NASA's upcoming Technology Demonstration Missions are intended to "transform its space communications, deep space navigation and in-space propulsion capabilities." Three project proposals have been selected for these missions, which should be launching in 2015 and 2016. One of those projects, the Laser Communications Relay Demonstration, we've told you about already. Another, however, will be demonstrating a mission-capable solar sail. While NASA has recently tested a solar sail measuring 100 square feet (9.29 square meters), this one will be the largest ever flown, spanning a whopping 409 square feet, or 38 square meters. .. Continue Reading NASA to demonstrate largest-ever solar sail in space
Section: Aero Gizmo
Tags: NASA, Satellite, Solar Sail, Space Travel
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By Yudhijit Bhattacharjee, ScienceNOW
Testing gravity is simple: walk out of a second-floor window and see what happens. It’s a lot tougher to test Albert Einstein’s theory of gravity — the general theory of relativity — which says that the gravity of an object warps space and time around it. Although researchers have proved general relativity on the scale of the solar system, validating it on cosmic scales has been more challenging. That’s exactly what a group of astrophysicists in Denmark have now done.
 The researchers, led by Radek Wojtak of the Niels Bohr Institute at the University of Copenhagen, set out to test a classic prediction of general relativity: that light will lose energy as it is escaping a gravitational field. The stronger the field, the greater the energy loss suffered by the light. As a result, photons emitted from the center of a galaxy cluster — a massive object containing thousands of galaxies — should lose more energy than photons coming from the edge of the cluster because gravity is strongest in the center. And so, light emerging from the center should become longer in wavelength than light coming from the edges, shifting toward the red end of the light spectrum. The effect is known as gravitational redshifting.
Wojtak and his colleagues knew that measuring gravitational redshifting within a single galaxy cluster would be difficult because the effect is very small and needs to be teased apart from the redshifting caused by the orbital velocity of individual galaxies within the cluster and the redshifting caused by the expansion of the universe. The researchers approached the problem by averaging data collected from 8000 galaxy clusters by the Sloan Digital Sky Survey. The hope was to detect gravitational redshift “by studying the properties of the redshift distribution of galaxies in clusters rather than by looking at redshifts of individual galaxies separately,” Wojtak explains.
Sure enough, the researchers found that the light from the clusters was redshifted in proportion to the distance from the center of the cluster, as predicted by general relativity. “We could measure small differences in the redshift of the galaxies and see that the light from galaxies in the middle of a cluster had to ‘crawl’ out through the gravitational field, while it was easier for the light from the outlying galaxies to emerge,” Wojtak says. The findings appear online today in Nature.
Besides confirming general relativity, the results strongly support the Lambda-Cold Dark Matter model of the universe, an already popular cosmological model according to which most of the cosmos is made up of invisible stuff that does not interact with matter constituting stars and planets. The test also lends support for dark energy, the mysterious force that appears to be pushing the universe apart.
David Spergel, an astrophysicist at Princeton University, compliments Wojtak and his colleagues on “cleverly combining” a large cluster data set to detect a “subtle effect.” Spergel says, “This is another victory for Einstein. … This cluster test suggests that we do live in a strange universe with dark matter and dark energy, but one in which Einstein’s theory of gravity is valid on large scales.”
This story provided by ScienceNOW, the daily online news service of the journal Science.
Image: NASA/CXC/ITA/INAF/J. Merten et al./NAOJ/Subaru/ESO/VLT/STScI/R. Dupke
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Like kids traipsing through freshly fallen snow, Apollo astronauts left unambiguous tracks in lunar soil. Recently released high-resolution NASA images provide the best detail yet of the extent to which we have left our mark on the moon.
Flying high above the Moon’s surface, the Lunar Reconnaissance Orbiter (LRO) snapped these new pictures, which show details as small as 25 cm across. In them, you can see zigzagging paths that astronauts walked, crisp parallel lines from the lunar rover, and the many instruments and objects that remain from each mission.
In comparison, images taken in 1966-67 by NASA’s original Lunar Orbiter missions can only resolve the surface down to about 60 meters. While mankind has yet to send people to follow in the Apollo mission’s trail, the contrast between these photographs underscores how far we've come technologically in the intervening decades.
Above:
Apollo 17’s Greatest hits
This video pans around the Apollo 17 landing site, showing off areas of interest seen from orbit and juxtaposing them with photographs the astronauts took while on the ground.
Video: NASA/Goddard/ASU [high-resolution version available]
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A gamma ray burst is an opportunity to assess the nature of the apparent 'empty space' vacuum that exists between you and it. In GRB 041219A's case, that's 300 million light years of vacuum. Credit: ESA.
The very small wavelength of gamma ray light offers the potential to gain high resolution data about very fine detail – perhaps even detail about the quantum substructure of a vacuum – or in other words, the granularity of empty space.
