Tagged: U Arizona Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 1:29 pm on November 29, 2018 Permalink | Reply
    Tags: , , , , , OSIRIS-REx asteroid sample return mission, U Arizona   

    From University of Arizona: “We’re at Bennu! What’s Next?” 

    U Arizona bloc

    From University of Arizona

    Nov. 28, 2018
    Daniel Stolte

    1

    The UA-led OSIRIS-REx mission kicks into high gear while the spacecraft is on its final approach, closing in on asteroid Bennu and scheduled for arrival on Dec. 3. UA mission experts explain what comes next.

    NASA OSIRIS-REx Spacecraft

    Since it launched on Sept. 8, 2016, the spacecraft of the University of Arizona-led OSIRIS-REx asteroid sample return mission has been catching up with its destination, asteroid Bennu, on its trip around the sun. On Dec. 3, the spacecraft is scheduled for arrival. UANews asked mission experts about what lies ahead for the robotic explorer and its human companions here on Earth.

    Once OSIRIS-REx arrives at Bennu, why will it have to stay in orbit for two years before going for the sampling?

    Dante Lauretta, OSIRIS-REx Principal Investigator: “The OSIRIS-REx spacecraft will enter orbit around Bennu by moving at a very slow velocity, relative to the asteroid, on the order of 4 inches (10 centimeters) per second. To accomplish this feat, we must characterize the mass, shape and rotation state of the asteroid. Fortunately, the equations for orbital stability hold even for a very low mass object like Bennu. The challenge lies in the fact that other forces acting on the spacecraft, such as solar radiation pressure, spacecraft outgassing and thermal radiation, are of the same order of magnitude as Bennu’s gravity. The team must perform regular optical navigation-based orbit determination. This process is not required to keep us in orbit. Instead, it is needed for us to understand where in the orbit we are. Although small, these forces can move the spacecraft by as much as 180 degrees along its track within a few short days. If we lost track of the spacecraft position in orbit, we would not know where to point the science instruments to collect our data.”

    Christian Drouet d’Aubigny, OSIRIS-REx Camera Suite Deputy Instrument Scientist: “We need to know exactly where we are with respect to Bennu. To an astronaut, it would be obvious: “The asteroid is over there and all I have to do is point the camera.” But with a robot, it’s always a challenge. The spacecraft knows exactly where it is with respect to stars, because it knows the constellations it sees with great precision, but it doesn’t know exactly where it is with respect to Bennu. When we plan our operations, weeks ahead of time, we have to take into account that when we execute the observation, the spacecraft position with respect to Bennu won’t be known exactly. The spacecraft’s own knowledge of where it is located is based on observations that are at least a day old. It knows where it should be based on where it was yesterday.”

    Bashar Rizk, OSIRIS-REx Camera Suite Instrument Scientist: “We don’t have all the information we need to successfully and safely take a sample from the asteroid at this time. We have given ourselves enough time and margin to gather all the information we need to be able to analyze and chew on that information so it can successfully inform the next step in the process.”

    How does the spacecraft stay in orbit around Bennu?

    Rizk: “Driving a spacecraft around an object like Bennu is a fine art, and we’re learning it as we go along. Unlike a spacecraft that orbits a planet such as Mars, the relative velocities are not high – we are crawling along – but because the gravitational forces are so weak, other effects begin to matter. Our spacecraft is constantly exposed to solar pressure and thermal asymmetry: whichever side happens to be facing the sun gets warmer and emits its own thermal radiation. That radiation carries momentum – a very slight momentum, but given enough time, it is going to make itself felt. In addition, you have the effects of the micro-thrusting maneuvers that help us move around. So far, every aspect about this object has been very successfully predicted, so we have high hopes, but there is no denying that there are challenges.”

    What “eyes” does the spacecraft use to see and study the asteroid?

    d’Aubigny: “The spacecraft has three science cameras – all were built here at the University of Arizona – PolyCam, MapCam and SamCam, plus a suite of wide-angle cameras made by Malin Space Science Systems for Lockheed Martin that are used for navigation. When the asteroid still was far away, we used PolyCam to acquire the first images from 1.2 million miles (2 million kilometers) away because it is the most sensitive of all the OSIRIS-REx cameras. On Nov. 15, when the spacecraft was only 75 miles (120 km) from Bennu, we switched to MapCam. We are progressively switching from higher magnification and narrower field of view to lower magnification and a wider field of view. It’s similar to what you would do with an optical zoom lens, but done with different cameras. MapCam and PolyCam will be used to study the asteroid from up close. MapCam is going to map Bennu’s surface. As we go past the asteroid and see different parts, we will point the spacecraft in various directions, take mosaic images and stitch them together. We’ll go through different phases, getting progressively closer to Bennu, starting from 12.4 miles (20 km) and getting into orbit as close as .9 mile (1.5 km) from the asteroid. The closest approach will be is when we do our reconnaissance passes at 656 feet (200 meters) above the surface. The images with the highest resolution will be taken by PolyCam, which will serve as our high-power telephoto lens. At closest approach, the field of view comes down to a 10-foot-by-10-foot (3 m) square, or approximately the size of a bedroom, and with enough resolving power we could see a pea on a table. Using MapCam, which has not quite the high resolution and magnification of PolyCam, we’re going to map the whole surface down to a scale of one-quarter of a meter (.82 feet), about the size of a soccer ball.”

    How will you prepare for the sampling?

    d’Aubigny: “Based on the images and combined information from all the instruments, such as LIDAR and the spectrometers, we will narrow down the search for sites that are interesting from a science standpoint, have the surface with material of the size we need for sampling and are free of hazards. We have to focus on up to five sites, we will image those with really high resolution with PolyCam from orbit, but also as we narrow down that list, at some point we will have just two – a primary and a secondary samples site – and that is where we will do the close reconnaissance passes.”

    Dani DellaGiustina, Lead Image Processing Scientist: “The first thing we need to do before we can start mapping the surface and finding anything that could pose a hazard to the sampling mechanism is to relate the images taken by our cameras to the shape model of the asteroid. To do this, we take the images and map them into something that is similar to Google Earth, a special framework on which we can co-locate the features. We take two approaches to mapping out hazards: one is old-fashioned counting. Keara Burke, a UA undergraduate student who has taken the initiative to develop software for this project, is leading that work. Her team will count boulders on Bennu’s surface. The other is using a crowdsourcing effort: we want to triage the areas that look really smooth and map them out. For this, we are partnering with CosmoQuest, a citizen science program. Early next year, we’re going to launch “Bennu Mappers,” which will enable citizen scientists to help OSIRIS-REx map the locations and the sizes of all the boulders on Bennu. We define any boulder that is bigger than 8.3 inches (21 cm) as a hazard, because that is the width of the inner chamber of our sampling mechanism and it could become clogged. When we’ve gotten to the point where we’ve mapped the surface to where we have narrowed down two potential sampling sites, we will look at cobbles and pebbles while searching for anything as small as .8 inch (2 cm). Particles that size or smaller are easily ingested by our sampling mechanism.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

    U Arizona mirror lab


    An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

    Advertisements
     
  • richardmitnick 2:19 pm on October 25, 2018 Permalink | Reply
    Tags: , , , , Phaeton blue asteroid, Rare Blue Asteroid Reveals Itself During Fly-By, U Arizona   

    From University of Arizona: “Rare Blue Asteroid Reveals Itself During Fly-By” 

    U Arizona bloc

    From University of Arizona

    10.25.18
    Teddy Kareta
    UA Lunar and Planetary Laboratory

    1
    An artist’s illustration of what Phaeton might look like up close. (Image: Heather Roper)

    A team led by UA doctoral student Teddy Kareta obtained a rare glimpse of the bizarre, blue asteroid that is responsible for Geminid Meteor Shower.

