DNA Bird Vaccine, Snow Fleas!
Nanorobots, Nanocars,
Super-Massive Black Hole!
 Magic-sized quantum dots in a glass flow tube produce white light when stimulated by an ultraviolet laser beam. Photo by Daniel Dubois. |
Vanderbilt
University News Release
By David F. Salisbury
October 20, 2005 - Take an LED that produces intense, blue light. Coat it
with a thin layer of special microscopic beads called quantum dots. And
you have what could become the successor to the venerable light bulb.
The resulting hybrid LED gives off a warm white light with a slightly
yellow cast, similar to that of the incandescent lamp.
Until now quantum dots have been known primarily for their ability to
produce a dozen different distinct colors of light simply by varying the
size of the individual nanocrystals: a capability particularly suited to
fluorescent labeling in biomedical applications. But chemists at
Vanderbilt University discovered a way to make quantum dots spontaneously
produce broad-spectrum white light. The report of their discovery, which
happened by accident, appears in the communication "White-light
Emission from Magic-Sized Cadmium Selenide Nanocrystals" published
online October 18 by the Journal of the American Chemical Society.
In the last few years, LEDs (short for light emitting diodes) have begun
replacing incandescent and fluorescent lights in a number of niche
applications. Although these solid-state lights have been used for decades
in consumer electronics, recent technological advances have allowed them
to spread into areas like architectural lighting, traffic lights,
flashlights and reading lights. Although they are considerably more
expensive than ordinary lights, they are capable of producing about twice
as much light per watt as incandescent bulbs; they last up to 50,000 hours
or 50 times as long as a 60-watt bulb; and, they are very tough and hard
to break. Because they are made in a fashion similar to computer chips,
the cost of LEDs has been dropping steadily. The Department of Energy has
estimated that LED lighting could reduce U.S. energy consumption for
lighting by 29 percent by 2025, saving the nation’s households about
$125 million in the process.
Until 1993 LEDs could only produce red, green and yellow light. But then
Nichia Chemical of Japan figured out how to produce blue LEDs. By
combining blue LEDs with red and green LEDs – or adding a yellow
phosphor to blue LEDs – manufacturers were able create white light,
which opened up a number of new applications. However, these LEDs tend to
produce white light with a cool, bluish tinge.
The white-light quantum dots, by contrast, produce a smoother distribution
of wavelengths in the visible spectrum with a slightly warmer, slightly
more yellow tint, reports Michael Bowers, the graduate student who made
the quantum dots and discovered their unusual property. As a result, the
light produced by the quantum dots looks more nearly like the "full
spectrum" reading lights now on the market which produce a light
spectrum closer to that of sunlight than normal fluorescent tubes or light
bulbs. Of course, quantum dots, like white LEDs, have the advantage of not
giving off large amounts of invisible infrared radiation unlike the light
bulb. This invisible radiation produces large amounts of heat and largely
accounts for the light bulb’s low energy efficiency.
Bowers works in the laboratory of Associate professor of Chemistry Sandra
Rosenthal. The accidental discovery was the result of the request of one
of his coworkers, post-doctoral student and electron microscopist James
McBride, who is interested in the way in which quantum dots grow. He
thought that the structure of small-sized dots might provide him with new
insights into the growth process, so he asked Bowers to make him a batch
of small-sized quantum dots that he could study.
"I made him a batch and he came back to me and asked if I could make
them any smaller," says Bowers. So he made a second batch of even
smaller nanocrystals. But once again, McBride asked him for something
smaller. So Bowers made a batch of the smallest quantum dots he knew how
to make. It turns out that these were crystals of cadmium and selenium
that contain either 33 or 34 pairs of atoms, which happens to be a
"magic size" that the crystals form preferentially. As a result,
the magic-sized quantum dots were relatively easy to make even though they
are less than half the size of normal quantum dots.
After Bowers cleaned up the batch, he pumped a solution containing the
nanocrystals into a small glass cell and illuminated it with a laser.
"I was surprised when a white glow covered the table," Bowers
says. "The quantum dots were supposed to emit blue light, but instead
they were giving off a beautiful white glow."
