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miércoles, 31 de octubre de 2012

The Night Life: Why We Need Bats All the Time--Not Just on Halloween


Many species of bats in a cave in Trinidad.
Credit: Gerry Carter
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A leaf-nosed bat from the New World. The purpose of the leaf structure on the bat's face is not known for sure, but it may be important for echolocation.
Credit: Brock Fenton
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A vampire bat. Only three of the more than 1,100 species of bats are vampire bats. Contrary to popular belief, vampire bats are not true vampires because they do not suck blood. Rather, they cut a tiny slit in their prey's skin with their razor-sharp front teeth and lick up the resulting blood. Chemicals in the bat's saliva prevent clotting in order to keep the blood flowing until that bat has consumed its fill, which is generally less than an ounce. These anti-clotting chemicals are currently being researched for possible use as anticoagulants for people who are at high risk for blood clots, such as people who have recently suffered strokes.
Credit: Brock Fenton
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 The buds of this flower--a Pseudobombax ellipticum--open explosively at night and are primarily pollinated by bats.
Credit: Brock Fenten
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A little brown bat is released by a University of California, Santa Cruz graduate student. There are more than 1,000 bat species with varied wing spans, weights and facial features. Bats account for about 20 percent of all mammalian species.
Credit: Kate Langwig
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Hanging out: Hibernating little brown bats that have white-nose syndrome in a mine in New York.
Credit: Kate Langwig
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This bat has a long tongue for nectar feeding. The ears of bats are shaped to maximize detection of sound waves for echolocation. Bats emit sounds for echolocation through their mouths or noses, depending on the species.
Credit: Brock Fenton
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The sight of bats hanging upside down in creepy caves or fleeing in fluttery flocks from their subterranean haunts at dusk like "bats out of hell" may spook even the most rational, otherwise unflappable observer.
Nevertheless, on every day (and night) but Halloween, these much maligned creaturesof the night should be loved, not feared. Why? Because, contrary to popular belief, bats do not attack people; bats do not tangle in people's hair; and even vampire bats are not true vampires. (Vampire bats lick blood but do not suck blood.)
What's more, unbeknownst to most people, bats make important contributions to ecology, the economy and even to the search for new technologies.
Important ecological roles of bats
Bats, which live on all continents except Antarctica, are essential members of many types of ecosystems, ranging from rain forests to deserts. By fulfilling their ecological roles, bats promote biodiversity and support the health of their ecosystems.
The ecological roles of bats include pollinating and dispersing the seeds of hundreds of species of plants. For example, bats serve as major pollinators of many types of cacti that open their flowers only at night, when bats are active. In addition, bats eat copious quantities of insects and other arthropods. On a typical night, a bat consumes the equivalent of its own body weight in these creatures.
Economic value of bats
As bats fulfill their ecological roles, they provide many economically important services. For example, bats serve as essential pollinators for various types of commercially-valuable crops, including bananas, mangos and guavas. In addition, bats consume many crop-eating insects and thereby reduce farmers' need for pesticides.
All told, according to a 2011 study published in Science, insect consumption by bats reduces the pesticide bill of the agriculture industry in the United States by roughly $22.9 billion per year on average. Another study, partially funded by the National Science Foundation (NSF), calculated the average annual value of Brazilian free-tailed bats as pest control for cotton production in eight counties of south-central Texas at about $741,000.
Inspiration for high-tech innovations
Bats offer much to the field of biomimetics, which is the science of modeling cutting-edge technologies based on natural forms. After all, the development of sonar for ships and ultrasound was partly inspired by bat echolocation. Echolocation is the navigation system used by most bats to find and follow their quick-moving insect prey at night, sometimes via daring aerial dogfights and speedy chases--all without crashing into trees, buildings or other obstructions.
Here's how bat echolocation works: A bat emits a structured high frequency sound, usually beyond the range of human hearing, which bounces off surrounding objects and then returns echoes to the bat. By comparing the delay and structure of the echoes to those of the original sound, a bat can calculate its own distance from the objects and determine size and shape of those objects and thereby construct a three-dimensional map of its environment.
Even though a bat's brain is only peanut-sized, bat echolocation is so sensitive that a bat flying 25 miles per hour in complete darkness would recognize differences in echo delays of less than a microsecond, allowing the bat to distinguish even a junebug from an underlying leaf, according to Universal Sense: How Hearing Shapes the Mind, which was authored by neuroscientist Seth S. Horowitz, whose earlier work was funded by NSF.
How do bats stay focused on sonar echoes from their target prey without being overwhelmed by the cacophony of echoes from other objects? That question is answered by an NSF video about recent research on bat echolocation.
Another bat trait that provides potential grist for future application is the flying ability of bats, which are the only mammals that can fly on their own power. The aerodynamic repertoire of bats, which includes changing flight direction by turning 180 degrees within just three wing beats while flying at full tilt, would be the envy of any fighter pilot, said Horowitz.
