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On September 26-27 Cassini executed its latest flyby of Titan, T-86, coming within 594 miles (956 km) of the cloud-covered moon in order to measure the effects of the Sun’s energy on its dense atmosphere and determine its variations at different altitudes.
The image above was captured as Cassini approached Titan from its night side, traveling about 13,000 mph (5.9 km/s). It’s a color-composite made from three separate raw images acquired in red, green and blue visible light filters.
Titan’s upper-level hydrocarbon haze is easily visible as a blue-green “shell” above its orange-colored clouds.


Cassini captured this image as it approached Titan’s sunlit limb, grabbing a better view of the upper haze. Some banding can be seen in its highest reaches.
The haze is the result of UV light from the Sun breaking down nitrogen and methane in Titan’s atmosphere, forming hydrocarbons that rise up and collect at altitudes of 300-400 kilometers. The sea-green coloration is a denser photochemical layer that extends upwards from about 200 km altitude.

In this image, made from data acquired on Sept. 27, Titan’s south polar vortex can be made out just within the southern terminator. The vortex is a relatively new feature in Titan’s atmosphere, first spotted earlier this year. It’s thought that it’s a region of open-cell convection forming above the moon’s pole, a result of the approach of winter to Titan’s southern half.
Read: Cassini Spots Surprising Swirls Above Titan’s South Pole
This T-86 flyby was was one of a handful of opportunities to profile Titan’s ionosphere from the outermost edge of Titan’s atmosphere. In addition Cassini was able to look for any changes to Ligeia Mare, a methane lake last observed in spring of 2007.
Now that Titan has been under scrutiny for a full year of Saturn’s seasons — which lasts 29.7 Earth-years — astronomers now know that varying amounts of solar radiation can drastically change situations both within Saturn’s atmosphere and on its surface.
“As with Earth, conditions on Titan change with its seasons. We can see differences in atmospheric temperatures, chemical composition and circulation patterns, especially at the poles,” said Dr. Athena Coustenis from the Paris-Meudon Observatory in France. “For example, hydrocarbon lakes form around the north polar region during winter due to colder temperatures and condensation. Also, a haze layer surrounding Titan at the northern pole is significantly reduced during the equinox because of the atmospheric circulation patterns. This is all very surprising because we didn’t expect to find any such rapid changes, especially in the deeper layers of the atmosphere.”

The image above, acquired on Sept. 28, was added to this post on Oct. 1. It was taken from a distance of 649,825 miles (1,045,792 kilometers.)
Cassini’s next targeted approach to Titan — T-87 — will occur on November 13.

http://www.universetoday.com

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Two Stars Do a Short-Orbit Tango Around the Milky Way’s Black Hole

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Astronomers have known for some time there was one star orbiting fairly close to the black hole at the center of our galaxy. But now another star has been found dipping close and orbiting even faster around the Milky Way’s central black hole. Astronomer Andrea Ghez from UCLA says the ability to watch these two stars in a short-period ‘tango’ around the black hole will help scientist measure the effects of space-time curvature, and they should be able to determine whether Albert Einstein was right in his prediction of how black holes could warp space and time.
“I’m extremely pleased to find two stars that orbit our galaxy’s supermassive black hole in much less than a human lifetime,” said Ghez. “It is the tango of [these stars] that will reveal the true geometry of space and time near a black hole for the first time. This measurement cannot be done with one star alone.”
There are nearly 3,000 stars that orbit somewhat close to the black hole, and most of them have orbits of 60 years or longer.
The previously known close-in star, S0-2, orbits the black hole every 15.5 years. And now, the newly found star, called S0-102, orbits the black hole in a blazing 11.5 years, the shortest known orbit of any star near this black hole.






Reconstruction of the orbits of two stars—S0-2 and S0-102—near the black hole at the Milky Way’s center. (Other stars’ orbits are also depicted by fainter lines.) The background is a real high-resolution infrared image of the region. Credit: Andrea Ghez et al./UCLA/Keck
In the same way that planets orbit around the sun, S0-102 and S0-2 are each in an elliptical orbit around the central black hole. Ghez said that the planetary motion in our solar system was the ultimate test for Newton’s gravitational theory 300 years ago, and now the motion of S0-102 and S0-2 will be the ultimate test for Einstein’s theory of general relativity, which describes gravity as a consequence of the curvature of space and time

