A new look at old data has given scientists more insight into the Moon's core. Credit: Science
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A new look at data from seismic experiments left on the Moon by Apollo astronauts has given researchers a better understanding of the lunar interior. The Moon’s core appears to be very similar to the Earth’s — with a solid inner core and molten liquid outer core — and its size is right in the middle of previous estimates.
“While the presence of a liquid core had previously been inferred from other geophysical measurements, we have made the first direct seismic observation of a liquid outer core,” said Dr. Renee Weber, a planetary scientist at NASA’s Marshall Space Flight Center, who led the team of researchers.
Apollo Passive Seismic Experiment from Apollo 15. Credit: NASA
The Apollo Passive Seismic Experiment measured seismic waves on the Moon and consisted of four seismometers deployed on the lunar near side during the Apollo missions between 1969 and 1972. The instruments continuously recorded ground motion until late-1977. But the data was thought to be rather weak because of the small number of stations, the lack of observation of far-side events, and interference from “moon quakes.” As this was the only direct measurements from the Moon available, various researchers differed on key characteristics such as the core’s radius, composition, and state (i.e., whether it was solid or molten.)
“The moon’s deepest interior, especially whether or not it has a core, has been a blind spot for seismologists,” said Ed Garnero, a professor at Arizona State University and a member of the research team. “The seismic data from the old Apollo missions were too noisy to image the moon with any confidence.”
Weber and her colleagues re-analyzed the Apollo data using a method usually used for processing seismic data on Earth. Called array processing, seismic recordings are added together or “stacked” in a special way and studied together. The multiple recordings processed together allow researchers to extract very faint signals. The depth of layers that reflect seismic energy can be identified, ultimately signifying the composition and state of matter at varying depths.
This method can enhance faint, hard-to-detect seismic signals by adding seismograms together.
“If seismic wave energy goes down and bounces off of some deep interface at a particular depth, like the Moon’s core-mantle boundary, then that signal “echo” should be present in all the recordings, even if below the background noise level,” said Patty Lin, a postdoctoral candidate at ASU and another member of the team. “But when we add the signals together, that core reflection amplitude becomes visible, which lets us map the deep Moon.”
Weber told Universe Today that the shear waves do not penetrate fluid regions. “So while we have observed compression reflections off the solid inner core, we have not (as expected) observed shear reflections off the inner core, since that energy is reflected at the outer core layer.”
Recent studies suggested the Moon had a relatively small iron-rich core, sized between about 250 and 430 km, or roughly 15 to 25% of its 1,737.1 km mean radius. The new measurements put the core slightly larger.
“We have placed the core-mantle boundary at a radius of 330 km, roughly 19% of the Moon’s mean radius,” Weber said in an email.
The iron-rich core has a solid inner ball nearly 240 km (150 miles) in radius, and an 90 km (55-mile) thick outer fluid shell.
The new research also points to volatile-depleted interior, with the lunar core containing a small percentage of light elements such as sulfur, similar to light elements in Earth’s core – sulfur, oxygen and others.
The retooled 30-year-old data also appears to confirm the the leading theory of how the Moon formed.
“The presence of a melt layer and a molten outer core supports the widely-accepted large-impact model of lunar formation, which predicts that the Moon could have formed in a completely molten state,” Weber said.
Google Lunar X PRIZE proposed landing sites. Copyright 2011 Phillip J. Stooke and Evadot.com. Used by permission.
Here’s the map of the future: a look where all the contestants in the Google Lunar X PRIZE intend to land on the Moon, in hopes of nabbing the $30 million in prizes available to the first privately funded teams to safely land a robot on the surface of the Moon. Dr. Philip J. Stooke of The University of Western Ontario has put together a this very nifty proposed landing site map based on published data from the Google Lunar X PRIZE Teams. According to Michael Doornbos from the Evadot website, assisting in the visualization, they will be updating the map regularly as the public information gets updated. Click on the image to see the original (and larger version) on Evadot.com
If you remember, the participants in the Google Lunar X PRIZE not only have to land their robot, but it also has to travel 500 meters over the lunar surface and send images and data back to the Earth. Teams must be at least 90% privately funded. The GLXP hopes to ignite a new era of lunar exploration by offering this largest international incentive prize of all time.
