vendredi 11 juillet 2014
CERN - European Organization for Nuclear Research logo.
July 11, 2014
At the ATLAS experiment at CERN, physicists and engineers are testing their subdetector systems – using particles from outer space.
During its last 3-year run, the Large Hadron Collider (LHC) achieved its highest-energy collisions at 8 TeV. But when the LHC starts up again in 2015 it will hit 13 TeV, which means new challenges for the large detectors ATLAS, CMS, ALICE and LHCb. Subdetectors on the ATLAS experiment will have to be thoroughly tested for performance at high energy. But how do you test a general-purpose particle physics detector for high-energy collisions when there are no particle collisions taking place? "Cosmic rays," says ATLAS run coordinator Alessandro Polini.
These high-energy particles from outer space are mainly (89%) protons but they also include nuclei of helium (10%) and heavier nuclei (1%), all the way up to uranium. The energies of the primary cosmic rays range from around 1 GeV – the energy of a relatively small particle accelerator – to as much as 108 TeV, far higher than the beam energy of the LHC. We don’t feel them, but because they register as tracks in the ATLAS detector, physicists can use cosmic rays to calibrate and align the subdetectors when the LHC is switched off. "If there are gaps or certain tracks aren’t aligned at specific points, there is more work to be done," says Polini.
Image above: An engineer inspects the ATLAS detector during maintenance work last year (Image: Anna Pantelia/CERN).
Each subdetector is set up and tested in isolation, then joined to other subdetectors and finally installed into the whole. “It is a bit like an orchestra: the different instruments practice on their own, then we bring them together one by one," says Polini. "You need to tune and get them in the best shape possible first, only then can the ensemble work."
ATLAS took 27 inverse femtobarns of data (roughly 2 × 10 15 proton-proton collisions) during the LHC's first run, allowing for the discovery of the Higgs boson and many other results. In the second run, bunches of protons will be accelerated to nearly twice the energy and timed to collide every 25 nanoseconds in the detector. This means up to 40 million collisions per second, two times more than during the previous run.
Polini says there will be a "final rehearsal" in November with an extended cosmic-ray run when all the layers of the ATLAS detector will come together and the magnetic fields will be switched on. "ATLAS will then be ready for its symphony,” he says.
CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.
The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.
Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 20 Member States.
Large Hadron Collider (LHC): http://home.web.cern.ch/topics/large-hadron-collider
LHC large detectors:
Image. Text, Credits: CERN / Abha Eli Phoboo.
Publié par Orbiter.ch à 17:31
NASA - Hubble Space Telescope patch.
July 11, 2014
This view, captured by the NASA/ESA Hubble Space Telescope, shows a nearby spiral galaxy known as NGC 1433. At about 32 million light-years from Earth, it is a type of very active galaxy known as a Seyfert galaxy — a classification that accounts for 10% of all galaxies. They have very bright, luminous centers that are comparable in brightness to that of our entire galaxy, the Milky Way.
Galaxy cores are of great interest to astronomers. The centers of most, if not all, galaxies are thought to contain a supermassive black hole, surrounded by a disk of in-falling material.
NGC 1433 is being studied as part of a survey of 50 nearby galaxies known as the Legacy ExtraGalactic UV Survey (LEGUS). Ultraviolet radiation is observed from galaxies, mainly tracing the most recently formed stars. In Seyfert galaxies, ultraviolet light is also thought to emanate from the accretion discs around their central black holes. Studying these galaxies in the ultraviolet part of the spectrum is incredibly useful to study how the gas is behaving near the black hole. This image was obtained using a mix of ultraviolet, visible, and infrared light.
LEGUS will study a full range of properties from a sample of galaxies, including their internal structure. This Hubble survey will provide a unique foundation for future observations with the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA). ALMA has already caught unexpected results relating to the center of NGC 1433, finding a surprising spiral structure in the molecular gas close to the center of NGC 1433. The astronomers also found a jet of material flowing away from the black hole, extending for only 150 light-years — the smallest such molecular outflow ever observed in a galaxy beyond our own.
For images and more information about Hubble, visit: http://www.nasa.gov/hubble and http://www.spacetelescope.org/
Image, Text, Credits: ESA/Hubble & NASA, Acknowledgements: D. Calzetti (UMass) and the LEGUS Team.
Publié par Orbiter.ch à 17:05
ESA Venus Express Mission patch.
11 July 2014
After a month surfing in and out of the atmosphere of Venus down to just 130 km from the planet’s surface, ESA’s Venus Express is about to embark on a 15 day climb up to the lofty heights of 460 km.
Since its arrival at Venus in 2006, the spacecraft has been conducting science observations from an elliptical 24-hour orbit that took it from a distant 66 000 km over the south pole – affording incredible global views – to altitudes around 250 km at the north pole, just above the top of the planet’s atmosphere.
Venus Express aerobraking
After eight years in orbit and with fuel for its propulsion system running low, a daring aerobraking campaign was planned as a final assignment for Venus Express, during which it would dip progressively lower into the atmosphere on its closest approaches to the planet.
Thus routine science operations concluded on 15 May, and the spacecraft’s altitude was allowed to drop naturally from the effect of gravity, culminating in a month ‘surfing’ between 131 km and 135 km above the surface.
Additional small thruster burns were used to drop the spacecraft to lower altitudes, reaching 130.2 km earlier this week. Tomorrow, it is expected to dip to 129.1 km.
“We have explored uncharted territory, diving deeper into the atmosphere than ever before,” says Håkan Svedhem, ESA’s Venus Express project scientist.
“We’ve measured the effects of atmospheric drag on the spacecraft, which will teach us how the density of the atmosphere varies on local and global scales.”
Indeed, the additional drag exerted by the denser atmosphere at lower altitudes reduced the spacecraft’s orbital period by more than an hour.
Small changes in the spacecraft’s acceleration were also recorded due to variations in the atmospheric density along its orbital path. Differences in acceleration were also noticed between the day and night side of the planet.
The forces experienced by the spacecraft at different altitudes equate to a difference in atmospheric density of about thousand times between 165 km and 130 km, causing significantly increased stress on the spacecraft.