    Blue asteroids are rare, and blue comets are almost unheard of. An international team led by Teddy Kareta, a doctoral student at the University of Arizona’s Lunar and Planetary Laboratory, investigated (3200) Phaethon, a bizarre asteroid that sometimes behaves like a comet, and found it even more enigmatic than previously thought.

    Kareta presented the results during a press conference on Oct. 23 at the 50th annual meeting of the American Astronomical Society’s Division for Planetary Science in Knoxville, Tennessee.

    Using telescopes in Hawaii and Arizona, the team studied sunlight reflected off Phaethon, which is known to be blue in color. Blue asteroids, which reflect more light in the blue part of the spectrum, make up only a fraction of all known asteroids. A majority of asteroids are dull grey to red, depending on the type of material on their surface.

    Phaethon sets itself apart for two reasons: it appears to be one of the “bluest” of similarly colored asteroids or comets in the solar system; and its orbit takes it so close to the sun that its surface heats up to about 800 degrees Celsius (1,500 degrees Fahrenheit), hot enough to melt aluminum.

    Astronomers have been intrigued by Phaethon for other reasons, too. It has the qualities of both an asteroid and a comet based on its appearance and behavior.

    Phaethon always appears as a dot in the sky, like thousands of other asteroids, and not as a fuzzy blob with a tail, like a comet. But Phaethon is the source of the annual Geminid meteor shower, easily seen in early-to-mid December.

    Meteor showers occur when Earth passes through the trail of dust left behind on a comet’s orbit. When they occur and where they appear to originate from depends on how the comet’s orbit is oriented with respect to the Earth. Phaethon is thought to be the “parent body” of the Geminid meteor shower because its orbit is very similar to the orbit of the Geminid meteors.

    Until Phaeton was discovered in 1983, scientists linked all known meteor showers to active comets and not asteroids.

    “At the time, the assumption was that Phaethon probably was a dead, burnt-out comet,” Kareta said, “but comets are typically red in color, and not blue. So, even though Phaeton’s highly eccentric orbit should scream ‘dead comet,’ it’s hard to say whether Phaethon is more like an asteroid or more like a dead comet.”

    Phaethon also releases a tiny dust tail when it gets closest to the sun in a process that is thought to be similar to a dry riverbed cracking in the afternoon heat. This kind of activity has only been seen on two objects in the entire solar system – Phaeton and one other, similar object that appears to blur the line traditionally thought to set comets and asteroids apart.

    The team obtained several new insights about Phaethon after analyzing data obtained from NASA’s Infrared Telescope Facility on Mauna Kea in Hawaii and the Tillinghast telescope, operated by the Smithsonian Astrophysical Observatory on Mount Hopkins in Arizona. They think Phaethon might be related or have broken off from (2) Pallas, a large blue asteroid farther out in the solar system.

    NASA Infrared Telescope facility Mauna Kea, Hawaii, USA, 4,207 m (13,802 ft) above sea level

    CfA Whipple 1.5 meter Tillinghast telescope

    “Interestingly, we found Phaethon to be even darker than had been previously observed, about half as reflective as Pallas,” Kareta said. “This makes it more difficult to say how Phaethon and Pallas are related.”

    The team also observed that Phaethon’s blue color is the same on all parts of its surface, which indicates it has been cooked evenly by the Sun in the recent past.

    The team is now conducting observations of 2005 UD, another small blue asteroid astronomers think is related to Phaethon, to see if they share the same rare properties. This and follow-up work will help to untangle the mystery of what Phaethon is really like.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

    U Arizona mirror lab


    An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 8:01 pm on July 26, 2018 Permalink | Reply
    Tags: , , , , , U Arizona, UA Students Find Foundations for Galaxy's Most Massive Stars   

    From University of Arizona: “UA Students Find Foundations for Galaxy’s Most Massive Stars” 

    U Arizona bloc

    From University of Arizona

    In a unique study, University of Arizona astronomy students searched 101 clouds of gas to find those that may be in the first phases of forming massive stars.

    July 25, 2018
    Emily Walla
    NASA Space Grant Intern

    For three years, Jenny Calahan led fellow undergraduate students at the University of Arizona in research to help unravel the mystery of how the galaxy’s most massive stars are born.

    On July 23, just two months after Calahan graduated with a bachelor’s degree in physics and astronomy, the resulting research paper, Searching for Inflow Towards Massive Starless Clump Candidates Identified in the Bolocam Galactic Plane Survey, was published in The Astrophysical Journal. Her co-authors include students who assisted with the survey and research.

    “There’s still a pretty open question in astronomy when it comes to massive star formation,” Calahan said. “How do stars weighing more than eight solar masses form from clouds of dust and gas?”

    Astronomers understand this process for stars the size of our sun. Particles in clouds are attracted to each other and begin to clump together. Gravity takes hold and the gases flow to the center of the cloud as it collapses. Over millions of years, the gas is put under so much pressure that it begins to burn, and the star is born when nuclear fusion finally begins in the core of the compressed gas.

    Theories about how much gas and time it takes to make a star like our sun can be proven through observations, because each stage of a sun-like star’s life — from the collapse of gas clouds into a pre-stellar core to the star’s expansion into a red giant and collapse into a white dwarf — can be been seen throughout the galaxy.

    But astronomers have yet to understand how stars more than eight times the mass of our sun form. Stars of this size explode into supernovae at the end of their lives, leaving behind black holes or neutron stars.

    “There are a few theories for massive star formation that work in simulations, but we haven’t seen those initial conditions out in the wild universe,” Calahan said.

    One theory is the formation of massive cores, says Yancy Shirley, associate professor in the UA’s Department of Astronomy. The massive cores are dense collections of gas several times larger than the star they create. For massive stars, the cores must be at least 30 times the mass of our sun.

    “People are having trouble finding objects like that,” Shirley said.

    The other theory is that multiple low-mass cores form within a gas clump. The low-mass cores grow as they compete for material in the clump, and eventually, one of the cores grows large enough to form a massive star.

    “This is the debate: which of these two pictures is more correct, or is it some combination of the two?” Shirley said.

    The first step in answering the question is identifying the earliest phase of star formation, so Calahan, under the advisement of Shirley, set out to find clumps showing signs of collapsing gas motion, called “inflow.”

    Calahan selected 101 subjects from a list of more than 2,000 huge, cold and seemingly starless clouds of gas called starless clump candidates, or SCCs.

    Though astronomers have studied SCCs in the past, many of them focused on the brightest and most massive objects. Calahan’s study was unique in that it was a blind survey.

    Ranging in size from a few hundred times the mass of our sun to a few thousand solar masses, the SCCs Calahan selected are a representative sample of all gas clouds that have the potential to form massive stars.

    Using the Arizona Radio Observatory’s 12-meter radio telescope at the UA’s Steward Observatory on Kitt Peak, Calahan detected and tracked radio waves emitted by the molecular gas oxomethylium (HCO+), which emits a specific radio wavelength.