"The exciting thing about this is that it is a nano-nanoscience
phenomenon," Rosenthal comments. In the larger nanocrystals, which
produce light in narrow spectral bands, the light originates in the center
of the crystal. But, as the size of the crystal shrinks down to the magic
size, the light emission region appears to move to the surface of the
crystal and broadens out into a full spectrum.
 The crude hybrid white-light LED that Bowers made by mixing magic-sized quantum dots with Minwax and using the mixture to coat a blue LED. Photo by Daniel Dubois. |
Another student in
the lab got the idea of using polyurethane wood finish for thin film
research while working on his parent’s summer cabin. He had even brought
some Minwax into the lab. That gave Bowers the idea of mixing the
magic-sized quantum dots with the polyurethane and coating an LED. The
result was a bit lumpy, but it proved that the magic-sized quantum dots
could be used to make a white light source.
The Vanderbilt researchers are the first to report making quantum dots
that spontaneously emit white light, but they aren’t the first to report
using quantum dots to produce hybrid, white-light LEDs. The other reports
– one by a group at the University of St. Andrews in Scotland and one by
a group at Sandia National Laboratories – describe achieving this effect
by adding additional compounds that interact with the tiny crystals to
produce a white-light spectrum.
The magic-sized
quantum dots, by contrast, produce white light without any extra chemical
treatment: The full spectrum emission is an intrinsic effect.
One difference between the Vanderbilt approach and the others is the
process they used to make the quantum dots, Bowers observes. They use
synthesis methods that take between a week and a month to complete;
whereas, the Vanderbilt method takes less than an hour.
A second significant difference, according to Rosenthal, is that it should
be considerably easier to use the magic-sized quantum dots to make an
"electroluminescent device" – a light source powered directly
by electricity – because they can be used with a wider selection of
binding compounds without affecting their emissions characteristics. Other
research groups have reported stimulating quantum dots to produce light by
applying an electrical current. Of course, those produced colored light.
So, one of the projects at the top of Rosenthal’s list is to duplicate
that feat with magic-sized nanocrystals to see if they will produce white
light when electrically stimulated.
The light bulb is made out of metal and glass using primarily mechanical
processes. Current LEDs are made using semiconductor manufacturing
techniques developed in the last 50 years. But, if the quantum dot
approach pans out, it could transform lighting production into a primarily
chemical process. Such a fundamental change could open up a wide range of
new possibilities, such as making almost any object into a light source by
coating it with luminescent paint capable of producing light in a rainbow
of different shades, including white.
Vanderbilt University - http://sitemason.vanderbilt.edu/news
October 19, 2005 - Researchers scrambling to combat a virulent form of bird flu that could mutate into a form easily spread among humans should consider developing vaccines based on DNA, according to British biochemical engineers. DNA vaccines, they say, can be produced more rapidly than conventional vaccines and could possibly save thousands of lives if a global influenza outbreak occurs.
A DNA-based vaccine could be a potent weapon against this emerging threat, particularly if enough conventional vaccine isn't available, according to Peter Dunnill, DSc., and his colleagues at University College London. However, they caution that any DNA vaccine should only be used as needed to slow the spread of the disease because the technique is largely untested in humans. The analysis appears in the November-December issue of the journal Biotechnology Progress, a co-publication of the American Chemical Society and the American Institutes of Chemical Engineers.
The avian virus, H5N1, has spread among birds throughout Southeast Asia and has been recently detected in Eastern Europe. The virus has killed more than 60 people in Asia since 2003 and forced the slaughter of millions of birds. There are no confirmed cases of human-to-human transmission of this flu, but that could change as the virus continues to mutate, Dunnill says.
If that occurs, current production facilities are unlikely to meet global demands for conventional vaccines in time to avert a pandemic, Dunnill says. But it might be possible to quickly produce a DNA vaccine by adapting the manufacturing processes of selected biopharmaceutical and antibiotic plants in countries such as the United States, China and India.
"A DNA vaccine is not a panacea, however it could be useful if the situation gets out of hand," Dunnill says. "But if we're going to try it, we need to move. You can't expect to walk into a production facility, hand over the instructions, and expect them to make it on the spot. It's going to take some weeks, and we really don't know how much time we have."