Visualisation of the Venus Express aerobraking manoeuvre
Indeed, the Venus Express team monitored the rapid heating that the spacecraft experienced as it skimmed through the upper reaches of the atmosphere during each orbit at about 36 000 km/h.
“During several of the 100-second long passages through the atmosphere, the solar panel temperature sensor reading increased by over 100ºC,” describes Adam Williams, ESA’s Venus Express spacecraft operations manager.
“Analysing the spacecraft’s response to such rapid heating will be useful for planning future spacecraft systems and subsystem design.”
Commands have now been sent to the spacecraft ready to begin a series of 15 manoeuvres that will raise the lowest part of the orbit to about 460 km. These begin tomorrow and should be completed by 26 July.
Once Venus Express reaches this higher altitude orbit it will be allowed to decay naturally, eventually sinking into the atmosphere by December, ending its mission.
Image above: Visualisation of Venus Express during the aerobraking manoeuvre, which will see the spacecraft orbiting Venus at an altitude of around 130 km from 18 June to 11 July 2014.
However, it is possible that the remaining fuel will run out during the thruster burns required to raise its orbit.
If this occurs, it will no longer be possible to communicate with the craft and its orbit will once again decay.
“We have already gained valuable experience in operating a spacecraft in these challenging conditions that will be important for future missions that may require it. Once we have completed the orbit raise, we look forward to processing and analysing the scientific data collected on the atmosphere,” says Patrick Martin, ESA’s Venus Express mission manager.
For updates during the orbital raising manoeuvres follow the Rocket Science Blog and @esaoperations on Twitter.
Notes for Editors:
The recorded atmospheric density at an altitude of 165 km was 10-11 kg/m3 and at 130 km it was 10-8 kg/m3. While these values may seem small – atmospheric density at Earth’s sea level is 1 kg/m3 – the density is a thousand times greater at the lowest altitudes.
On Monday 7 July, Venus Express completed 3000 orbits around Venus.
For more information about Venus Express mission, visit: http://www.esa.int/Our_Activities/Space_Science/Venus_Express
Rocket Science Blog: http://blogs.esa.int/rocketscience/
Images, Video, Text, Credits: ESA / C. Carreau.
Publié par Orbiter.ch à 16:52
ESA - XMM-Newton Mission patch.
11 July 2014
ESA’s XMM-Newton observatory has helped to uncover how the Universe’s first stars ended their lives in giant explosions.
Astronomers studied the gamma-ray burst GRB130925A – a flash of very energetic radiation streaming from a star in a distant galaxy 5.6 billion light years from Earth – using space- and ground-based observatories.
Exploding blue supergiant star
They found the culprit producing the burst to be a massive star, known as a blue supergiant. These huge stars are quite rare in the relatively nearby Universe where GRB130925A is located, but are thought to have been very common in the early Universe, with almost all of the very first stars having evolved into them over the course of their short lives.
But unlike other blue supergiants we see nearby, GRB130925A's progenitor star contained very little in the way of elements heavier than hydrogen and helium. The same was true for the first stars to form in the Universe, making GRB130925A a remarkable analogue for similar explosions that occurred just a few hundred million years after the Big Bang.
“There have been several theoretical studies predicting what a gamma-ray burst produced by a primordial star would look like,” says Luigi Piro of the Istituto Astrofisica e Planetologia Spaziali in Rome, Italy, and lead author of a new paper appearing in The Astrophysical Journal Letters. “With our discovery, we’ve shown that these predictions are likely to be correct.”
Astronomers believe that primordial stars were very large, perhaps several hundred times the mass of the Sun. This large bulk then fuelled ultralong gamma-ray bursts lasting several thousand seconds, up to a hundred times the length of a ‘normal’ gamma-ray burst.
Indeed, GRB130925A had a very long duration of around 20 000 seconds, but it also exhibited additional peculiar features not previously spotted in a gamma-ray burst: a hot cocoon of gas emitting X-ray radiation and a strangely thin wind.
Both of these phenomena allowed astronomers to implicate a blue supergiant as the stellar progenitor. Crucially, they give information on the proportion of the star composed of elements other than hydrogen and helium, elements that astronomers group together under the term ‘metals’.
After the Big Bang, the Universe was dominated by hydrogen and helium and therefore the first stars that formed were very metal-poor. However, these first stars made heavier elements via nuclear fusion and scattered them throughout space as they evolved and exploded.
This process continued as each new generation of stars formed, and thus stars in the nearby Universe are comparatively metal-rich.
Finding GRB130925A's progenitor to be a metal-poor blue supergiant is significant, offering the chance to explore an analogue of one of those very first stars at close quarters. Dr Piro and his colleagues speculate that it might have formed out of a pocket of primordial gas that somehow survived unaltered for billions of years.
As a nearby counterpart, however, GRB130925A has offered astronomers the opportunity to gain some insight into these first stars today.
“XMM-Newton’s space-based location and sensitive X-ray instruments were key to observing the later stages of this blast, several months after it first appeared,” says ESA's XMM-Newton project scientist Norbert Schartel.
XMM-Newton x-ray observatory
“At these times, the fingerprints of the progenitor star were clearer, but the source itself was so dim that only XMM-Newton’s instruments were sensitive enough to take the detailed measurements needed to characterise the explosion.”
A number of space- and ground-based missions were involved in the discovery and characterisation of GRB130925A. Alongside the XMM-Newton observations, the astronomers involved in this study also used X-ray data gathered at different times with NASA’s SwiftBurst Alert Telescope, and radio data from the CSIRO's Australia Telescope Compact Array.
“Combining these observations was crucial to get a full picture of this event,” added Eleonora Troja of NASA’s Goddard Space Flight Center in Maryland, USA, a co-author of the paper.
“This new understanding of GRB130925A means that we now have strong indications how a primordial explosion might look — and therefore what to search for in the distant Universe,” says Dr Schartel.
The search will require powerful facilities. The NASA/ESA/CSA James Webb Space Telescope, an infrared successor to the Hubble Space Telescope due for launch in 2018, and ESA’s planned Athena mission, a large X-ray observatory following on from XMM-Newton in 2028, will both have key roles to play.