Bats are such nimble flyers because of the dexterity of their wings, which--unlike insect and bird wings--are structured to fold during flight, similar to the way that a human hand folds. Also, their wings are draped by stretchy skin and are powered by special muscles. Ongoing research about the structure of bat wings and the mechanics of bat flight may ultimately lead to the development of technologies that improve the maneuverability of airplanes.
See the wonders of bat flight in a Science Nation video that describes an NSF-funded project.
A new, fast-spreading bat epidemic
The multi-faceted importance of bats only compounds the tragic dimensions of a new fatal epidemic in bats known as white-nose syndrome. The disease, which is named for a fungal growth around the muzzles, wings and other body parts of hibernating bats, was first discovered in the United States during the winter of 2006-2007 in a popular tourist cave in upstate New York.
Since then, the continually spreading disease, which has reached the central United States and Canada, has killed more than five million bats, including up to 95 percent of some bat species in some locations. Scientists believe that white-nose syndrome--which is currently incurable, untreatable and unstoppable--will inevitably drive some bat species to extinction. The disease is similar to a fungal epidemic that is ravaging frog populations in the United States.
The white-nose fungus causes skin lesions on the wings of hibernating bats, which may damage the animals' hydration, electrolyte balance, circulation and temperature regulation, ultimately causing death by starvation and dehydration. Behavioral changes in infected bats include a failure to wake normally in response to disturbances and premature emergence from hibernation.
The white-nose fungus is known to have existed in bats in Europe before its arrival in the United States. But, as far as scientists know, the fungus does not kill European bats, possibly because European bats species are genetically protected from the disease. Because the presence of the disease-causing fungus in Europe predates its arrival in the United States, and because the fungus was first found in the United States in a tourist cave, scientists suspect that the disease was imported to the United States from Europe, perhaps on the clothing or equipment of traveling cavers.
Differences in susceptibility
White-nose syndrome is currently known to affect six North American bat species--two of which are less susceptible to the disease than the four others. With NSF funding, Marm Kilpatrick of the University of California at Santa Cruz, Kate Langwig of the University of California, Santa Cruz and Boston University and their colleagues are currently working to identify the reasons for these differences in susceptibility.
So far, a recent study led by Langwig showed that social behavior may influence mortality rates. Specifically, the study indicates that as the size of infected colonies shrinks because of deaths from white-nose fungus, death rates within colonies of species that hibernate singly tend to stabilize. By contrast, death rates within colonies of species that hibernate in tightly packed groups do not.
Amazingly, the research also has shown that the little brown bat, a species common in the northeast of North America and widely affected by white-nose syndrome, has been--for unknown reasons--becoming less gregarious, going from a species that tended to hibernate in dense clusters to one that now tends to hibernate singly. By changing their behavior, these bats may be reducing disease transmission within their colonies and thereby saving themselves from extinction. By contrast, the Indiana bat, a gregarious species that is listed as an endangered species, is continuing to hibernate in dense clusters and will therefore probably go extinct.
"Our research gives us an indication of which species face the highest likelihood of extinction, so we can focus management efforts and resources on protecting those species," said Langwig. For example, the U.S. Fish and Wildlife Service is incorporating Langwig's study results about little brown bats into ongoing deliberations about whether to classify the species as endangered.
Kilpatrick and Langwig are currently researching other factors, in addition to social behavior, that may influence disease susceptibility. One possibility, Kilpatrick says, is that some bat species are less susceptible to white-nose syndrome because their skin hosts bacterial communities that have anti-fungal properties and so protect them from the white-nose fungus.
In addition, Kilpatrick is currently investigating whether and how particular microclimates in caves and mines used by hibernating bats may be affecting the spread of white-nose syndrome. "Some bat species or some individual bats may prefer to hibernate in caves or mines that are relatively hot or cold, or wet or dry," Kilpatrick said. "We want to know whether such environmental conditions impact susceptibility to white-nose syndrome."
Impacts of bat losses
Other topics that are ripe for research involve the responses of ecosystems to plummeting bat populations. "Insect populations are very variable," said Langwig. "So in order to identify the impacts of bat declines on insect populations, we would need many years of data on insect populations before the arrival of white-nose syndrome as well as many years of data after its arrival for comparison." But because white-nose syndrome is so new and has spread so fast, scientists do not yet have enough data to determine how the absence of bats will impact their ecosystems, he said.
Other threats to bat survival besides white-nose syndrome
Other threats to bat survival include the use of pesticides and insecticides, habitat loss and the hunting of bats for bushmeat in some regions. In addition, for reasons that are not fully understood, migrating bats are apparently attracted to wind turbines; large numbers of bats have been killed on wind farms in recent years.
More bat facts
Learn more about bats from a Halloween chat with Horowitz sponsored by The Washington Post.
--  Lily Whiteman, National Science Foundation (703) 292-8310 lwhitema@nsf.gov
Investigators Thomas Kunz
Kate Langwig
James Simmons
Seth Horowitz
Gary McCracken
Jeffrey Foster
Winifred Frick
A. Marm Kilpatrick
Related Institutions/Organizations Brown University
Trustees of Boston University
Total Grants $895,322
Related Websites
Science Nation Video; Butterflies and Bats Reveal Clues About Spread of Infectious Disease: http://www.nsf.gov/news/special_reports/science_nation/butterfliesbats.jsp
 The National Science Foundation (NSF)
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NASA - A Ghost in Cepheus