Amazing Swedish view of Jan 4, 2011 partial solar eclipse, which reached its maximum – about 85%- in this stunner from Stockholm, Sweden. Poor weather and obscuring clouds momentarily relented at just the perfect time. Credit: Peter Rosen
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Millions across Earth enjoyed one of nature’s most awesomely spectacular events during today’s (Jan. 4) partial solar eclipse – the first of four set to occur in 2011. And there was nothing partial about it, for those lucky eyewitnesses where it was visible in parts of Europe, Africa and Central Asia. The eclipse reached its maximum, about 85%, in Sweden. See the maximum stunner above – taken despite pessimistic weather forecasts -by Peter Rosen in Stockholm, Sweden, with more photos from the sequence here at spaceweather.com
Probably the most technically amazing feat is the double solar eclipse captured in one image by renowned astrophotographer Theirry Legault – see below – boasting both the ISS and the Moon on the eclipsed sun’s face. Legault had traveled to the deserts of the Sultanate of Oman, near to the capital of Muscat, for this rare spectacle of nature. The ISS was calculated to be visible in a thin strip barely 11 kilometers wide, according to Astronomie Info news. The ISS transit lasted just about 1 second, speeding by at 28,000 km/sec.
See a global compilation of gorgeous eclipse photos here and comment or send us more. Update 1/6/11: this is a work in progress so please check back again.
New readers photos and eyewitness accounts added below today; as received
Click to enlarge all photos
First up: Double Solar Eclipse by renowned astrophotographer Theirry Legault in Oman
Amazing Double Solar Eclipse with the ISS and the Moon captured in one image in the deserts of the Sultanate of Oman. Credit: Theirry Legault
Check out this exciting gallery of images contributed by eclipse watchers from multiple locations around the world, on Flickr
Composition of 8 different exposures between 8.10 and 9.18 (local) recorded with solar filter and added to a unfiltered picture at the beginning of sequence. Taken with a Sony DSCW-1 with 35mm equivalent focal length. Credit: Marco Di Lorenzo, Pescara, Italy
Here is a collection of images and an eyewitness report sent to me by Marco Di Lorenzo, in Pescara, Italy
Filtered and unfiltered views at 9.11 local time. Credit: Marco Di Lorenzo
Marco writes; Pescara is located at 42.467°N and 14.225°E, about in the center of Italy on the Adriatic sea. I chose my location at the new pedestrian bridge because it is a modern structure which offers a nice foreground and also an open, elevated viewpoint. I used a couple of cameras plus a digital video camera. All the cameras were mounted on a tripod.
The weather was cold and the situation didn’t improve in the mid morning. Illumination was comparable to a slightly foggy day. The frigid temperature didn’t encourage people to go out and check. However some people did venture out. Someone asked me some info on eclipses and how to take pictures of it – very hard indeed, especially if you use a cellular phone ! Combo of 2 pictures taken few seconds apart using solar filter and different exposure; local time was 9.11 AM, near maximum. Marco Di Lorenzo
Urijian Poernick sent these photos and description:
“Colorful Solar Eclipse” at Halley Astronomical Observatory, Heesch, The Netherlands Partial Solar eclipse and flock of birds from Heesch, The Netherlands. Credit: Urijian Poernick
The weather forecast predicted overcast skies with only a few small bright intervals in all parts of The Netherlands. Nevertheless, dozens of members of Halley Astronomical Society and visitors, including many children, challenged the cold winter weather and came together on the flat roof of Halley Astronomical Observatory in The Netherlands.
Partial Solar eclipse from Heesch, The Netherlands. Credit: Urijian PoernickAfter sunrise at 7:44 UT (8:44 local time) they all looked at a narrow opening in the cloud deck near the eastern horizon. At 8:00 UT the sun showed itself: first we saw the left horn of the eclipse and a few moments later the right one.