A DNA vaccine could be produced in as little as two or three weeks, Dunnill says. To do it, scientists would create a "loop" of DNA that contains the construction plans for a protein on the outer surface of the H5N1 virus. When that DNA is injected into cells, it would quickly reproduce the protein and trigger immunization in much the same way as a conventional vaccine.
In contrast, producing conventional vaccines from viruses incubated in fertilized eggs can take up to six months, which is too long to effectively prevent an influenza pandemic, Dunnill says.
Although no commercial influenza DNA vaccine is currently available, these vaccines have worked well in animals. However, human trials are still in the early stages so the safety and efficacy of these vaccines isn't fully established in people. But these trials could be accelerated, Dunnill says, particularly if the H5N1virus eventually causes large numbers of human deaths and out paces the supply of conventional vaccine. In the worst case scenario, he suggests, using a DNA vaccine could be a "stop-gap" measure until enough conventional vaccine is available to corral the pandemic.
American Chemical Society - http://www.acs.org
 A snow flea (Queen’s University) |
Queen’s
University News Release
Kingston, Ontario Friday October 21, 2005 – A new antifreeze protein
discovered in tiny snow fleas by Queen’s University researchers may
lengthen the shelf life of human organs for transplantation.
Drs. Laurie Graham and Peter Davies, from the Department of Biochemistry,
found that the potent protein produced by the fleas to protect themselves
against freezing is capable of inhibiting ice growth by about six Celsius
degrees. This would allow organs to be stored at lower temperatures,
expanding the time allowed between removal and transplant.
The results of the Queen’s study, funded by the Canadian Institutes for
Health Research (CIHR), are published today in the international journal
Science.
"Transplant organs must now be kept at the freezing point or slightly
warmer," says Dr. Graham. "If we can drop the temperature at
which the organ is safely stored, there will be a longer preservation
period."
The hyperactive antifreeze protein produced by snow fleas is different
from two other insect proteins discovered earlier at Queen’s, the
researchers say.
"Unlike the antifreeze proteins in beetles and moths, AFPs in snow
fleas break down and lose their structure at higher temperatures,"
explains Dr Davies, Canada Research Chair in Protein Engineering.
"This means that if used to store organs for transplants, they will
be cleared from a person’s system very quickly, reducing the possibility
of harmful antibodies forming."
An ancient species related to modern insects, snow fleas are also known as
"springtails" because of the distinctive springing organ under
their abdomen which allows them to leap hundreds of times their
one-millimeter length. Dr. Graham first noticed them while cross-country
skiing, and brought several samples into the lab. "It was
serendipity," she says now. "They looked like dots of pepper
sprinkled on the snow. Later we were able to collect large numbers for
testing at the Queen’s University Biological Station."
Using a process called ice affinity purification, the team isolated the
new protein, which is rich in an amino acid called glycine. "When you
grow a ‘popsicle’ of ice in the presence of these proteins, the AFPs
bind to the ice and become included, while other proteins are
excluded," says Dr. Davies. "We use their affinity for ice as a
tool to purify the protein."
The antifreeze mechanism of snow fleas has been reported in other parts of
the world, including Antarctica, but until now no one has isolated the
protein. As well as its potential for use in organ transplants, the
researchers suggest it could help to increase frost resistance in plants,
and inhibit crystallization in frozen foods.
October 21, 2005 - How do you build an infrared (IR) camera that is small enough to fit on a mini-unmanned aerial vehicle (UAV) without cryogenic cooling? Call in the nanobots.
Researchers working with the Office of Naval Research (ONR) have developed a way to build extremely small sensors using nanorobot fabrication. This new process, created by Harold Szu and James Buss of ONR and implemented by Xi Ning of Michigan State University, allows a human operator using a powerful microscope and hand-held controller to manipulate nano-sized contact points remotely--like using extremely small hands--to construct the pixel elements that will form the heart of the sensor. Each pixel will be composed of carbon nanotubes, which have nanoscale diameters and submicron lengths. Because of the one-dimensional nature of carbon nanotubes, they have significantly lower thermal noise than traditional semi-conductors. A full-sized camera incorporating this technology would be inexpensive and lightweight--about one tenth the cost, weight, and size of a conventional digital camera.
