Mayur's Posterous http://agentm.posterous.com Most recent posts at Mayur's Posterous posterous.com Sun, 22 May 2011 09:16:00 -0700 APOD: 2011 May 22 - Io: The Prometheus Plume http://agentm.posterous.com/apod-2011-may-22-io-the-prometheus-plume http://agentm.posterous.com/apod-2011-may-22-io-the-prometheus-plume
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Fri, 06 May 2011 13:43:00 -0700 NASA Announces Results of Epic Space-Time Experiment - NASA Science http://agentm.posterous.com/nasa-announces-results-of-epic-space-time-exp http://agentm.posterous.com/nasa-announces-results-of-epic-space-time-exp

May 4, 2011: Einstein was right again. There is a space-time vortex around Earth, and its shape precisely matches the predictions of Einstein's theory of gravity.

Researchers confirmed these points at a press conference today at NASA headquarters where they announced the long-awaited results of Gravity Probe B (GP-B).

"The space-time around Earth appears to be distorted just as general relativity predicts," says Stanford University physicist Francis Everitt, principal investigator of the Gravity Probe B mission.

GP-B (twist, 550px)

 

An artist's concept of GP-B measuring the curved spacetime around Earth. [more]

"This is an epic result," adds Clifford Will of Washington University in St. Louis. An expert in Einstein's theories, Will chairs an independent panel of the National Research Council set up by NASA in 1998 to monitor and review the results of Gravity Probe B. "One day," he predicts, "this will be written up in textbooks as one of the classic experiments in the history of physics."

Time and space, according to Einstein's theories of relativity, are woven together, forming a four-dimensional fabric called "space-time." The mass of Earth dimples this fabric, much like a heavy person sitting in the middle of a trampoline. Gravity, says Einstein, is simply the motion of objects following the curvaceous lines of the dimple.

If Earth were stationary, that would be the end of the story. But Earth is not stationary. Our planet spins, and the spin should twist the dimple, slightly, pulling it around into a 4-dimensional swirl. This is what GP-B went to space in 2004 to check.

The idea behind the experiment is simple:

Put a spinning gyroscope into orbit around the Earth, with the spin axis pointed toward some distant star as a fixed reference point. Free from external forces, the gyroscope's axis should continue pointing at the star--forever. But if space is twisted, the direction of the gyroscope's axis should drift over time. By noting this change in direction relative to the star, the twists of space-time could be measured.

In practice, the experiment is tremendously difficult.

GP-B (gyro, 200px)

 

One of the super-spherical gyroscopes of Gravity Probe B. [more]

The four gyroscopes in GP-B are the most perfect spheres ever made by humans. These ping pong-sized balls of fused quartz and silicon are 1.5 inches across and never vary from a perfect sphere by more than 40 atomic layers. If the gyroscopes weren't so spherical, their spin axes would wobble even without the effects of relativity.

According to calculations, the twisted space-time around Earth should cause the axes of the gyros to drift merely 0.041 arcseconds over a year. An arcsecond is 1/3600th of a degree. To measure this angle reasonably well, GP-B needed a fantastic precision of 0.0005 arcseconds. It's like measuring the thickness of a sheet of paper held edge-on 100 miles away.

"GP-B researchers had to invent whole new technologies to make this possible," notes Will.

They developed a "drag free" satellite that could brush against the outer layers of Earth's atmosphere without disturbing the gyros. They figured out how to keep Earth's magnetic field from penetrating the spacecraft. And they created a device to measure the spin of a gyro--without touching the gyro. More information about these technologies may be found in the Science@NASA story "A Pocket of Near-Perfection."

Pulling off the experiment was an exceptional challenge. But after a year of data-taking and nearly five years of analysis, the GP-B scientists appear to have done it.

"We measured a geodetic precession of 6.600 plus or minus 0.017 arcseconds and a frame dragging effect of 0.039 plus or minus 0.007 arcseconds," says Everitt.

For readers who are not experts in relativity: Geodetic precession is the amount of wobble caused by the static mass of the Earth (the dimple in spacetime) and the frame dragging effect is the amount of wobble caused by the spin of the Earth (the twist in spacetime). Both values are in precise accord with Einstein's predictions.

"In the opinion of the committee that I chair, this effort was truly heroic. We were just blown away," says Will.

GP-B (black hole, 200px)

 

An artist's concept of twisted spacetime around a black hole. Credit: Joe Bergeron of Sky & Telescope magazine.