Quantum physics suggests that a vacuum is anything but empty, with virtual particles regularly popping in and out of existence within Planck instants of time. The proposed particle nature of gravity also requires graviton particles to mediate gravitational interactions. So, to support a theory of quantum gravity we should expect to find evidence of a degree of granularity in the substructure of space-time.(...)
Read the rest of Astronomy Without A Telescope – Granularity (514 words)
© Steve Nerlich for Universe Today, 2011. | Permalink | 5 comments | Add to del.icio.us
Post tags: quantum gravity theory
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 (Getty Images)more pics »  Space Shuttle launch (Getty Images) Hundreds of thousands gathered to watch as Space Shuttle Atlantis blasted off into space today, marking the final flight for the NASA program.
With flames bursting from underneath its belly, Atlantis rocketed upwards for the final time, thirty years after its NASA first sent a shuttle into space. Seven million pounds of thrust carried the shuttle into orbit.
The crew consisted of Commander Chris Ferguson, Pilot Doug Hurley and Mission Specialists Sandy Magnus and Rex Walheim. For one day, at least, they were celebrities, as over 750,000 people showed up in Florida to catch Atlantis' last journey.
The flight is the 135th in the U.S. program, and its end will spell the loss of thousands of jobs. For more pictures of Atlantis, look no further:
Space Shuttle Atlantis rolls toward launch pad 39-a at the Kennedy Space Center September 4, 2008 in Cape Canaveral, Florida. Atlantis is scheduled for a mission to repair the Hubble Space Telescope. (Getty Images)more pics »
Space Shuttle Atlantis rolls onto launch pad 39-a at the Kennedy Space Center September 4, 2008 in Cape Canaveral, Florida. Atlantis is scheduled for a mission to repair the Hubble Space Telescope. (Getty Images)more pics »
Space Shuttle Atlantis STS-125 astronauts, (R-L) commander Scott Altman, pilot Greg Johnson, mission specialist Megan McArthur, mission specialist John Grunsfeld, mission specialist Andrew J. Feustel, mission specialist Michael T. Good and mission specialist Mike Massimino wave as they prepare to head to the launch pad after walking out of the Operations and Checkout building for a 2:01pm launch today at Kennedy Space Center on May 11, 2009 in Cape Canaveral, Florida. The Space Shuttle Atlantis is scheduled to liftoff on a mission to service the Hubble telescope. (Photo by Matt Stroshane/Getty Images) *** Local Caption *** Scott Altman;Megan McArthur;Greg Johnson;John Grunsfeld Andrew Feustel;Michael good (Getty Images)more pics »
The Space Shuttle Atlantis STS-125 blasts off from launch pad 39-A at Kennedy Space Center on May 11, 2009 in Cape Canaveral, Florida. Atlantis is scheduled for an 11-day mission to service the Hubble telescope. (Getty Images)more pics »
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An ordinary star may have lived through a catastrophic explosion that created one of the most famous supernova remnants in astronomy. A new look at the cosmic debris cloud known as Tycho’s supernova remnant shows an arc of material that could explain what creates a key type of supernova.
“It looks like this companion star was right next to an extremely powerful explosion and it survived relatively unscathed,” said astronomer Q. Daniel Wang of the University of Massachusetts in Amherst in a press release. The study appears in the May 1 Astrophysical Journal.
The remnant is named for the great Danish astronomer Tycho Brahe, infamously known for his metal nose and more respectably for describing in 1572 the stellar explosion that bears his name. It was formed by a Type 1a supernova, which are useful in measuring astronomical distances because of their reliable brightness. Type 1a supernovas have also been used to show that the universe’s expansion is accelerating, and to probe the mysterious force called dark energy that’s pushing the universe apart.
Astronomers have two hypotheses for how Type 1a supernovas are sparked. One is that two dense white dwarf stars merge together, and blow up in a cataclysmic blast that leaves no trace of either star. The other is that one white dwarf lives close to an ordinary, sun-like companion star, and steals material from the companion until it explodes. In that case, some bits of the companion might survive.
The new observations of Tycho, made with the Chandra X-Ray Observatory, support the idea of a battered companion. The material that showed up in x-ray images was probably blasted off the companion star in the explosion and shaped into an arc by a shock wave. A dark shadow next to the arc may have been sheltered from the blast.
Previous images with optical telescopes showed a fast-moving star within the remnant that could be the missing companion.
“This stripped stellar material was the missing piece of the puzzle for arguing that Tycho’s supernova was triggered in a binary [system] with a normal stellar companion,” said astronomer Fangjun Lu of the Chinese Academy of Sciences in Beijing in a release. “We now seem to have found this piece.”
Working backward from the X-ray data and the current position of the possible companion star, the astronomers calculated that the star originally sat only 9 million miles from the doomed white dwarf — less than a tenth the distance from the Earth to the sun.
Images: NASA/CXC/Chinese Academy of Sciences/F. Lu et al.
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