Breaking science news and multimedia, heavy on astronomy and physics (and heavy on citing) New vids, pics, articles, and the occasional research post for http://researchblogging.org/ Join me on http://www.facebook.com/Astronasty for all the juicy in-between-posts picture sharing :)

Sunday, February 20, 2011

Time Lapse of the Clear Night Sky

The ALMA Array Operations Site in Chile gave us this wonderful video that I MUST share!



To quote djxatlanta in his YouTube description:
"Time-lapse of a whole night at the ALMA Array Operations Site (AOS), located at 5000 meters altitude on the Chajnantor plateau, in the II Region of Chile. As the Moon sets at the beginning of the night, three of the first ALMA antennas start tests as part of the ongoing Commissioning and Science Verification process. Because they are pointing at the same target in the sky at any moment, their movements are perfectly synchronized. 


As the sky appears to rotate clockwise around the south celestial pole (roughly on the upper left edge of the video), the Milky Way goes down slowly, until it is lying almost horizontal before sunrise. The center of our galaxy becomes visible during the second half of the night as a yellowish bulge crossed by dark lanes in the center of the image, just above the antennas.


The flashes on the ground are the car lights of the guards patrolling at the AOS. ALMA, the Atacama Large Millimeter/submillimeter Array is the largest astronomical project in existence and is a truly global partnership between the scientific communities of East Asia, Europe and North America with Chile. ESO is the European partner in ALMA."

Found via Gizmodo


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Friday, February 18, 2011

How exactly is a composite Hubble image assembled?

HubbleSiteChannel on YouTube (to which I happily subscribe) has a new video posted, showing us behind the scenes the processing of a composite Hubble image!
"Hubble images are made, not born. Images must be woven together from the incoming data from the cameras, cleaned up and given colors that bring out features that eyes would otherwise miss. In this video from HubbleSite.org, online home of the Hubble Space Telescope, a Hubble-imaged galaxy comes together on the screen at super-fast speed"



Video Credit: NASA



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Sunday, February 13, 2011

CORKSCREW LIGHT: Measuring Orbital Angular Momentum Will Give Us Extra Information About Black Holes and Frame Dragging

Frame Dragging, an effect spinning black holes have on spacetime and on the light in its vicinity, is causing a measurable corkscrew effect on photons, newly discovered and published in this issue of Nature Physics.  "Twisting of light around rotating black holes"

Simplified, frame dragging occurs when massive objects such as a black hole drags spacetime around with it while moving.  Imagine gently stirring a tiny circle within a big bowl of elmers glue.  Translate that into a graph and overlay this information on top of your familiar image of curved spacetime, and you have a dynamic and realistic scenario of general relativity in motion. When you aim your telescope at a spinning black hole, the light you're receiving is distorted, and this requires scientists to dig deep into the meat of general relativity.  This effect is different than the smooth curvature of spacetime as seen in the picture below.

Photons are massless, but they can interact with matter by a quantitative effect measured as momentum.  The angular momentum of photons expressed as Spin has been studied at great lengths, but a new measurement of orbital angular momentum has just been discovered by Fabrizio Tamburini and his team at the University of Padua in Italy.  

In the current issue of Nature Physics, we measure photons exhibiting a corkscrew spin, a technique that Martin Bojowald of Pennsylvania State University says can be incorporated into our telescopic equipment in the future.


So what exactly is this corkscrew effect?  The orbital angular momentum is explained in Universe Today: "The authors suggest visualizing this as non-planar wavefronts of this twisted light like a cylindrical spiral staircase, centered around the light beam. The intensity pattern of twisted light transverse to the beam shows a dark spot in the middle — where no one would walk on the staircase — surrounded by concentric circles


This new information gives us another way to measure the size of black holes.  New Scientist explains, "Currently, astronomers infer the spin by measuring the distance between the black hole and the nearest matter around it, a technique that requires high-resolution observations. Using twisted light would require less spatial resolution and therefore "should make it possible to measure the spin of black holes farther away", Bojowald says."


Nature Physics requires an 18$ fee to read the entire article, but the abstract can be seen here, as posted below:

ABSTRACT: "Twisting of light around rotating black holes"
"Kerr black holes are among the most intriguing predictions of Einstein’s general relativity theory1, 2. These rotating massive astrophysical objects drag and intermix their surrounding space and time, deflecting and phase-modifying light emitted near them. We have found that this leads to a new relativistic effect that imprints orbital angular momentum on such light. Numerical experiments, based on the integration of the null geodesic equations of light from orbiting point-like sources in the Kerr black hole equatorial plane to an asymptotic observer3, indeed identify the phase change and wavefront warping and predict the associated light-beam orbital angular momentum spectra4. Setting up the best existing telescopes properly, it should be possible to detect and measure this twisted light, thus allowing a direct observational demonstration of the existence of rotating black holes. As non-rotating objects are more an exception than a rule in the Universe, our findings are of fundamental importance."

CITATION
Tamburini, F., Thidé, B., Molina-Terriza, G., & Anzolin, G. (2011). Twisting of light around rotating black holes Nature Physics DOI: 10.1038/nphys1907



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Saturday, February 5, 2011

Science Pictures and Videos in the News: Feb. 5, 2011

BBC posted a beautiful video capturing the northern lights.  I'm awestruck!  "Photographer captures Northern Lights phenomenon"
"A photographer has managed to capture the Northern Lights phenomenon in Northern Norway, after he decided to place his camera on top of a mountain to shoot a time lapse of the sky."



Video Credit: BBC/Eirik Evjen




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