Tag Archives: imaging

Using images from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have discovered fast-moving wave-like features in the dusty disc around the nearby star AU Microscopii. These odd structures are unlike anything ever observed, or even predicted, before now.

The top row shows a Hubble image of the AU Mic disc from 2010, the middle row Hubble from 2011 and the bottom row VLT/SPHERE data from 2014. The black central circles show where the brilliant light of the central star has been blocked off to reveal the much fainter disc, and the position of the star is indicated schematically.

The scale bar at the top of the picture indicates the diameter of the orbit of the planet Neptune in the Solar System (60 AU).

Note that the brightness of the outer parts of the disc has been artificially brightened to reveal the faint structure.

Credit:
ESO, NASA & ESA

Mysterious Ripples Found Racing Through Planet-forming Disc: ESO

Unique structures spotted around nearby star


 

Using images from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have discovered fast-moving wave-like features in the dusty disc around the nearby star AU Microscopii. These odd structures are unlike anything ever observed, or even predicted, before now. The top row shows a Hubble image of the AU Mic disc from 2010, the middle row Hubble from 2011 and the bottom row VLT/SPHERE data from 2014. The black central circles show where the brilliant light of the central star has been blocked off to reveal the much fainter disc, and the position of the star is indicated schematically. The scale bar at the top of the picture indicates the diameter of the orbit of the planet Neptune in the Solar System (60 AU). Note that the brightness of the outer parts of the disc has been artificially brightened to reveal the faint structure. Credit: ESO, NASA & ESA
Using images from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have discovered fast-moving wave-like features in the dusty disc around the nearby star AU Microscopii. These odd structures are unlike anything ever observed, or even predicted, before now.
The top row shows a Hubble image of the AU Mic disc from 2010, the middle row Hubble from 2011 and the bottom row VLT/SPHERE data from 2014. The black central circles show where the brilliant light of the central star has been blocked off to reveal the much fainter disc, and the position of the star is indicated schematically.
The scale bar at the top of the picture indicates the diameter of the orbit of the planet Neptune in the Solar System (60 AU).
Note that the brightness of the outer parts of the disc has been artificially brightened to reveal the faint structure.
Credit:
ESO, NASA & ESA

Using images from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have discovered never-before-seen structures within a dusty disc surrounding a nearby star. The fast-moving wave-like features in the disc of the star AU Microscopii are unlike anything ever observed, or even predicted, before now. The origin and nature of these features present a new mystery for astronomers to explore. The results are published in the journal Nature on 8 October 2015.

AU Microscopii, or AU Mic for short, is a young, nearby star surrounded by a large disc of dust [1]. Studies of such debris discs can provide valuable clues about how planets, which form from these discs, are created.

Astronomers have been searching AU Mic’s disc for any signs of clumpy or warped features, as such signs might give away the location of possible planets. And in 2014 they used the more powerful high-contrast imaging capabilities of ESO’s newly installed SPHERE instrument, mounted on the Very Large Telescope for their search — and discovered something very unusual.

Our observations have shown something unexpected,” explains Anthony Boccaletti, LESIA (Observatoire de Paris/CNRS/UPMC/Paris-Diderot), France, and lead author on the paper. “The images from SPHERE show a set of unexplained features in the disc which have an arch-like, or wave-like, structure, unlike anything that has ever been observed before.

Five wave-like arches at different distances from the star show up in the new images, reminiscent of ripples in water. After spotting the features in the SPHERE data the team turned to earlier images of the disc taken by the NASA/ESA Hubble Space Telescope in 2010 and 2011 to see whether the features were also visible in these [2]. They were not only able to identify the features on the earlier Hubble images — but they also discovered that they had changed over time. It turns out that these ripples are moving — and very fast!

We reprocessed images from the Hubble data and ended up with enough information to track the movement of these strange features over a four-year period,” explains team member Christian Thalmann (ETH Zürich, Switzerland). “By doing this, we found that the arches are racing away from the star at speeds of up to about 40 000 kilometres/hour!