Notes for Editors:
“A Hot Cocoon in the Ultralong GRB 130925A: Hints of a PopIII-like Progenitor in a Low Density Wind Environment” by L. Piro et al. is published in The Astrophysical Journal Letters.
GRB130925A triggered the SwiftBurst Alert Telescope on 25 September 2013 at 04:11:24 GMT. Early gamma-ray emission was detected by Integral, and the burst was subsequently observed by the Fermi Gamma-Ray Burst Monitor, Konus-Wind, Swift’s X-ray telescope, Chandra, the Gamma-Ray Burst Optical/Near-Infrared Detector, the Hubble Space Telescope and the CSIRO's Australia Telescope Compact Array. GRB130925A was located in a galaxy so far away that its light has been travelling for 3.9 billion years.
ESA’s XMM-Newton was launched in December 1999. The largest scientific satellite to have been built in Europe, it is also one of the most sensitive X-ray observatories ever flown. More than 170 wafer-thin, cylindrical mirrors direct incoming radiation into three high-throughput X-ray telescopes. XMM-Newton's orbit takes it almost a third of the way to the Moon, allowing for long, uninterrupted views of celestial objects.
XMM-Newton overview: http://www.esa.int/Our_Activities/Space_Science/XMM-Newton_overview
XMM-Newton image gallery: http://xmm.esac.esa.int/external/xmm_science/gallery/public/index.php
XMM-Newton in-depth: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=23
Images, Text, Credits: ESA/NASA/Swift/A. Simonnet, Sonoma State Univ.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 06:09
jeudi 10 juillet 2014
ESA - Hubble Space Telescope logo.
10 July 2014
Hubble snaps a violent galactic merger and chain of star formation
Droplets of star formation and two merging galaxies in SDSS J1531+3414
The Universe is filled with objects springing to life, evolving and dying explosive deaths. This new image from the NASA/ESA Hubble Space Telescope captures a snapshot of some of this cosmic movement. Embedded within the egg-shaped blue ring at the centre of the frame are two galaxies. These galaxies have been found to be merging into one and a "chain" of young stellar superclusters are seen winding around the galaxies’ nuclei.
Image above: Wide field image of the region around two merging galaxies in SDSS J1531+3414 (ground based telescope).
At the centre of this image lie two elliptical galaxies, part of a galaxy cluster known as [HGO2008]SDSS J1531+3414, which have strayed into each other’s paths. While this region has been observed before, this new Hubble picture shows clearly for the first time that the pair are two separate objects. However, they will not be able to hold on to their separate identities much longer, as they are in the process of merging into one .
Image above: Hubble Space Telescope photographed a 100,000-light-year-long structure that looks like a string of pearls twisted into a corkscrew shape winds around the cores of the two massive galaxies. The “pearls” are superclusters of blazing, blue-white, newly born stars. Image Credit: NASA/ESA.
Finding two elliptical galaxies merging is rare, but it is even rarer to find a merger between ellipticals rich enough in gas to induce star formation. Galaxies in clusters are generally thought to have been deprived of their gaseous contents; a process that Hubble has recently seen in action. Yet, in this image, not only have two elliptical galaxies been caught merging but their newborn stellar population is also a rare breed.
The stellar infants — thought to be a result of the merger — are part of what is known as "beads on a string" star formation. This type of formation appears as a knotted rope of gaseous filaments with bright patches of new stars and the process stems from the same fundamental physics which causes rain to fall in droplets, rather than as a continuous column .
Zooming in on merging galaxies and a string of star formation in SDSS J1531+3414
Nineteen compact clumps of young stars make up the length of this "string", woven together with narrow filaments of hydrogen gas. The star formation spans 100,000 light years, which is about the size of our galaxy, the Milky Way. The strand is dwarfed, however, by the ancient, giant merging galaxies that it inhabits. They are about 330,000 light years across, nearly three times larger than our own galaxy. This is typical for galaxies at the centre of massive clusters, as they tend to be the largest galaxies in the Universe.
The electric blue arcs making up the spectacular egg-like shape framing these objects are a result of the galaxy cluster’s immense gravity. The gravity warps the space around it and creates bizarre patterns using light from more distant galaxies.
Panning across merging galaxies and a string of star formation in SDSS J1531+3414
Astronomers have ruled out the possibility that the blue strand is also just a lensed mirage from distant galaxies and now their challenge is to understand the origin of the cold gas that is fuelling the growth of the stellar superclusters. Was the gas already in the merging galaxies? Did it condense like rain from the rapidly cooling X-ray plasma surrounding the two galaxies? Or, did it cool out of a shock in the X-ray gas as the ten-million-degree gaseous halos surrounding the galaxies collided together? Future observations with both space- and ground-based observatories are needed to unravel this mystery.
Water droplet animation and the link to stellar superclusters
 Mergers occur when two or more galaxies stray too close to one another, causing them to coalesce into one large body (heic0912). The violent process strips gas, dust and stars away from the galaxies involved and can alter their appearances dramatically, forming large gaseous tails, glowing rings, and warped galactic discs (heic0810).
 The merging system is forming stellar superclusters in equally spaced beads just like evenly spaced drops from a tap. The only real difference is that surface tension in the falling water is analogous to gravity in the context of the star-forming chain. This is a wonderful demonstration that the fundamental laws of physics really are scale-invariant - we see the same physics in rain drops that we do on 100 000 light-year scales.
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
NASA release: http://hubblesite.org/newscenter/archive/releases/2014/26
Hubblecast 76: Merging galaxies and droplets of starbirth: http://www.spacetelescope.org/videos/heic1414a/
For images and more information about Hubble, visit: http://www.nasa.gov/hubble and http://www.spacetelescope.org/
Images, Text, Credits: NASA, ESA/Hubble and G. Tremblay (European Southern Observatory)/Digitized Sky Survey (DSS).
Acknowledgement: M. Gladders & M. Florian (University of Chicago, USA), S. Baum, C. O'Dea & K. Cooke (Rochester Institute of Technology, USA), M. Bayliss (Harvard-Smithsonian Center for Astrophysics, USA), H. Dahle (University of Oslo, Norway), T. Davis (European Southern Observatory), J. Rigby (NASA Goddard Space Flight Center, USA), K. Sharon (University of Michigan, USA), E. Soto (The Catholic University of America, USA) and E. Wuyts (Max-Planck-Institute for Extraterrestrial Physics, Germany).
Videos Credits: Directed by: Georgia Bladon/Visual design and editing: Martin Kornmesser/Written by: Nicky Guttridge and Georgia Bladon/Narration: Sara Mendes da Costa/Images: NASA, ESA/Videos: NASA, ESA/Dripping water video (04:33): Dirk Essl/Galaxy formation animation (04:44): Klaus Dolag (MPA, Garching)/Music: Steve Buick/Web and technical support: Mathias Andre and Raquel Yumi Shida/Executive producer: Lars Lindberg Christensen.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 17:04
NASA - Mars Reconnaissance Orbiter (MRO) logo.
July 10, 2014
Repeated high-resolution observations made by NASA’s Mars Reconnaissance Orbiter (MRO) indicate the gullies on Mars’ surface are primarily formed by the seasonal freezing of carbon dioxide, not liquid water.
The first reports of formative gullies on Mars in 2000 generated excitement and headlines because they suggested the presence of liquid water on the Red Planet, the eroding action of which forms gullies here on Earth. Mars has water vapor and plenty of frozen water, but the presence of liquid water on the neighboring planet, a necessity for all known life, has not been confirmed. This latest report about gullies has been posted online by the journal Icarus.
"As recently as five years ago, I thought the gullies on Mars indicated activity of liquid water," said lead author Colin Dundas of the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Arizona. "We were able to get many more observations, and as we started to see more activity and pin down the timing of gully formation and change, we saw that the activity occurs in winter."
Image above: This pair of images covers one of many sites on Mars where researchers use the HiRISE camera on NASA's Mars Reconnaissance Orbiter to study changes in gullies on slopes. Changes such as the ones visible in deposits near the lower end of this gully occur during winter and early spring on Mars. Image Credit: NASA/JPL.
Dundas and collaborators used the High Resolution Imaging Science Experiment (HiRISE) camera on MRO to examine gullies at 356 sites on Mars, beginning in 2006. Thirty-eight of the sites showed active gully formation, such as new channel segments and increased deposits at the downhill end of some gullies.
Using dated before-and-after images, researchers determined the timing of this activity coincided with seasonal carbon dioxide frost and temperatures that would not have allowed for liquid water.
Frozen carbon dioxide, commonly called dry ice, does not exist naturally on Earth, but is plentiful on Mars. It has been linked to active processes on Mars such as carbon dioxide gas geysers and lines on sand dunes plowed by blocks of dry ice. One mechanism by which carbon dioxide frost might drive gully flows is by gas that is sublimating from the frost providing lubrication for dry material to flow. Another may be slides due to the accumulating weight of seasonal frost buildup on steep slopes.
The findings in this latest report suggest all of the fresh-appearing gullies seen on Mars can be attributed to processes currently underway, whereas earlier hypotheses suggested they formed thousands to millions of years ago when climate conditions were possibly conducive to liquid water on Mars.
Dundas's co-authors on the new report are Serina Diniega of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, and Alfred McEwen of the University of Arizona, Tucson.
Image above: This pair of before (left) and after (right) images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter documents formation of a new channel on a Martian slope between 2010 and 2013. Image Credit: NASA/JPL-Caltech/Univ. of Arizona.
"Much of the information we have about gully formation, and other active processes, comes from the longevity of MRO and other orbiters,” said Diniega. “This allows us to make repeated observation of sites to examine surface changes over time."
Although the findings about gullies point to processes that do not involve liquid water, possible action by liquid water on Mars has been reported in the past year in other findings from the HiRISE team. Those observations were of a smaller type of surface flow feature.
An upcoming special issue of Icarus will include multiple reports about active processes on Mars, including smaller flows that are strong indications of the presence of liquid water on Mars today.
"I like that Mars can still surprise us," Dundas said. "Martian gullies are fascinating features that allow us to investigate a process we just don't see on Earth."
HiRISE is operated by the University of Arizona, Tucson. The instrument was built by Ball Aerospace & Technologies Corp. of Boulder, Colorado. JPL manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate in Washington.
For more information about HiRISE, visit: http://hirise.lpl.arizona.edu
Additional information about MRO is online at: http://www.nasa.gov/mro
For recent findings suggesting the presence of liquid water on Mars, visit: http://go.nasa.gov/1q1VRLS
Images (mentioned), Text, Credits: NASA / J.D. Harrington / JPL / Guy Webster.
Publié par Orbiter.ch à 16:28
ESA - Rosetta Mission patch.
July 10, 2014
Postcards from space as Rosetta draws closer to its destination comet
Comet on 4 July 2014
Comet 67P/Churyumov-Gerasimenko, taken by the narrow angle camera of Rosetta’s scientific imaging system, OSIRIS, on 4 July 2014, at a distance of 37 000 km. The three images are separated by 4 hours, and are shown in order from left to right. The comet has a rotation period of about 12.4 hours. It covers an area of about 30 pixels, and although individual features are not yet resolved, the image is beginning to reveal the comet’s irregular shape.
For more information about Rosetta Mission, visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta
Images, Text, Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.
Publié par Orbiter.ch à 16:18
ESA / Arianespace - Flight VS08 Mission poster.
July 10, 2014
Soyuz Flight VS08
Launch of Soyuz and 03b satellites network
O3b Networks’ mission to bridge the digital divide marked a significant step forward with today’s Arianespace Soyuz flight that deployed its next four connectivity satellites – which will complete the basic constellation for this customer’s pioneering connectivity service and help make the O3b vision a reality.
The launch success – which had a total payload lift performance of more than 3,200 kg. – continues the partnership between Arianespace and O3b Networks, and builds upon the on-target Soyuz mission that orbited O3b’s initial four spacecraft in June 2013.
Arianespace launches O3b satellites on Soyuz mission
Soyuz is the medium-lift member of Arianespace’s launcher family operated from French Guiana, joined by the heavy-lift Ariane 5 and lightweight Vega. For today’s mission, it delivered O3b Networks’ satellites during a flight lasting 2 hours and 22 minutes – which included three burns of the Fregat upper stage, with the four passengers released in two phases from a dispenser system.
The latest O3b Networks connectivity satellites are equipped with Ka-band transponders, and will be positioned at a medium-orbit altitude of 8,062 km. Along with the four spacecraft launched last year, they form the network framework to provide billions of consumers and businesses in nearly 180 countries with low-cost, high-speed, low-latency Internet and mobile connectivity.
First release in target orbit of the 03b 2 and 4 satellites
O3b Networks’ satellite constellation is fully scalable to meet market demand and operates from a medium-orbit altitude of 8,062 km. From this low altitude, latency is dramatically reduced – bringing it on par with a long-haul fiber transmission. The O3b spacecraft were designed, integrated and tested by Thales Alenia Space.
Arianespace continues to set the standard in launch services worldwide. With the Soyuz, Ariane 5 and Vega launchers fully operational at the Spaceport in French Guiana, it is the only launch services company capable of delivering any payload into any orbit – from the smallest spacecraft to the largest geostationary satellites, as well as satellite clusters for constellations and cargo missions to the International Space Station.
Second release in target orbit of the 03b 1 and 3 satellites
Today’s Soyuz success marked the medium-lift vehicle’s eighth flight from the Spaceport since its 2011 introduction at French Guiana, as well as the fifth Arianespace mission from this equatorial launch site in 2014.
Artist's view of the 03b satellites network constellation in orbit
The next mission in Arianespace’s 2014 manifest is the July 24 Ariane 5 flight that will deliver Europe’s fifth, and final, Automated Transfer Vehicle (ATV) for servicing of the International Space Station. The ATV program – managed by the European Space Agency (ESA) – is part of Europe’s contribution to the International Space Station’s operation.
Relive the first moments of Flight VS08 on YouTube: https://www.youtube.com/watch?v=kAWxLQ7rH5o
See the Arianespace VS08 launch kit for further details: http://www.arianespace.com/news-launch-kits/2013-2014-archive.asp
O3b Networks website: http://www.o3bnetworks.com/homepage.aspx
Blog for O3b Networks: http://www.o3bnetworks.com/additional-pages/blog
Thales Alenia Space website: http://www.thalesgroup.com/space
Arianespace website: http://www.arianespace.com/index/index.asp
Images, Video, Text, Credits: Arianespace / Arianespace TV / Alenia Space / Screen captures: Orbiter.ch Aerospace.
Publié par Orbiter.ch à 15:10
ESA - Mars Express Mission patch.
10 July 2014
The surface of Mars is pocked and scarred with giant impact craters and rocky ridges, as shown in this new image from ESA’s Mars Express that borders the giant Hellas basin in the planet’s southern hemisphere.
The Hellas basin, some 2300 km across, is the largest visible impact structure in the Solar System, covering the equivalent of just under half the land area of Brazil.
Perspective view of Hellespontus Montes
The images presented here were taken on 13 January 2014 by the high-resolution stereo camera on Mars Express and feature a portion of the western rim of the Hellas basin, which slopes into the foreground.
This view highlights the Hellespontus Montes, a rough chain of mountain-like terrain that runs around the rim of the basin, seen here as an uneven ridge curving across the top of the main colour, topography and 3D images, and extending to the right in the perspective view.
Hellespontus Montes in context
This feature is a product of the final stages of the formation of the vast Hellas impact basin itself, most likely as the basin walls – which were first pushed outwards by the extraordinary forces at work during the formation of the basin – later collapsed and sank inwards to create the observed stair-stepped shape.
Several craters throughout the scene display wrinkled and rippled features: the close-up of the crater in the foreground of the perspective view highlights a particularly interesting example where the wrinkles form a roughly concentric pattern, with ever-smaller arcs towards the structure’s centre.
Hellespontus Montes topography
This type of feature is known as ‘concentric crater fill’, and is thought to be associated with snowfall and freezing cycles in an earlier and wetter period of martian history.
During this period, snow fell and covered the surface and later moved downhill into the crater. Once inside the crater, the snow became trapped and soon covered by surface dust, before compacting to form ice.
The number of concentric lines indicates many cycles of this process and it is possible that craters like these may still be rich in ice hidden beneath just tens of metres of surface debris.
Meanwhile, the largest impact crater in the image (top left in the main colour, topography and 3D images) shows a degraded, layered crater deposit with several ‘islands’ of material that have been eroded by powerful winds.
Here and elsewhere in the scene, the formation of dunes building up around impact structures and at the base of Hellespontus Montes further indicates the role of strong winds shaping this scene.
Hellespontus Montes in 3D
Last but certainly not least, intricate valleys lead down from the Hellespontus Montes and weave through and across the smoother surrounding plains.
This complex region shows that many of nature’s forces have left their mark here over time, from the formation of the Hellas basin billions of years ago, to the slow and steady changes created by wind and snowfall over millions of years.
High Resolution Stereo Camera: http://berlinadmin.dlr.de/Missions/express/indexeng.shtml
Behind the lens...: http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Behind_the_lens
Frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Frequently_asked_questions
ESA Planetary Science archive (PSA): http://www.rssd.esa.int/PSA
NASA Planetary Data System: http://pds-geosciences.wustl.edu/missions/mars_express/hrsc.htm
HRSC data viewer: http://hrscview.fu-berlin.de/
Mars Express top 10 discoveries: http://sci.esa.int/jump.cfm?oid=51820
Images, Text, Credits: ESA / DLR / FU Berlin / NASA MGS MOLA Science Team / Freie Universitaet Berlin.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 05:35
mercredi 9 juillet 2014
NASA - Messenger Mission to Mercury patch / NASA - STEREO Mission logo.
July 9, 2014
Understanding the sun from afar isn't easy. How do you figure out what powers solar flares – the intense bursts of radiation coming from the release of magnetic energy associated with sunspots – when you must rely on observing only the light and particles that make their way to near-Earth’s orbit?
One answer: you get closer. NASA's MESSENGER spacecraft -- which orbits Mercury, and so is as close as 28 million miles from the sun versus Earth's 93 million miles -- is near enough to the sun to detect solar neutrons that are created in solar flares. The average lifetime for one of these neutrons is only 15 minutes. How far they travel into space depends on their speed, and slower neutrons don't travel far enough to be seen by particle detectors in orbit around Earth. Results showing that MESSENGER has likely observed solar neutrons appeared in the Journal of Geophysical Research: Space Physics on July 9, 2014.
Image above: A solar flare erupted on the far side of the sun on June 4, 2011, and sent solar neutrons out into space. Solar neutrons don't make it to all the way to Earth, but NASA's MESSENGER, orbiting Mercury, found strong evidence for the neutrons, offering a new technique to study these giant explosions. Image Credit: NASA/STEREO/Helioviewer.
"To understand all the processes on the sun we look at as many different particles coming from the sun as we can – photons, electrons, protons, neutrons, gamma rays –to gather different kinds of information," said David Lawrence, first author of the paper at The Johns Hopkins Applied Physics Lab in Laurel, Maryland. "Closer to Earth we can observe charged particles from the sun, but analyzing them can be a challenge as their journey is affected by magnetic fields."
Such charged particles twirl and gyrate around the magnetic field lines created by the vast magnetic systems that surround the sun and Earth. Neutrons, however, as they are not electrically charged, travel in straight lines from the flaring region. They can carry information about flare processes unperturbed by the environment through which they move. This information can be used by scientists to decipher one aspect of the complicated acceleration processes that are responsible for the creation of highly energetic and fast solar particles.
Lawrence and his team looked at MESSENGER data from June 4 and 5, 2011, corresponding to solar flares that were accompanied by fast-moving, energetic charged particles. The flare occurred on the far side of the sun so Earth-based views of the flare region could not be obtained. However, a solar telescope on NASA's Solar Terrestrial Relations Observatory, or STEREO, spacecraft did have a clear view of the far-side flare region. STEREO provided useful observations of the flare. This combined use of NASA mission data makes each individual mission more effective in addressing unsolved science questions.
The MESSENGER data showed an increase in the number of – not electrically charged -- neutrons at Mercury’s orbit hours before the large number of charged particles reached the spacecraft. This indicated that the neutrons were most likely produced by accelerated flare particles striking the lower solar atmosphere, releasing neutrons as a result of high-energy collisions. So, together, the MESSENGER and STEREO data can provide new information about how particles are accelerated in solar flares.
For more information about MESSENGER, visit: http://www.nasa.gov/messenger
For information about STEREO, visit: http://www.nasa.gov/stereo
Image (mentioned), Text, Credits: NASA's Goddard Space Flight Center / Karen C. Fox.
Publié par Orbiter.ch à 14:14
ESO - European Southern Observatory logo.
9 July 2014
New observations reveal how stardust forms around a supernova
Artist’s impression of dust formation around a supernova explosion
A group of astronomers has been able to follow stardust being made in real time — during the aftermath of a supernova explosion. For the first time they show that these cosmic dust factories make their grains in a two-stage process, starting soon after the explosion, but continuing for years afterwards. The team used ESO's Very Large Telescope (VLT) in northern Chile to analyse the light from the supernova SN2010jl as it slowly faded. The new results are published online in the journal Nature on 9 July 2014.
The origin of cosmic dust in galaxies is still a mystery . Astronomers know that supernovae may be the primary source of dust, especially in the early Universe, but it is still unclear how and where dust grains condense and grow. It is also unclear how they avoid destruction in the harsh environment of a star-forming galaxy. But now, observations using ESO’s VLT at the Paranal Observatory in northern Chile are lifting the veil for the first time.
An international team used the X-shooter spectrograph to observe a supernova — known as SN2010jl — nine times in the months following the explosion, and for a tenth time 2.5 years after the explosion, at both visible and near-infrared wavelengths . This unusually bright supernova, the result of the death of a massive star, exploded in the small galaxy UGC 5189A.
The dwarf galaxy UGC 5189A, site of the supernova SN 2010jl
“By combining the data from the nine early sets of observations we were able to make the first direct measurements of how the dust around a supernova absorbs the different colours of light,” said lead author Christa Gall from Aarhus University, Denmark. “This allowed us to find out more about the dust than had been possible before.”
The team found that dust formation starts soon after the explosion and continues over a long time period. The new measurements also revealed how big the dust grains are and what they are made of. These discoveries are a step beyond recent results obtained using the Atacama Large Millimeter/submillimeter Array (ALMA), which first detected the remains of a recent supernova brimming with freshly formed dust from the famous supernova 1987A (SN 1987A; eso1401).
The team found that dust grains larger than one thousandth of a millimetre in diameter formed rapidly in the dense material surrounding the star. Although still tiny by human standards, this is large for a grain of cosmic dust and the surprisingly large size makes them resistant to destructive processes. How dust grains could survive the violent and destructive environment found in the remnants of supernovae was one of the main open questions of the ALMA paper, which this result has now answered — the grains are larger than expected.
The dwarf galaxy UGC 5189A, site of the supernova SN 2010jl (annotated)
“Our detection of large grains soon after the supernova explosion means that there must be a fast and efficient way to create them,” said co-author Jens Hjorth from the Niels Bohr Institute of the University of Copenhagen, Denmark, and continued: “We really don’t know exactly how this happens.”
But the astronomers think they know where the new dust must have formed: in material that the star shed out into space even before it exploded. As the supernova's shockwave expanded outwards, it created a cool, dense shell of gas — just the sort of environment where dust grains could seed and grow.
Results from the observations indicate that in a second stage — after several hundred days — an accelerated dust formation process occurs involving ejected material from the supernova. If the dust production in SN2010jl continues to follow the observed trend, by 25 years after the supernova, the total mass of dust will be about half the mass of the Sun; similar to the dust mass observed in other supernovae such as SN 1987A.
“Previously astronomers have seen plenty of dust in supernova remnants left over after the explosions. But they also only found evidence for small amounts of dust actually being created in the supernova explosions. These remarkable new observations explain how this apparent contradiction can be resolved,” concludes Christa Gall.
 Cosmic dust consists of silicate and amorphous carbon grains — minerals also abundant on Earth. The soot from a candle is very similar to cosmic carbon dust, although the size of the grains in the soot are ten or more times bigger than typical grain sizes for cosmic grains.
 Light from this supernova was first seen in 2010, as is reflected in the name, SN 2010jl. It is classed as a Type IIn supernova. Supernovae classified as Type II result from the violent explosion of a massive star with at least eight times the mass of the Sun. The subtype of a Type IIn supernova — “n” denotes narrow — shows narrow hydrogen lines in its spectra. These lines result from the interaction between the material ejected by the supernova and the material already surrounding the star.
This research was presented in a paper “Rapid formation of large dust grains in the luminous supernova SN 2010jl”, by C. Gall et al., to appear online in the journal Nature on 9 July 2014.
The team is composed of Christa Gall (Department of Physics and Astronomy, Aarhus University, Denmark; Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Denmark; Observational Cosmology Lab, NASA Goddard Space Flight Center, USA), Jens Hjorth (Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Denmark), Darach Watson (Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Denmark), Eli Dwek (Observational Cosmology Lab, NASA Goddard Space Flight Center, USA), Justyn R. Maund (Astrophysics Research Centre School of Mathematics and Physics Queen’s University Belfast, UK; Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Denmark; Department of Physics and Astronomy, University of Sheffield, UK), Ori Fox (Department of Astronomy, University of California, Berkeley, USA), Giorgos Leloudas (The Oskar Klein Centre, Department of Physics, Stockholm University, Sweden; Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Denmark), Daniele Malesani (Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Denmark) and Avril C. Day-Jones (Departamento de Astronomia, Universidad de Chile, Chile).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Research paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1421/eso1421a.pdf
ALMA Spots Supernova Dust Factory: http://www.eso.org/public/news/eso1401/
More about X-Shooter: http://www.eso.org/sci/facilities/paranal/instruments/xshooter.html
More about the VLT: http://www.eso.org/public/teles-instr/vlt/
Images, Text, Credits: ESO / M. Kornmesser.
Publié par Orbiter.ch à 13:43
mardi 8 juillet 2014
NASA - Mars Reconnaissance Orbiter (MRO) patch / NASA - Mars Science Laboratory (MSL) patch.
July 8, 2014
NASA Mars rover Curiosity has driven out of the ellipse, approximately 4 miles wide and 12 miles long (7 kilometers by 20 kilometers), that was mapped as safe terrain for its 2012 landing inside Gale Crater.
The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter photographed the rover on June 27 at the end of a drive that put Curiosity right on the ellipse boundary. An image from that observation is online at: http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA18399
NASA's Mars Reconnaissance Orbiter spacecraft. Image Credit: NASA/JPL-Caltech
The landing ellipse is the area within which the rover had a very high probability of touching down when it arrived at Mars on Aug. 5, 2012, PDT (Aug. 6, UTC). The area needed to meet requrements for providing access to scientifically interesting sites while presenting few landing hazards, such as steep slopes or large boulders. Many areas of scientific interest have slopes ineligible for landing safety, and Curiosity was designed to have the capability of driving far enough to get to slopes ouside of the landing ellipse. Since landing, Curiosity has driven slightly more than 5 miles (8 kilometers).
Image above: This June 27, 2014, image from the HiRISE camera on NASA's Mars Reconnaissance Orbiter shows NASA's Curiosity Mars rover on the rover's landing-ellipse boundary, which is superimposed on the image. The 12-mile-wide ellipse was mapped as safe terrain for its 2012 landing inside Gale Crater. Image Credit: NASA/JPL-Caltech/Univ. of Arizona.
NASA's Mars Science Laboratory (MSL), alias "Curiosity" rover. Image Credit: NASA/JPL-Caltech
NASA's Mars Science Laboratory Project is using Curiosity to assess ancient habitable environments and major changes in Martian environmental conditions. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter and Mars Science Laboratory projects for NASA's Science Mission Directorate in Washington. HiRISE is operated by the University of Arizona, Tucson. The instrument was built by Ball Aerospace & Technologies Corp., Boulder, Colorado.
For more information about the Mars Reconnaissance Orbiter, which has been studying Mars from orbit since 2006, visit: http://www.nasa.gov/mro
For more information about Curiosity, visit: http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/
You can follow the mission on Facebook at: http://www.facebook.com/marscuriosity and on Twitter at: http://www.twitter.com/marscuriosity
Images (mentioned), Text, Credits: NASA / JPL / Guy Webster.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 13:33
Soyuz-2.1b with these payloads on the lanch-pad
July 8 at 19 hours 58 minutes Moscow time from the launch complex Sq. 31 took the Baikonur Cosmodrome launch vehicle (LV) Soyuz-2.1b with the upper stage (RB) Frigate spacecraft (SC) Meteor-M № 2 and six small spacecraft MCA-FCI «SkySat-2», «DX-1», «TechDemoSat-1», «UKube-1», «AISSAT-2."
From the Baikonur Cosmodrome launch of spacecrafts Meteor-M № 2 and six small satellites
In accordance with cyclogram flight 20 hour 07 minutes after the regular department head unit from the third stage booster RB Fregat continued removal of spacecraft into the desired orbit.
Meteor-M № 2 is intended to provide timely global hydrometeorological information for weather forecasting, monitoring of the ozone layer and radiation environment in near-Earth space, as well as for monitoring the sea surface, determine its temperature, including ice conditions for the purpose of navigation in the polar areas. Spacecraft mass is 2778 kg, payload weight is approximately equal to 1250 kg, lifetime - 5 years.
Meteor-M № 2 satellite
Spacecraft Meteor-M successfully launched into the target orbit
In accordance with cyclogram flight Meteor-M № 2 (production of JSC "Corporation VNIIEM") displayed on the target orbit.
Trail of the Soyuz rocket into the skies of Baikonur
He will join the existing national meteorological orbital grouping. Meteor-M № 2 is designed for the global and local images of clouds, the earth's surface, ice and snow cover data to determine sea surface temperature and the radiation temperature of the underlying surface, the earth's surface radar images, data on the distribution of ozone in the atmosphere and its overall content, information about the geophysical conditions in near-Earth space.
Rocket Soyuz-2.1b created in JSC "RCC" Progress (Samara) and is a modification of Soyuz-2. Compared to option "1a" she has an engine with high power characteristics for the third stage. The Soyuz-2.1b in relation to a previous version of the above injection accuracy, stability and control, increased payload weight. Upper stage Fregat made in FSUE "NPO. Lavochkin".
ROSCOSMOS Press Release: http://www.federalspace.ru/20761/ and http://www.federalspace.ru/20762/
Images, Text, Credits: Roscosmos press service / ROSCOSMOS / Translation: Orbiter.ch Aerospace.
Publié par Orbiter.ch à 12:42
NASA / ESA - Cassini Mission to Saturn patch.
July 8, 2014
Vortex and Rings
The Cassini spacecraft captures three magnificent sights at once: Saturn's north polar vortex and hexagon along with its expansive rings.
The hexagon, which is wider than two Earths, owes its appearance to the jet stream that forms its perimeter. The jet stream forms a six-lobed, stationary wave which wraps around the north polar regions at a latitude of roughly 77 degrees North.
This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on April 2, 2014 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers.
The view was obtained at a distance of approximately 1.4 million miles (2.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 43 degrees. Image scale is 81 miles (131 kilometers) per pixel.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
For more information about the Cassini-Huygens mission visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .
The Cassini ESA wesite: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens
Image, Text, Credits: NASA / JPL-Caltech / Space Science Institute.
Publié par Orbiter.ch à 08:52
lundi 7 juillet 2014
NASA - Voyager-1 Mission patch.
July 7, 2014
NASA's Voyager 1 spacecraft has experienced a new "tsunami wave" from the sun as it sails through interstellar space. Such waves are what led scientists to the conclusion, in the fall of 2013, that Voyager had indeed left our sun's bubble, entering a new frontier.
"Normally, interstellar space is like a quiet lake," said Ed Stone of the California Institute of Technology in Pasadena, California, the mission's project scientist since 1972. "But when our sun has a burst, it sends a shock wave outward that reaches Voyager about a year later. The wave causes the plasma surrounding the spacecraft to sing."
Voyager 1 Entering Interstellar Space (Artist Concept)
Image above: This artist's concept depicts NASA's Voyager 1 spacecraft entering interstellar space, or the space between stars. Interstellar space is dominated by the plasma, or ionized gas, that was ejected by the death of nearby giant stars millions of years ago. Image Credit: NASA/JPL-Caltech.
Data from this newest tsunami wave generated by our sun confirm that Voyager is in interstellar space -- a region between the stars filled with a thin soup of charged particles, also known as plasma. The mission has not left the solar system -- it has yet to reach a final halo of comets surrounding our sun -- but it broke through the wind-blown bubble, or heliosphere, encasing our sun. Voyager is the farthest human-made probe from Earth, and the first to enter the vast sea between stars.
"All is not quiet around Voyager," said Don Gurnett of the University of Iowa, Iowa City, the principal investigator of the plasma wave instrument on Voyager, which collected the definitive evidence that Voyager 1 had left the sun's heliosphere. "We're excited to analyze these new data. So far, we can say that it confirms we are in interstellar space."
Our sun goes through periods of increased activity, where it explosively ejects material from its surface, flinging it outward. These events, called coronal mass ejections, generate shock, or pressure, waves. Three such waves have reached Voyager 1 since it entered interstellar space in 2012. The first was too small to be noticed when it occurred and was only discovered later, but the second was clearly registered by the spacecraft's cosmic ray instrument in March of 2013.
Voyager Captures Sounds of Interstellar Space
Video above: The first two tsunami waves to reach Voyager 1 caused surrounding ionized matter to ring like a bell at frequencies expected in interstellar space. The third tsunami caused similar ringing, confirming that Voyager 1 continues it journey into interstellar space. Video Credit: NASA's Voyager 1 spacecraft captured these sounds of interst.
Cosmic rays are energetic charged particles that come from nearby stars in the Milky Way galaxy. The sun's shock waves push these particles around like buoys in a tsunami. Data from the cosmic ray instrument tell researchers that a shock wave from the sun has hit.
Meanwhile, another instrument on Voyager registers the shock waves, too. The plasma wave instrument can detect oscillations of the plasma electrons.
"The tsunami wave rings the plasma like a bell," said Stone. "While the plasma wave instrument lets us measure the frequency of this ringing, the cosmic ray instrument reveals what struck the bell -- the shock wave from the sun."
This ringing of the plasma bell is what led to the key evidence showing Voyager had entered interstellar space. Because denser plasma oscillates faster, the team was able to figure out the density of the plasma. In 2013, thanks to the second tsunami wave, the team acquired evidence that Voyager had been flying for more than a year through plasma that was 40 times denser than measured before -- a telltale indicator of interstellar space.
Why is it denser out there? The sun's winds blow a bubble around it, pushing out against denser matter from other stars.
Now, the team has new readings from a third wave from the sun, first registered in March of this year. These data show that the density of the plasma is similar to what was measured previously, confirming the spacecraft is in interstellar space. Thanks to our sun's rumblings, Voyager has the opportunity to listen to the singing of interstellar space -- an otherwise silent place.
Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft and is expected to enter interstellar space in a few years.
JPL, a division of Caltech, built and operates the twin Voyager spacecraft. The Voyagers Interstellar Mission is a part of NASA's Heliophysics System Observatory, sponsored by the Heliophysics Division of NASA's Science Mission Directorate in Washington. NASA's Deep Space Network, managed by JPL, is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions. The spacecraft's nuclear batteries were provided by the Department of Energy.
For more information on the Voyager mission, visit: http://voyager.jpl.nasa.gov
Image (mentioned), Video (mentioned), Text, Credits: NASA / JPL / Whitney Clavin.
Publié par Orbiter.ch à 17:10