The reason for making such a small sensor has to do with the largest of things--protecting multibillion-dollar aircraft carriers and their thousands of Sailors. Today, missiles have gotten smaller, stealthier, and more difficult to detect than ever--and you don't need to have the budget of a superpower (or even be a power at all) to buy or manufacture them. To improve the ability of carrier strike groups to detect these missiles over the horizon, the U.S. Navy is searching for ways to augment its surveillance capabilities with a covert team of mini-UAVs equipped with passive sensors that can cruise near the ocean surface at slow speeds for many hours.
One of the salient features distinguishing a missile plume from flare camouflage is the unique characteristics of a plume's IR signature, especially in the mid-IR spectrum. The signal-to-noise ratio of a conventional IR detector array operating in the ocean environment, however, demands the use of cumbersome liquid nitrogen cryogenic cooling for all current mid-IR spectrum cameras. Unfortunately, a mini-UAV's payload limitation does not allow such a bulky technology on board--but a small UAV is possible with the advent of nano-based sensors.
The proposed IR camera is being considered for other applications as well, including the field of breast cancer detection. "This new technology will revolutionize how sensors, cameras, and countless other medical devices will be made by a nanorobot, which can respond to public demands of non-contact examinations for early cancer screening at every household," said Father Giofranco Basti of the Pontifical Lateran University at the Vatican City, Rome, Italy. Next spring, the university will conduct a screening test bed of early breast tumor treatment using this new technology in collaboration with ONR.
Office of Naval Research - http://www.onr.navy.mil
October 20, 2005 - Research estimates that health inequalities between white and black Americans cause 84,000 extra deaths every year – equating to a virtual hurricane Katrina every week, says an editorial in this week's BMJ.
But because the victims die gradually from diseases such as diabetes, heart disease, cancer, HIV, and from drug and alcohol abuse, the public are generally unaware of the scale of the fatalities.
Hurricane Katrina has exposed US health inequalities, though these are not unique to America's racial legacy, argue the authors. Poverty, unemployment, alienation and neglect all contribute to the health divide for the poorest and for minority communities across the US, the UK and other western countries.
In America, however, the result is a health gap which has endured despite years of health developments and economic growth, and progress on race issues.
The hurricane's devastating aftermath exposes the policy changes – from both government and the private sector – which must be introduced to tackle the health divide, say the authors. These include investing in prevention not just rescue strategies, strengthening public health systems, and supporting responsible choices by individuals. For instance, promoting healthy eating and exercise is only of limited benefit in poor communities where "parks and supermarkets are less common than fast food chains and stores selling alcohol."
As the US rushes to rebuild its southern states, Americans should think carefully about how they could create healthier and more equal communities. "It is even more important that we and others apply these lessons to help the many other individuals and communities with poor health who continue to languish out of the public eye," they conclude.
BMJ-British Medical Journal - http://www.bmj.com
 Credit: Y. Shira/Rice University |
HOUSTON, Oct. 20,
2005 – Rice University scientists have constructed the world's smallest
car -- a single molecule "nanocar" that contains a chassis,
axles and four buckyball wheels.
The "nanocar" is described in a research paper that is available
online and due to appear in an upcoming issue of the journal Nano Letters.
"The synthesis and testing of nanocars and other molecular machines
is providing critical insight in our investigations of bottom-up molecular
manufacturing," said one of the two lead researchers, James M. Tour,
the Chao Professor of Chemistry, professor of mechanical engineering and
materials science and professor of computer science.
"We'd eventually like to move objects and do work in a controlled
fashion on the molecular scale, and these vehicles are great test beds for
that. They're helping us learn the ground rules."
The nanocar consists of a chassis and axles made of well-defined organic
groups with pivoting suspension and freely rotating axles. The wheels are
buckyballs, spheres of pure carbon containing 60 atoms apiece. The entire
car measures just 3-4 nanometers across, making it slightly wider than a
strand of DNA. A human hair, by comparison, is about 80,000 nanometers in
diameter.
