncover more examples of this type of variable object that have until now gone unnoticed. Future X-ray observations by Chandra and other X-ray telescopes may also reveal the same phenomenon from other objects.

If the X-ray source was caused by a GRB triggered by the merger of a neutron star with a black hole or another neutron star, then gravitational waves would also have been produced. If such an event were to occur much closer to Earth, within a few hundred million light years, it may be detectable with the Laser Interferometer Gravitational-Wave Observatory (LIGO).

A paper describing this result appears in the June 2017 issue of the Monthly Notices of the Royal Astronomical Society and is available online. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.

For more Chandra images, multimedia and related materials, visit: http://www.nasa.gov/chandra

Images (mentioned),, Animation (mentioned), Text, Credits: NASA/Lee Mohon/Marshall Space Flight Center/Molly Porter/Chandra X-ray Center/Megan Watzke.

Best regards, Orbiter.ch

SpaceX SES-10 Mission successfully Launch












SpaceX - Falcon 9 / SES-10 Mission patch.

March 31, 2017

Falcon 9 carrying SES-10 satellite launch

SpaceX took a step into the future Thursday as it reused – for the first time – a recovered first stage of a previously-flown Falcon 9 rocket. Thursday’s mission, carrying the SES-10 communications satellite, lifted off from Pad 39A at Florida’s Kennedy Space Center Thursday 30 March at 18:27 local time (22:27 UTC) and once again landed the booster.

video
Falcon 9 launch of SES-10

Thursday’s mission made use Falcon 9 the second orbit-capable rocket – after the Space Shuttle – to achieve partial reusability. The Falcon 9 flew from Launch Complex 39A at the Kennedy Space Center, the same pad from which the Shuttle began eighty-two of its missions, including its first and final flights.

Reusability has long been a key objective for SpaceX. Making the company’s first launch in March 2006, the small Falcon 1 vehicle carried a parachute system intended to bring its spent first stage back to Earth.

Falcon 9 first stage landed on drone barge

SpaceX’s Falcon 9 rocket deliver SES-10, a commercial communications satellite for SES, to a Geostationary Transfer Orbit (GTO). SES is a world-leading satellite operator, providing reliable and secure satellite communications solutions across the globe.

SES-10 satellite

The SES-10 mission mark a historic milestone on the road to full and rapid reusability as the world’s first reflight of an orbital class rocket. Falcon 9’s first stage for the SES-10 mission previously supported the successful CRS-8 mission in April 2016.

For more information about SpaceX, visit: http://www.spacex.com/

Images, Video, Text, Credits: SpaceX/SES.

Greetings, Orbiter.ch

jeudi 30 mars 2017

Spacewalkers Successfully Connect Adapter for Commercial Crew Vehicles














ISS - Expedition 50 Mission patch / EVA - Extra Vehicular Activities patch.

March 30, 2017

Expedition 50 Commander Shane Kimbrough and Flight Engineer Peggy Whitson of NASA concluded their spacewalk at 2:33 p.m. EDT. During the spacewalk, which lasted just over seven hours, the two astronauts successfully reconnected cables and electrical connections on the Pressurized Mating Adapter-3. PMA-3 will provide the pressurized interface between the station and the second of two international docking adapters to be delivered to the complex to support the dockings of U.S. commercial crew spacecraft in the future.


Image above: Spacewalkers Shane Kimbrough (spacesuit with red stripe on legs) and Peggy Whitson are pictured shortly after exiting the Quest airlock this morning. Image Credits: @Thom_Astro.

The duo were also tasked with installing four thermal protection shields on the Tranquility module of the International Space Station. The shields were required to cover the port where the PMA-3 was removed earlier in the week and robotically installed on the Harmony module. During the spacewalk, one of the shields was inadvertently lost. The loss posed no immediate danger to the astronauts and Kimbrough and Whitson went on to successfully install the remaining shields on the common berthing mechanism port.

A team from the Mission Control Center at NASA’s Johnson Space Center in Houston devised a plan for the astronauts to finish covering the port with the PMA-3 cover Whitson removed earlier in the day. The plan worked, and the cover was successfully installed, providing thermal protection and micrometeoroid and orbital debris cover for the port.

To round out the spacewalk, Kimbrough and Whitson also installed a different shield around the base of the PMA-3 adapter for micrometeoroid protection. The shield was nicknamed a cummerbund as it fits around the adapter similar to a tuxedo’s cummerbund worn around the waist.


Image above: Astronaut Peggy Whitson signs her autograph near an Expedition 50 mission patch attached to the inside the International Space Station. Image Credit: NASA.

Having completed her eighth spacewalk, Whitson now holds the record for the most spacewalks and accumulated time spacewalking by a female astronaut.

Spacewalkers have now spent a total of 1,243 hours and 42 minutes outside the station during 199 spacewalks in support of assembly and maintenance of the orbiting laboratory.

Related links:

International docking adapters: https://www.nasa.gov/feature/meet-the-international-docking-adapter

Peggy Whitson spacewalk record: https://blogs.nasa.gov/spacestation/2017/03/29/astronaut-peggy-whitson-set-to-break-spacewalk-record-thursday/

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

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

Best regards, Orbiter.ch

NASA's MAVEN Reveals Most of Mars' Atmosphere Was Lost to Space












NASA - MAVEN Mission logo.

March 30, 2017


Image above: This artist’s concept depicts the early Martian environment (right) – believed to contain liquid water and a thicker atmosphere – versus the cold, dry environment seen at Mars today (left). NASA's Mars Atmosphere and Volatile Evolution is in orbit of the Red Planet to study its upper atmosphere, ionosphere and interactions with the sun and solar wind. Image Credits: NASA’s Goddard Space Flight Center.

Solar wind and radiation are responsible for stripping the Martian atmosphere, transforming Mars from a planet that could have supported life billions of years ago into a frigid desert world, according to new results from NASA's MAVEN spacecraft.

"We've determined that most of the gas ever present in the Mars atmosphere has been lost to space," said Bruce Jakosky, principal investigator for the Mars Atmosphere and Volatile Evolution Mission (MAVEN), University of Colorado in Boulder. The team made this determination from the latest results, which reveal that about 65 percent of the argon that was ever in the atmosphere has been lost to space. Jakosky is lead author of a paper on this research to be published in Science on Friday, March 31.

In 2015, MAVEN team members previously announced results that showed atmospheric gas is being lost to space today and described how atmosphere is stripped away. The present analysis uses measurements of today’s atmosphere for the first estimate of how much gas was lost through time.

Liquid water, essential for life, is not stable on Mars' surface today because the atmosphere is too cold and thin to support it. However, evidence such as features resembling dry riverbeds and minerals that only form in the presence of liquid water indicates the ancient Martian climate was much different – warm enough for water to flow on the surface for extended periods.

“This discovery is a significant step toward unraveling the mystery of Mars' past environments,“ said Elsayed Talaat, MAVEN Program Scientist, at NASA Headquarters in Washington. “In a broader context, this information teaches us about the processes that can change a planet’s habitability over time.”

There are many ways a planet can lose some of its atmosphere. For example, chemical reactions can lock gas away in surface rocks, or an atmosphere can be eroded by radiation and a stellar wind from a planet's parent star. The new result reveals that solar wind and radiation were responsible for most of the atmospheric loss on Mars, and the depletion was enough to transform the Martian climate. The solar wind is a thin stream of electrically conducting gas constantly blowing out from the surface of the sun.


Image above: This infographic shows how Mars lost argon and other gasses over time due to ‘sputtering.’ Click to enlarge. Image Credits: NASA’s Goddard Space Flight Center.

The early Sun had far more intense ultraviolet radiation and solar wind, so atmospheric loss by these processes was likely much greater in Mars' history. According to the team, these processes may have been the dominant ones controlling the planet's climate and habitability. It's possible microbial life could have existed at the surface early in Mars’ history. As the planet cooled off and dried up, any life could have been driven underground or forced into rare surface oases.

Jakosky and his team got the new result by measuring the atmospheric abundance of two different isotopes of argon gas. Isotopes are atoms of the same element with different masses. Since the lighter of the two isotopes escapes to space more readily, it will leave the gas remaining behind enriched in the heavier isotope. The team used the relative abundance of the two isotopes measured in the upper atmosphere and at the surface to estimate the fraction of the atmospheric gas that has been lost to space.

As a "noble gas" argon cannot react chemically, so it cannot be sequestered in rocks; the only process that can remove noble gases into space is a physical process called "sputtering" by the solar wind. In sputtering, ions picked up by the solar wind can impact Mars at high speeds and physically knock atmospheric gas into space. The team tracked argon because it can be removed only by sputtering. Once they determined the amount of argon lost by sputtering, they could use this information to determine the sputtering loss of other atoms and molecules, including carbon dioxide (CO2). 

CO2 is of interest because it is the major constituent of Mars' atmosphere and because it's an efficient greenhouse gas that can retain heat and warm the planet. "We determined that the majority of the planet's CO2 was also lost to space by sputtering," said Jakosky. "There are other processes that can remove CO2, so this gives the minimum amount of CO2 that's been lost to space."

video
Mars Atmosphere Loss: Sputtering

Video above: This 2013 video explains how the process called "sputtering" may have caused Mars to lose its atmosphere. Video Credits: NASA Goddard.

The team made its estimate using data from the Martian upper atmosphere, which was collected by MAVEN's Neutral Gas and Ion Mass Spectrometer (NGIMS). This analysis included measurements from the Martian surface made by NASA's Sample Analysis at Mars (SAM) instrument on board the Curiosity rover.

"The combined measurements enable a better determination of how much Martian argon has been lost to space over billions of years," said Paul Mahaffy of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Using measurements from both platforms points to the value of having multiple missions that make complementary measurements." Mahaffy, a co-author of the paper, is principal investigator on the SAM instrument and lead on the NGIMS instrument, both of which were developed at NASA Goddard.

The research was funded by the MAVEN mission. MAVEN's principal investigator is based at the University of Colorado's Laboratory for Atmospheric and Space Physics, Boulder, and NASA Goddard manages the MAVEN project. MSL/Curiosity is managed by NASA's Jet Propulsion Laboratory, Pasadena, California.

For more information on MAVEN, visit: http://www.nasa.gov/maven

Images (mentioned), Text, Credits: NASA/Jim Wilson/Katherine Brown/Goddard Space Flight Center/Bill Steigerwald/Nancy Jones.

Greetings, Orbiter.ch

Search for stellar survivor of a supernova explosion












ESA - Hubble Space Telescope logo.

30 March 2017

Supernova remnant N103B


Astronomers have used the NASA/ESA Hubble Space Telescope to observe the remnant of a supernova explosion in the Large Magellanic Cloud. Beyond just delivering a beautiful image, Hubble may well have traced the surviving remains of the exploded star’s companion.

A group of astronomers used Hubble to study the remnant of the Type Ia supernova explosion SNR 0509-68.7 — also known as N103B (seen at the top). The supernova remnant is located in the Large Magellanic Cloud, just over 160 000 light-years from Earth. In contrast to many other Supernova remnants N103B does not appear to have a spherical shape but is strongly elliptical. Astronomers assume that part of material ejected by the explosion hit a denser cloud of interstellar material, which slowed its speed. The shell of expanding material being open to one side supports this idea.

The relative proximity of N103B allows astronomers to study the life cycles of stars in another galaxy in great detail. And probably even to lift the veil on questions surrounding this type of supernova. The predictable luminosity of Type Ia supernovae means that astronomers can use them as cosmic standard candles to measure their distances, making them useful tools in studying the cosmos. Their exact nature, however, is still a matter of debate. Astronomers suspect Type Ia supernovae occur in binary systems in which at least one of the stars in the pair is a white dwarf [1].

Wide-field image of Magellanic clouds (ground-based image)

There are currently two main theories describing how these binary systems become supernovae. Studies like the one that has provided the new image of N103B — that involve searching for remnants of past explosions — can help astronomers to finally confirm one of the two theories.

One theory assumes that both stars in the binary are white dwarfs. If the stars merge with one another it would ultimately lead to a supernova explosion of type Ia.

The second theory proposes that only one star in the system is a white dwarf, while its companion is a normal star. In this theory material from the companion star is accreted onto the white dwarf until its mass reaches a limit, leading to a dramatic explosion. In that scenario, the theory indicates that the normal star should survive the blast in at least some form. However, to date no residual companion around any type Ia supernova has been found.

video
Zoom into N103B

Astronomers observed the N103B supernova remnant in a search for such a companion. They looked at the region in H-alpha — which highlights regions of gas ionised by the radiation from nearby stars —  to locate supernova shock fronts. They hoped to find a star near the centre of the explosion which is indicated by the curved shock fronts. The discovery of a surviving companion would put an end to the ongoing discussion about the origin of type Ia supernova.

And indeed they found one candidate star that meets the criteria — for star type, temperature, luminosity and distance from the centre of the original supernova explosion. This star has approximately the same mass as the Sun, but it is surrounded by an envelope of hot material that was likely ejected from the pre-supernova system.

video
Pan across N103B

Although this star is a reasonable contender for N103B’s surviving companion, its status cannot be confirmed yet without further investigation and a spectroscopic confirmation. The search is still ongoing.

Notes:

[1] A white dwarf is the small, dense core of a medium-mass star that is left behind after it has reached the end of its main-sequence lifetime and blown off its outer layers. Our own Sun is expected to become a white dwarf in around five billion years.

More information:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Links:

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

Link to science paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1707/heic1707a.pdf

Images, Videos, Text, Credits: ESA/NASA/A. Fujii/Nick Risinger (skysurvey.org), R. Gendler & ESO/Music: Johan Monell.

Best regards, Orbiter.ch

mercredi 29 mars 2017

Weekly Recap From the Expedition Lead Scientist, Week of March 20, 2017











ISS - Expedition 50 Mission patch.

March 29, 2017

(Highlights: Week of March 20, 2017) - While preparing for a March 24 spacewalk outside the International Space Station, crew members used the microgravity environment of the orbiting laboratory to better examine how metals are formed as they cool from a liquid to a solid.