    Arizona Radio Observatory at Kitt Peak, AZ USA, U Arizona Steward Observatory at altitude 2,096 m (6,877 ft)

    Once Shirley and the undergraduate students he advises use the telescope to identify objects of special interest, like collapsing SCCs, the clumps of interest are then further studied using ALMA, which can peer deeper into the gas and find stars or other objects that cannot be seen with the 12-meter telescope.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    Oxomethylium, one of the more abundant ion molecules in space, is a highly reactive ion that would not survive in our Earth’s atmosphere. When oxomethylium moves towards an observer, the wavelengths are compressed; when the gas moves away from an observer, the wavelengths are stretched.

    By analyzing the wavelengths, Calahan identified six SCCs that showed the telltale signs of collapse, suggesting that gas collapse happens quickly, accounting for only 6 percent of the formation process of massive stars.

    “One side is falling away from us and one side is falling towards us,” Calahan said.

    “The way we’re using it right now is as a pathfinder,” Shirley said. He and the undergraduate students he advises use the 12-meter telescope to conduct surveys that identify objects of special interest, like collapsing SCC’s. These clumps of interest are then further studied using ALMA, which can peer deeper into the gas and find stars or other objects that cannot be seen with the 12-meter telescope.

    Surveys take many dozens of hours to complete. Calahan and Shirley spent 19 weekends over the course of eight months to study the SCCs.

    “I’ve now seen every part of this research,” Calahan said. “I got to be part of asking the question, observing and doing the data reduction.”

    Groups of undergraduate students traveled with Calahan and Shirley to telescope, where they learned astronomical observation and data analysis techniques.

    “The first time we went up, I learned how to use the telescope and I learned how to analyze the data,” Calahan said. “By the third time, I could teach other students.”

    Shirley has served as adviser to several students who have published the research they did at UA, but Calahan is the first student of his whose paper was accepted before graduation.

    “I don’t think I could have done this at any other university,” Calahan said. “We have the resources and the faculty to teach us how to reduce real-life data and observe on a real-life telescope. That’s really unique to this institution.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

    U Arizona mirror lab

    An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 12:52 pm on June 15, 2018 Permalink | Reply
    Tags: , , , , Planet-Forming Disks May Resemble Solar System 5 Billion Years Ago, U Arizona   

    From University of Arizona: “Planet-Forming Disks May Resemble Solar System 5 Billion Years Ago” 

    U Arizona bloc

    From University of Arizona

    6.14.18
    Emily Litvack

    The findings, published in The Astrophysical Journal, may provide insights into the birth of our own solar system.

    1
    The Orion Nebula is a star-forming region in the Milky Way, and one of the most famous of the astronomical nebulas. Here, insets show where planetary systems are forming in the Orion. (Image: NASA, ESA, M. Robberto of STScI/ESA, HST Orion Treasury project team, and L. Ricci ESO)

    To make a planet, you need stuff.

    Protoplanetary disks — cosmic frisbees of gas and dust orbiting young stars across the galaxy — spin out new planets. But the size of those planets depends on just how much material these disks have to give.

    A team of scientists led by the University of Arizona has imaged a cluster of protoplanetary disks in the Orion Nebula and discovered that they are smaller than those previously studied in closer, less-dense regions. The smallness of these newly imaged disks suggests that making giant planets such as Jupiter (which is 2.5 times more massive than all the other planets in our solar system combined) could be especially difficult.

    What’s more, the Orion Nebula looks a lot like other planet-forming regions in the Milky Way, meaning our own solar system likely formed in an Orion-like environment. The team’s findings have been published in The Astrophysical Journal.

    The scientists used the largest telescope in the world, an interferometric array of radio telescopes in Chile called ALMA, to observe about 110 protoplanetary disks in the Orion Nebula in the deepest survey of the region yet.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    Orion Nebula ESO/VLT

    Orion Nebula M. Robberto NASA ESA Space Telescope Science Institute Hubble

    “The general motivation for the whole field is that we want to understand more about how planets are formed,” says Josh Eisner, a UA professor of astronomy who led the study.

    In their pursuit of that understanding, scientists have spent decades looking to star-forming regions such as Taurus, a mere 500 light-years away (as compared to Orion’s 1,344). While its nearby location makes a slice of the universe such as Taurus easier to observe with less-powerful telescopes, it’s not what one might call a “typical” planet-forming region.

    Orion, on the other hand, with its many stars (and orbiting disks) clustered together in relatively small area, is typical. It requires a more powerful telescope to take sharp observations, but in terms of regions where planets — or entire solar systems — form, it’s a better model.

    “Orion is not at all an oddball region. The disks there look a lot like what we think our solar system looked like when it was a protoplanetary disk,” Eisner says. “And now with the advent of ALMA, we can study regions like Orion well.”

    Based on the images, the team — which also included astronomy and astrophysics graduate student Ryan Boyden, Steward Observatory postdoctoral researchers Nicholas Ballering and Min Fang, Steward Observatory associate astronomer Jinyoung Kim, and Lunar and Planetary Laboratory associate professor Ilaria Pascucci — was able to calculate the mass of protoplanetary disks in the Orion Nebula.

    “Disk mass tells you how much stuff there is in the disk and that gives you a budget for what you can build out of it,” Eisner says. “And what we found was, in this region, mass is actually quite constraining.”

    Unlike those studied in nearby regions such as Taurus, planet-forming disks in the Orion Nebula don’t have enough stuff to build large planets such as Jupiter, for which you would need tens of Earth masses. According to Eisner, this may mean that much of the stuff already has been used to make young planets. Disks in Orion also appear smaller in size than those in Taurus-like regions.

    “It’s pretty tantalizing that Orion looks so different from all these lower-density, closer regions but it’s just one. We want to fill in the data with more of these high-density regions to see if they all look like Orion,” says Eisner, who is already seeking grant funding and telescope observing time to do so.

    The discovery also will be tantalizing for those interested in what our solar system looked like as it was cooking some 5 billion years ago.

    “The initial conditions for planet formation can tell us a lot about the constraints and how the process really unfolds,” Eisner says.

    One theory about our solar system’s formation, called the Nice Model, argues that, early on, the configuration of the planets within a disk was small and compact until resonance finally flung Neptune and Uranus onto longer orbits.

    The fact that the small, compact systems Eisner’s team observed in the Orion’s disks match up so nicely with the initial planetary configuration in the Nice Model, Eisner says, is a compelling hint at the origins of our solar system.

    “The solar system probably formed in an Orion-like environment,” he says. “Now we’ve actually got an idea of what systems there look like.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition


    five-ways-keep-your-child-safe-school-shootings

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 3:38 pm on June 8, 2018 Permalink | Reply
    Tags: , , , , How Do You Weigh a Galaxy? Especially the One You're In?, U Arizona   

    From University of Arizona: “How Do You Weigh a Galaxy? Especially the One You’re In?” 

    U Arizona bloc

    From University of Arizona

    June 6, 2018
    Daniel Stolte

    1
    Our Milky Way’s largest neighbor, the Andromeda Galaxy, spans about 220,000 light-years across. Two of its dwarf satellite galaxies, Messier 110 (bottom left) and Messier 32 (above Andromeda’s central bulge), are visible as bright white spots in this image taken by UA astrophotographer Adam Block.

    Pinning down the mass of a galaxy may seem like an esoteric undertaking, but scientists think it holds the key to unraveling the nature of the elusive, yet-to-be-seen dark matter, and the fabric of our cosmos.