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MARS: NASA Rover's First Soil Studies Help Fingerprint Martian Minerals


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NASA Rover's First Soil Studies Help Fingerprint Martian Minerals
PASADENA, Calif. -- NASA's Mars rover Curiosity has completed initial experiments showing the mineralogy of Martian soil is similar to weathered basaltic soils of volcanic origin in Hawaii.
The minerals were identified in the first sample of Martian soil ingested recently by the rover. Curiosity used its Chemistry and Mineralogy instrument (CheMin) to obtain the results, which are filling gaps and adding confidence to earlier estimates of the mineralogical makeup of the dust and fine soil widespread on the Red Planet.
"We had many previous inferences and discussions about the mineralogy of Martian soil," said David Blake of NASA Ames Research Center in Moffett Field, Calif., who is the principal investigator for CheMin. "Our quantitative results provide refined and in some cases new identifications of the minerals in this first X-ray diffraction analysis on Mars."
The identification of minerals in rocks and soil is crucial for the mission's goal to assess past environmental conditions. Each mineral records the conditions under which it formed. The chemical composition of a rock provides only ambiguous mineralogical information, as in the textbook example of the minerals diamond and graphite, which have the same chemical composition, but strikingly different structures and properties.
CheMin uses X-ray diffraction, the standard practice for geologists on Earth using much larger laboratory instruments. This method provides more accurate identifications of minerals than any method previously used on Mars. X-ray diffraction reads minerals' internal structure by recording how their crystals distinctively interact with X-rays. Innovations from Ames led to an X-ray diffraction instrument compact enough to fit inside the rover.
These NASA technological advances have resulted in other applications on Earth, including compact and portable X-ray diffraction equipment for oil and gas exploration, analysis of archaeological objects and screening of counterfeit pharmaceuticals, among other uses.
"Our team is elated with these first results from our instrument," said Blake. "They heighten our anticipation for future CheMin analyses in the months and miles ahead for Curiosity."
The specific sample for CheMin's first analysis was soil Curiosity scooped up at a patch of dust and sand that the team named Rocknest. The sample was processed through a sieve to exclude particles larger than 0.006 inch (150 micrometers), roughly the width of a human hair. The sample has at least two components: dust distributed globally in dust storms and fine sand originating more locally. Unlike conglomerate rocks Curiosity investigated a few weeks ago, which are several billion years old and indicative of flowing water, the soil material CheMin has analyzed is more representative of modern processes on Mars.
"Much of Mars is covered with dust, and we had an incomplete understanding of its mineralogy," said David Bish, CheMin co-investigator with Indiana University in Bloomington. "We now know it is mineralogically similar to basaltic material, with significant amounts of feldspar, pyroxene and olivine, which was not unexpected. Roughly half the soil is non-crystalline material, such as volcanic glass or products from weathering of the glass. "
Bish said, "So far, the materials Curiosity has analyzed are consistent with our initial ideas of the deposits in Gale Crater recording a transition through time from a wet to dry environment. The ancient rocks, such as the conglomerates, suggest flowing water, while the minerals in the younger soil are consistent with limited interaction with water."
During the two-year prime mission of the Mars Science Laboratory Project, researchers are using Curiosity's 10 instruments to investigate whether areas in Gale Crater ever offered environmental conditions favorable for microbial life.
NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the project for NASA's Science Mission Directorate, Washington, and built Curiosity and CheMin.
For more information about Curiosity and its mission, 
For more information about a commercial application of the CheMin technology, 
You can follow the mission on Facebook and Twitter 
 
 
Guy Webster / D.C. Agle 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@jpl.nasa.gov / agle@jpl.nasa.gov

Rachel Hoover 650-604-4789
NASA Ames Research Center, Moffett Field, Calif.
rachel.hoover@nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown@nasa.gov
NASA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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martes, 30 de octubre de 2012

ESA - Living Planet Programme - MetOp-A captures Hurricane Sandy


 Europe's polar orbiting weather satellite, MetOp-A, captured this image of Hurricane Sandy just as the huge storm hit the east coast of the US yesterday. The MetOp programme is developed as a joint undertaking between ESA and Eumetsat for operational meteorology.
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Sandy approaches

Hurricane Sandy as it hit the US east coast - as seen by the AVHRR instrument onboard EUMETSAT's Metop-A satellite on 29/10/12 at 14:16 UTC.
Copyright: 2012 EUMETSAT
ESA
Guillermo Gonzalo Sánchez Achutegui
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NASA's Fermi to Reveal New Findings About the Early Universe


NASA's Fermi to Reveal New Findings About the Early Universe
 
 
WASHINGTON -- NASA will hold a media teleconference at 2 p.m. EDT on Thursday, Nov. 1, to discuss new measurements using gamma rays to investigate ancient starlight with the agency's Fermi Gamma-ray Space Telescope. 

Science Journal has embargoed details until 2 p.m. on Nov. 1. 