Due to the clouds and veils it was a very colorful eclipse, with all tints of red and yellow. After twenty minutes the sun and the moon disappeared behind the overcast skies again and they didn’t come back before the end of the eclipse (9:39 UT).
During this short period everyone could watch the eclipse through the telescope and we were all enthusiastic. It was a beautiful spectacle! www.sterrenwachthalley.nl
Gianluca Masi is the National Coordinator of Astronomers Without Borders in Italy and captured this pair of photos from partially overcast Rome, Italy. The clouds contributed to make for a delightfully smoky eclipsed sun Smoky eclipsed sun from Rome, Italy. Credit: Gianluca Masi Credit: Gianluca Masi
Edwin van Schijndel sent me this report from the Netherlands:
I made some pictures in the southwest of the Netherlands. The weather conditions were not so good in the early morning, most places were covered by clouds so we decided to move about 70 miles to the southwest from our hometown. Finally we stopped not far from the city of Bergen op Zoom and were able to see sunrise while most of the sun was covered. It was splendid!
Eclipsed sunrise from Bergen op Zoom, the Netherlands. Credit: Edwin van Schijndel
Unfortunately there came more clouds so the rising sun disappeared and we drove 20 miles to the north just before Rotterdam and the sky was more clear at this place. Again we took some pictures but the maximum covering of the sun had been a few minutes before. After all this wasn’t really a pity, we were very lucky to have seen the rising of the sun and be able to make some nice pictures of the partial eclipse. Many people in the Netherlands saw less or even nothing.
Credit: Edwin van Schijndel Credit: Edwin van Schijndel
Send us or comment more solar eclipse photos to post here. ken : [kremerken at yahoo.com]
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More Readers Photos and Eyewitness Accounts. Beautiful, Thanks ! ken
Story and Photos sent me by Stefano De Rosa. Turin, Italy
Early in the morning, I moved to a site close to Turin (Italy) where the forecast was not so bad as in my city to try to observe and photograph the partial solar eclipse. Unfortunately, when I arrived it was cloudy and foggy and so decided to go back home. Technical details: Canon Eos 1000d, F/22; 150-500mm lens @ 500mm; ISO. 1/1600 sec Turin, Italy. Credit: Stefano De Rosa
Suddenly, as I was sadly driving on the motorway, close to the city of Alessandria, noticed a little break on the clouds from my rearview mirror: I stopped the car and, after a quick set up, managed to capture the crescent Sun!
http://ofpink.wordpress.com Well, I hope you carefully looked back before hitting the brakes ! – ken Turin, Italy. Credit: Stefano De Rosa
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Story and Photos sent me by Roy Keeris, Zeist, The Netherlands
Middelkerke, The Netherlands. Credit: Roy Keeris
Me and a friend (Casper ter Kuile) wanted to see the eclipse from The Netherlands. If clouds should intervene, we planned to drive a little (max. a couple of hours) to a place with a better chance for a clear sky. During the night we checked weather forecasts and satellite images. We were pretty unsure if we would succeed in seeing the eclipse, because it was pretty cloudy, and especially the low clouds tend to be quite unpredictable. In the end we chose to drive to Middelkerke (near Oostende) in Belgium because of a clear spot approaching from the North Sea.
Middelkerke, The Netherlands. Credit: Roy Keeris
We arrived at the Belgian coast just in time before sunrise. There we witnessed the eclipse from the top of a dune. About 25 minutes after sunrise the sun appeared from behind the lower clouds, just when the eclipse was at its maximum. It was magical!
First we saw the right ‘horn’ and then the left one appeared. From then on we watched the rest of the eclipse and took many pictures. [no pics from Casper ??]
Later we heard that despite the clouds, many people in The Netherlands were able to see the eclipse. There was a long stretch with a clear zone in the clouds- near the border of Germany.