    A new technique for estimating the mass of galaxies promises more reliable results, especially when applied to large datasets generated by current and future surveys, according to a research team led by Ekta Patel at the University of Arizona. Published in The Astrophysical Journal, the study is the first to combine the observed full three-dimensional motions of several of the Milky Way’s satellite galaxies with extensive computer simulations to obtain a high-accuracy estimate for the mass of our home galaxy.

    Determining the mass of galaxies plays a crucial part in unraveling fundamental mysteries about the architecture of the universe. According to current cosmological models, a galaxy’s visible matter, such as stars, gas and dust, accounts for a mere 15 percent of its mass. The remaining 85 percent is believed to reside in dark matter, a mysterious component that never has been observed and whose physical properties remain largely unknown. The vast majority of a galaxy’s mass (mostly dark matter) is located in its halo, a vast, surrounding region containing few, if any, stars and whose shape is largely unknown.

    In a widely accepted cosmological model, dark-matter filaments span the entire universe, drawing luminous (“regular”) matter with them. Where they intersect, gas and dust accumulate and coalesce into galaxies. Over billions of years, small galaxies merge to form into larger ones, and as those grow in size and their gravitational pull reaches farther and farther into space, they attract a zoo of other small galaxies, which then become satellite galaxies. Their orbits are determined by their host galaxy, much like the sun’s gravitational pull directs the movement of planets and bodies in the solar system.

    “We now know that the universe is expanding,” says Patel, a fourth-year graduate student in the UA’s Department of Astronomy and Steward Observatory. “But when two galaxies come close enough, their mutual attraction is greater than the influence of the expanding universe, so they begin to orbit each other around a common center, like our Milky Way and our closest neighbor, the Andromeda Galaxy.”

    Local Group. Andrew Z. Colvin 3 March 2011

    Although Andromeda is approaching the Milky Way at 110 kilometers per second, the two won’t merge until about 4.5 billion years from now. According to Patel, tracking Andromeda’s motion is “equivalent to watching a human hair grow at the distance of the moon.”

    2
    An artist’s interpretation of what happens as a satellite merges with its host galaxy: These streams of stars arcing high over the Milky Way are remnants of galaxies and star clusters, mangled and torn apart by our galaxy’s gravitational stresses over billions of years. Extending over much of the northern sky, the streams lie between 13,000 and 130,000 light-years from Earth. (Credit: NASA/JPL-Caltech/R. Hurt/SSC/Caltech)

    Because it’s impossible to “weigh” a galaxy simply by looking at it — much less when the observer happens to be inside of it, as is the case with our Milky Way — researchers deduce a galaxy’s mass by studying the motions of celestial objects as they dance around the host galaxy, led by its gravitational pull. Such objects — also called tracers, because they trace the mass of their host galaxy — can be satellite galaxies or streams of stars created from the scattering of former galaxies that came too close to remain intact.

    Unlike previous methods commonly used to estimate a galaxy’s mass, such as measuring its tracers’ velocities and positions, the approach developed by Patel and her co-authors uses their angular momentum, which yields more reliable results because it doesn’t change over time. The angular momentum of a body in space depends on both its distance and speed. Since satellite galaxies tend to move around the Milky Way in elliptical orbits, their speeds increase as they get closer to our galaxy and decrease as they get farther away. Because the angular momentum is the product of both position and speed, there is no net change regardless of whether the tracer is at its closest or farthest position in its orbit.

    “Think of a figure skater doing a pirouette,” Patel says. “As she draws in her arms, she spins faster. In other words, her velocity changes, but her angular momentum stays the same over the whole duration of her act.”

    The study, which Patel presents on Thursday, June 7, at the 232nd meeting of the of the American Astronomical Society in Denver, is the first to look at the full three-dimensional motions of nine of the Milky Way’s 50 known satellite galaxies at once and compare their angular momentum measurements to a simulated universe containing a total of 20,000 host galaxies that resemble our own galaxy. Together those simulated galaxies host about 90,000 satellite galaxies.

    Patel’s team pinned down the Milky Way’s mass at 0.96 trillion solar masses. Previous estimates had placed our galaxy’s mass between 700 billion and 2 trillion solar masses. The results also reinforce estimates suggesting that the Andromeda Galaxy (M31) is more massive than our Milky Way.

    The authors hope to apply their method to the ever-growing data as they become available by current and future galactic surveys such as the Gaia space observatory and LSST, the Large Synoptic Survey Telescope. According to co-author Gurtina Besla, an assistant professor of astronomy at the UA, constraints on the mass of the Milky Way will improve as new observations are obtained that clock the speed of more satellite galaxies, and as next-generation simulations will provide higher resolution, allowing scientists to get better statistics for the smallest mass tracers, the so-called ultra-faint galaxies.

    “Our method allows us to take advantage of measurements of the speed of multiple satellite galaxies simultaneously to get an answer for what cold dark matter theory would predict for the mass of the Milky Way’s halo in a robust way,” Besla says. “It is perfectly suited to take advantage of the current rapid growth in both observational datasets and numerical capabilities.”

    Additional co-authors on the paper, “Estimating the Mass of the Milky Way Using the Ensemble of Classical Satellite Galaxies,” are Kaisey Mandel at the Institute of Astronomy and the University of Cambridge, U.K., and Sangmo Tony Sohn with the Space Telescope Science Institute in Baltimore.

    Funding for this project was provided by the National Science Foundation and NASA.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 12:59 pm on February 23, 2018 Permalink | Reply
    Tags: , , , , , , U Arizona   

    From University of Arizona: “UA Leads Project on Big Data and Black Holes” 

    U Arizona bloc

    University of Arizona

    Feb. 21, 2018
    Daniel Stolte

    Chi-Kwan Chan waves his hand a few inches above a matchbox-size device. On a dark computer monitor, a million light dots appear as a solid sheet, each dot representing a light particle.

    1
    The Event Horizon Telescope is a virtual Earth-size telescope, achieving its globe-spanning baseline by combining precisely synchronized observations made at various sites around the world. (Image: Dan Marrone)

    The photon sheet hovers above a black disc simulating a black hole. With a slow turn of the hand, the sheet approaches the black hole. As it passes, the gravitational monster swallows any light particles in its direct path, creating a circular cutout in the sheet of particles. The rest of the particles are on track to move past the black hole, or so it seems. But they don’t get very far: Instead of continuing along their straight lines of travel, their paths bend inward and they loop around the black hole and converge in one point, forming a sphere of photons around it.

    “What you see here is light trapped in the fabric of space and time, curving around the black hole by its massive gravity,” explains Chan, an assistant astronomer at the University of Arizona’s Steward Observatory, who developed the computer simulation as part of his research into how black holes interact with things that happen to be nearby.

    U Arizona Steward Observatory at Kitt Peak, AZ, USA, altitude 2,096 m (6,877 ft)

    The demonstration was part of an event at UA’s Flandrau Science Center & Planetarium on Feb. 16 to kick off a UA-led, international project to develop new technologies that enable scientists to transfer, use and interpret massive datasets.

    Known as Partnerships for International Research and Education program, or PIRE, the effort is funded with $6 million over five years by the National Science Foundation, with an additional $3 million provided by partnering institutions around the world. While the award’s primary goal is to spawn technology that will help scientists take the first-ever picture of the supermassive black hole at the center of our Milky Way, the project’s scope is much bigger.