The teleconference panelists are: 

- Justin Finke, astrophysicist, Naval Research Laboratory, Washington 
- Marco Ajello, astrophysicist, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, and the Space Sciences Laboratory, University of California at Berkeley 
- Volker Bromm, associate professor, department of astronomy, University of Texas at Austin 

For dial-in information, journalists should e-mail their name, media affiliation and telephone number to J.D. Harrington atj.d.harrington@nasa.gov. 

Audio of the teleconference will be streamed live on NASA's website at: 



For more information about NASA's Fermi Gamma-ray Space Telescope, visit: 



NASA's Fermi Space Telescope Explores New Energy Extremes


 



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New sources emerge and old sources fade as the LAT's view extends into higher energies. Credit: NASA/DOE/Fermi LAT Collaboration and A. Neronov et al. 

Fermi's view of the gamma-ray sky continually improves. This image of the entire sky includes three years of observations by Fermi's Large Area Telescope (LAT). It shows how the sky appears at energies greater than 1 billion electron volts (1 GeV). Brighter colors indicate brighter gamma-ray sources. A diffuse glow fills the sky and is brightest along the plane of our galaxy (middle). Discrete gamma-ray sources include pulsars and supernova remnants within our galaxy as well as distant galaxies powered by supermassive black holes. Credit: NASA/DOE/Fermi LAT Collaboration 
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This all-sky Fermi view includes only sources with energies greater than 10 GeV. From some of these sources, Fermi's LAT detects only one gamma-ray photon every four months. Brighter colors indicate brighter gamma-ray sources.
Credit: NASA/DOE/Fermi LAT Collaboration



More than half of the sources above 10 GeV are black-hole-powered active galaxies. More than a third of the sources are completely unknown, having no identified counterpart detected in other parts of the spectrum. Credit: NASA's Goddard Space Flight Center 

"As Fermi's exposure constantly improves our view of hard sources, ground-based telescopes are becoming more sensitive to lower-energy gamma rays, allowing us to bridge these two energy regimes," Fortin added.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership. Fermi is managed by Goddard. It was developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

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WASHINGTON -- After more than three years in space, NASA's Fermi Gamma-ray Space Telescope is extending its view of the high-energy sky into a largely unexplored electromagnetic range. Today, the Fermi team announced its first census of energy sources in this new realm.


ermi's Large Area Telescope (LAT) scans the entire sky every three hours, continually deepening its portrait of the sky in gamma rays, the most energetic form of light. While the energy of visible light falls between about 2 and 3 electron volts, the LAT detects gamma rays with energies ranging from 20 million to more than 300 billion electron volts (GeV).

At higher energies, gamma rays are rare. Above 10 GeV, even Fermi's LAT detects only one gamma ray every four months from some sources.



"Before Fermi, we knew of only four discrete sources above 10 GeV, all of them pulsars," said David Thompson, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md. "With the LAT, we've found hundreds, and we're showing for the first time just how diverse the sky is at these high energies."

Any object producing gamma rays at these energies is undergoing extraordinary astrophysical processes. More than half of the 496 sources in the new census are active galaxies, where matter falling into a supermassive black hole powers jets that spray out particles at nearly the speed of light.

Only about 10 percent of the known sources lie within our own galaxy. They include rapidly rotating neutron stars called pulsars, the expanding debris from supernova explosions, and in a few cases, binary systems containing massive stars.

More than a third of the sources are completely unknown, having no identified counterpart detected in other parts of the spectrum. With the new catalog, astronomers will be able to compare the behavior of different sources across a wider span of gamma-ray energies for the first time.

Just as bright infrared sources may fade to invisibility in the ultraviolet, some of the gamma-ray sources above 1 GeV vanish completely when viewed at higher, or "harder," energies.

One example is the well-known radio galaxy NGC 1275, which is a bright, isolated source below 10 GeV. At higher energies it fades appreciably and another nearby source begins to appear. Above 100 GeV, NGC 1275 becomes undetectable by Fermi, while the new source, the radio galaxy IC 310, shines brightly.

The Fermi hard-source list is the product of an international team led by Pascal Fortin at the Ecole Polytechnique's Laboratoire Leprince-Ringuet in Palaiseau, France, and David Paneque at the Max Planck Institute for Physics in Munich.

The catalog serves as an important roadmap for ground-based facilities called Atmospheric Cherenkov Telescopes, which have amassed about 130 gamma-ray sources with energies above 100 GeV. They include the Major Atmospheric Gamma Imaging Cherenkov telescope (MAGIC) on La Palma in the Canary Islands, the Very Energetic Radiation Imaging Telescope Array System (VERITAS) in Arizona, and the High Energy Stereoscopic System (H.E.S.S.) in Namibia.

"Our catalog will have a significant impact on ground-based facilities' work by pointing them to the most likely places to find gamma-ray sources emitting above 100 GeV," Paneque said.