“The exciting thing about seeing stars go through their complete orbit is not only that you can prove that a black hole exists but you have the first opportunity to test fundamental physics using the motions of these stars,” Ghez said. “Showing that it goes around in an ellipse provides the mass of the supermassive black hole, but if we can improve the precision of the measurements, we can see deviations from a perfect ellipse — which is the signature of general relativity.”
As the stars come to their closest approach, their motion will be affected by the curvature of spacetime, and the light traveling from the stars to us will be distorted, Ghez said.
S0-2, which is 15 times brighter than S0-102, will go through its closest approach to the black hole in 2018. S0-102 makes its closest approach in 2021, so the team will be keeping an eye on these stars as they get tantalizingly close, but not close enough to get - in, Ghez said.
Ghez and her colleagues have been observing S0-2 since 1995. In 2000, she and her team reported — for the first time – that astronomers had seen stars accelerate around the supermassive black hole. Their research demonstrated that three stars had accelerated by more than 250,000 mph a year as they orbited the black hole. The speed of S0-102 and S0-2 should also accelerate by more than 250,000 mph at their closest approach, Ghez said.
“The fact that we can find stars that are so close to the black hole is phenomenal,” said Ghez. “Now it’s a whole new ballgame, in terms of the kinds of experiments we can do to understand how black holes grow over time, the role supermassive black holes play in the center of galaxies, and whether Einstein’s theory of general relativity is valid near a black hole, where this theory has never been tested before. It’s exciting to now have a means to open up this window.”
The research was done using the Keck Telescopes. The team’s paper was published Oct. 5 in the journal Science

Source: UCLA

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Eye-Like Helix Nebula Turns Blue in New Image

A combined image of the Helix Nebula from the Spitzer Space Telescope,the Galaxy Evolution Explorer (GALEX) and the Wide-field Infrared Survey Explorer (WISE).. Credit: NASA/Caltech

The Helix Nebula has been called the “Eye of God,” or the “Eye of Sauron,” and there’s no denying this object appears to be a cosmic eye looking down on us all. And this new image – a combined view from Spitzer and GALEX — gives a blue tint to the eye that we’ve seen previously in gold, green and turquoise hues from other telescopes. But really, this eye is just a dying star. And it is not going down without a fight. The Helix Nebula continues to glow from the intense ultraviolet radiation being pumped out by the hot stellar core from the white dwarf star, which, by the way, is just a tiny white pinprick right at the center of the nebula.

The Helix nebula, or NGC 7293, lies 650 light-years away in the constellation of Aquarius. Planetary nebulae are the remains of Sun-like stars, and so one day – in about five billion years – our own Sun may look something like this — from a distance. Earth will be toast.
The team from the Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX) that cooperated to create this image describe what is going on:
When the hydrogen fuel for the fusion reaction runs out, the star turns to helium for a fuel source, burning it into an even heavier mix of carbon, nitrogen and oxygen. Eventually, the helium will also be exhausted, and the star dies, puffing off its outer gaseous layers and leaving behind the tiny, hot, dense core, called a white dwarf. The white dwarf is about the size of Earth, but has a mass very close to that of the original star; in fact, a teaspoon of a white dwarf would weigh as much as a few elephants!
The intense ultraviolet radiation from the white dwarf heats up the expelled layers of gas, which shine brightly in the infrared. GALEX has picked out the ultraviolet light pouring out of this system, shown throughout the nebula in blue, while Spitzer has snagged the detailed infrared signature of the dust and gas in red, yellow and green. Where red Spitzer and blue GALEX data combine in the middle, the nebula appears pink. A portion of the extended field beyond the nebula, which was not observed by Spitzer, is from NASA’s all-sky Wide-field Infrared Survey Explorer (WISE).
Source: JPL

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Curiosity’s “Bootprint” on Mars

Looking very similar to the iconic first footprint on the Moon from the Apollo 11 landing, this new raw image from the Curiosity rover on Mars shows one of the first “scuff” marks from the rover’s wheels on a small sandy ridge. This image was taken today by Curiosity’s right Navcam on Sol 57 (2012-10-03 19:08:27 UTC).

Besides being on different worlds, the two prints likely have a very different future. NASA says the first footprints on the Moon will be there for a million years, since there is no wind to blow them away. Research on the tracks left by Spirit and Curiosity revealed the time scale for track erasure by wind is typically only one Martian year or two Earth years.
Here’s one of Buzz Aldrin’s bootprint, to compare:

The GRIN website (Great Images in NASA) says this is an image of Buzz Aldrin’s bootprint from the Apollo 11 mission. Neil Armstrong and Buzz Aldrin walked on the Moon on July 20, 1969. Credit: NASA
Curiosity chief scientist John Grotzinger compared earlier images of some of the first tracks left on Mars by Curiosity to images of the footprints left by Aldrin and Armstrong on the Moon. “I think instead of a human, it’s a robot pretty much doing the same thing,” he said.
Lead Image Credit: NASA/JPL-Caltech

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Shiny Object on Mars Update: Likely ‘Benign’ Plastic

Curiosity sol 62 ChemCam image detail. Image: NASA/JPL-Caltech. Image processing courtesy 2di7 & titanio44 on Flickr.
Lost earring? Cigarette butt? Those were just a couple of ideas tossed around loosely by the public about what this unusual object could be, found laying near the Mars Curiosity rover. The rover team is still looking closely at the shiny object, seen in images of the sandy regolith near the rover, and they issued a report today saying their initial assessment is that the bright object is something from the rover, and not Martian material. It appears to be a shred of plastic material, “likely benign,” they said, but it has not been definitively identified.
A loose piece of plastic or insulating tape may have jarred free during the rover’s shaking of the sample of Martian regolith it recently scooped up.