    What looks like a fun little animation on Chan’s computer screen is in fact a remarkable feat of computing and programming: As the computational astrophysicist drags virtual photons around a virtual black hole, a powerful graphics processor solves complex equations that dictate how each individual light particle would behave under the influence of the nearby black hole — simultaneously and in real time.

    Study Relies on Simulations

    Unlike the crew in the movie “Interstellar,” astrophysicists can’t travel to a black hole and study it from close range. Instead, they have to rely on simulations that mimic black holes based on their physical properties that are known to — or thought to — govern these most extreme objects in the universe.

    Chan belongs to a group of researchers in an international collaboration called the Event Horizon Telescope, or EHT, that is gearing up to capture the first picture of a black hole — not just any black hole, but the supermassive black hole in the center of our galaxy. Called Sagittarius A* (referred to as “Sgr A Star,” pronounced Sag A Star), this object has the mass of more than 4 million suns.

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    Since nothing, not even light, can escape a black hole, it casts a silhouette in the background of in-falling plasma that is too small to be resolved by any single telescope. So far, the existence of Sgr A* has been inferred from indirect observations only, such as the intriguing choreography of stars in its vicinity, whose orbits clearly outline an unseen, incomprehensibly large mass.

    “Imaging the black hole at the center of our galaxy from Earth is like trying to read the date on a dime on the East Coast from the UA campus,” says Feryal Özel, a professor of astronomy and physics at Steward and a co-investigator on the project. “There is not one telescope in existence that could do that.”

    The EHT is an array of radio telescopes on five continents that together act as a virtual telescope the size of the Earth — the aperture needed to image “the date on the dime,” or in this case the supermassive black hole Sag A*.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM NOEMA interferometer
    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Hawaii SAO
    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    NSF CfA Greenland telescope

    Greenland Telescope

    To accomplish this, the individual telescopes must be precisely synced in time. Because existing internet cables and even satellite communication are too coarse to ensure this, the researchers rely on atomic clocks and … FedEx (more on that later).

    “Our PIRE project is a prime example of the kind of innovation you can only get by leveraging the innovative, intellectual capital in academia,” says Dimitrios Psaltis, the principal investigator on the project. “By its very nature, this project is multidisciplinary and requires expertise in areas ranging from detector development to high-performance computing and theoretical physics.”

    At peak activity, the EHT will collect more data than any project before, according to Psaltis, a professor of astronomy and physics at the UA.

    “We’re talking petabytes every single night,” he says, and this is comparable to the three petabytes of video uploaded each day on YouTube. “Post-processing is a huge effort, and we will need additional data to improve the science that we hope will come from these observations.”

    The team uses graphic processing units, or GPUs — processors developed for gaming that are capable of performing many calculations in parallel. This makes them more efficient and energy-saving than “regular” computer processing units, or CPUs.

    “We hope that this technology will transfer to other areas of science and life,” said Joaquin Ruiz, dean of the UA College of Science, at the launch event.

    Applications Could Be Extensive

    The PIRE project is expected to spin off technologies that go beyond the project’s primary goal. The fast processing of large data in real time and the efficient use of resources distributed across the globe will have applications ranging from self-driving cars to renewable energy production and national defense. Examples also include augmented reality applications that are good at fast computing with real-time input and minimum computing resources, Özel explains.

    “This could be used, for example, in visual aids for security efforts around the globe where data connection bandwidth and energy supplies are limited,” she says, “so you want devices that make maximum use of precious resources available in those scenarios.”

    The PIRE project team integrates researchers in the U.S., Germany, Mexico and Taiwan. Education of students and early career scientists is a key component, providing internally collaborative, hands-on experience in instrument technology, high-performance computing, and big and distributed data science. There also are monthly webinars and hackathons, as well as summer schools, that will be sponsored every year.

    Fast and reliable real-time communication channels are crucial in syncing up telescopes scattered around the globe for observations, and improving such technology is one of PIRE’s goals. For now, EHT scientists rely on video chat, phones and whiteboards to keep track of each telescope location’s status. During a rare stretch of a few days in April 2017, skies were mostly clear in all nine observing sites that are part of the EHT array — including Arizona, Hawaii, Chile, Mexico and Antarctica.

    The South Pole Telescope, or SPT, site was incorporated under another NSF grant to the UA, with Dan Marrone as principal investigator. Last year was the first year that the full EHT observed as an array, and the first year in which the SPT participated.

    During that first observation run, the observing stations that together make up the EHT pointed at the Milky Way’s center and collected radio waves originating from the supermassive black hole over the course of several nights. By obtaining the first-ever images of black holes, researchers will be able to directly test Einstein’s theory of general relativity in extreme conditions.

    “Each telescope records its observation data onto a bunch of physical hard drives,” explains Marrone, an associate professor at Steward and a co-investigator on the PIRE award. “Precisely time-stamped, the drives are loaded into crates and delivered to processing centers in Cambridge, Massachusetts, and Bonn, Germany, via FedEx.”

    The EHT data are shipped on physical carriers because current internet data pipelines aren’t up to the scope this endeavor requires. Then data experts combine the literal truckloads of data, synchronize it according to their time stamps and process it to extract the signal from the black hole, which in the raw data is buried under a blanket of noise and error — the inevitable side effects of turning the Earth into one giant telescope.

    “PIRE is an international project that not only will revolutionize worldwide efforts to study black holes, but usher astronomical projects into the era of big and distributed data science,” Psaltis says. “By awarding the PIRE project, the NSF has tasked the UA and its collaborators to contribute solutions that may inform many areas of technology, including the internet of tomorrow.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 10:00 am on February 8, 2018 Permalink | Reply
    Tags: , , , Rapid Detection and Recovery: The Science of Hunting Meteorites, U Arizona   

    From University of Arizona: “Rapid Detection and Recovery: The Science of Hunting Meteorites” 

    U Arizona bloc

    University of Arizona

    Feb. 6, 2018
    Emily Walla

    Science contact
    Vishnu Reddy
    UA Lunar and Planetary Laboratory
    520-621-6963
    vishnureddy@email.arizona.edu

    1
    A sample of the Michigan meteorite recovered by citizen scientists using maps produced by UA assistant professor Vishnu Reddy’s Doppler radar technique (Photo: Vishnu Reddy)

    UA professor Vishnu Reddy is leading a NASA-funded project to find freshly fallen meteorites like the one in Michigan last month.

    2
    Composite image of weather radar signatures of the falling meteorite (Image: Marc Fries)

    At 8:10 p.m. on Jan. 16, hundreds of people in Michigan reported the bright glow of a meteor streaking through the sky, rattling windows as it broke the sound barrier. The meteor then broke apart in the Earth’s atmosphere, and its pieces rained quietly to the ground.

    Using predictions by the Rapid Detection and Recovery of Meteorites, or RADARMET, project, scientists and meteorite hunters were able to recover more than half a dozen fragments of the rock within two days of the fall.

    RADARMET is led by Vishnu Reddy, assistant professor in the University of Arizona’s Lunar and Planetary Laboratory. He procured funding from NASA to operate RADARMET, which uses National Weather Service Doppler radar data and computer models to locate meteorites within hours of their fall.

    “Historically, people would see a meteor in the sky and they would say, ‘I saw it go that way behind the tree,'” Reddy said. “Even if someone takes a picture of the meteor, using the image to trace a trajectory for the meteorite is difficult and can be quite time-consuming.”