Middelkerke, The Netherlands. Credit: Roy Keeris
If they had a clear horizon, people could look underneath the clouds and were just able to see the sunrise. I could even have seen it at home from my apartment on the 13th floor! But the trip was fun. It’s always nice to hunt for the right place to be at these events.
Here are some pictures I took from Middelkerke. They were shot with a Canon 400D in combination with a Meade ETS-70 telescope and a Tamron 20-200mm lens.
Thanks – Yes the hunt is half the fun. ken
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Story and Photos sent me by Igal Pat-El, Director, Givatayim Observatory, Tel Aviv, Israel
We took some images of the Jan. 4 Solar Eclipse from the Givatayim Observatory, just near Tel-Aviv, Israel. We were pleased to have Prof. Jay Passachoff as a guest during the eclipse. We had a live broadcast in plan but we had to cancel it due to heavy rain from the first contact, therefore we closed the dome’s shutter and went to the balcony trying to take some quick photos of the eclipse.
Tel Aviv, Israel. All Photos Credit: Igal Pat-El, Givatayim Observatory.
Collage assembled by Ken Kremer
We had the portable PST Coronado CaK telescope with a Ca filter On a Alt-Az mount (we could not do any alignment due to the rain). We took about 5 images against all odds in this very dim filter, using the Orion SS II Planetary imager, all of them through the haze and clouds.
Thanks, Igal. Another good lesson learned. Take a chance. You never know what you’ll get till you try !
I’ve combined Igal’s photos into a collage for an enhanced view. ken
See more photos and a video in comments section below
Love observing the Moon? There’s a new iPhone, iPod and iPad app that will provide everything you need to know. LunarCalc shows moon phases from any date between the years 1900 and 2200. It also provides ecliptic latitude and longitude, zodiacal position, distance from Earth, and apogee and perigee dates. The iPad version also provides moonrise, moonset and culmination, percent illuminated and lunation period.
LunarCalc is available in eight languages: English, Spanish, French, Italian, German Portuguese, Russian and Japanese.
Courtesy of the app’s creator, Fabio Rendelucci, Universe Today has 3 LunarCalc apps to giveaway. The first three correct answers to the following question will win. Post your answer in the comment section.
Question: When will the next total lunar eclipse take place?
To find out more or to buy the app, search “LunarCalc” in iTunes to download it.
Lunar transit of the International Space Station on Dec. 20,2010. Credit: Theirry Legault. Used by permission.
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From our vantage point on Earth, it takes just a half second for the International Space Station to fly across the face of the Moon, so catching a transit is tricky. But award-winning French astrophotographer Theirry Legault captured an amazingly sharp and detailed transit image that makes the ISS look like it is sitting on the Moon’s surface! Legault took this image from Avranches (Normandy, France) a few hours before the eclipse, on December 20th at 21:34 UT. He used a Meade 10″ ACF on Takahashi EM400, with a Canon 5D mark II. The transit duration was just 0.55 seconds, as the ISS is traveling at 7.5km/s or 28,0000 km/h (17,500 mph). See below for a close-up crop of the image which shows the amount of detail visible of the space station.
Close-up of the ISS transiting the Moon. Credit: Theirry Legault. Used by permission.
Red Moon, Red Mars. Top - Dec 21, 2010 Lunar Eclipse photos of the Red Moon taken near Princeton, NJ on an exquisitely clear night with a 250 mm lens and 1 sec exposure. Credit: Ken Kremer. Bottom Left: Red Mars from the Hubble Space Telescope. Credit: NASA. Right: Red Mars through a telescope in 2010 from The Plantation in Florida (not to scale). Credit: Ernie Rossi
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In this season of Christmas tidings, many of us were blessed to witness the eerie Red Moon of the total lunar eclipse a few nights ago on Dec. 21. Here in “bonechilling” New Jersey, it was miraculously crystal clear the entire night from the beginning around 1:30 a.m. EST to the end – about three and one half hours later at around 5 a.m.