The features further away from the star seem to be moving faster than those closer to it. At least three of the features are moving so fast that they could well be escaping from the gravitational attraction of the star. Such high speeds rule out the possibility that these are conventional disc features caused by objects — like planets — disturbing material in the disc while orbiting the star. There must have been something else involved to speed up the ripples and make them move so quickly, meaning that they are a sign of something truly unusual [3].

Everything about this find was pretty surprising!” comments co-author Carol Grady of Eureka Scientific, USA. “And because nothing like this has been observed or predicted in theory we can only hypothesise when it comes to what we are seeing and how it came about.

The team cannot say for sure what caused these mysterious ripples around the star. But they have considered and ruled out a series of phenomena as explanations, including the collision of two massive and rare asteroid-like objects releasing large quantities of dust, and spiral waves triggered by instabilities in the system’s gravity.

But other ideas that they have considered look more promising.

One explanation for the strange structure links them to the star’s flares. AU Mic is a star with high flaring activity — it often lets off huge and sudden bursts of energy from on or near its surface,” explains co-author Glenn Schneider of Steward Observatory, USA. “One of these flares could perhaps have triggered something on one of the planets — if there are planets — like a violent stripping of material which could now be propagating through the disc, propelled by the flare’s force.

It is very satisfying that SPHERE has proved to be very capable at studying discs like this in its first year of operation,” adds Jean-Luc Beuzit, who is both a co-author of the new study and also led the development of SPHERE itself.

The team plans to continue to observe the AU Mic system with SPHERE and other facilities, including ALMA, to try to understand what is happening. But, for now, these curious features remain an unsolved mystery.

Notes

[1] AU Microscopii lies just 32 light-years away from Earth. The disc essentially comprises asteroids that have collided with such vigour that they have been ground to dust.

[2] The data were gathered by Hubble’s Space Telescope Imaging Spectrograph (STIS).

[3] The edge-on view of the disc complicates the interpretation of its three-dimensional structure.

More information

This research was presented in a paper entitled “Fast-Moving Structures in the Debris Disk Around AU Microscopii”, to appear in the journal Nature on 8 October 2015.

Source: ESO

eso1523a

A Celestial Butterfly Emerges from its Dusty Cocoon

eso1523aSPHERE reveals earliest stage of planetary nebula formation


Some of the sharpest images ever made with ESO’s Very Large Telescope (VLT) have, for the first time, revealed what appears to be an ageing star giving birth to a butterfly-like planetary nebula. These observations of the red giant star L2 Puppis, from the ZIMPOL mode of the newly installed SPHERE instrument, also clearly showed a close companion. The dying stages of stars continue to pose astronomers with many riddles, and the origin of such bipolar nebulae, with their complex and alluring hourglass figures, doubly so. This new imaging mode means that the VLT is currently the sharpest astronomical direct imaging instrument in existence.

At about 200 light-years away, L2 Puppis is one of the closest red giants to Earth known to be entering its final stages of life. The new observations with the ZIMPOL mode of SPHERE were made in visible light using extreme adaptive optics, which corrects images to a much higher degree than standard adaptive optics, allowing faint objects and structures close to bright sources of light to be seen in greater detail. They are the first published results from this mode and the most detailed of such a star.

ZIMPOL can produce images that are three times sharper than those from the NASA/ESA Hubble Space Telescope, and the new observations show the dust that surrounds L2 Puppis in exquisite detail [1]. They confirm earlier findings, made using NACO, of the dust being arranged in a disc, which from Earth is seen almost completely edge-on, but provide a much more detailed view. The polarisation information from ZIMPOL also allowed the team to construct a three dimensional model of the dust structures [2].

The astronomers found the dust disc to begin about 900 million kilometres from the star — slightly farther than the distance from the Sun to Jupiter — and discovered that it flares outwards, creating a symmetrical, funnel-like shape surrounding the star. The team also observed a second source of light about 300 million kilometres — twice the distance from Earth to the Sun — from L2 Puppis. This very close companion star is likely to be another red giant of slightly lower mass, but less evolved.

The combination of a large amount of dust surrounding a slowly dying star, along with the presence of a companion star, mean that this is exactly the type of system expected to create a bipolar planetary nebula. These three elements seem to be necessary, but a considerable amount of good fortune is also still required if they are to lead to the subsequent emergence of a celestial butterfly from this dusty chrysalis.