Compared to Fermi's LAT, these ground-based observatories have much smaller fields of view. They also make fewer observations because they cannot operate during daytime, bad weather or a full moon.
NASA
Guillermo Gonzalo Sánchez Achutegui
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lunes, 29 de octubre de 2012

ESO: 84 millones de estrellas y contando;VISTA crea el mayor catálogo del centro de nuestra galaxia llevado a cabo hasta el momento


Mosaico gigapíxel de las partes centrales de la Vía Láctea obtenido por VISTA
 Esta sorprendente imagen de la zona central de la Vía Láctea se obtuvo con el telescopio de sondeo VISTA, instalado en el Observatorio Paranal de ESO, en Chile. Esta enorme imagen es de 108.200 por 81.500 píxeles, y contiene un total de casi nueve mil millones de píxeles. Fue creada combinando miles de imágenes individuales de VISTA, obtenidas con tres filtros infrarrojos diferentes, creando un único y monumental mosaico. Estos datos forman parte del sondeo público VVV y han sido utilizados para estudiar el mayor número de estrellas individuales en las zonas centrales de la Vía Láctea estudiadas hasta el momento. Dado que VISTA tiene una cámara sensible a la luz infrarroja, puede ver a través de gran parte del polvo que bloquea el rango óptico, pese a lo cual pueden distinguirse en esta imagen muchos filamentos de polvo opacos.
Esta imagen es demasiado grande para poder verla en toda su resolución y puede apreciarse mejor utilizando la herramienta de zoom.
Crédito:
ESO/VVV Consortium
Acknowledgement: Ignacio Toledo, Martin Kornmesser
Visión de amplio campo de la Vía Láctea, en la que se aprecia el tamaño de una imagen gigapíxel de VISTA.
Esta visión de muy amplio campo de la Vía Láctea muestra el tamaño de la nueva imagen infrarroja del centro de la galaxia obtenida por VISTA. Estos datos cubren la región conocida como núcleo de la galaxia, y han sido utilizados para estudiar el mayor número de estrellas individuales en las zonas centrales de la Vía Láctea estudiadas hasta el momento. La región cubierta por el nuevo mosaico de VISTA se muestra dentro de un rectángulo.
Crédito:
ESO/Nick Risinger (skysurvey.org)
Music: Disasterpeace
 
Comparación óptico-infrarroja de las partes centrales de la Vía Láctea
 Esta espectacular imagen compara un enorme mosaico en luz infrarroja del telescopio de sondeo VISTA y un mosaico en el rango visible de la misma región tomada con un telescopio pequeño. Dado que VISTA tiene una cámara sensible a la luz infrarroja, puede ver a través de gran parte del polvo que bloquea la visión y dar una imagen clara de la multitud de estrellas situadas en la zona central de la Vía Láctea.
Crédito:
ESO/VVV Consortium/Nick Risinger (skysurvey.org)
Acknowledgement: Ignacio Toledo, Martin Kornmesser
Diagrama color–magnitud del núcleo galáctico
Este diagrama plasma, para unos 84 millones de estrellas de la zona central de la Vía Láctea, el brillo de cada estrella frente a su color, medidas en numerosas imágenes del telescopio VISTA como parte del sondeo VVV. Esta es la primera vez que se ha llevado a cabo un diagrama color-magnitud de este tipo para todo el núcleo galáctico, lo que ha dado como resultado el diagrama color–magnitud más rico jamás creado. Las estrellas más brillantes aparecen hacia la parte superior, las más débiles hacia la parte inferior, las más rojas hacia la derecha y las más azules hacia la izquierda. La mayor parte de las estrellas se encuentran en las regiones amarillas, y unas pocas aparecen en la parte azul del diagrama. Las estrellas gigantes azules, más evolucionadas, aparecen en la parte superior derecha, y las estrellas enanas, más débiles, en la parte inferior.
Crédito: ESO/VVV Consortium 
Mapa de la visión de VISTA del centro de la Vía Láctea con anotaciones
Esta visión infrarroja de la parte central de la Vía Láctea del sondeo VVV VISTA ha sido etiquetada con el fin de mostrar una selección de las numerosas nebulosas y cúmulos que hay en esta parte del cielo. Messier 8 (la Nebulosa de La Laguna), Messier 20 (la Nebulosa Trífida), NGC 6357 (la Nebulosa Guerra y Paz) y NGC 6334 (la Nebulosa Pata de Gato) son todas nebulosas fácilmente visibles. El resto de objetos etiquetados son cúmulos globulares de estrellas. Nótese que esta imagen es de menor resolución que la imagen completa y los objetos pueden verse mejor en la versión con zoom. 
Crédito:
ESO/VVV Consortium
Acknowledgement: Ignacio Toledo, Martin Kornmesser