UPDATE: Check out more readers “Red Moon, Red Planet” astropix contributions below !
The eclipse occurred as the moon passed through the Earth’s inner dark shadow, or umbra and changed dramatically to varying shades of red, orange and brown.
Lunar Eclipse 12-21-2010 from The Plantation in Florida. Credit: Ernie RossiDuring totality – when the moon was completely immersed in the umbral shadow for about 72 minutes – the red moon changed from a faint red glow to a brilliant crimson red. At times it appeared to be blood red and as though the surface was stirring and oozing droplets of warm and viscous blood. It was surreal and looked to me as though it had been magically and majestically painted up into the night sky.
Well all this redness hanging in the sky during totality caused me to ponder Mars – the Red Planet – especially with the avalanche of good news streaming back lately.
And the wispy white light at near total eclipse harkened to the Martian polar ice caps.
Mars at Opposition in 2003 from New Jersey. 3.5 in Questar 0.1 seconds. Credit: Robert Vanderbei
Bright red Mars at Opposition in 2003 - The year that Spirit and Opportunity launched.
So please send your telescopic shots and descriptions of the Red Planet and/or the Red Moon and I’ll post them here. Email kremerken at yahoo dot com or post as comments to add here.
Lunar Eclipse from New Jersey 12-21-2010. Credit: Robert Vanderbei
Despite the shadow the moon does not completely disappear. The red moon’s glow was caused by sunlight refracted through the earth’s atmosphere and cast upon the lunar surface. The hue varies depending on a variety of atmospheric conditions and can be intensified by floating clouds of volcanic ash and dust. The recent volcanic eruptions at Mount Merapi in Indonesia in October and at Mount Eyjafjallajökull in Iceland last April sent massive plumes of particles skyward which may have influenced the thrilling event.
Red Moon, Red Planet. One day we’ll journey there and back again.
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Send me your astropix of Red Moon and/or Red Mars to post here:
Check out these gorgeous views of Mars in January 2010 from Efrain Morales Rivera at the Jaicoa Observatory in Aquadilla, Puerto Rico Efrain writes; On this session (01/21/10) on Mars of this years apparition many details could be seen for its size. Image at left at closest to Earth and at the limb (L) Mount Olympus largest volcano in our system, Image at right (01/27/10) closest to the Sun. Credit: Efrain Morales Rivera, Jaicoa Observatory, Aquadilla, Puerto Rico
From Robert Vanderbei of Amateur Astronomers Association Of Princeton in New Jersey; A Lunar Eclipse Montage ! Just ahead of the monster blizzard which struck the northeast Corridor of the US on Dec 26.
Dec. 21, 2010 Lunar Eclipse Montage as imaged from New Jersey. Credit: Robert Vanderbei
Some pictures of the eclipse put together as a composite from beginning to totality by Russell King of Willingboro Astronomical Society, New Jersey.
All pictures were taken with my Canon EOS Digital Rebel XSi from my home in Neptune, New Jersey. I used my Canon 75 to 300MM lens and shot all exposures at 300MM. Camera was set on a fixed photo tripod. The pictures range from 1/2500 second at full moon to 1 second during totality. Images were processed in Photoshop 2 and Ulead. Credit: Russell King. http://www.rddnj.com
The Moon's south pole, as see by the Lunar Reconnaissance Orbier. Credit: NASA/GSFC/Arizona State University.
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No, this is not a wheel of moldy Swiss Cheese. It’s an illumination map of the South Pole of the Moon. There are some areas on the poles of the Moon, particularly the interior of craters, that lie in permanent shadow while other areas remain sunlit for the majority of the year. This image was taken by the Lunar Reconnaissance Orbiter Camera, which has a primary objective of unambiguously identifying these regions. This composite image contains over 1,700 images taken of the same area by the LROC Wide Angle Camera (WAC) over a six month period, which works out to six lunar days.