Other research groups have created nanoscale objects that are shaped like
automobiles, but study co-author Kevin F. Kelly, assistant professor of
electrical and computer engineering, said Rice's vehicle is the first that
actually functions like a car, rolling on four wheels in a direction
perpendicular to its axles.
Kelly and his group, experts in scanning tunneling microscopy (STM),
provided the measurements and experimental evidence that verified the
rolling movement.
"It's fairly easy to build nanoscale objects that slide around on a
surface," Kelly said. "Proving that we were rolling – not
slipping and sliding – was one of the most difficult parts of this
project."
 Credit: T. Sasaki/Rice University |
To do that, Kelly
and graduate student Andrew Osgood measured the movement of the nanocars
across a gold surface. At room temperature, strong electrical bonds hold
the buckyball wheels tightly against the gold, but heating to about 200
degrees Celsius frees them to roll. To prove that the cars were rolling
rather than sliding, Kelly and Osgood took STM images every minute and
watched the cars progress. Because nanocars' axles are slightly longer
than the wheelbase – the distance between axles – they could determine
the way the cars were oriented and whether they moved perpendicular to the
axles.
In addition, Kelly's team found a way to grab the cars with an STM probe
tip and pull them. Tests showed it was easier to drag the cars in the
direction of wheel rotation than it was to pull them sideways.
Synthesis of the nanocars also produced major challenges. Tour's research
group spent almost eight years perfecting the techniques used to make
them. Much of the delay involved finding a way to attach the buckyball
wheels without destroying the rest of the car. Palladium was used as a
catalyst in the formation of the axle and chassis, and buckyballs had a
tendency to shut down the palladium reactions, so finding the right method
to attach the wheels involved a good bit of trial and error.
The Rice team has already followed up the nanocar work by designing a
light-driven nanocar and a nanotruck that's capable of carrying a payload.
Other members of the research team include chemistry graduate student
Yasuhiro Shirai and post doctoral associate Yuming Zhao.
The research was funded by the Welch Foundation, Zyvex Corporation and the
National Science Foundation.
Rice University - http://media.rice.edu
October 20, 2005 - Human activities are degrading the Amazonian forest at twice the rate previously estimated, suggests a new study that adds the effects of logging to those of clear-cutting. The research appears in the 21 October issue of the journal Science, published by AAAS, the nonprofit science society.
Until now, satellite-based methods for measuring deforestation across large areas have only been capable of detecting clear-cut swaths of land, where all the trees are removed to clear space for farming or grazing.
A new satellite imaging method, developed by Gregory Asner of the Carnegie Institution of Washington and colleagues, detects deforestation on a finer scale, allowing researchers to identify areas where trees have been thinned, due mostly to "selective logging." In this type of deforestation, only certain marketable tree species are cut and logs are transported offsite to saw-mills. Little has been known about the extent or impacts of selective logging in Amazonia until now, according to the authors.
To detect and quantify the amount of selective logging in the five major timber production states of the Brazilian Amazon, the researchers used the new Carnegie Landsat Analysis System. This technology allowed them to delve into each pixel of the image produced by a trio of satellites and determine the percentage of forested and deforested land within each pixel. (In contrast, the conventional interpretation of a satellite image would consider each pixel as entirely forested or deforested.)
"This method gives us an incredible map of the ubiquitous but very diffuse types of disturbances that exist in Brazil or in any tropical forest," Asner said.
The researchers found that, from 1999 to 2002, selective logging added 60 to 128 percent more damaged forest area than was reported for deforestation alone in the same study period.
The total volume of harvested trees represents roughly 10 to 15 million metric tons of carbon removed from the ecosystem, according to the authors. They estimate that this amount represents a 25 percent increase in the overall flow of carbon from the Amazonian forest to the atmosphere.
Logging causes major ecological disruptions as well. Vines threading through the trees can pull down large amounts of vegetation when a tree falls. The forest also becomes drier and more flammable, as the shady canopy is thinned.
"Logged forests are areas of extraordinary damage," Asner said. "A tree crown can be 25 meters. When you knock down a tree it causes a lot of damage in the understory. It's a debris field down there."