    3
    Computed strewn field of the meteorite. The dark orange shows where the largest, heaviest pieces of the meteorite fell, and the yellow shows where the lightest and smallest pieces fell. (Image: Marc Fries)

    Upper-atmosphere winds make extrapolation challenging, Reddy said. For a meteor to survive the trip through the atmosphere and fall onto the ground as a meteorite, it has to slow from its cosmic velocity. The friction from the atmosphere makes the meteor glow visibly between 30 and 65 miles above ground.

    “Typically, meteorite-dropping meteors need to slow down to around 6,700 mph, the speed when they no longer glow brightly while descending into the atmosphere,” Reddy said.

    Falling at Terminal Velocity

    The meteor then enters a period known as “dark flight,” during which it falls at terminal velocity. During this dark flight, winds in the upper atmosphere can buffet the meteorite miles away from where its glowing bright flight ends.

    Marc Fries, Reddy’s co-investigator for RADARMET and a scientist at NASA’s Johnson Space Center, developed a method that can predict how a meteorite would travel during its dark flight. He also has developed software tools to calculate where meteorites land under the influence of winds, and to estimate the total mass that reaches the ground.

    Tanner Campbell, a UA graduate student in aerospace and mechanical engineering, adapted Fries’ dark flight model into a computer program that quickly and accurately determines where a meteorite will fall.

    “We can accomplish this because the kinetics of an object in near freefall are known quite well,” Campbell said. “Since these meteorites are typically fairly small, we can make some assumptions about how they travel through the atmosphere. We can then take whatever data can be gathered on the meteorite while it is glowing in the sky, and measured atmospheric data from near the event, and use it to predict the path to the ground.”

    Atmospheric data include wind speeds and information collected by weather radar stations, which detect anything falling through the air, whether it is rain, birds, airplanes or meteorites. Although the radar cannot distinguish between a sparrow and a space rock, the RADARMET team has a method to do just that.

    “The first trigger is eyewitness reports from the public,” Reddy said.

    Using an online tool on the American Meteor Society website, members of the public can log their location, which direction they were facing and how long the meteor was visible in the sky. When an event has corroborating videos and other evidence such as sonic booms, Reddy and his co-investigators download radar data from the nearest weather station and power up the dark flight model.

    Accuracy of Location Is Vital

    Within hours of the event, the RADARMET team can locate the exact area where meteorite fragments have fallen. The information is quickly shared with the public, including scientists and meteorite hunters. RADARMET’s method is so accurate that hunters have been able to travel to a location, park their cars and find meteorites within that parking lot.

    When hunting meteorites, time is of the essence. The sooner a sample is found, the more scientists can learn from it.

    “The longer a meteorite sits on the Earth, the less scientifically useful it becomes, because the weathering process degrades the minerals and destroys it,” Reddy said.

    Rain can dissolve and wash away minerals, microbes can contaminate any evidence of the building blocks of life, and oxygen can rust the iron in the meteorite within a day.

    Although recovering pieces of the Michigan meteorite took slightly more than a day, some samples were found in nearly pristine condition. One piece was found in ice, protected from exposure to liquid water. Pristine samples such as this one enable scientists to study materials that are easily destroyed or of astrobiological significance.

    Reddy and students in the UA Department of Planetary Sciences plan to be involved in the study of the meteorite.

    “While we’re not out there hunting the meteorites, we’re doing the science,” Reddy said.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 9:29 am on January 31, 2018 Permalink | Reply
    Tags: , , , TMDs--transition metal dichalcogenides, U Arizona   

    From University of Arizona: “UA Researchers Observe Electrons Zipping Around in Crystals” 

    U Arizona bloc

    University of Arizona

    Jan. 29, 2018
    Daniel Stolte

    For the first time, scientists have tracked electrons moving through exotic materials that may make up the next generation of computing hardware, revealing intriguing properties not found in conventional, silicon-based semiconductors.

    1
    Extreme conditions are used to protect and preserve the TMDs during the experiments. As shown here, all samples are stored and manipulated in a vacuum that is close to the conditions in space. (Photo: Kyle Mittan/UANews.)

    The end of the silicon age has begun. As computer chips approach the physical limits of miniaturization and power-hungry processors drive up energy costs, scientists are looking to a new crop of exotic materials that could foster a new generation of computing devices that promise to push performance to new heights while skimping on energy consumption.

    Unlike current silicon-based electronics, which shed most of the energy they consume as waste heat, the future is all about low-power computing. Known as spintronics, this technology relies on a quantum physical property of electrons — up or down spin — to process and store information, rather than moving them around with electricity as conventional computing does.

    On the quest to making spintronic devices a reality, scientists at the University of Arizona are studying an exotic crop of materials known as transition metal dichalcogenides, or TMDs. TMDs have exciting properties lending themselves to new ways of processing and storing information and could provide the basis of future transistors and photovoltaics — and potentially even offer an avenue toward quantum computing.

    2
    Calley Eads, a fifth-year doctoral student in the UA’s Department of Chemistry and Biochemistry, aligns a laser system used to track electrons on time-scales at the limits of what can be measured. In her research, she investigates materials that could one day bring faster computing and more efficient solar cells. (Photo: Kyle Mittan/UANews.

    For example, current silicon-based solar cells convert realistically only about 25 percent of sunlight into electricity, so efficiency is an issue, says Calley Eads, a fifth-year doctoral student in the UA’s Department of Chemistry and Biochemistry who studies some of the properties of these new materials. “There could be a huge improvement there to harvest energy, and these materials could potentially do this,” she says.

    There is a catch, however: Most TMDs show their magic only in the form of sheets that are very large, but only one to three atoms thin. Such atomic layers are challenging enough to manufacture on a laboratory scale, let alone in industrial mass production.

    Many efforts are underway to design atomically thin materials for quantum communication, low-power electronics and solar cells, according to Oliver Monti, a professor in the department and Eads’ adviser. Studying a TMD consisting of alternating layers of tin and sulfur, his research team recently discovered a possible shortcut, published in the journal Nature Communications.

    “We show that for some of these properties, you don’t need to go to the atomically thin sheets,” he says. “You can go to the much more readily accessible crystalline form that’s available off the shelf. Some of the properties are saved and survive.”

    Understanding Electron Movement

    This, of course, could dramatically simplify device design.

    “These materials are so unusual that we keep discovering more and more about them, and they are revealing some incredible features that we think we can use, but how do we know for sure?” Monti says. “One way to know is by understanding how electrons move around in these materials so we can develop new ways of manipulating them — for example, with light instead of electrical current as conventional computers do.”

    To do this research, the team had to overcome a hurdle that never had been cleared before: figure out a way to “watch” individual electrons as they flow through the crystals.

    “We built what is essentially a clock that can time moving electrons like a stopwatch,” Monti says. “This allowed us to make the first direct observations of electrons move in crystals in real time. Until now, that had only been done indirectly, using theoretical models.”

    The work is an important step toward harnessing the unusual features that make TMDs intriguing candidates for future processing technology, because that requires a better understanding of how electrons behave and move around in them.

    Monti’s “stopwatch” makes it possible to track moving electrons at a resolution of a mere attosecond — a billionth of a billionth of a second. Tracking electrons inside the crystals, the team made another discovery: The charge flow depends on direction, an observation that seems to fly in the face of physics.