Here’s how the LROC team described how they created the image:
“Each image was map projected and converted to a binary image (if the ground was illuminated that pixel was set to one, and if shadowed zero) to differentiate between sunlit and shadowed regions. All the binary images were then stacked, and then for each pixel it was determined what percentage of the time during six months that spot was illuminated. Presto – an illumination map! The LROC team is making daily (which is about 28 Earth days) and yearly illumination maps for both poles. Such maps will provide the foundation for planning future robotic and human missions to the poles.”
Sketches made by the Apollo 17 crew of rays created by lofted lunar dust. Credit: NASA
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There are times when Moon appears to have a tenuous atmosphere of moving dust particles that are leaping up from and falling back to the Moon’s surface. First seen during the Surveyor and Apollo eras, these observations were completely unexpected, and scientists today are still trying to understand this phenomenon.
The first indication that something strange was going on with the lunar surface was in the 1960’s when cameras on the Surveyor spacecraft pointing towards the western horizon noticed a brighter hovering cloud that persisted for several hours.
“There are many other bits and pieces of observations of this kind,” said Dr. Mihaly Horanyi from the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics. “For example, the astronauts in the Apollo command modules that stayed in orbit about the Moon were hoping to take images of the dark sky, but of course there is scattered light from the dust in interplanetary space. But the brightness also appeared to follow the lunar surface, indicating that somehow dust is coming off the surface of the Moon.”
While astronauts from Apollo 8, 10, and 15 all reported such dust clouds, Apollo 17 in 1972 repeatedly saw and sketched what they called “bands,” “streamers” or “twilight rays” for about 10 seconds before lunar sunrise or lunar sunset.
Adding to the mystery, also on Apollo 17 was a dust detector placed on the surface by the astronauts, the Lunar Ejecta and Meteorite experiment, which was supposed to measure the high speed impacts of micrometeorites hitting the moon.
An Apollo 17 astronaut digs in the lunar regolith to study the mechanical behavior of moon dust. Credit: NAS
“Instead the measurements showed an increase of particle fluxes that went up a hundred fold when day turned to night and night turned into day at that location on the Moon,” Horanyi said.
“Every single one of these measurements has an alternate explanation somehow. But it seems that the whole body of these observations is best explained by recognizing that dust — even on an airless body — can move around and come to life.”
Even thought the Moon has no atmosphere, Horanyi said other processes that are likely related to the plasma and radiation environment of the Moon, “the electro-dynamic processes of the near surface lunar environment that can have strong enough electric fields and the surface can have enough electrostatic charges that can break the dust free and somehow shuffle it or move it around the surface.”
In other words, electrostatic charging of the lunar surface causes the dust to levitate, precipitated – somehow – by changes in sunlight.
Horanyi said this type of thing has been seen on other airless bodies, like on Mercury, comets and asteroids.
“For example, the near-landing on the asteroid Eros,”Horanyi said, “people noticed that the bottom of the craters are filled with fine dust, and there is not enough atmosphere, and certainly the body is too small have asteroid shakes – the asteroid version of earthquakes — so the possible transport that would trap or make dust pile up in some regions and move it from others, is most likely a plasma effect.”
Horanyi and other scientists have done lab experiments to try and replicate the lunar environment to see if a dust transport takes place.
“For the first set of experiments, imagine just a piece of surface with dust particles on it, and we shine light on this surface,” he said, “so that half is illuminated, half is not, pretending that there is a terminator region, that the sun is set on one side and is still shining light on the other. When you shine light on the surface with properties that are appropriate, you can emit photo electrons, but you only emit electrons from the lit side, and some of those electrons land on the dark side, — you have a positive charge surplus on the lit and a negative charge pile-up on the night side. Across a couple of millimeters you can easily generate a potential difference of maybe a watt, or a handful of watts, which translates actually as a small-scale, but incredibly strong electric fields. This could be like a kilowatt over a meter. But of course, it only exists over a sharp boundary, and that sharp boundary may be the key to understanding how you get dust moving to begin with.”