NASA astronaut Peggy Whitson exchanged sample cartridges for the Materials Science Lab Batch 2b (MSL SCA Batch 2b), which serves two projects investigating how different phases of matter organize into a structure when metallic alloys are solidified. Both projects will provide data to help develop new light-weight, high-performance structural material for space and Earth applications.


Image above: European Space Agency astronaut Thomas Pesquet works on the Canadarm2 during a spacewalk outside the International Space Station on March 24. Canadarm2 is a remote-controlled arm used to transfer cargo and release satellites on the space station. Image Credit: NASA.

The Metastable Solidification of Composites (METCOMP) project studies how the remaining liquid bronze reacts with an already formed solid as the liquid bronze is cooling to become a second solid. The other project, Solidification along a Eutectic path in Ternary Alloys (SETA), looks at how two phases that form together organize into aluminum fiber structures when cooling.

ESA (European Space Agency) astronaut Thomas Pesquet inspected the Bigelow Expandable Activity Module (BEAM) attached to the orbiting laboratory. Expandable habitats are designed to take up less room on a spacecraft while providing greater volume for living and working in space once expanded. Pesquet was conducting a periodic checkup of BEAM, which was deployed May 28, 2016. He inspected the various sensors and radiation monitors, checking for leaks and taking surface samples to assess the microbe environment inside the expandable node.


Image above: Pesquet captured this nighttime image of Mount Etna in Sicily from the International Space Station. The bright red lines in the lower left quadrant is a lava flow from an active volcano that can be seen from space. Image Credit: NASA.

BEAM, the first test of an expandable module, allows investigators to gauge how well the habitat performs -- specifically, how well it protects against solar radiation, space debris and the temperature extremes of space. Crew members will continue to inspect the module every three months to check for stability. Durable, reliable and safe expandable structures have applications on Earth as well. Expandable modules can be used as pop-up habitats in disaster areas or remote locations; storm surge protection devices; pipeline or subway system plugs to prevent flooding; fluid storage containers; or hyperbaric chambers for pressurized oxygen delivery.

Whitson prepared the ultrasound equipment for Russian cosmonaut Sergey Ryzhikov to take measurements for the study of Fluid Shifts Before, During, and After Prolonged Space Flight and Their Association with Intracranial Pressure and Visual Impairment (Fluid Shifts). One of the main risks for humans during long-duration space missions is change in vision. More than half of American astronauts experience vision changes and other physical alterations to parts of their eyes during and after long-duration spaceflight. It is hypothesized that the fluid shift toward the head that occurs during spaceflight leads to increased pressure in the brain, which may push on the back of the eye, causing it to change shape. Fluid Shifts measures how much fluid moves from the lower body to the upper body, in or out of cells and blood vessels, and determines the impact these shifts have on fluid pressure in the head, changes in vision and eye structures.


Image above: NASA astronaut Shane Kimbrough captured this image he took from the space station looking west over the Red Sea, with Saudi Arabia on the bottom of the picture and Egypt on the top. He shared it to his social media account on Twitter, tagging it #EarthArt. Image Credits: Twitter.com/astro_kimbrough.

Scientists want to develop preventive measures against these and other physiological changes during spaceflight. Results from the Fluid Shifts investigation may also improve understanding of how blood pressure in the brain specifically affects eye shape and vision, which could benefit people confined to long-term bed rest, or suffering from disease states that increase swelling and pressure in the brain.

International Space Station (ISS). Image Credit: NASA

Other human research investigations conducted this week include Intracranial Pressure & Visual Impairment (IPVI), Habitability, Space Headaches, and Dose Tracker.

Progress was made on other investigations, outreach activities, and facilities this week, including Google Street View, ISS Ham Radio, MAGVECTOR, and Manufacturing Device.

Related links:

Materials Science Lab Batch 2b (MSL SCA Batch 2b): https://www.nasa.gov/mission_pages/station/research/experiments/1978.html

Bigelow Expandable Activity Module (BEAM): http://www.nasa.gov/mission_pages/station/research/experiments/1804.html

Fluid Shifts: http://www.nasa.gov/mission_pages/station/research/experiments/1257.html

Intracranial Pressure & Visual Impairment (IPVI): https://www.nasa.gov/mission_pages/station/research/experiments/1950.html

Habitability: https://www.nasa.gov/mission_pages/station/research/experiments/1772.html

Space Headaches: https://www.nasa.gov/mission_pages/station/research/experiments/181.html


Dose Tracker: http://www.nasa.gov/mission_pages/station/research/experiments/1933.html

ISS Ham Radio: http://www.nasa.gov/mission_pages/station/research/experiments/346.html

MAGVECTOR: https://www.nasa.gov/mission_pages/station/research/experiments/1176.html

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

Images (mentioned), Text, Credits: NASA/Kristine Rainey/Jorge Sotomayor, Lead Increment Scientist Expeditions 49 & 50.

Best regards, Orbiter.ch