    Collaborating with Mahesh Neupane, a computational physicist at Army Research Laboratories, and Dennis Nordlund, an X-ray spectroscopy expert at Stanford University’s SLAC National Accelerator Laboratory, Monti’s team used a tunable, high-intensity X-ray source to excite individual electrons in their test samples and elevate them to very high energy levels.

    “When an electron is excited in that way, it’s the equivalent of a car that is being pushed from going 10 miles per hour to thousands of miles per hour,” Monti explains. “It wants to get rid of that enormous energy and fall back down to its original energy level. That process is extremely short, and when that happens, it gives off a specific signature that we can pick up with our instruments.”

    The researchers were able to do this in a way that allowed them to distinguish whether the excited electrons stayed within the same layer of the material, or spread into adjacent layers across the crystal.

    “We saw that electrons excited in this way scattered within the same layer and did so extremely fast, on the order of a few hundred attoseconds,” Monti says.

    In contrast, electrons that did cross into adjacent layers took more than 10 times longer to return to their ground energy state. The difference allowed the researchers to distinguish between the two populations.

    “I was very excited to find that directional mechanism of charge distribution occurring within a layer, as opposed to across layers,” says Eads, the paper’s lead author. “That had never been observed before.”

    Closer to Mass Manufacturing

    The X-ray “clock” used to track electrons is not part of the envisioned applications but a means to study the behavior of electrons inside them, Monti explains, a necessary first step in getting closer toward technology with the desired properties that could be mass-manufactured.

    “One example of the unusual behavior we see in these materials is that an electron going to the right is not the same as an electron going to the left,” he says. “That shouldn’t happen — according to physics of standard materials, going to the left or the right is the exact same thing. However, for these materials that is not true.”

    This directionality is an example of what makes TMDs intriguing to scientists, because it could be used to encode information.

    “Moving to the right could be encoded as ‘one’ and going to the left as ‘zero,'” Monti says. “So if I can generate electrons that neatly go to the right, I’ve written a bunch of ones, and if I can generate electrons that neatly go to the left, I have generated a bunch of zeroes.”

    Instead of applying electrical current, engineers could manipulate electrons in this way using light such as a laser, to optically write, read and process information. And perhaps someday it may even become possible to optically entangle information, clearing the way to quantum computing.

    “Every year, more and more discoveries are occurring in these materials,” Eads says. “They are exploding in terms of what kinds of electronic properties you can observe in them. There is a whole spectrum of ways in which they can function, from superconducting, semiconducting to insulating, and possibly more.”

    The research described here is just one way of probing the unexpected, exciting properties of layered TMD crystals, according to Monti.

    “If you did this experiment in silicon, you wouldn’t see any of this,” he says. “Silicon will always behave like a three-dimensional crystal, no matter what you do. It’s all about the layering.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 7:59 am on January 17, 2018 Permalink | Reply
    Tags: , , , , , , Steward Observatory, U Arizona   

    From U Arizona: “Students Help Little Telescope Do Big Things” 

    U Arizona bloc

    University of Arizona

    Jan. 11, 2018
    Daniel Stolte

    A four-year effort involving UA students helped a team of astronomers measure the masses of a large sample of supermassive black holes in the farthest reaches of the universe. As part of a robotic telescope network in southern Arizona, instruments such as the Bok Telescope could play a crucial role in future “grand challenge” science endeavors.

    2.3-metre Bok Telescope at the Steward Observatory at Kitt Peak in Arizona, USA, altitude 2,096 m (6,877 ft)


    U Arizona Steward Observatory at Kitt Peak, AZ, USA, altitude 2,096 m (6,877 ft)

    The Bok Telescope on Kitt Peak is the largest telescope operated solely by the UA’s Steward Observatory. Named in honor of Bart Bok, who was Steward’s director from 1966-1969, the telescope operates every night of the year except Christmas Eve and a maintenance period scheduled during the summer rainy season.

    By today’s standards, the University of Arizona’s Bok Telescope, perched on Kitt Peak southwest of Tucson, is a small telescope: Its primary mirror stands a mere five inches taller than Dušan Ristić, the 7-foot center of the UA men’s basketball team.

    Yet, despite its modest size and advanced age of almost 50 years, the instrument keeps churning out big science, helping us unravel some of the biggest questions about the cosmos. Using observations made with the Bok Telescope, a team of astronomers managed to directly measure the masses of an unprecedented number of the universe’s most distant supermassive black holes, also called quasars. Lurking in the centers of nearly every large galaxy, these Leviathans range from 5 million to 1.7 billion times the mass of the sun.

    “This is the first time that we have directly measured masses for so many supermassive black holes so far away,” said Catherine Grier, a postdoctoral fellow at the Penn State University, who led the research. “These new measurements, and future measurements like them, will provide vital information for people studying how galaxies grow and evolve throughout cosmic time.”

    The results, presented at the American Astronomical Society meeting in National Harbor, Maryland, are published in The Astrophysical Journal and represent a major step forward in our ability to measure supermassive black hole masses in large numbers of distant quasars and galaxies. In addition to the Bok Telescope, the project used the Sloan Digital Sky Survey, or SDSS, and the Canada-France-Hawaii Telescope, or CFHT, atop Hawaii’s Mauna Kea volcano.

    SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft)


    Apache Point Observatory, near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft)


    CFHT Telescope, Maunakea, Hawaii, USA, at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    3
    An artist’s rendering of the inner regions of a quasar, with a supermassive black hole at the center surrounded by a disk of hot material falling in. The two light curves at the bottom illustrates how astronomers use reverberation to map black holes. (Image: Nahks Tr’Ehnl and Catherine Grier/Penn State, SDSS)

    “The Bok Telescope provided key data that allow measurement of how the quasars vary over time, which tells us about the size of the light-emitting region around the black hole,” said Xiaohui Fan, a Regents’ Professor of Astronomy at the UA’s Steward Observatory and a member of the Sloan Digital Sky Survey. “The data is then used to determine the mass of the black hole.”

    Producing ‘World-Class Results’

    The Bok Telescope’s large field of view, combined with the sensitive detectors, means that astronomers can monitor many quasars at the same time, a feat that is crucial to establish the large sample used in the study.

    “This result shows that the Bok can still produce world-class results,” said Ian McGreer, an assistant astronomer at Steward and one of the study’s authors, who managed the observations with the Bok Telescope. “We got involved because the SDSS did a survey of facilities that could support this program, and the Bok came out as one of the few with the required capabilities.”

    The Bok investment was quite substantial, McGreer explained, with more than 100 nights spread over four years so far.

    “The data in this paper are based on the first year, 2014, when the monitoring was the most intense,” he said. “Sixty nights that year were covered by a rotating cast of observers, many of whom were UA undergrads, grads and visiting students.

    “The Bok does not have a nighttime operator, which means the students received valuable training not only in collecting the data and operating the instrument, but in learning how to operate a telescope at night. This is a fairly rare opportunity these days.”

    As they suck in nearby dust and gas, supermassive black holes heat the material to such high temperatures that it glows brightly enough to be seen all the way across the universe. These bright disks of hot gas are known as quasars, and they are clear indicators of the presence of supermassive black holes. By studying these quasars, we learn not only about supermassive black holes, or SMBHs, but also about the distant galaxies they live in. But to do all of this requires measurements of the properties of the SMBHs, most importantly their masses.