Horanyi said in the transient region where boundaries match up – lit and dark boundaries, or boundaries between where the surface is exposed to a plasma and where it is not – those sharp transitions could actually overcome adhesion between dust and the rest of the surface and start moving.
“And that’s where the story gets really interesting,” he said.
Hopefully, a new mission called LADEE (Lunar Atmosphere and Dust Environment Explorer) can help explain this mystery. It is slated to launch in 2013 and fly in low lunar orbit, as close to the surface as 30-50 km. Since NASA may not be sending astronaut to the Moon anytime soon, LADEE’s mission may now be a little different than previously thought, but it still has some important science to conduct.
It will carry three instruments, an infrared imager, a neutral mass spectrometer and a dust detector, which Horanyi is helping to build.
“That hopefully will be capable of measuring tiny, tiny, small particles that people argue are lofted from the surface,” Horanyis said. “And we hope that in combination these instruments might put an end to this argument that we’ve had since the early 1970’s whether dust is really actively transported and shuffled around on the lunar surface or not.”
Seeking to detect mysterious, ultra-high-energy neutrinos from distant regions of space, a team of astronomers used the Moon as part of an innovative telescope system for the search. Their work gave new insight on the possible origin of the elusive subatomic particles and points the way to opening a new view of the Universe in the future.
The team used special-purpose electronic equipment brought to the National Science Foundation’s Very Large Array (VLA) radio telescope, and took advantage of new, more-sensitive radio receivers installed as part of the Expanded VLA (EVLA) project. Prior to their observations, they tested their system by flying a small, specialized transmitter over the VLA in a helium balloon.
In 200 hours of observations, Ted Jaeger of the University of Iowa and the Naval Research Laboratory, and Robert Mutel and Kenneth Gayley of the University of Iowa did not detect any of the ultra-high-energy neutrinos they sought. This lack of detection placed a new limit on the amount of such particles arriving from space, and cast doubt on some theoretical models for how those neutrinos are produced.
Neutrinos are fast-moving subatomic particles with no electrical charge that readily pass unimpeded through ordinary matter. Though plentiful in the Universe, they are notoriously difficult to detect. Experiments to detect neutrinos from the Sun and supernova explosions have used large volumes of material such as water or chlorine to capture the rare interactions of the particles with ordinary matter.
The ultra-high-energy neutrinos the astronomers sought are postulated to be produced by the energetic, black-hole-powered cores of distant galaxies; massive stellar explosions; annihilation of dark matter; cosmic-ray particles interacting with photons of the Cosmic Microwave Background; tears in the fabric of space-time; and collisions of the ultra-high-energy neutrinos with lower-energy neutrinos left over from the Big Bang.
Radio telescopes can’t detect neutrinos, but the scientists pointed sets of VLA antennas around the edge of the Moon in hopes of seeing brief bursts of radio waves emitted when the neutrinos they sought passed through the Moon and interacted with lunar material. Such interactions, they calculated, should send the radio bursts toward Earth. This technique was first used in 1995 and has been used several times since then, with no detections recorded. The latest VLA observations have been the most sensitive yet done.
“Our observations have set a new upper limit — the lowest yet — for the amount of the type of neutrinos we sought,” Mutel said. “This limit eliminates some models that proposed bursts of these neutrinos coming from the halo of the Milky Way Galaxy,” he added. To test other models, the scientists said, will require observations with more sensitivity.
“Some of the techniques we developed for these observations can be adapted to the next generation of radio telescopes and assist in more-sensitive searches later,” Mutel said. “When we develop the ability to detect these particles, we will open a new window for observing the Universe and advancing our understanding of basic astrophysics,” he said.
The scientists reported their work in the December edition of the journal Astroparticle Physics.
NASA’s Cassini Spacecraft is doing some awesome stuff. Stay tuned to NASA’s twitter feed Space Cadets, today should be interesting. I’m Benjamin Higginbotham and this is your SpacePod for November 30th, 2010. Continue reading “Cassini visits Enceladus – SpacePod 2010.11.30”