Lead author of the paper, Pierre Kervella, explains: “The origin of bipolar planetary nebulae is one of the great classic problems of modern astrophysics, especially the question of how, exactly, stars return their valuable payload of metals back into space — an important process, because it is this material that will be used to produce later generations of planetary systems.”

In addition to L2 Puppis’s flared disc, the team found two cones of material, which rise out perpendicularly to the disc. Importantly, within these cones, they found two long, slowly curving plumes of material. From the origin points of these plumes, the team deduces that one is likely to be the product of the interaction between the material from L2 Puppis and the companions star’s wind and radiation pressure, while the other is likely to have arisen from a collision between the stellar winds from the two stars, or be the result of an accretion disc around the companion star.

Although much is still to be understood, there are two leading theories of bipolar planetary nebulae, both relying on the existence of a binary star system [3]. The new observations suggest that both of these processes are in action around L2 Puppis, making it appear very probable that the pair of stars will, in time, give birth to a butterfly.

Pierre Kervella concludes: “With the companion star orbiting L2 Puppis only every few years, we expect to see how the companion star shapes the red giant’s disc. It will be possible to follow the evolution of the dust features around the star in real time — an extremely rare and exciting prospect.”

Notes
[1] SPHERE/ZIMPOL use extreme adaptive optics to create diffraction-limited images, which come a lot closer than previous adaptive optics instruments to achieving the theoretical limit of the telescope if there were no atmosphere. Extreme adaptive optics also allows much fainter objects to be seen very close to a bright star. These images are also taken in visible light — shorter wavelengths than the near-infrared regime, where most earlier adaptive optics imaging was performed. These two factors result in significantly sharper images than earlier VLT images. Even higher spatial resolution has been achieved with VLTI, but the interferometer does not create images directly.

[2] The dust in the disc was very efficient at scattering the stars’ light towards Earth and polarising it, a feature that the team could use to create a three-dimensional map of the envelope using both ZIMPOL and NACO data and a disc model based on the RADMC-3D radiative transfer modeling tool, which uses a given set of parameters for the dust to simulate photons propagating through it.

[3] The first theory is that the dust produced by the primary, dying star’s stellar wind is confined to a ring-like orbit about the star by the stellar winds and radiation pressure produced by the companion star. Any further mass lost from the main star is then funneled, or collimated, by this disc, forcing the material to move outwards in two opposing columns perpendicular to the disc.

The second holds that most of the material being ejected by the dying star is accreted by its nearby companion, which begins to form an accretion disc and a pair of powerful jets. Any remaining material is pushed away by the dying star’s stellar winds, forming an encompassing cloud of gas and dust, as would normally occur in a single star system. The companion star’s newly created bipolar jets, moving with much greater force than the stellar winds of the dying star, then carve dual cavities through the surrounding dust, resulting in the characteristic appearance of a bipolar planetary nebula.

Source: ESO

Electrical and computer engineering Professor Barry Van Veen wears an electrode net used to monitor brain activity via EEG signals. His research could help untangle what happens in the brain during sleep and dreaming.

Photo Credit: Nick Berard/UW-Madison

Imagination, reality flow in opposite directions in the brain

By Scott Gordon


As real as that daydream may seem, its path through your brain runs opposite reality.

Aiming to discern discrete neural circuits, researchers at the University of Wisconsin–Madison have tracked electrical activity in the brains of people who alternately imagined scenes or watched videos.

“A really important problem in brain research is understanding how different parts of the brain are functionally connected. What areas are interacting? What is the direction of communication?” says Barry Van Veen, a UW-Madison professor of electrical and computer engineering. “We know that the brain does not function as a set of independent areas, but as a network of specialized areas that collaborate.”

Van Veen, along with Giulio Tononi, a UW-Madison psychiatry professor and neuroscientist, Daniela Dentico, a scientist at UW–Madison’s Waisman Center, and collaborators from the University of Liege in Belgium, published results recently in the journalNeuroImage. Their work could lead to the development of new tools to help Tononi untangle what happens in the brain during sleep and dreaming, while Van Veen hopes to apply the study’s new methods to understand how the brain uses networks to encode short-term memory.