The team will proceed cautiously and will spend another day investigating new images before deciding whether to resume processing of the sample in the scoop. Plans include imaging of surroundings with the Mastcam, and perhaps looking at the rover itself, too, for any chips or loose parts.
One of the rover drivers, Scott Maxwell said on Twitter that the entire team was working hard to figure that out what could have possibly come loose from the rover and they are “crawling over rover model, tracking down testing records, etc. We simply don’t know yet.”
A sample of sand and dust scooped up on Sol 61 remains in the scoop, and plan to transfer it from the scoop into other chambers of the sample-processing device were postponed as a precaution during planning for Sol 62 after the small, bright object was detected.

Curiosity sol 62 ChemCam view of the bright object on the ground. Image: NASA/JPL -Caltech. Anaglyph processing courtesy 2di7 & titanio44 on Flickr.
The shaking being done by the rover is to clean it of any residual oils that may be left inside, which could skew any results from the two onboard chemical labs, known as Sample Analysis at Mars (SAM), and the Chemical and Mineralogy experiment (CheMin.)
Daniel Limonadi, the Lead Systems Engineer for Curiosity’s Surface Sampling and science systems told reporters last week that the cleansing was required even though the hardware is “super-squeaky-clean when it’s delivered and assembled. By virtue of its just being on Earth, you get a kind of residual oily film that is impossible to avoid,” he said.

Once the soil has been shaken and stirred through the chambers, it’ll be ejected from the mechanism and ‘poop’ it back onto the Martian surface. “We effectively use it to rinse out our mouth three times and then kind of spit out,” Limonadi said.
The images here were sent in by Universe Today reader Elisabetta Bonora who zoomed in and created 3-D views of the images of the shiny piece. See more here.
Interesting to note, closeup views reveal more spherical “blueberries” similar to what the Opportunity rover found at its landing site in Meridiani Planum and at its current location near Endeavour Crater, too.

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Quantum teleportation performed with light from a quantum dot embedded in an LED

Experimental set-up of the quantum teleportation device including an entangled light-emitting diode (ELED) and an assortment of beam splitters polarization controllers, detectors, and photodiodes. The researchers demonstrated that the device can generate single pairs of entangled photons with advantages compared with using a laser due to the electrical control provided by the ELED. Credit: J. Nilsson, et al. ©2013 Macmillan Publishers Limited. All rights reserved. (Phys.org) —In a new study, physicists have teleported photonic qubits made of pairs of entangled photons that are generated by an LED containing an embedded quantum dot. The novel set-up has advantages compared to the conventional method of generating entangled photons using a laser, and could lead to a simplified technique for implementing quantum teleportation in quantum information applications. The researchers, J. Nilsson, et al., at Toshiba Research Europe Limited and the University of Cambridge, both in Cambridge, UK, have published their paper on demonstrating quantum teleportation using an LED in a recent issue of Nature Photonics. As the scientists explain, quantum teleportation—a process in which quantum information is destroyed so that it may be transferred simultaneously to another location—has been proposed as a way to create quantum communication networks and quantum computing protocols despite the no-cloning theorem. According to the no-cloning theorem, quantum information cannot be copied. Although no-cloning enables quantum cryptography to have a high degree of security, it also limits the options to create quantum communication networks and increases the losses in quantum computing due to imperfect measurements. Teleporting the information may offer a solution for these two areas. In quantum communication networks, teleportation can establish a quantum channel between two nodes. In quantum computing, teleportation can transfer qubits from successful logic operations, while the other qubits can be thrown out. Although quantum teleportation can be implemented with different systems, the researchers here argue that photonic qubits are best suited for the largest number of applications. One of the most important parts of the photonic teleportation process is having a light source that produces single pairs of entangled photons. Although lasers can be used to generate the photons, they involve practical complexities and sometimes generate multiple photon pairs, and these problems have inhibited their use in quantum information technologies. "We can also produce entangled photon pairs by pumping a non-linear crystal with a laser," coauthor Andrew Shields at Toshiba Research Europe Limited told Phys.org. "Although this has facilitated many experiments in quantum optics in the past, it has the disadvantage that the process sometimes produces two (or more) pairs. These multiple pairs cause errors in quantum information processing schemes that become increasingly problematic as we scale to larger numbers of photons. Thus developing true quantum light sources (i.e., one that produces just one entangled pair at a time) is seen as essential to achieving useful applications in quantum communications and photonic quantum computing." As an alternative, the researchers here created an entangled-light-emitting diode (ELED) with an indium arsenide quantum dot to generate pairs of entangled photons one at a time. Using the ELEDs, the researchers demonstrated an average teleportation fidelity that exceeds the maximum that can be achieved using only classical correlations, proving the quantum nature of the teleportation. A key difference with this set-up compared with laser-based set-ups is that here the photons are generated electrically rather than optically. One benefit of electric generation is that the emission wavelength of the quantum dot can be easily tuned using electric fields, which could make it compatible with a wide range of input photons of different wavelengths. "It is actually quite straightforward to embed a quantum dot in an LED," Shields said. "The quantum dot is formed by a self-organizing method during the growth of the semiconductor layers. The quantum dot is comprised of indium arsenide, which has a larger lattice constant than the gallium arsenide substrate. This results in a very thin layer (about 2 monolayers thick) self-assembling into quantum dots. After growing the rest of semiconductor structure, we are left with a layer of quantum dots embedded inside the LED." The researchers hope that the ability of the ELEDs to generate single pairs of entangled photons, along with future improvements in light collection efficiency and entanglement fidelity, will lead to the realization of a variety of teleportation-based quantum information applications. "Quantum teleportation is an important primitive in quantum information processing," Shields said. "We are planning to apply it to quantum communications and deterministic photonic quantum logic gates." More information: J. Nilsson, et al. "Quantum teleportation using a light-emitting diode." Nature Photonics. DOI: 10.1038/NPHOTON.2013.10 Journal reference: Nature Photonics Copyright 2013 Phys.org