Utilizando una enorme imagen multi gigapíxel del telescopio de sondeo VISTA, instalado en el Observatorio Paranal de ESO, un equipo internacional de astrónomos ha creado un catálogo de más de 84 millones de estrellas situadas en las zonas centrales de la Vía Láctea. Este gigantesco conjunto de datos contiene más de diez veces más estrellas que estudios previos y es un importante avance para el conocimiento de nuestra galaxia anfitriona. La imagen da al espectador una visión sobre la cual puede hacerse zoom, acercándose a la parte central de nuestra galaxia.
“Observando en detalle los millares de estrellas que rodean el centro de la Vía Láctea, podemos aprender mucho más sobre la formación y evolución, no sólo de nuestra galaxia, sino también sobre la de las galaxias espirales en general,” explica Roberto Saito (Pontificia Universidad Católica de Chile, Universidad de Valparaíso y miembro de The Milky Way Millennium Nucleus, Chile), investigador principal de este estudio.
Muchas galaxias espirales, incluyendo nuestra galaxia anfitriona, la Vía Láctea, tienen una alta concentración de estrellas viejas rodeando el centro, lo que los astrónomos denominan núcleo (bulge en inglés). Comprender la formación y evolución del núcleo de la Vía Láctea es vital para el conocimiento de la galaxia como un todo. Sin embargo, conseguir observaciones detalladas de esta región no es una tarea sencilla.
Observar el núcleo de la Vía Láctea es muy difícil, ya que está oscurecido por el polvo,” afirma Dante Minniti (Pontificia Universidad Catolica de Chile, Chile), coautor del estudio. “Para penetrar en el corazón de la galaxia, necesitamos observar en el rango infrarrojo de la luz, el cual se ve menos afectado por el polvo”.
ESO cuenta con el telescopio de sondeo VISTA  (Visible and Infrared Survey Telescope for Astronomy), que cuenta con un espejo de gran tamaño (4,1 metros de diámetro), un amplio campo de visión y detectores infrarrojos muy sensibles, lo que lo convierte en la mejor herramienta disponible para llevar a cabo esta tarea. El equipo de astrónomos está utilizando datos del programa VISTA Variables in the Via Lactea (VVV) [1], uno de los seis sondeos públicos llevados a cabo por VISTA. Los datos han sido utilizados para crear una inmensa imagen en color de 54.000 por 40.500 píxeles, que contiene un total de dos mil millones de píxeles. Esta es una de las imágenes astronómicas más grandes jamás elaborada. El equipo ha utilizado estos datos para compilar el mayor catálogo creado hasta el momento de la concentración de estrellas en la región central de la Vía Láctea [2].
Para ayudar en el análisis de este enorme catálogo, el brillo de cada estrella se plasma en un diagrama frente a su color para unos 84 millones de estrellas con el fin de crear un diagrama color-magnitud. Este análisis contiene más de diez veces más estrellas que ningún estudio previo y es la primera vez que se ha hecho con todo el núcleo. Los diagramas de color-magnitud son herramientas muy valiosas utilizadas frecuentemente por los astrónomos para estudiar las diferentes propiedades físicas de las estrellas, como sus temperaturas, masas y edades [3].
Cada estrella ocupa un punto particular en este diagrama en cualquier momento de su vida. El lugar en el que caiga depende de cuán brillante y caliente sea. Dado que los nuevos datos nos ofrecen una foto de todas las estrellas de una vez, podemos hacer un censo de todas las estrellas en esta parte de la Vía Láctea,” explica Dante Minniti.
El nuevo diagrama color–magnitud del núcleo contiene un tesoro oculto de información sobre la estructura y los contenidos de la Vía Láctea. Un resultado interesante revelado por los nuevos datos indica el gran número de estrellas enanas rojas débiles que existen en la zona. Se trata de estrellas candidatas a albergar pequeños exoplanetas, objetos que pueden ser descubiertos utilizando la técnica de los tránsitos [4].
Otro aspecto que hace que el sondeo VVV sea tan importante es que se trata de uno de los sondeos públicos de ESO VISTA. Esto significa que todos los datos se ponen a disposición del público a través del archivo de ESO, por lo cual esperamos que esta enorme fuente de información siga ofreciéndonos resultados interesantes", concluye Roberto Saito.

Notas

[1] El sondeo VVV (VISTA Variables in the Via Lactea) es un sondeo público de ESO centrado en la exploración del plano austral y el núcleo de la Vía Láctea a través de cinco filtros de infrarrojo cercano. Comenzó en el año 2010 y obtuvo un total de 1.929 horas de tiempo de observación durante un periodo de cinco años.
[2] La imagen utilizada en este trabajo cubre unos 315 grados cuadrados del cielo (algo menos de un 1% del cielo completo) y las observaciones fueron llevadas a cabo utilizando tres filtros infrarrojos diferentes. El catálogo define las posiciones de las estrellas junto con el brillo medido a través de diferentes filtros. Contiene unos 173 millones de objetos, de los cuales unos 84 millones han sido confirmados como estrellas. Los demás objetos o eran demasiado débiles, o se confundían con objetos demasiado próximos, o estaban afectados por algún artefacto, de manera que no era posible obtener información precisa. Otros eran objetos extensos como galaxias distantes.
[3] Un diagrama color–magnitud es un gráfico que sitúa el brillo aparente de una serie de objetos  frente a su color. El color se mide comparando el aspecto de los objetos brillantes a través de varios filtros. Es parecido a un diagrama Hertzsprung-Russell (HR) pero este último marca la luminosidad (o magnitud absoluta) más que el brillo aparente y también es necesario conocer la distancia de las estrellas.
[4] El método del tránsito para encontrar planetas busca la pequeña alteración que provoca el planeta al pasar frente a su estrella, bloqueando su luz hacia nosotros. El pequeño tamaño de las estrellas enanas rojas, típicamente de tipo espectral K y M, hace que esa alteración en su brillo sea relativamente mayor cuando planetas de baja masa pasan frente a ellas, haciendo más fácil la búsqueda de planetas a su alrededor.