American Association for the Advancement of Science - http://www.aaas.org
Tropical Trees Important to Ecosystem
The Earth Institute at Columbia University News Release
October 21, 2005 - The Earth Institute at Columbia University, October 2005 -- With human emissions of carbon dioxide on the rise, there is growing interest in maintaining the Earth's natural mechanisms that absorb and store carbon. A new study released this week in the on-line edition of the journal Science suggests that tree diversity in tropical forests plays a crucial role in determining how much carbon these natural storehouses are able to hold, as well as their ability to provide other crucial ecosystem services such as preventing erosion.
The study was led by Daniel Bunker and Shahid Naeem from the Department of Ecology, Evolution and Environmental Biology at Columbia University and Fabrice DeClerck from the Earth Institute at Columbia University. They simulated variations in forest diversity that resulted from a range of different extinction scenarios: those governed by biological characteristics such as low growth rate or limited growing range, those resulting from human activities such as selective logging, and those arising from environmental changes such as widespread drought. As a result of the simulations, they found that the types of trees remaining after each scenario played out had a large and widely varying effect on the amount of carbon a forest would be able to store.
"Carbon sequestration is just one of the many services that tropical forests provide," said DeClerck. "The more ecosystem functions you look at, the more important diversity becomes."
The study was based on data from the 120-acre Forest Dynamics Plot, a tropical forest on Barro Colorado Island in the Panama Canal run by the Smithsonian Tropical Research Institute that has been surveyed every five years since 1985. Previous studies have found that nearly half of the estimated 52 billion tons of carbon stored in the Earth's biomass is found in tropical forests. By simulating different extinction scenarios and analyzing the resulting mix of tree species, the team was able to determine how much carbon the forest was able to hold.
They found, for example, that converting tropical forests to less-diverse tree plantations containing only species with high wood density such as teak resulted in a 75 percent increase in the forest's carbon-storage capacity--so long as the trees are not harvested. By contrast, selectively logging trees with high wood density was found to reduce carbon storage by as much as 70 percent. Other scenarios, such as disease outbreaks that result in a selective loss of large or slow-growing trees, also produced a marked decline in the forest's ability to sequester carbon.
Moreover, the study concludes that forest diversity provides a measure of "biological insurance" that prevents large swings in carbon sequestration or any other service a healthy forest provides such as soil stability or fruit production that might arise from a single extinction scenario.
"In general, we found that when you have more species, things are more predictable," said Bunker, who was lead author on the study. "It's like having a diversified investment portfolio. Having many different types of trees lowers overall variability of a forest's ability to provide crucial services."
The Earth Institute at Columbia University is the world's leading academic center for the integrated study of Earth, its environment and society. The Earth Institute builds upon excellence in the core disciplines--earth sciences, biological sciences, engineering sciences, social sciences and health sciences--and stresses cross-disciplinary approaches to complex problems. Through research, training and global partnerships, The Earth Institute mobilizes science and technology to advance sustainable development, while placing special emphasis on the needs of the world's poor.
For more information, visit http://www.earth.columbia.edu
 ESO PR Photo 33a/05 is a colour-composite image of the central 5,500 light-years wide region of the spiral galaxy NGC 1097, obtained with the NACO adaptive optics on the VLT. More than 300 star forming regions - white spots in the image - are distributed along a ring of dust and gas in the image. At the centre of the ring there is a bright central source where the active galactic nucleus and its super-massive black hole are located. |
October 19, 2005 -
Astronomers using the European Southern Observatory's (ESO) Very Large
Telescope have released images showing in unprecedented detail how matter
spirals toward the black hole at the centre of a galaxy, in this case NGC
1097.
"This is the first time that a detailed view of the channelling
process of matter, from the main part of the galaxy down to the very end
in the nucleus is released," says Almudena Prieto (Max-Planck
Institute, Heidelberg, Germany), lead author of the paper describing these
results.
"These observations provide astronomers with new insights on how
supermassive black holes lurking inside galaxies get fed" adds
co-author Dr Witold Maciejewski from the University of Oxford.