The results of Gravity Probe B give physicists renewed confidence that the strange predictions of Einstein's theory are indeed correct, and that these predictions may be applied elsewhere. The type of spacetime vortex that exists around Earth is duplicated and magnified elsewhere in the cosmos--around massive neutron stars, black holes, and active galactic nuclei.

"If you tried to spin a gyroscope in the severely twisted space-time around a black hole," says Will, "it wouldn't just gently precess by a fraction of a degree. It would wobble crazily and possibly even flip over."

In binary black hole systems--that is, where one black hole orbits another black hole--the black holes themselves are spinning and thus behave like gyroscopes. Imagine a system of orbiting, spinning, wobbling, flipping black holes! That's the sort of thing general relativity predicts and which GP-B tells us can really be true.

The scientific legacy of GP-B isn't limited to general relativity. The project also touched the lives of hundreds of young scientists:

"Because it was based at a university many students were able to work on the project," says Everitt. "More than 86 PhD theses at Stanford plus 14 more at other Universities were granted to students working on GP-B. Several hundred undergraduates and 55 high-school students also participated, including astronaut Sally Ride and eventual Nobel Laureate Eric Cornell."

NASA funding for Gravity Probe B began in the fall of 1963. That means Everitt and some colleagues have been planning, promoting, building, operating, and analyzing data from the experiment for more than 47 years—truly, an epic effort.

What's next?

Everitt recalls some advice given to him by his thesis advisor and Nobel Laureate Patrick M.S. Blackett: "If you can't think of what physics to do next, invent some new technology, and it will lead to new physics."

"Well," says Everitt, "we invented 13 new technologies for Gravity Probe B. Who knows where they will take us?"

This epic might just be getting started, after all….


Author: Dr. Tony Phillips | Credit: Science@NASA

via NASA

 

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Sat, 02 Apr 2011 20:17:58 -0700 APOD: 2010 July 1 - Above Aurora Australis http://agentm.posterous.com/apod-2010-july-1-above-aurora-australis http://agentm.posterous.com/apod-2010-july-1-above-aurora-australis
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Explanation: On May 29, looking southward from a vantage point about 350 kilometers above the southern Indian Ocean, astronauts onboard the International Space Station watched this enormous, green ribbon shimmering below. Known as aurora australis or southern lights, the shifting, luminous bands are commonly seen at high northern latitudes as well, there known as the aurora borealis or northern lights. North or south their cause is the same though, as energetic charged particles from the magnetosphere pile into the atmosphere near the Earth's poles. To produce the characteristic greenish glow, the energetic particles excite oxygen atoms at altitudes of 100 kilometers or more. Aurora on May 29 were likely triggered by the interaction of the magnetosphere with a coronal mass ejection erupting from the Sun on May 24.

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Sun, 06 Feb 2011 22:17:00 -0800 NASA - STEREO Reveals the entire Sun http://agentm.posterous.com/nasa-multimedia-video-gallery http://agentm.posterous.com/nasa-multimedia-video-gallery
Launched in October 2006, STEREO traces the flow of energy and matter from the sun to Earth. It also provides unique and revolutionary views of the sun-Earth system. STEREO has given us the first view of the entire sun on February 6, 2011 and when coupled with SDO, will give us complete views of the sun's entire surface and atmosphere for the next 8 years.

Video after the jump.

 

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Sat, 29 Jan 2011 16:36:00 -0800 NASA's Hubble Finds Most Distant Galaxy Candidate Ever Seen in Universe http://agentm.posterous.com/nasas-hubble-finds-most-distant-galaxy-candid http://agentm.posterous.com/nasas-hubble-finds-most-distant-galaxy-candid

Astronomers have pushed NASA's Hubble Space Telescope to its limits by finding what is likely to be the most distant object ever seen in the universe. The object's light traveled 13.2 billion years to reach Hubble, roughly 150 million years longer than the previous record holder. The age of the universe is approximately 13.7 billion years.

The tiny, dim object is a compact galaxy of blue stars that existed 480 million years after the big bang. More than 100 such mini-galaxies would be needed to make up our Milky Way. The new research offers surprising evidence that the rate of star birth in the early universe grew dramatically, increasing by about a factor of 10 from 480 million years to 650 million years after the big bang.