During imagination, the researchers found an increase in the flow of information from the parietal lobe of the brain to the occipital lobe — from a higher-order region that combines inputs from several of the senses out to a lower-order region.

Electrical and computer engineering Professor Barry Van Veen wears an electrode net used to monitor brain activity via EEG signals. His research could help untangle what happens in the brain during sleep and dreaming. Photo Credit: Nick Berard/UW-Madison
Electrical and computer engineering Professor Barry Van Veen wears an electrode net used to monitor brain activity via EEG signals. His research could help untangle what happens in the brain during sleep and dreaming.
Photo Credit: Nick Berard/UW-Madison

In contrast, visual information taken in by the eyes tends to flow from the occipital lobe — which makes up much of the brain’s visual cortex — “up” to the parietal lobe.

“There seems to be a lot in our brains and animal brains that is directional, that neural signals move in a particular direction, then stop, and start somewhere else,” says. “I think this is really a new theme that had not been explored.”

The researchers approached the study as an opportunity to test the power of electroencephalography (EEG) — which uses sensors on the scalp to measure underlying electrical activity — to discriminate between different parts of the brain’s network.

Brains are rarely quiet, though, and EEG tends to record plenty of activity not necessarily related to a particular process researchers want to study.

To zero in on a set of target circuits, the researchers asked their subjects to watch short video clips before trying to replay the action from memory in their heads. Others were asked to imagine traveling on a magic bicycle — focusing on the details of shapes, colors and textures — before watching a short video of silent nature scenes.

Using an algorithm Van Veen developed to parse the detailed EEG data, the researchers were able to compile strong evidence of the directional flow of information.

“We were very interested in seeing if our signal-processing methods were sensitive enough to discriminate between these conditions,” says Van Veen, whose work is supported by the National Institute of Biomedical Imaging and Bioengineering. “These types of demonstrations are important for gaining confidence in new tools.”

Source: UW-Madison News

Time to Wake Up: Artist’s impression of NASA’s New Horizons spacecraft, currently en route to Pluto. Operators at the Johns Hopkins University Applied Physics Laboratory are preparing to “wake” the spacecraft from electronic hibernation on Dec. 6, when the probe will be more than 2.9 billion miles from Earth. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

New Horizons Set to Wake Up for Pluto Encounter

NASA’s New Horizons spacecraft comes out of hibernation for the last time on Dec. 6. Between now and then, while the Pluto-bound probe enjoys three more weeks of electronic slumber, work on Earth is well under way to prepare the spacecraft for a six-month encounter with the dwarf planet that begins in January.

“New Horizons is healthy and cruising quietly through deep space – nearly three billion miles from home – but its rest is nearly over,” says Alice Bowman, New Horizons mission operations manager at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. “It’s time for New Horizons to wake up, get to work, and start making history.”

Since launching in January 2006, New Horizons has spent 1,873 days in hibernation – about two-thirds of its flight time – spread over 18 separate hibernation periods from mid-2007 to late 2014 that ranged from 36 days to 202 days long.

In hibernation mode much of the spacecraft is unpowered; the onboard flight computer monitors system health and broadcasts a weekly beacon-status tone back to Earth. On average, operators woke New Horizons just over twice each year to check out critical systems, calibrate instruments, gather science data, rehearse Pluto-encounter activities and perform course corrections when necessary.

New Horizons pioneered routine cruise-flight hibernation for NASA. Not only has hibernation reduced wear and tear on the spacecraft’s electronics, it lowered operations costs and freed up NASA Deep Space Network tracking and communication resources for other missions.

Ready to Go

Next month’s wake-up call was preprogrammed into New Horizons’ on-board computer in August, commanding it come out of hibernation at 3 p.m. EST on Dec. 6. About 90 minutes later New Horizons will transmit word to Earth that it’s in “active” mode; those signals, even traveling at light speed, will need four hours and 25 minutes to reach home. Confirmation should reach the mission operations team at APL around 9:30 p.m. EST. At the time New Horizons will be more than 2.9 billion miles from Earth, and just 162 million miles – less than twice the distance between Earth and the sun – from Pluto.