Located about 45 million light-years away in the southern constellation
Fornax (the Furnace), NGC 1097 is a relatively bright, spiral galaxy seen
face-on. An image of NGC 1097 and its small companion, NGC 1097A, was
taken in December 2004 with the VIMOS instrument on ESO's Very Large
Telescope (VLT). In this image, available as ESO PR Photo 35d/04, NGC 1097
has a strongly elongated, non-circular feature called a bar, and a
prominent ring inside the bar.
NGC 1097 is a very moderate example of a galaxy with an active nucleus: it
emits more energy than can be accounted for through standard stellar
emission. The additional emission is thought to arise from matter (gas and
stars) falling into oblivion in a central black hole. However, NGC 1097
possesses a comparatively faint nucleus, and the black hole in its centre
must be on a very strict "diet": only a small amount of gas and
stars are apparently being swallowed by the black hole at any given
moment.
Astronomers have been trying for a long time to understand how the matter
is "gulped" down towards the black hole. Directly watching the
feeding process requires very high spatial resolution at the centre of
galaxies. This can be achieved with adaptive optics [1].
Thus, astronomers [2] obtained images of NGC 1097 with the adaptive optics
NACO instrument attached to Yepun, the fourth Unit Telescope of ESO's Very
Large Telescope (VLT). These new images probe with unprecedented detail
the presence and extent of material in the very proximity of the nucleus.
The resolution achieved with the images is about 0.15 arcsecond,
corresponding to about 30 light-years across. For comparison, this is only
8 times the distance between the Sun and its nearest star, Proxima
Centauri.
The newly released NACO near-infrared images show that the prominent ring
in the centre of NGC 1097 consists of more than 300 regions of star
formation, a factor four larger than previously known from Hubble Space
Telescope images. These regions can be seen as white spots all over the
ring in ESO PR Photo 33a/05. At the centre of the ring, a moderate active
nucleus is located. Details from the nucleus and its immediate
surroundings are however outshone by the overwhelming stellar light of the
galaxy seen as the bright diffuse emission inside the ring.
 ESO PR Photo 33b/05: The image shows the same central region but after a masking process has been applied to suppress the central stellar light of the galaxy. The central spiral arms are now seen as dark channels, some extending up to the star-forming ring. |
The astronomers
therefore applied a masking technique that allowed them to suppress the
stellar light (see ESO PR Photo 33b/05). This unveils a bright nucleus at
the centre, but mostly a complex central network of filamentary structures
spiralling down to the centre.
"Our analysis of the VLT/NACO images of NGC 1097 shows that these
filaments end up at the very centre of the galaxy", says co-author
Juha Reunanen from ESO.
"This network closely resembles those seen in computer models",
adds Witold Maciejewski from the University of Oxford, UK. "The
nuclear filaments revealed in the NACO images are the tracers of cold dust
and gas being channelled towards the centre to eventually ignite the
AGN."
The astronomers also note that the curling of the spiral pattern in the
innermost 300 lightyears seem indeed to confirm the presence of a
super-massive black hole in the centre of NGC 1097. Such a black hole in
the centre of a galaxy causes the nuclear spiral to wind up as it
approaches the centre, while in its absence the spiral would be unwinding
as it moves closer to the centre.
More information
This ESO Press Photo is based on research published in the October issue
of Astronomical Journal, vol. 130, p. 1472 ("Feeding the Monster: The
Nucleus of NGC 1097 at Subarcsecond Scales in the Infrared with the Very
Large Telescope", by M.Almudena Prieto, Witold Maciejewski, and Juha
Reunanen).
Notes
[1] "Adaptive Optics" is a modern technique by which
ground-based telescopes can overcome the undesirable blurring effect of
atmospheric turbulence. With adaptive optics, the images of stars and
galaxies captured by these instruments are at the theoretical limit, i.e.,
almost as sharp as if the telescopes were in space.
[2] The astronomers are M. Almudena Prieto (Max-Planck Institute for
Astronomy, Heidelberg, Germany), Witold Maciejewski (University of Oxford,
UK), and Juha Reunanen (ESO, Garching, Germany).
Particle Physics & Astronomy Research Council - http://www.pparc.ac.uk