Información adicional

Este trabajo fue presentado en el artículo “Milky Way Demographics with the VVV Survey I. The 84 Million Star Colour–Magnitude Diagram of the Galactic Bulge“, por R. K. Saito et al., que aparecerá en la revista Astronomy & Astrophysics.
El equipo está compuesto por R. K. Saito (Pontificia Universidad Católica de Chile, Santiago, Chile; Universidad de Valparaíso, Chile; The Milky Way Millennium Nucleus, Chile); D. Minniti (Pontificia Universidad Católica de Chile; Observatorio del Vaticano); B. Dias (Universidad de São Paulo, Brasil); M. Hempel (Pontificia Universidad Católica de Chile); M. Rejkuba (ESO, Garching, Alemania); J. Alonso-García (Pontificia Universidad Católica de Chile); B. Barbuy (Universidad de São Paulo); M. Catelan (Pontificia Universidad Católica de Chile); J. P. Emerson (Queen Mary University of London, Reino Unido); O. A. Gonzalez (ESO, Garching, Alemania); P. W. Lucas (Universidad de Hertfordshire, Hatfield, Reino Unido); y M. Zoccali (Pontificia Universidad Católica de Chile).
El año 2012 marca el 50 aniversario de la creación del Observatorio Europeo Austral (European Southern Observatory, ESO). ESO es la principal organización astronómica intergubernamental de Europa y el observatorio astronómico más productivo del mundo. Quince países apoyan esta institución: Alemania, Austria, Bélgica, Brasil, Dinamarca, España, Finlandia, Francia, Holanda, Italia, Portugal, el Reino Unido, República Checa, Suecia y Suiza. ESO desarrolla un ambicioso programa centrado en el diseño, construcción y operación de poderosas instalaciones de observación terrestres que permiten a los astrónomos hacer importantes descubrimientos científicos. ESO también desarrolla un importante papel al promover y organizar la cooperación en investigación astronómica. ESO opera tres sitios únicos de observación de categoría mundial en Chile: La Silla, Paranal y Chajnantor. En Paranal, ESO opera el Very Large Telescope, el observatorio óptico más avanzado del mundo, y dos telescopios de rastreo. VISTA trabaja en el infrarrojo y es el telescopio de rastreo más grande del mundo, y el VST (sigla en inglés del Telescopio de Rastreo del VLT) es el telescopio más grande diseñado exclusivamente para rastrear el cielo en luz visible. ESO es el socio europeo de un revolucionario telescopio, ALMA, el proyecto astronómico más grande en desarrollo. Actualmente ESO está planificando el European Extremely Large Telescope, E-ELT, el telescopio óptico y de infrarrojo cercano de categoría 40 metros, que llegará a ser “el ojo más grande del mundo para mirar el cielo”.

Enlaces

 ESO
 http://www.eso.org/public/chile/videos/eso1242a/
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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ESA Portal - Spain - Una burbuja en el caldero cósmico

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Its orbit takes it almost a third of the way to the Moon, so that astronomers can enjoy long, uninterrupted views of celestial objects.
This unique X-ray observatory was launched by Ariane 5 from the European spaceport at Kourou in French Guiana on 10 December 1999. It derives its name from its X-ray multi-mirror design and honours Sir Isaac Newton. 
Credits: ESA - D. Ducros
Burbuja de Wolf-Rayet
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 A giant bubble blown by the massive Wolf-Rayet star HD 50896, the pink star in the centre of the image.

X-ray data from XMM-Newton’s EPIC camera are shown in blue, while optical images were acquired using the Michigan Curtis Schmidt Telescope at Cerro Tololo Inter-American Observatory (CTIO) and presented in red (H-alpha) and green (OIII).

The bubble, known as S 308, is about 60 light-years across and is located 5000 light-years away in the constellation of Canis Major.

Credits: ESA, J. Toala & M. Guerrero (IAA-CSIC), Y.-H. Chu & R. Gruendl (UIUC), S. Arthur (CRyA–UNAM), R. Smith (NOAO/CTIO), S. Snowden (NASA/GSFC) and G. Ramos-Larios (IAM)

 El telescopio espacial XMM-Newton de la ESA nos envía una imagen de este fantasmagórico rostro en rayos X para celebrar Halloween. Se trata de una burbuja producida por el intenso viento de una estrella que ‘vivirá rápido y morirá joven’.

Esta burbuja se encuentra a 5000 años luz de la Tierra, en la constelación de Canis Major, el ‘Can Mayor’, y parece la cara de un perro o de un lobo.
La burbuja abarca unos 60 años luz, y se creó bajo la acción del intenso viento emitido por la estrella de Wolf-Rayet HD 50896 – la estrella rosa en el centro de la imagen, que sería el ojo derecho de este peculiar espectro.
Las estrellas de Wolf-Rayet son astros calientes y masivos – con una masa unas 35 veces mayor que la de nuestro Sol – que expulsan grandes cantidades de materia a través de un intenso viento estelar, una corriente de plasma a millones de grados centígrados que emite rayos X, representados en azul en esta imagen.
El material que rodea a la estrella se enciende en tonos rojizos al interactuar con el fuerte viento estelar, como se puede ver en la zona de la ‘mejilla’.
El halo verde es el resultado de la colisión de una onda de choque que escapa de la estrella con las capas de materia expulsada con anterioridad.
Una ‘llamarada’ de rayos X en la esquina superior izquierda da forma a la oreja del ‘lobo’, y la región más densa de la esquina inferior derecha se asemeja a un hocico.
La ‘hora de las brujas’ se acerca para esta burbuja y para su estrella. La burbuja explotará y se terminará dispersando, mientras que la estrella terminará sus días con una dramática explosión de supernova.
El artículo X-Ray Emission from the Wolf-Rayet Bubble S 308, de J. Toala et al, ha sido publicado en el Astrophysical Journal 755, 77 (2012).
ESA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com 
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domingo, 28 de octubre de 2012

ESA - Space Science - Earth’s magnetosphere behaves like a sieve


Solar wind entry at low latitudes
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 When Earth’s magnetic field and the interplanetary magnetic field are aligned, for example in a northward orientation as indicated by the white arrow in this graphic, Kelvin–Helmholtz waves are generated at low (equatorial) latitudes. 
Credits: AOES Medialab

ESA’s quartet of satellites studying Earth’s magnetosphere, Cluster, has discovered that our protective magnetic bubble lets the solar wind in under a wider range of conditions than previously believed.

Earth’s magnetic field is our planet’s first line of defence against the bombardment of the solar wind. This stream of plasma is launched by the Sun and travels across the Solar System, carrying its own magnetic field with it.
Depending on how the solar wind’s interplanetary magnetic field – IMF – is aligned with Earth’s magnetic field, different phenomena can arise in Earth’s immediate environment.
One well-known process is magnetic reconnection, where magnetic field lines pointing in opposite directions spontaneously break and reconnect with other nearby field lines. This redirects their plasma load into the magnetosphere, opening the door to the solar wind and allowing it to reach Earth.
Under certain circumstances this can drive ‘space weather’, generating spectacular aurorae, interrupting GPS signals and affecting terrestrial power systems.  
Solar wind entry at high latitudes
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When the interplanetary magnetic field, indicated by the white arrow, is oriented westward (dawnward) or in the opposite, eastward (duskward) direction, magnetopause boundary layers at higher latitude become most subject to Kelvin–Helmholtz instabilities. 
Credits: AOES Medialab

In 2006, Cluster made the surprising discovery that huge, 40 000 km swirls of plasma along the boundary of the magnetosphere – the magnetopause – could allow the solar wind to enter, even when Earth’s magnetic field and the IMF are aligned.
These swirls were found at low, equatorial latitudes, where the magnetic fields were most closely aligned.
These giant vortices are driven by a process known as the Kelvin–Helmholtz (KH) effect, which can occur anywhere in nature when two adjacent flows slip past each other at different speeds.
Examples include waves whipped up by wind sliding across the surface of the ocean, or in atmospheric clouds.
Analysis of Cluster data has now found that KH waves can also occur at a wider range of magnetopause locations and when the IMF is arranged in a number of other configurations, providing a mechanism for the continuous transport of the solar wind into Earth’s magnetosphere.
“We found that when the interplanetary magnetic field is westward or eastward, magnetopause boundary layers at higher latitude become most subject to KH instabilities, regions quite distant from previous observations of these waves,” says Kyoung-Joo Hwang of NASA’s Goddard Space Flight Center and lead author of the paper published in the Journal of Geophysical Research.
“In fact, it’s very hard to imagine a situation where solar wind plasma could not leak into the magnetosphere, since it is not a perfect magnetic bubble.”
The findings confirm theoretical predictions and are reproduced by simulations presented by the authors of the new study.
“The solar wind can enter the magnetosphere at different locations and under different magnetic field conditions that we hadn’t known about before,” says co-author Melvyn Goldstein, also from Goddard Space Flight Center.
“That suggests there is a ‘sieve-like’ property of the magnetopause in allowing the solar wind to continuously flow into the magnetosphere.”
The KH effect is also seen in the magnetospheres of Mercury and Saturn, and the new results suggest that it may provide a possible continuous entry mechanism of solar wind into those planetary magnetospheres, too.
“Cluster’s observations of these boundary waves have provided a great advance on our understanding of solar wind – magnetosphere interactions, which are at the heart of space weather research,” says Matt Taylor, ESA’s Cluster project scientist.
“In this case, the relatively small separation of the four Cluster satellites as they passed through the high-latitude dayside magnetopause provided a microscopic look at the processes ripping open the magnetopause and allowing particles from the Sun direct entry into the atmosphere.”
 

Notes for Editors
ESA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com