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Physics duo discover 13 new solutions to Newtonian three-body orbit problem

The (translucent) shape-space sphere, with its back side also visible here. Three two-body collision points (bold red circles) - punctures in the sphere - lie on the equator. Credit: Milovan Suvakov, V. Dmitrasinovic / arxiv.org/abs/1303.0181 (Phys.org) —Physicists Milovan Šuvakov and V. Dmitrašinović of the Institute of Physics, Belgrade in Serbia have discovered using computer simulations, 13 new solutions to the three-body problem—predicting patterns that describe how three bodies will orbit around each other in space in a repeating pattern. The two describe how they came up with their solutions using computer simulations in their paper published in Physical Review Letters. When two bodies in space orbit one another, such as a planet and a star, their paths can be easily described by Newton's laws of gravity—they are elliptical. When another body is introduced, however, things become so complex that scientists have not been able to find a way to predict the sorts of patterns that are possible for a stable system (where they don't run into one another eventually) to come about. Until now, just three families have been identified: The Lagrange-Euler, the Broucke-Hénon, and the figure-eight. To discover a repeating pattern that describes how three bodies will orbit one another in stable fashion requires some degree of luck, the Lagrange-Euler family for example was discovered by the mathematicians for whom it is named and is demonstrated by the way the sun, Jupiter and the asteroid Trojan orbit one another. Another way requires some degree of brute force—that's the approach taken in this new effort. The two researchers started with a known solution then changed some of the parameters in their computer simulations and ran the results to see what would happen. As it turned out, their way resulted in the discovery of 13 new families of patterns—stable orbits that eventually lead to all three bodies existing in the same place as they were when the simulation started. Because they found so many new solutions, the two came up with a way to classify them using what they call a shape-sphere to graphically show what the orbits look like and then gave each a name, based on what they thought they resembled: yarn, butterfly, goggles, etc. Thus far, the 13 new families haven't been tested thoroughly enough to verify that their orbits would remain stable over long periods of time (which would mean holding their pattern despite slight perturbations), however—the researchers plan to do just that as part of their next effort. If it turns out some or all of them can withstand the test of time, then scientists can begin looking for instances of them in real systems and perhaps learning more about those systems as a result. More information: Three Classes of Newtonian Three-Body Planar Periodic Orbits, Phys. Rev. Lett. 110, 114301 (2013) DOI:10.1103/PhysRevLett.110.114301 (on ArXiv) Abstract We present the results of a numerical search for periodic orbits of three equal masses moving in a plane under the influence of Newtonian gravity, with zero angular momentum. A topological method is used to classify periodic three-body orbits into families, which fall into four classes, with all three previously known families belonging to one class. The classes are defined by the orbits' geometric and algebraic symmetries. In each class we present a few orbits' initial conditions, 15 in all; 13 of these correspond to distinct orbits. Journal reference: Physical Review Letters © 2013 Phys.org

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