Closeup of HUDF WFC3/IR Image Surrounding Object  UDFj-39546284The farthest and one of the very earliest galaxies ever seen in the universe appears as a faint red blob in this ultra-deep–field exposure taken with NASA's Hubble Space Telescope. This is the deepest infrared image taken of the universe. Based on the object's color, astronomers believe it is 13.2 billion light-years away. (Credit: NASA, ESA, G. Illingworth (University of California, Santa Cruz), R. Bouwens (University of California, Santa Cruz, and Leiden University), and the HUDF09 Team)
› Larger image 

"NASA continues to reach for new heights, and this latest Hubble discovery will deepen our understanding of the universe and benefit generations to come,” said NASA Administrator Charles Bolden, who was the pilot of the space shuttle mission that carried Hubble to orbit. “We could only dream when we launched Hubble more than 20 years ago that it would have the ability to make these types of groundbreaking discoveries and rewrite textbooks.”

Astronomers don't know exactly when the first stars appeared in the universe, but every step farther from Earth takes them deeper into the early formative years when stars and galaxies began to emerge in the aftermath of the big bang. 

"These observations provide us with our best insights yet into the earlier primeval objects that have yet to be found," said Rychard Bouwens of the University of Leiden in the Netherlands. Bouwens and Illingworth report the discovery in the Jan. 27 issue of the British science journal Nature.

This observation was made with the Wide Field Camera 3 starting just a few months after it was installed in the observatory in May 2009, during the last NASA space shuttle servicing mission to Hubble. After more than a year of detailed observations and analysis, the object was positively identified in the camera's Hubble Ultra Deep Field-Infrared data taken in the late summers of 2009 and 2010. 

The object appears as a faint dot of starlight in the Hubble exposures. It is too young and too small to have the familiar spiral shape that is characteristic of galaxies in the local universe. Although its individual stars can't be resolved by Hubble, the evidence suggests this is a compact galaxy of hot stars formed more than 100-to-200 million years earlier from gas trapped in a pocket of dark matter.

This video is a zoom into the Hubble Space Telescope infrared Ultra Deep Field, first taken in 2009. It is a very small patch of sky in the southern constellation Fornax. The zoom centers on the farthest identified object in the field. The object, possibly a galaxy, looks red because its light has been stretched by the expansion of the universe. Credit: NASA/ESA/G. Bacon, STScI


"We're peering into an era where big changes are afoot," said Garth Illingworth of the University of California at Santa Cruz. "The rapid rate at which the star birth is changing tells us if we go a little further back in time we're going to see even more dramatic changes, closer to when the first galaxies were just starting to form."

The proto-galaxy is only visible at the farthest infrared wavelengths observable by Hubble. Observations of earlier times, when the first stars and galaxies were forming, will require Hubble’s successor, the James Webb Space Telescope (JWST).

The hypothesized hierarchical growth of galaxies -- from stellar clumps to majestic spirals and ellipticals -- didn't become evident until the Hubble deep field exposures. The first 500 million years of the universe's existence, from a z of 1000 to 10, is the missing chapter in the hierarchical growth of galaxies. It's not clear how the universe assembled structure out of a darkening, cooling fireball of the big bang. As with a developing embryo, astronomers know there must have been an early period of rapid changes that would set the initial conditions to make the universe of galaxies what it is today.

"After 20 years of opening our eyes to the universe around us, Hubble continues to awe and surprise astronomers," said Jon Morse, NASA's Astrophysics Division director at the agency's headquarters in Washington. "It now offers a tantalizing look at the very edge of the known universe -- a frontier NASA strives to explore."

Hubble is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

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Mon, 17 Jan 2011 10:52:00 -0800 User made NASA TV spot http://agentm.posterous.com/user-made-nasa-tv-spot http://agentm.posterous.com/user-made-nasa-tv-spot

The guy who made the previous NASA video made this one too. You can't help but pump your fist in the air while shouting "FUCK YEAH" out loud :)

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Thu, 13 Jan 2011 23:48:46 -0800 NASA - The Frontier Is Everywhere http://agentm.posterous.com/nasa-the-frontier-is-everywhere http://agentm.posterous.com/nasa-the-frontier-is-everywhere

Carl Sagan will always be one of my personal heroes. Watching Cosmos: A Personal Voyage or reading his book Pale Blue Dot: A Vision of the Human Future in Space always puts me in a super good mood :)

One of the questions that I get asked a lot is why I post so much about space when we most likely won't ever get to experience it in our lifetimes. Please take 3 minutes from your time, put on some headphones and watch the video - I cannot begin to express how dearly I hold space exploration. 

To the amazing person who created this - thank you.

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