domingo, 24 de febrero de 2013

ESA - Week in Images-Star HH 151

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A glowing jet from a young star

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This image shows an object known as HH 151, a bright jet of glowing material trailed by an intricate, orange-hued plume of gas and dust. It is located some 460 light-years away in the constellation of Taurus (The Bull), near to the young, tumultuous star HL Tau.

In the first few hundred thousand years of life, new stars like HL Tau pull in material that falls towards them from the surrounding space. This material forms a hot disc that swirls around the coalescing body, launching narrow streams of material from its poles. These jets are shot out at speeds of several hundred kilometres per second and collide violently with nearby clumps of dust and gas, creating wispy, billowing structures known as Herbig-Haro objects — like HH 151 seen in the image above.

Such objects are very common in star-forming regions. They are short-lived, and their motion and evolution can actually be seen over very short timescales, on the order of years. They quickly race away from the newly-forming star that emitted them, colliding with new clumps of material and glowing brightly before fading away.

A version of this image was entered into the Hidden Treasures image processing competition by Gilles Chapdelaine.

Credit:

ESA/Hubble & NASA. Acknowledgement: Gilles Chapdelaine

About the Image

Id:	potw1307a
Release date:	18 February 2013, 10:00
Size:	1033 x 1058 px

About the Object

Name:	HH 151, HL Tau, LDN 1551
Type:	• Milky Way : Star : Evolutionary Stage : Young Stellar Object • Milky Way : Star : Circumstellar Material : Outflow • Stars Images/Videos

Colours & filters

Band	Wavelength	Telescope
Optical H-alpha	656 nm	Hubble Space Telescope WFPC2
Optical SII	673 nm	Hubble Space Telescope WFPC2
Optical R	675 nm	Hubble Space Telescope WFPC2
Infrared I	814 nm	Hubble Space Telescope WFPC2

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ESA
Guillermo Gonzalo Súnchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com

ESA - SMOS – la historia de éxito global continúa

Salinidad de la superficie del mar y de las corrientes

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22 febrero 2013 La misión del agua de la ESA arroja luz sobre la evolución de la serpenteante Corriente del Golfo. Este es tan solo uno de los muchos logros del satélite SMOS que se han presentado hoy en un encuentro celebrado en ESAC, Madrid.
Lanzado en 2009, el satélite SMOS de la ESA para el estudio de la humedad del suelo y la salinidad de los océanos (Soil Moisture and Ocean Salinity) nos está ayudando a comprender el ciclo del agua.
A lo largo de los últimos tres años la misión ha estado proporcionando datos globales más precisos sobre la humedad de los suelos y la salinidad de los océanos, utilizados para estudiar nuestro ciclo del agua.

Disminución de la humedad de los suelos de Europa

Se han adquirido nuevos conocimientos sobre el movimiento de la Corriente del Golfo – uno de los sistemas de corrientes más estudiados.
Esta corriente, que se origina en el Caribe y fluye hacia el Atlántico Norte, juega un importante papel en la trasferencia de calor y sal, influyendo en el clima de la costa este de Norte América y la costa oeste de Europa.
Los datos sobre salinidad de SMOS muestran que el agua caliente y salada impulsada hacia el norte por la Corriente del Golfo converge con aguas más frías y menos saladas, transportadas hacia el sur a lo largo de la costa este de Norte América por la Corriente del Labrador. Esta convergencia causa fuertes gradientes laterales que llevan a procesos de mezcla entre las masas de agua más allá del Cabo Hatteras.
Las observaciones de SMOS pueden delimitar y monitorizar los remolinos resultantes que han sido ‘arrancados’ de la corriente, formando pequeñas áreas de agua caliente y salada en la Corriente del Labrador, y zonas de agua más fresca y fría en la Corriente del Golfo. SMOS puede monitorizar la dinámica de este proceso gracias a su alta resolución y su frecuencia de renovación de datos.

SMOS en órbita

Esto está proporcionando a los científicos nueva información sobre cómo se mueve la sal entre los limites de las corrientes – una clave para comprender mejor el 'cinturón de convección' de la circulación oceánica global.
Este y otros logros científicos alcanzados durante los tres años de funcionamiento de la misión SMOS han sido presentados durante una conferencia llevada a cabo hoy en ESAC (European Space Astronomy Centre), centro de la ESA situado en Villanueva de la Cañada, cerca de Madrid (España).
Tras un discurso de bienvenida de Álvaro Giménez, Director de ESAC, Luis Valero, Secretario General de Industria y PYMEs, habló sobre el futuro de la tecnología espacial en España.
El Director de los Programas de Observación de la Tierra de ESA, Volker Liebig, presentó cuáles serán los siguientes pasos que se darán dentro del programa de observación de la Tierra de la ESA y en las misiones de Exploración de la Tierra.

El Huracán Sandy visto por SMOS

“SMOS es el segundo Explorador de la Tierra que hemos puesto en órbita – y está proporcionando nueva información muy importante sobre la humedad de los suelos y la salinidad de los océanos desde un punto de vista global, información que está disponible para un amplio rango de aplicaciones”, afirmó Volker Liebig.
SMOS ha sido llevado a cabo con contribuciones especiales por parte de Francia y España.
Los investigadores que lideran la misión, Yann Kerr y Jordi Font, son el punto de referencia para la investigación científica de la misión y lideran las discusiones sobre los descubrimientos relacionados con la humedad de los suelos y la salinidad de los océanos.
Nicolás Reul, de Ifremer, también destacó resultados inesperados que demuestran la versatilidad de esta misión europea de colaboración, como los descubrimientos sobre la Corriente del Golfo.
Los datos de SMOS, que han sobrepasado cualquier expectativa, se están utilizando para monitorizar la extensión y el grosor de los hielos del mar Ártico, proporcionando cobertura diaria del Océano Ártico.
Además, el satélite puede determinar la velocidad de los vientos durante un huracán – tal y como sucedió el año pasado con el Huracán Sandy, que devastó zonas de la costa este de los Estados Unidos – midiendo la radiación de microondas emitida por los mares revueltos.

ARTÍCULOS RELACIONADOS:

Super storm tracked by ESA water mission09 noviembre 2012

ESA satellites looking deeper into sea ice05 octubre 2012

SMOS has a better look at salinity01 octubre 2012

ESA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

ESA - ESA chooses instruments for its Jupiter icy moons explorer

JUICE

21 February 2013

The JUpiter ICy moons Explorer mission, JUICE, will carry a total of 11 scientific experiments to study the gas giant planet and its large ocean-bearing moons, ESA announced today.

JUICE is the first Large-class mission in ESA’s Cosmic Vision 2015–2025 programme. Planned for launch in 2022 and arrival at Jupiter in 2030, it will spend at least three years making detailed observations of the biggest planet in the Solar System and three of its largest moons, Ganymede, Callisto and Europa.

These moons are thought to harbour vast water oceans beneath their icy surfaces and JUICE will map their surfaces, sound their interiors and assess their potential for hosting life in their oceans.

Today, ESA’s Science Programme Committee approved a complement of instruments that includes cameras and spectrometers, a laser altimeter and an ice-penetrating radar. The mission will also carry a magnetometer, plasma and particle monitors, and radio science hardware.

The instruments will be developed by scientific teams from 15 European countries, the US and Japan, through corresponding national funding.

“The selection of JUICE’s instruments is a key milestone in ESA’s flagship mission to the outer Solar System, which represents an unprecedented opportunity to showcase leading European technological and scientific expertise,” says Alvaro Giménez Cañete, ESA’s Director of Science and Robotic Exploration.

“The suite of instruments addresses all of the mission’s science goals, from in-situ measurements of Jupiter’s vast magnetic field and plasma environment, to remote observations of the surfaces and interiors of the three icy moons,” adds Luigi Colangeli, coordinator of ESA’s Solar System Missions.

Throughout its mission, JUICE will observe Jupiter’s atmosphere and magnetosphere, and the interaction of all four Galilean satellites – the three icy moons plus Io – with the gas giant planet.

The spacecraft will perform a dozen flybys of Callisto, the most heavily cratered object in the Solar System, and will fly past Europa twice in order to make the first measurements of the thickness of its icy crust.

JUICE will end up in orbit around Ganymede, where it will study the moon’s icy surface and internal structure, including its subsurface ocean.

The largest moon in the Solar System, Ganymede is the only one known to generate its own magnetic field, and JUICE will observe the unique magnetic and plasma interactions with Jupiter’s magnetosphere in detail.

“Jupiter and its icy moons constitute a kind of mini-Solar System in their own right, offering European scientists and our international partners the chance to learn more about the formation of potentially habitable worlds around other stars,” says Dmitrij Titov, ESA’s JUICE Study Scientist.

The selection of the instruments today helps to ensure that JUICE remains on schedule for launch in 2022.

Eleven instrument suites will be developed by scientific teams from Austria, Belgium, Czech Republic, Finland, France, Germany, Hungary, Ireland, Italy, Netherlands, Poland, Spain, Sweden, Switzerland, UK, US and Japan, through corresponding national funding.

List of selected experiments:
JANUS: Jovis, Amorum ac Natorum Undique Scrutator, camera system
MAJIS: Moons and Jupiter Imaging Spectrometer
UVS: UV Imaging Spectrograph
SWI: Sub-millimetre Wave Instrument
GALA: Ganymede Laser Altimeter
RIME: Radar for Icy Moons Exploration
J-MAG: Magnetometer for JUICE
PEP: Particle Environment Package
RPWI: Radio & Plasma Wave Investigation
3GM: Gravity & Geophysics of Jupiter and Galilean Moons
PRIDE: Planetary Radio Interferometer & Doppler Experiment (note this does not include spacecraft hardware but will exploit VLBI – Very Large Base Interferometry – to conduct radio science)

For further information, please contact:
Markus Bauer 
ESA Science and Robotic Exploration Communication Officer 
Tel: +31 71 565 6799 
Mob: +31 61 594 3 954 
Email: markus.bauer@esa.int
Luigi Colangeli
Head of ESA’s Solar System Missions Division and Coordinator of Solar System Missions
Email: luigi.colangeli@esa.int
Dmitrij Titov
ESA’s JUICE Study Scientist
Email: dmitri.titov@esa.int

ESA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com

ESA - Últimas noticias y evaluación del impacto del asteroide en Rusia

Asteroid trace over Chelyabinsk, Russia, on 15 February 2013

Estela del asteroide sobre Chelyabinsk, Rusia, el 15 de febrero de 2013

20 febrero 2013 Los primeros datos sobre el impacto de un asteroide en Rusia, el mayor del último siglo, el pasado día 15 de febrero comienzan a estar claros. La ESA está evaluando cuidadosamente esta información, un aporte fundamental para el desarrollo del programa de la Agencia para la monitorización de asteroides.
A las 03:20 GMT del 15 de febrero, un objeto natural ingresó en la atmósfera terrestre y se desintegró en el cielo sobre Chelyabinsk, Rusia.
Una larga colección de vídeos amateur muestran que el asteroide siguió una trayectoria de noreste a suroeste, con un ángulo de apenas 20° sobre la horizontal. Se calcula que su velocidad de entrada fue de unos 18 km/s – más de 64.000 km/h.
Según los cálculos de Peter Brown, de la Universidad del Oeste de Ontario en Canadá, basados en las ondas acústicas de baja frecuencia detectadas por una red global de monitorización, el objeto tendría unos 17 metros de diámetro y una masa de 7.000 – 10.000 toneladas cuando entró en contacto con la atmósfera.
El bólido liberó una energía equivalente a 500 kilotones de TNT – unas 30 veces más que la bomba atómica de Hiroshima – cuando explotó a unos 15 – 20 kilómetros sobre la superficie de nuestro planeta.

Los modelos actuales indican que se podría esperar un evento de esta magnitud una vez cada varias decenas o cientos de años.

Órbita del asteroide

Nicolas Bobrinsky, Responsable del programa de la ESA para el Conocimiento del Medio Espacial (SSA), y Detlef Koschny, responsable de las actividades de este programa relacionadas con los Objetos Próximos a la Tierra, responden a nuestras preguntas sobre el evento.
¿Hubo alguna relación entre este evento y la aproximación del asteroide 2012 DA14, que ese mismo día a las 19:27 GMT pasó a tan sólo 28.000 km de la Tierra?
DVK: La trayectoria, el punto de entrada en la atmósfera y la separación temporal entre los dos eventos indican que el objeto caído en Rusia no guardaba ninguna relación con el asteroide 2012 DA14.
¿Cuál fue la causa de los daños registrados?¿Alguno de los fragmentos alcanzó a personas o edificaciones?
DVK: Muchos medios informaron de que la onda expansiva había roto ventanas y causado daños estructurales en varios edificios de la ciudad de Chelaybinsk. Estadísticamente, los primeros daños se producen cuando la presión de la onda es 5 veces superior a la normal a nivel del mar. La rotura generalizada de ventanas ocurre cuando se supera unas 10-20 veces este valor.
La explosión y la bola de fuego avanzaron a lo largo de una trayectoria muy estrecha; la onda expansiva resultante, cilíndrica, se pudo haber propagado directamente hacia el suelo, concentrando su intensidad.

Es muy probable que la fase final de la explosión tuviese lugar directamente sobre Chelyabinsk, lo que contribuyó en gran medida a los daños generalizados en la ciudad.
Estamos esperando a que las autoridades rusas confirmen la recuperación de trozos del objeto – fragmentos del meteorito – en la región. No conocemos ningún informe que indique que alguno de estos fragmentos haya alcanzado a personas o estructuras.

Approximate final trajectory - Chelyabinsk impactor

Trayectoria final

¿Se han producido eventos similares en el pasado?
DVK: Sí. Quizás el suceso más famoso de la historia reciente sea el acaecido en Tunguska en 1908, cuando un gran meteoroide o un fragmento de cometa, de unos 40 metros de diámetro, explotó a unos 5-10 kilómetros sobre el terreno. Es el mayor evento del que se guarda un registro, aunque la historia geológica de nuestro planeta presenta pruebas de impactos mucho más potentes.
El 12 de febrero de 1947 cayó un objeto en Sijoté-Alín, en la antigua Unión Soviética. En esa ocasión el bólido era de hierro, lo que significa que depositó la mayor parte de su energía, unos 10 kilotones de TNT, directamente sobre el terreno, en lugar de explotar en el aire como el de la semana pasada.
El 8 de octubre de 2009 se pudo observar una bola de fuego similar a la de la semana pasada sobre las islas de Indonesia. Su energía fue de unos 5 kilotones.
¿Cuál es la probabilidad de que se produzca un evento similar en el futuro?
DVK: Los Objetos Próximos a la Tierra (NEOs, en su acrónimo inglés) son asteroides o cometas en órbita al Sol, de unos pocos metros a decenas de kilómetros de diámetro, cuya trayectoria se cruza o pasa cerca de la de nuestro planeta.
A día de hoy, sabemos que existen más de 600.000 asteroides en el Sistema Solar; de los que más de 9000 están catalogados como NEOs. En cuanto se descubre un nuevo objeto, se calcula su trayectoria y se elabora un perfil de riesgo. La ESA mantiene una lista pública en http://neo.ssa.esa.int/web/guest/risk-page.

¿De dónde obtiene la información el equipo de SSA de la ESA?
DVK: Al igual que la NASA u otras agencias espaciales de carácter nacional, la ESA mantiene una estrecha colaboración con organismos de intercambio de información científica y técnica y con cuerpos gubernamentales. También colaboramos con los equipos de NEOs de la NASA y de las distintas agencias espaciales nacionales de Europa.
¿Cómo se desarrollaría una alerta de asteroide?
DVK: Un buen ejemplo es el caso 2008 TC3, un objeto de 80 toneladas y 2-5 metros de diámetro que impactó en el desierto de Sudán el 7 de octubre de 2008. Era muy pequeño, por lo que fue descubierto por casualidad apenas 20 horas antes del impacto. Las primeras simulaciones indicaban un área de impacto de unos 2.000 kilómetros de extensión, pero con el paso de las horas esta estimación se refinó hasta determinar que caería sobre el desierto de Sudán.
Si se produjese un evento similar en el futuro, las autoridades civiles podrían avisar a la población en la zona de impacto para que se mantenga alejada de las ventanas, cristales u otras estructuras y para que permanezca en casa. El riesgo de que una explosión en el aire causase daños físicos se reduciría considerablemente.

Este artículo continúa

El 15 de febrero de 2013 se avistó una gran bola de fuego sobre Chelyabinsk, Rusia.

Hora del impacto: 03:20:26 GMT
Ubicación: 55° 10' N, 61° 25' E
Ángulo de entrada: 20° sobre la horizontal
Velocidad de entrada: inferior a 20 km/s
Trayectoria: de noreste a suroeste
Diámetro del asteroide antes de la entrada: 17 metros
Energía cinética: equivalente a 500 kt de TNT, unas 30 veces la energía de la bomba de Hiroshima
Altitud de la explosión: 15-25 kilómetros

Estos resultados son preliminares y podrían ser actualizados a medida que se confirmen nuevos datos.

ARTICULOS RELACIONADOS:

Chelyabinsk asteroid vapour trail seen by Meteosat

Russian asteroid strike15 febrero 2013

Artist's impression of NEO asteroids passing Earth ESA SSA

Stranger in the night: space rock to make close Earth flyby07 febrero 2013

Asteroid deflection mission seeks smashing ideas 15 enero 2013

ESA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com

ESA - ESA ascending to stratospheric heights

ESA patch during stratospheric balloon ride

20 February 2013 Already astronomically well-travelled, ESA’s logo has now reached the edge of space. It is seen here 34.6 km up, aboard a weather balloon testing parachute designs for future Mars landings.

With the Red Planet’s atmosphere around a hundred times thinner than Earth’s, the terrestrial stratosphere makes a workable match for Mars. Once the helium-filled balloon bursts – shortly after this snap was taken – the parachute can begin its fall back to Earth.
Its flight is carefully monitored using cameras, GPS, accelerometers, rate gyros and environmental sensors.
This photo came from a series of test flights performed by UK company Vorticity Ltd, specialising in entry, descent and landing systems for space vehicles.

Based in Oxfordshire, the company has contributed to a variety of space missions, most notably designing the parachute system that landed ESA’s Huygens probe on Titan.
These balloon flights are part of an ESA contract with Vorticity to study the best options for subsonic parachutes to land on Mars, backed through the Agency’s Basic Technology Research Programme for promising new engineering concepts.
A two-parachute approach provides the best weight efficiency for a Mars landing. With the first parachute deploying at supersonic velocity, a ‘disk-gap-band’ parachute is the standard, incorporating an open ring to allow air to pass through. This design has been used for all successful Mars missions since the 1970s Viking landers.

The best choice for the subsonic parachute remains open, however. This project aims to determine the optimum parachute type for subsonic descent, making use of flight-tests to see how candidate parachutes inflate and then fly down to the ground.
Because of the way meteorology balloons operate, a secondary payload is required on the way up. This gave local schools the chance to fly small scientific payloads up to the stratosphere.
This ESA patch was flown on 22 January as part of one such payload contributed by Sponne School in Towcester, captured by one of the package’s cameras just south of Bicester in Oxfordshire just before the balloon burst.

ESA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com

ESA - ESA’s Navigation Lab helps set global time

Galileo is based on time

20 February 2013

ESA is helping to set the world’s time. Ultra-accurate atomic clocks of the Agency’s Navigation Laboratory, which will be used to assess performance of the Galileo satnav system, have joined the global effort setting Coordinated Universal Time down to a billionth of a second.

The replacement for Greenwich Mean Time, Coordinated Universal Time (UTC) is part of all our daily lives: it is the timing used for Internet, banking and aviation standards and other international timescales, maintained by the Paris-based Bureau International de Poids et Mesures (BIPM).

Participating measurement institutes and observatories around the globe use collections of atomic clocks to estimate a current value for UTC. These clock data are fed through to the BIPM to be carefully weighted and averaged to derive a combined global value. The complexity of this effort is such that it takes around six weeks to arrive at a definitive final figure.

ESTEC Director Franco Ongaro has signed an agreement with BIPM to mark the international recognition of the ESA timescale and the addition of ESA’s atomic clock data to the UTC calculations.

Atomic clocks at ESTEC

“This is an independent timing capability that ESA’s Navigation Laboratory – based in ESTEC in the Netherlands – built up to support validation of Galileo timing performances, and before it the experimental Galileo GIOVE satellites,” explained Pierre Waller of ESA’s RF Payload Systems division.
“But it makes sense to apply it more widely, and this BIPM recognition reflects the quality of our data. Our UTC estimate – formally known as UTC (ESTEC) – is also available for projects within ESA: there are many space applications beyond just navigation, such as precision technical experiments or synchronisation of telecommunications and deep-space ground stations.
“Incidentally, it is important to note that our contribution to UTC does not replace the existing input from the Netherlands’ own national timing metrology institute, Van Swinden Laboratories (VSL) in Delft. Instead we are adding to it, for enhanced global accuracy overall.”

Galileo

Galileo, like all other satellite navigation systems, is based on the highly precise measurement of time. A receiver on the ground pinpoints its position by calculating how long signals from satellites in orbit take to reach it.
Matching the receiver and satellite clocks then multiplying the time taken by the speed of light gives the range between the user and the satellite. This allows the receiver to fix its longitude, latitude and time when in contact with four or more satellites. Atomic clocks on each satellite keep time to a matter of nanoseconds – billionths of a second – synchronised by a worldwide ground network.

Galileo runs on ‘Galileo System Time’ (GST), which will be calculated by two Galileo Precise Timing Facilities equipped with active hydrogen masers and caesium atomic clocks in the system’s twin control centres, Fucino in Italy and Oberpfaffenhofen in Germany.
“UTC is the basis for legal time,” added Galileo’s Alexander Mudrak. “GST is derived independently of UTC but will be kept close to it. Galileo will also disseminate the offset between GST and UTC in its navigation message. Close GST–UTC agreement also ensures Galileo and GPS are interoperable.”
“In addition, Galileo will become an important source of precise time measurement in its own right, in addition to its navigation function, in the same way GPS is now.”

For now, the current four Galileo satellites broadcast dummy navigation signals with no time data during testing.
That will change later this year, when all four satellites are operational and GST begins to be available to users. From then on ESA’s Navigation Lab will play an important role independently validating Galileo timing performance.

ESTEC

ESTEC’s Navigation Lab is fitted with caesium and also active hydrogen maser atomic clocks – an order of magnitude more accurate than the passive hydrogen masers aboard each Galileo satellite, themselves accurate to one second in three million years.
To ensure their stable running, the clocks are maintained in a carefully controlled environment with conditioned power and a continuous generator back-up.

ESA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

ESA - A cool discovery about the Sun’s next-door twin

Cool layer in a Sun-like star

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One of the great curiosities in solar science is that our Sun’s outer atmosphere – the corona – is heated to millions of degrees when its visible surface is ‘only’ about 6000 degrees. Even stranger is a curious temperature minimum of 4000 degrees lying between the two layers, in the chromosphere. Now, using ESA’s Herschel space observatory, scientists have made the first discovery of an equivalent cool layer in the atmosphere of the Sun-like star, Alpha Centauri A.

ESA’s Herschel space observatory has detected a cool layer in the atmosphere of Alpha Centauri A, the first time this has been seen in a star beyond our own Sun. The finding is not only important for understanding the Sun’s activity, but could also help in the quest to discover proto-planetary systems around other stars.

The Sun’s nearest neighbours are the three stars of the Alpha Centauri system. The faint red dwarf, Proxima Centauri, is nearest at just 4.24 light-years, with the tight double star, Alpha Centauri AB, slightly further away at 4.37 light-years.

Alpha Centauri B has recently been in the news after the discovery of an Earth-mass planet in orbit around it. But Alpha Centauri A is also very important to astronomers: almost a twin to the Sun in mass, temperature, chemical composition and age, it provides an ideal natural laboratory to compare other characteristics of the two stars.

One of the great curiosities in solar science is that the Sun’s wispy outer atmosphere – the corona – is heated to millions of degrees while the visible surface of the Sun is ‘only’ about 6000ºC. Even stranger, there is a temperature minimum of about 4000ºC between the two layers, just a few hundred kilometres above the visible surface in the part of Sun’s atmosphere called the chromosphere.

Both layers can be seen during a total solar eclipse, when the Moon briefly blocks the bright face of the Sun: the chromosphere is a pink-red ring around the Sun, while the ghostly white plasma streamers of the corona extend out millions of kilometres.

The heating of the Sun’s atmosphere has been a conundrum for many years, but is likely to be related to the twisting and snapping of magnetic field lines sending energy rippling through the atmosphere and out into space – possibly in the direction of Earth – as solar storms. Why there is a temperature minimum has also long been of interest to solar scientists.

Now, by observing Alpha Centauri A in far-infrared light with Herschel and comparing the results with computer models of stellar atmospheres, scientists have made the first discovery of an equivalent cool layer in the atmosphere of another star.

“The study of these structures has been limited to the Sun until now, but we clearly see the signature of a similar temperature inversion layer at Alpha Centauri A,” says René Liseau of the Onsala Space Observatory, Sweden, and lead author of the paper presenting the results.

“Detailed observations of this kind for a variety of stars might help us decipher the origin of such layers and the overall atmospheric heating puzzle.”

Understanding the temperature structure of stellar atmospheres may also help to determine the presence of dusty planet-forming discs around other stars like the Sun.
“Although it is likely only a small effect, a temperature minimum region in other stars could result in us underestimating the amount of dust present in a cold debris disc surrounding it,” says Dr Liseau.
“But armed with a more detailed picture of how Alpha Centauri A shines, we can hope to make more accurate detections of the dust in potential planet-bearing systems around other Sun-like stars.”
“These observations are an exciting example of how Herschel can be used to learn more about processes in our own Sun, as well as in other Sun-like stars and the dusty discs that may exist around them,” says Göran Pilbratt, ESA’s Herschel Project Scientist.

“α Centauri A in the far infrared. First measurement of the temperature minimum of a star other than the Sun,” by R. Liseau et al. is published in Astronomy & Astrophysics 549, L7 (2013).

The survey was conducted as part of the DUNES (Dust around Nearby Stars) Herschel Key Programme. Data were collected by the PACS instrument at 100 μm and 160 μm for the DUNES survey, and PACS 70 μm and 160μm and SPIRE 250 μm, 350 μm and 500 μm data obtained as part of the Hi-GAL programme were also analysed. Additional space- and ground-based infrared data were also included.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

For further information, please contact:

Markus Bauer  
ESA Science and Robotic Exploration Communication Officer  
Tel: +31 71 565 6799  
Mob: +31 61 594 3 954  
Email: markus.bauer@esa.int

René Liseau
Chalmers University of Technology, Onsala Space Observatory, Sweden
Tel: +46 31 772 55 05
Email: rene.liseau@chalmers.se

Göran Pilbratt 
ESA Herschel Project Scientist  
Tel: +31 71 565 3621  
Email: gpilbratt@rssd.esa.int

ESA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com

domingo, 17 de febrero de 2013

ESA - 2012 DA14 nears

Asteroid 2012 DA14 seven hours before closest approach

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This image was acquired by amateur astronomer Dave Herald, Murrumbateman, Australia, earlier today. It shows the approximately 50 m-diameter object about seven hours before closest approach.

Asteroid 2012 DA14 is predicted to make closest approach to Earth at 20:27 CET on 15 February 2013.

It will not impact Earth, however it will pass within about 28 000 km.

“This is well inside the geostationary ring, where many communication satellites are located,” says Detlef Koschny, Head of NEO activities at ESA's Space Situational Awareness programme office.

“There is no danger to these satellites, however, as the asteroid will come ‘from below’ and not intersect the geostationary belt.”

While tiny against the vastness of our Solar System, it should be visible in Europe to anyone with a good pair of binoculars and an idea of where to look.

For more information see: "Stranger in the night: space rock to make close Earth flyby"

Details on how to spot 2012 DA14 from Europe.

Credits: Dave Herald. Used by permission.

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ESA
Guillermo Gonzalo Sánchez Achutegui
yabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com

ESA - Week in Images

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ESA

Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com

ESA - An awesome wave

This ESA image of the Ganges Delta is becoming one of the most iconic views of Earth from space, due in no small part to it appearing as the cover of British band Alt-J’s award-winning debut album An Awesome Wave.

Formed in 2007, the indie rock band Alt-J (‘Alt-J’ is the keyboard shortcut on computers for the delta symbol) released their first album last May in Europe. They won the British Mercury music prize in November, and their album was also announced as the BBC Radio 6 Album of the Year. The band has been nominated for three ‘Brit Awards’ (Best UK Band, Best UK Album and Best Newcomer), and has now sold 450 000 copies of their album worldwide.

Explaining how the band chose their album artwork, they said they were up against a deadline so they resorted to googling ‘delta’ for inspiration around the symbol of their name.

The band’s keyboard player Gus Unger-Hamilton said, “Instead of the delta symbol, it was coming up with satellite images of geographical deltas, which looked kind of amazing. So we thought perhaps we could use one of these images for the artwork, creating a visual pun on the idea of a delta.”

Fitting the artwork to the band's sound, Gus said, “The image is quite psychedelic, which is a term we definitely don’t mind having applied to our songs. Also, the abstract and indeterminate nature of the image – most people can’t figure out what it is – somehow fits with the hard-to-pin-down aspect of our music and its genre (or lack of).”

The image selected by the band is of the world’s largest delta, crossing the borders of Bangladesh and India. The delta plain, about 350-km wide along the Bay of Bengal, is formed by the confluence of the rivers Ganges, the Brahmaputra and Meghna.

It was taken by an instrument on ESA’s Envisat Earth observation satellite, called the Advanced Synthetic Aperture Radar, and its ‘psychedelic’ appearance was created by combining three versions of the image taken at different times over the same area. The colours result from variations in the surface that occurred between these acquisitions.

The world’s largest mangrove forest, the Sundarbans, is located where the land meets the water. The Sundarbans, which means ‘beautiful forest’ in Bengali, provide a critical habitat for numerous rare species, including the Bengal tiger and the estuarine crocodile.

By using images from space like this, scientists can study how pollution, human encroachment, soil erosion and rising sea levels threaten to submerge large parts of the forest into the sea. In the past two decades, four mangrove islands have sunk and more are threatened.

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ESA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

ESA - GOCE settles debate on sloping sea

Sea level station

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The sea level station at Vaca Key in Florida. The white tube extending down to the water is an acoustic tide gauge. The hut houses the electronics while the roof contains communications equipment and solar panels. The station is also equipped with a weather station and GPS equipment.

15 February 2013 For decades, scientists have disagreed about whether the sea is higher or lower heading north along the east coast of North America. Thanks to precision gravity data from ESA’s GOCE satellite, this controversial issue has now been settled. The answer? It’s lower.
Many might assume that the height of the sea is the same everywhere – but this is not true because winds, currents, tides and different temperatures cause seawater to pile up in some regions and dip in others.
However, it is difficult to determine relative heights of the sea, especially near the coast. To do this, tide gauge measurements need to be compared with a ‘level’ surface.
The old method of making these calculations involved conventional levelling, carrying surveying instruments thousands of kilometres and combining measurements in the national surveying datums that were assumed to be level reference surfaces.

Sea slope discussions

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The discussion between geodesists and oceanographers about whether the height of the sea increases or decreases along the east coast of North America go back to 1927 when William Bowie published Tilting of mean sea level.

Until recently, geodesists thought that the height of the sea increased with latitude along the Atlantic coast from Florida to Canada. Their conclusions, which go back to the 1920s, were based on traditional methods that connect values of mean sea level from tide gauge measurements.
This ran counter to the intuition of most oceanographers, who were aware of the influence that the Gulf Stream would have on the height of the sea along the coast.
Most modern computer models of ocean circulation suggest that sea level falls travelling north, especially along the Florida coast. As this major current then sweeps away from North Carolina, coastal sea level should be essentially flat thereafter. This contrasts with the Pacific coast where there is no significant slope with latitude.

GOCE geoid

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ESA's GOCE mission has delivered the most accurate model of the 'geoid' ever produced, which will be used to further our understanding of how Earth works.
The colours in the image represent deviations in height (–100 m to +100 m) from an ideal geoid. The blue shades represent low values and the reds/yellows represent high values.
A precise model of Earth's geoid is crucial for deriving accurate measurements of ocean circulation, sea-level change and terrestrial ice dynamics. The geoid is also used as a reference surface from which to map the topographical features on the planet. In addition, a better understanding of variations in the gravity field will lead to a deeper understanding of Earth's interior, such as the physics and dynamics associated with volcanic activity and earthquakes.

GOCE maps variations in Earth’s gravity with extreme detail. The result is a unique model of the ‘geoid’, which is essentially a virtual surface where water does not flow from one point to another.
The new geoid and in situ gravity measurements have been used as a reference to establish levelling heights. Combining the GOCE geoid and GPS heights at tide gauges provides indirect means of calculating sea heights by levelling along coastlines.
Through ESA’s Support to Science Element programme, scientists from the National Oceanographic Centre Liverpool in the UK, the Technical University of Munich in Germany and Newcastle University in the UK have developed a new method that largely uses GOCE data to determine a reference level surface.

Sea slope

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The red and blue dots show values of mean sea level (MSL) measured with respect to national datums in the US and Canada (red and blue, respectively). These data indicate that the height of the sea increases travelling north from Florida to Canada. However, most modern numerical models of ocean circulation (black dots) suggest that the slope of the sea should actually decrease travelling north and can be explained by the effects of the Gulf Stream in this region of the Atlantic Ocean. The new geoid from ESA’s GOCE gravity mission has resolved this long-debated mystery by providing conclusive proof that the height of the sea does, indeed, drop (yellow dots).

This work complements that of Dalhousie University in Canada and other oceanographic research groups also making use of new geoid information.
Philip Woodworth from the National Oceanographic Centre Liverpool said, “GOCE has resolved this old debate in the oceanographers’ favour.
“The results prove conclusively that sea level decreases going north along the North American Atlantic coastline, in agreement with the ocean models.”
Similar results agreeing with the ocean model have also been obtained along the North Pacific and European coastlines.

GOCE in orbit

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GOCE orbit is so low that it experiences drag from the outer edges of Earth's atmosphere. The satellite's streamline structure and use of electric propulsion system counteract atmospheric drag to ensure that the data are of true gravity.

Dru Smith from the US National Geodetic Survey said, “Since the issue was raised in 1927 studies showed a mismatch between classical and modern observations on land. The new results, however, settle the argument convincingly and are relevant for both North American coastlines. The findings are important for establishing a common height reference system between the US, Canada and Mexico.”
Reiner Rummel from the Technical University of Munich added, “We have to admit that we geodesists were wrong and the oceanographers were right. As both geoid and ocean models continue to improve, we can expect to learn many more interesting details about sea level and ocean circulation.
“Importantly, data from GOCE will lead to a unified global height system so that we can consistently study sea-level change apparent in tide gauge and satellite altimetry data.”

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ESA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

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domingo, 24 de febrero de 2013

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A glowing jet from a young star

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domingo, 17 de febrero de 2013

ESA - 2012 DA14 nears

ESA - Week in Images

ESA - An awesome wave

ESA - GOCE settles debate on sloping sea

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