Time to Wake Up: Artist’s impression of NASA’s New Horizons spacecraft, currently en route to Pluto. Operators at the Johns Hopkins University Applied Physics Laboratory are preparing to “wake” the spacecraft from electronic hibernation on Dec. 6, when the probe will be more than 2.9 billion miles from Earth. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
Time to Wake Up: Artist’s impression of NASA’s New Horizons spacecraft, currently en route to Pluto. Operators at the Johns Hopkins University Applied Physics Laboratory are preparing to “wake” the spacecraft from electronic hibernation on Dec. 6, when the probe will be more than 2.9 billion miles from Earth. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

After several days of collecting navigation-tracking data, downloading and analyzing the cruise science and spacecraft housekeeping data stored on New Horizons’ digital recorders, the mission team will begin activities that include conducting final tests on the spacecraft’s science instruments and operating systems, and building and testing the computer-command sequences that will guide New Horizons through its flight to and reconnaissance of the Pluto system. Tops on the mission’s science list are characterizing the global geology and topography of Pluto and its large moon Charon, mapping their surface compositions and temperatures, examining Pluto’s atmospheric composition and structure, studying Pluto’s smaller moons and searching for new moons and rings.

New Horizons’ seven-instrument science payload, developed under direction of Southwest Research Institute, includes advanced imaging infrared and ultraviolet spectrometers, a compact multicolor camera, a high-resolution telescopic camera, two powerful particle spectrometers, a space-dust detector (designed and built by students at the University of Colorado) and two radio science experiments. The entire spacecraft, drawing electricity from a single radioisotope thermoelectric generator, operates on less power than a pair of 100-watt light bulbs.

Distant observations of the Pluto system begin Jan. 15 and will continue until late July 2015; closest approach to Pluto is July 14.

“We’ve worked years to prepare for this moment,” says Mark Holdridge, New Horizons encounter mission manager at APL. “New Horizons might have spent most of its cruise time across nearly three billion miles of space sleeping, but our team has done anything but, conducting a flawless flight past Jupiter just a year after launch, putting the spacecraft through annual workouts, plotting out each step of the Pluto flyby and even practicing the entire Pluto encounter on the spacecraft. We are ready to go.”

“The final hibernation wake up Dec. 6 signifies the end of an historic cruise across the entirety of our planetary system,” added New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute. “We are almost on Pluto’s doorstep!”

The Johns Hopkins Applied Physics Laboratory manages the New Horizons mission for NASA’s Science Mission Directorate. Alan Stern, of the Southwest Research Institute (SwRI) is the principal investigator and leads the mission; SwRI leads the science team, payload operations, and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Ala. APL designed, built and operates the New Horizons spacecraft.

Source: JHUAPL

In a paper appearing in the Nov. 18 issue of Nature Communications, the researchers demonstrate the use of the particles, which carry distinct sensors for fluorescence and MRI, to track vitamin C in mice. Wherever there is a high concentration of vitamin C, the particles show a strong fluorescent signal but little MRI contrast. If there is not much vitamin C, a stronger MRI signal is visible but fluorescence is very weak.

Illustration: Christine Daniloff/MIT

Two sensors in one

Nanoparticles that enable both MRI and fluorescent imaging could monitor cancer, other diseases.

By Anne Trafton


 

MIT chemists have developed new nanoparticles that can simultaneously perform magnetic resonance imaging (MRI) and fluorescent imaging in living animals. Such particles could help scientists to track specific molecules produced in the body, monitor a tumor’s environment, or determine whether drugs have successfully reached their targets.

 

In a paper appearing in the Nov. 18 issue of Nature Communications, the researchers demonstrate the use of the particles, which carry distinct sensors for fluorescence and MRI, to track vitamin C in mice. Wherever there is a high concentration of vitamin C, the particles show a strong fluorescent signal but little MRI contrast. If there is not much vitamin C, a stronger MRI signal is visible but fluorescence is very weak.