    Measuring the masses of extragalactic SMBHs — in this study, up to 8 billion light-years away — is a daunting task and requires a technique called reverberation mapping. Reverberation mapping works by comparing the brightness of light coming from gas very close in to the black hole (referred to as the “continuum” light) to the brightness of light coming from fast-moving gas farther out. Changes occurring in the continuum region impact the outer region, but light takes time to travel outward, or “reverberate.” By measuring this time delay, astronomers can determine how far out the gas is from the black hole. Knowing that distance allows them to measure the mass of the supermassive black hole — even though they can’t see the details of the black hole itself.

    In this new work, the team used an industrial-scale application of the reverberation mapping technique, with the goal of measuring black hole masses in tens to hundreds of quasars. These new SDSS measurements increase the total number of active galaxies with SMBH mass measurements by about two-thirds, and push the measurements farther back in time to when the universe was only half of its current age.

    Faint Quasars Pose a Challenge

    The key to the success of the SDSS reverberation mapping project lies in the SDSS’ ability to study many quasars at once — the program is currently observing 850 quasars simultaneously. But even with the SDSS’ powerful telescope, this is a challenging task because these distant quasars are incredibly faint.

    “You have to calibrate these measurements very carefully to make sure you really understand what the quasar system is doing,” said Jon Trump, an assistant professor at the University of Connecticut and a member of the research team.

    Observing the quasars over the same season with the Bok Telescope and the CFHT improved these calibrations, allowing the team to find reverberation time delays for 44 quasars and use the time delay measurements to calculate black hole masses that range from about 5 million to 1.7 billion times the mass of our sun.

    In the words of McGreer, the future is bright for this kind of work, with plans to develop a robotic telescope network in southern Arizona using telescopes such as the Bok, which could help guide efforts to combine such a network with “grand challenge” science projects like the Large Synoptic Survey Telescope, or LSST.

    Slated to begin operations in 2023, the LSST will conduct an unprecedented 10-year survey, repeatedly imaging every part of the visible sky every few nights. The heart of the instrument, a 8.4-meter primary mirror, was cast and polished at the UA’s Richard F. Caris Mirror Lab.

    “The lessons learned from this reverberation mapping project serve as a pathfinder, or proof of concept, for something that could be done on a much larger scale when LSST arrives,” McGreer said.

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 7:43 am on November 14, 2017 Permalink | Reply
    Tags: , Introducing Titin - the Protein That Rules Our Hearts, , U Arizona   

    From U Arizona: “Introducing Titin, the Protein That Rules Our Hearts” 

    U Arizona bloc

    University of Arizona

    Nov. 13, 2017
    Emily Walla

    UA scientists have solved a muscle mystery by proving that the protein titin acts as a molecular ruler, determining the length of muscle fibers and influencing the strength of the muscles that make our hearts beat and bodies move.

    1
    Henk Granzier: “Biologists have always wondered what makes (muscles) so precisely structured.” No image credit.

    Although scientists have long speculated that a protein named titin measures thick filaments — the proteins that make muscles contract — no one has been able to provide evidence to support their theories.

    No one, that is, until a team of researchers in the University of Arizona’s Department of Cellular and Molecular Medicine took on the case. In a recent study published in Nature Communications, the team presented definitive proof that titin acts as a molecular ruler for the muscle’s thick filament.

    Throughout the muscles of the heart and body, the thick filaments have precise, uniform lengths.

    “Functionally and clinically, it is very important to regulate the thick filament precisely, otherwise muscles would not function well,” said Henk Granzier, senior author of the study and professor of molecular and cellular medicine. “Biologists have always wondered what makes them so precisely structured.”

    Studying mice with certain mutations in the gene encoding the blueprint for the titin protein, the researchers found that when titin was shortened, so were the thick filaments, resulting in weakened muscles and dilated cardiomyopathy, a condition that leads to heart failure.

    “We genetically engineered a mouse that doesn’t have normal titin,” said Granzier, a member of the BIO5 Institute. “It has a piece from titin deleted. Since titin is involved in somehow regulating the thick filament, then you expect if you make titin shorter, the thick filament length will be altered as well. And, lo and behold, that is the case.”

    A typical protein is made of a few hundred amino acids linked in a chain. Though still microscopically small, titin is gigantic compared to other proteins. Comprised of more than 30,000 amino acids, the supersize protein is made from super-repeated structures. The amino acid super-repeats of titin are like tick marks on a yardstick, measuring out uniform sections of the thick filament.

    By altering the gene for titin, Granzier’s team was able to make a mouse whose titin was missing several of its super-repeats.

    The resulting mice showed symptoms of dilated cardiomyopathy, or DCM. This condition stretches out the muscle in the heart and prevents it from pumping efficiently. While the heart still contracts, the muscle is weak, so each contraction only moves a fraction of the blood pumped by a normal heart.

    In humans, the most frequent cause of DCM is a mutation in titin that shortens the protein. DCM affects 1 in 500 people, and often patients must undergo a heart transplant to survive. Understanding the cause of the condition can better arm researchers as they search for novel ways to combat it.

    Methods of Discovery

    “In science, if you want to do conclusive work, you have to test your hypothesis multiple ways and get consistent results,” Granzier said. This meant that any abnormalities detected in the genetically engineered mice had to be deeply investigated.

    After testing the strength of the mice, his team removed the muscles of interest to inspect them in a setting they controlled, instead of a setting controlled by the complex biological systems of the mice. To make certain that differences in the mice were caused by titin, the muscle tissues were observed in vitro by removing them from the animals and artificially stimulating them to show that they produced less force. In the body, muscles contract when activated by calcium; under the microscope, flooding the isolated muscle tissue with a calcium solution mimics this activation process.

    Using ultrasound, the team showed that the hearts of the engineered mice were larger than those of mice with normal titin. The next step was to investigate how this enlargement weakened the heart.

    How Titin Controls Strength

    “The sarcomere is the smallest muscle unit you can tease out and still have all the properties of muscle: force development and shortening,” Granzier said.

    The sarcomeres are linked end-to-end in a chain that spans the entirety of a muscle. Just as a strong chain is made from links that are well made and uniform, sarcomere health and uniformity is vital to muscle strength.

    Each sarcomere is comprised of three filaments: thick, thin and titin filaments. The motor driving contraction — myosin — is held at precise points within the thick filament, and it pulls the thick filament across the thin filament, causing muscle contraction. Muscles are strongest when the thick and thin filaments overlap at an optimal length — around 2 micrometers, or one ten-thousandth of an inch. Stretch out the muscle, and the filaments cannot reach the point of optimum overlap, so the muscle is weakened. Overstretch the muscle, and the filaments do not overlap at all; the muscle cannot exert any force.

    When titin is mutated and short, the resulting shortened fibers cannot reach the optimal point of overlap, and the muscle cannot exert much force. The muscle is further weakened because shorter thick filaments cannot hold the optimal number of myosin motors. The thin and thick filaments do not overlap properly nor contract effectively when the thick filament is short.

    Paula Tonino and Balazs Kiss, lead authors of the study and scientific investigators in Granzier’s lab, observed the muscle fibers under electron and super-resolution microscopes. They determined that in the muscles of engineered mice, not only were the thick filaments shortened, but also that they were shortened by precise, uniform lengths that corresponded to the size of the super-repeats removed from titin.

    “We showed that titin is the regulator of the thick filament,” Granzier said, confirming that titin determines the strength of muscles and health of hearts.

    “You might say titin rules.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: