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Sonntag, 25. Oktober 2015 - 21:30 Uhr

Astronomie - Kleinste Galaxien ergeben große Antworten

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Faint light from hundreds of small, early galaxies may hold the key to our ability to see the rest of the universe.
An international research team led by Yale University postdoctoral researcher Hakim Atek recently discovered more than 250 distant galaxies, including some of the faintest, smallest galaxies in the universe. The team relied upon new images from the Hubble Space Telescope, focusing on a trio of cosmic magnifying glasses.
Scientists have long wondered how the universe pierced the heavy veil of hydrogen gas that enshrouded it for millions of years after the Big Bang. This opaque layer of hydrogen was thick enough to block ultraviolet light, and the process of clearing away the hydrogen is known as re-ionization.
Yet the universe’s largest and brightest galaxies did not produce enough energy to account for re-ionization. That’s where the newly discovered, faint galaxies proved crucial to understanding this cosmic phenomenon. Atek’s team found that the accumulated light from these tiny galaxies — added to the other light — would be enough to cause re-ionization.
“The most exciting part of this work was the fact that we keep unveiling fainter and fainter galaxies, and they happen to be more and more abundant,” said Atek, who conducted his research at Yale and the Ecole Polytechnique Fédérale de Lausanne, in Switzerland. “This raises the question: What are the faintest and smallest galaxies ever formed in the early universe?”
The research team looked at Hubble Frontier Fields images of three galaxy clusters. Powerful gravitational forces generated by these clusters magnify the faint light of galaxies located far behind them; this is called gravitational lensing.
“Hubble remains unrivaled in its ability to observe the most distant galaxies, and the sheer depth of the Hubble Frontier Fields data guarantees very precise understanding of the cluster magnification effect, allowing us to make discoveries like these,” said co-author Mathilde Jauzac, of Durham University-UK and the University of KwaZulu-Natal-South Africa.
The research represents one of the largest samples of dwarf galaxies ever discovered from the early universe, just 600 to 900 million years after the Big Bang. With the new information, the researchers said, they estimate the universe became fully transparent about 700 million years after the Big Bang.
Publication of the research in the Astrophysical Journal is pending. Priyamvada Natarajan, a Yale professor of astronomy and physics, is a co-author of the paper. Other co-authors represent the Observatoire de Lyon, Aix Marseille Université, and CNRS, in France; the Université de Genéve, in Switzerland; the University of Hawaii; and the University of Arizona.
Quelle: Yale University

Tags: Astronomie 

1693 Views

Sonntag, 25. Oktober 2015 - 20:45 Uhr

Astronomie - Erster Film von Sternflecken außerhalb des Sonnensystems

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Wissenschaftler des Leibniz-Instituts für Astrophysik Potsdam (AIP) haben einen Film erstellt, der erstmalig zeigt, wie sich Sternflecken auf einem anderen Stern als unserer Sonne entwickeln. Hochaufgelöste spektroskopische Langzeitbeobachtungen der robotischen STELLA Teleskope auf Teneriffa zeigen das Wachsen und Verschwinden riesiger Sternflecken auf dem Roten Riesenstern XX Tri über einen Zeitraum von sechs Jahren. Die Variabilität der Flecken weist auf einen Magnetzyklus des Sterns hin, der mit dem der Sonne vergleichbar ist, jedoch deutlich stärker ausfällt.

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Generell ist es nicht möglich, die Oberfläche von anderen Sternen als unserer Sonne direkt abzubilden. Ausgefeilte mathematische Methoden und Beobachtungstechniken wurden entwickelt, um Sternoberflächen indirekt aufzulösen. Diese Technik, „Doppler Imaging“ oder „Doppler Tomographie“ genannt, ist die am weitesten fortgeschrittene Methode zur Untersuchung von Sternen. Um die Sternoberfläche nicht nur abzubilden, sondern auch ihre Entwicklung zu rekonstruieren, werden Zeitreihen hoch aufgelöster Spektren  mehrerer Sternrotationen benötigt.
Solche spektroskopischen Abtastungen des Roten Riesensterns XX Tri ermöglichte nun erstmals das robotische Teleskop STELLA auf Teneriffa. Der Stern mit einer Rotationsperiode von 24 Tagen ist bekannt für einen Superfleck mit einer Ausdehnung von 12 x 20 Sonnenradien (Strassmeier 1999). Dank der sechsjährigen kontinuierlichen Beobachtung konnte nun die Entwicklung der Sternoberfläche rekonstruiert werden.
Insgesamt wurden zwischen Juli 2006 und April 2012 667 Spektren gewonnen und zu einem Film zusammengefügt, der 86 Rotationsperioden des Sterns zeigt. Dargestellt ist die Sternoberfläche in drei verschiedenen Projektionen: eine sphärische Projektion im Größenvergleich zur Sonne („real view“), eine Mercator-Projektion bei der die gesamte Oberfläche sichtbar ist und eine Sicht auf die Rotationsachse („pole-on view“).
Der Film zeigt die Verteilung der Sternflecken auf XX Tri und ihre sich ständig verändernde Morphologie, wie Fragmentierung und Verschmelzung von Flecken auf unterschiedlichen Zeitskalen. Sternflecken entstehen durch das oberflächliche Auftauchen magnetischer Flussröhren, die ihren Ursprung im inneren Dynamoprozess eines Sterns haben. Sie sind von astrophysikalischem Interesse, da sie eng mit starken Magnetfeldern verbunden sind. „Wir können unsere erste Anwendung als Prototyp für zukünftige Studien von Sternzyklen betrachten. Sie erlaubt die Vorhersage magnetischer Aktivitätszyklen auf drastisch kürzeren Zeitskalen als üblich,“ sagt Andreas Künstler, der bereits während seiner Promotion am Leibniz-Institut für Astrophysik Potsdam an der Untersuchung von XX Tri gearbeitet hat.
STELLA, kurz für “STELLare Aktivität”, sind zwei vollrobotische 1,2m Teleskopes am Teide Observatorium auf Teneriffa, Spanien, die gemeinsam von AIP und IAC betrieben werden. Auf einzigartige Weise kombinieren sie hochaufgelöste Spektroskopie und eine Weitwinkelkamera. Keine Beobachter sind vor Ort. STELLA wurde am AIP gebaut und ist ein langfristiges Projekt zur Beobachtungen der Aktivität von kühlen Sternen.
Die Arbeit "Spot evolution on the red giant star XX Triangulum. A starspot-decay analysis based on time-series Doppler imaging" von A. Künstler, T. A. Carroll und K. G. Strassmeier ist erschienen in Astronomy & Astrophysics (A&A) Volume 578, id.A101, 25 pp (2015).
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Diese einzigartige Zeitreihe von Doppler-Aufnahmen zeigt die Sternflecken an den Polen des Sterns XX Tri sowie einige kleinere Flecken am Äquator. Über den Beobachtungszeitraum von sechs Jahren ist eine systematische Veränderung ihrer Verteilung und Morphologie erkennbar. Credit: A. Künstler, T. A. Carroll und K. G. Strassmeier, Leibniz-Institut für Astrophysik Potsdam (AIP).
Quelle: Leibniz-Institut für Astrophysik Potsdam (AIP

Tags: Astronomie 

1640 Views

Sonntag, 25. Oktober 2015 - 16:40 Uhr

Raumfahrt-History - 1979: Re-Entry von Skylab

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Aus dem CENAP-Archiv:

Quelle: CENAP-Archiv


Tags: Raumfahrt 

1481 Views

Sonntag, 25. Oktober 2015 - 15:00 Uhr

Raumfahrt-History - NASA-flickr-Archiv: Apollo-13 Teil-1

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Fotos: NASA


Tags: Raumfahrt 

1373 Views

Sonntag, 25. Oktober 2015 - 12:00 Uhr

Astronomie - Experiment testet Einsteins "Gott würfelt nicht"

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Experiment tests Einstein's “God does not play dice”
Historic Delft Experiment tests Einstein’s “God does not play dice” using quantum “dice” made in Barcelona
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Random number generators developed at ICFO – The Institute of Photonic Sciences, by the groups of ICREA Professors Morgan W. Mitchell and Valerio Pruneri, played a critical role in the historic experiment was published online today in Nature by the group of Ronald Hanson at TU Delft. The experiment gives the strongest refutation to date of Albert Einstein’s principle of “local realism,” which says that the universe obeys laws, not chance, and that there is no communication faster than light. 
As described in Hanson’s group web the Delft experiment first “entangled” two electrons trapped inside two different diamond crystals, and then measured the electrons’ orientations. In quantum theory entanglement is powerful and mysterious: mathematically the two electrons are described by a single “wave-function” that only specifies whether they agree or disagree, not which direction either spin points. In a mathematical sense, they lose their identities. “Local realism” attempts to explain the same phenomena with less mystery, saying that the particles must be pointing somewhere, we just don’t know their directions until we measure them. 
When measured, the Delft electrons did indeed appear individually random while agreeing very well. So well, in fact, that they cannot have had pre-existing orientations, as realism claims. This behaviour is only possible if the electrons communicate with each other, something that is very surprising for electrons trapped in different crystals. But here’s the amazing part: in the Delft experiment, the diamonds were in different buildings, 1.3 km away from each other. Moreover, the measurements were made so quickly that there wasn’t time for the electrons to communicate, not even with signals traveling at the speed of light. This puts “local realism” in a very tight spot: if the electron orientations are real, the electrons must have communicated. But if they communicated, they must have done so faster than the speed of light. There’s no way out, and local realism is disproven. Either God does play “dice” with the universe, or electron spins can talk to each other faster than the speed of light. 
This amazing experiment called for extremely fast, unpredictable decisions about how to measure the electron orientations. If the measurements had been predictable, the electrons could have agreed in advance which way to point, simulating communications where there wasn’t really any, a gap in the experimental proof known as a “loophole.” To close this loophole, the Delft team turned to researchers at ICFO. The team constituted Carlos Abellan, Waldimar Amaya, Valerio Pruneri and Morgan Mitchell hold the record for the fastest quantum random number generators. ICFO designed a pair of “quantum dice” for the experiment: a special version of their patented random number generation technology, including very fast “randomness extraction” electronics. This produced one extremely pure random bit for each measurement made in the Delft experiment. The bits were produced in about 100 ns, the time it takes light to travel just 30 meters, not nearly enough time for the electrons to communicate. “Delft asked us to go beyond the state of the art in random number generation. Never before has an experiment required such good random numbers in such a short time.” Says Carlos Abellán, a PhD student at ICFO and a co-author of the Delft study. 
For the ICFO team, the participation in the Delft experiment was more than a chance to contribute to fundamental physics. Prof. Morgan Mitchell comments: “Working on this experiment pushed us to develop technologies that we can now apply to improve communications security and high-performance computing, other areas that require high-speed and high-quality random numbers.” 
With the help of ICFO’s quantum random number generators, the Delft experiment gives a nearly perfect disproof of Einstein's world-view, in which "nothing travels faster than light" and “God does not play dice.” At least one of these statements must be wrong. The laws that govern the Universe may indeed be a throw of the dice. 
Quelle: ICFO - The Institute of Photonic Sciences

Tags: Astronomie 

1609 Views

Sonntag, 25. Oktober 2015 - 10:54 Uhr

Luftfahrt - High Altitude Airship der US-ARMY

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The Lockheed Martin High Altitude Airship (HAA™) – and its sub-scale demonstrator, the High Altitude Long Endurance-Demonstrator (HALE-D) – is an un-tethered, unmanned lighter-than-air vehicle that will operate above the jet stream in a geostationary position to deliver persistent station keeping as a surveillance platform, telecommunications relay, or a weather observer. The HAA also provides the Warfighter affordable, ever-present Intelligence, Surveillance and Reconnaissance and rapid communications connectivity over the entire battle space. The technology is available now and ready for integration and flight test.
This updated concept of a proven technology takes lighter-than-air vehicles into a realm that gives users capabilities on par with satellites at a fraction of the cost (1 to 2 orders of magnitude less). The HAA will also integrate reconfigurable, multi-mission payload suites. HAA is significantly less costly to deploy and operate than other airborne platforms, and supports critical missions for defense, homeland security, and other civil applications. Its operational persistence eliminates the need for in-theater logistic support. In position, an airship would survey a 600-mile diameter area and millions of cubic miles of airspace.
Lockheed Martin and the U.S. Army launched the first-of-its-kinds HALE-D on July 27, 2011, demonstrating key technologies critical to the development of unmanned airships. We demonstrated a variety of advanced technologies, including launch and control of the airship, communications links, unique propulsion system, solar array electricity generation, remote piloting communications and control capability, and in-flight operations. High altitude airships can improve the military’s ability to communicate in remote areas such as those in Afghanistan, where mountainous terrain frequently interferes with communications signals. 
High-strength fabrics to minimize hull weight, thin-film solar arrays for the regenerative power supply, and lightweight propulsion units are key technologies ready to make a high-flying airship a reality. The combination of photovoltaic and advanced energy storage systems delivers the necessary power to perform the airship functions. Propulsion units will maintain the airship's geostationary position above the jet stream, propel it aloft and guide its takeoff and landing during ascent and descent. Lighter-than-air vehicles, operating at altitudes above controlled airspace under the control of a manned ground station, give users the flexibility to change payload equipment when the airship returns to its operational base to perform different tasks.
Lockheed Martin's unique experience with certificating commercial airships with the FAA gives it the understanding to address the concerns of flight through controlled airspace, especially with an unmanned airship. Lockheed Martin, Akron, received its first production contract for a lighter-than-air vehicle in 1928. Since that time, Lockheed Martin has built more than 8,000 lighter-than-air platforms.
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Quelle: Lockheed Martin

Tags: Luftfahrt 

1583 Views

Sonntag, 25. Oktober 2015 - 10:15 Uhr

Luftfahrt - VTOL UAS Konzept von Lockheed Martin

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VTOL Advanced Reconnaissance Insertion Organic Unmanned System (VARIOUS) is an advanced vertical take-off and landing Unmanned Aerial System (UAS) concept with multi-role capabilities. With a maximum payload of more than 1,900 pounds, no exposed rotors and a service ceiling in excess of 25,000 feet, VARIOUS provides the safety and flexibility to perform multiple missions. Able to carry a variety of payloads in one common stealthy Vertical Take-Off and Landing (VTOL) platform, it is designed to be responsive, survivable, lethal and persistent. VARIOUS is a survivable VTOL UAS concept for all armed services.

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Quelle: Lockheed Martin


Tags: Luftfahrt 

1493 Views

Samstag, 24. Oktober 2015 - 22:40 Uhr

UFO-Forschung - ESA Astronaut Alexander Gerst und Aliens

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Bei der langen Nacht der Wissenschaft in Erlangen, hielt der deutsche ESA Astronaut Alexander Gerst einen Vortrag über seinen Aufenthalt auf der ISS und beantwortete Fragen. Hierbei gab es ein interessantes Statement zur Alien-Thematik:

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Quelle: BR


Tags: UFO-Forschung 

1654 Views

Samstag, 24. Oktober 2015 - 21:00 Uhr

Raumfahrt-History - 1958: Prognose: Ein Himmel voller Satelliten

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Aus dem CENAP-Archiv:

Quelle: CENAP-Archiv


Tags: Raumfahrt 

1337 Views

Samstag, 24. Oktober 2015 - 17:30 Uhr

Raumfahrt-History - NASA-flickr-Archiv: Apollo-12 Teil-6

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Fotos: NASA


Tags: Raumfahrt 

1485 Views


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