In a paper appearing in the Nov. 18 issue of Nature Communications, the researchers demonstrate the use of the particles, which carry distinct sensors for fluorescence and MRI, to track vitamin C in mice. Wherever there is a high concentration of vitamin C, the particles show a strong fluorescent signal but little MRI contrast. If there is not much vitamin C, a stronger MRI signal is visible but fluorescence is very weak. Illustration: Christine Daniloff/MIT
In a paper appearing in the Nov. 18 issue of Nature Communications, the researchers demonstrate the use of the particles, which carry distinct sensors for fluorescence and MRI, to track vitamin C in mice. Wherever there is a high concentration of vitamin C, the particles show a strong fluorescent signal but little MRI contrast. If there is not much vitamin C, a stronger MRI signal is visible but fluorescence is very weak.
Illustration: Christine Daniloff/MIT

 

Future versions of the particles could be designed to detect reactive oxygen species that often correlate with disease, says Jeremiah Johnson, an assistant professor of chemistry at MIT and senior author of the study. They could also be tailored to detect more than one molecule at a time.

 

“You may be able to learn more about how diseases progress if you have imaging probes that can sense specific biomolecules,” Johnson says.

 

Dual action

 

Johnson and his colleagues designed the particles so they can be assembled from building blocks made of polymer chains carrying either an organic MRI contrast agent called a nitroxide or a fluorescent molecule called Cy5.5.

 

When mixed together in a desired ratio, these building blocks join to form a specific nanosized structure the authors call a branched bottlebrush polymer. For this study, they created particles in which 99 percent of the chains carry nitroxides, and 1 percent carry Cy5.5.

 

Nitroxides are reactive molecules that contain a nitrogen atom bound to an oxygen atom with an unpaired electron. Nitroxides suppress Cy5.5’s fluorescence, but when the nitroxides encounter a molecule such as vitamin C from which they can grab electrons, they become inactive and Cy5.5 fluoresces.

 

Nitroxides typically have a very short half-life in living systems, but University of Nebraska chemistry professor Andrzej Rajca, who is also an author of the new Nature Communications paper, recently discovered that their half-life can be extended by attaching two bulky structures to them.  Furthermore, the authors of the Nature Communications paper show that incorporation of Rajca’s nitroxide in Johnson’s branched bottlebrush polymer architectures leads to even greater improvements in the nitroxide lifetime. With these modifications, nitroxides can circulate for several hours in a mouse’s bloodstream — long enough to obtain useful MRI images.

 

The researchers found that their imaging particles accumulated in the liver, as nanoparticles usually do. The mouse liver produces vitamin C, so once the particles reached the liver, they grabbed electrons from vitamin C, turning off the MRI signal and boosting fluorescence. They also found no MRI signal but a small amount of fluorescence in the brain, which is a destination for much of the vitamin C produced in the liver. In contrast, in the blood and kidneys, where the concentration of vitamin C is low, the MRI contrast was maximal.

 

Mixing and matching

 

The researchers are now working to enhance the signal differences that they get when the sensor encounters a target molecule such as vitamin C. They have also created nanoparticles carrying the fluorescent agent plus up to three different drugs. This allows them to track whether the nanoparticles are delivered to their targeted locations.

 

“That’s the advantage of our platform — we can mix and match and add almost anything we want,” Johnson says.

 

These particles could also be used to evaluate the level of oxygen radicals in a patient’s tumor, which can reveal valuable information about how aggressive the tumor is.

 

“We think we may be able to reveal information about the tumor environment with these kinds of probes, if we can get them there,” Johnson says. “Someday you might be able to inject this in a patient and obtain real-time biochemical information about disease sites and also healthy tissues, which is not always straightforward.”

 

Steven Bottle, a professor of nanotechnology and molecular science at Queensland University of Technology, says the most impressive element of the study is the combination of two powerful imaging techniques into one nanomaterial.

 

“I believe this should deliver a very powerful, metabolically linked, multi-combination imaging modality which should provide a highly useful diagnostic tool with real potential to follow disease progression in vivo,” says Bottle, who was not involved in the study.

 

The research was funded by the National Institutes of Health, the Department of Defense, the National Science Foundation, and the Koch Institute for Integrative Cancer Research.

Source: MIT News