vendredi 8 mars 2013
Asteroid & Comet Watch.
March 8, 2013
Image above: For those in search of comet L4 PANSTARRS, look to the west after sunset in early and mid-March. This graphic shows the comet's expected positions in the sky. Image credit: NASA.
Comets visible to the naked eye are a rare delicacy in the celestial smorgasbord of objects in the nighttime sky. Scientists estimate that the opportunity to see one of these icy dirtballs advertising their cosmic presence so brilliantly they can be seen without the aid of a telescope or binoculars happens only once every five to 10 years. That said, there may be two naked-eye comets available for your viewing pleasure this year.
"You might have heard of a comet ISON, which may become a spectacular naked-eye comet later this fall," said Amy Mainzer, the principal investigator of NASA's NEOWISE mission at the Jet Propulsion Laboratory in Pasadena, Calif., and self-described cosmic icy dirtball fan. "But if you have the right conditions you don't have to wait for ISON. Within a few days, comet PANSTARRS will be making its appearance in the skies of the Northern Hemisphere just after twilight."
Discovered in June 2011, comet 2011 L4 (PANSTARRS) bears the name of the telescopic survey that discovered it -- the less than mellifluous sounding "Panoramic Survey Telescope and Rapid Response System" which sits atop the Haleakala volcano in Hawaii.
Image above: Close-up of comet C/2011 L4 PANSTARRS as seen from Mount Dale, Western Australia. Image credit: Astronomy Education Services/Gingin Observatory.
Since its discovery a year-and-a-half ago, observing comet PANSTARRS has been the exclusive dominion of comet aficionados in the Southern Hemisphere, but that is about to change. As the comet continues its well-understood and safe passage through the inner-solar system, its celestial splendor will be lost to those in the Southern Hemisphere, but found by those up north.
"There is a catch to viewing comet PANSTARRS," said Mainzer. "This one is not that bright and is going to be low on the western horizon, so you'll need a relatively unobstructed view to the southwest at twilight and, of course, some good comet-watching weather."
Well, there is one more issue -- the time of day, or night, to view it.
"Look too early and the sky will be too bright," said Rachel Stevenson, a NASA Postdoctoral Fellow at JPL. "Look too late, the comet will be too low and obstructed by the horizon. This comet has a relatively small window."
By March 8, comet PANSTARRS may be viewable for those with a totally unobstructed view of the western horizon for about 15 minutes after twilight. On March 10, it will make its closest approach to the sun about 28 million miles (45 million kilometers) away. As it continues its nightly trek across the sky, the comet may get lost in the sun's glare but should return and be visible to the naked eye by March 12. As time marches on in the month of March, the comet will begin to fade away slowly, becoming difficult to view (even with binoculars or small telescopes) by month's end. The comet will appear as a bright point of light with its diffuse tail pointing nearly straight up from the horizon like an exclamation point.
Image above: Comet C/2011 L4 PANSTARRS as seen from Mount Dale, Western Australia. The lights on the distant horizon are from the city of Armadale, which is southeast of Perth. Image credit: Astronomy Education Services/Gingin Observatory.
What, if any, attraction does seeing a relatively dim naked-eye comet with the naked eye hold for someone who works with them every day, with file after file of high-resolution imagery spilling out on her computer workstation?
"You bet I'm going to go look at it!" said Mainzer. "Comet PANSTARRS may be a little bit of a challenge to find without a pair of binoculars, but there is something intimately satisfying to see it with your own two eyes. If you have a good viewing spot and good weather, it will be like the Sword of Gryffindor, it should present itself to anyone who is worthy."
NASA detects, tracks and characterizes asteroids and comets passing relatively close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them, and predicts their paths to determine if any could be potentially hazardous to our planet.
JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington, DC. JPL is a division of the California Institute of Technology in Pasadena.
More information about asteroids and near-Earth objects is at: http://www.jpl.nasa.gov/asteroidwatch , and on Twitter: @asteroidwatch
Images (mentioned), Text, Credits: NASA / JPL / DC Agle.
Publié par Orbiter.ch à 13:29
ESA - GOCE Mission logo.
8 March 2013
Satellites map changes in Earth’s surface caused by earthquakes but never before have sound waves from a quake been sensed directly in space – until now. ESA’s hyper-sensitive GOCE gravity satellite has added yet another first to its list of successes.
Earthquakes not only create seismic waves that travel through Earth’s interior, but large quakes also cause the surface of the planet to vibrate like a drum. This produces sound waves that travel upwards through the atmosphere.
Earthquake sensed by GOCE
The size of these waves changes from centimetres at the surface to kilometres in the thin atmosphere at altitudes of 200–300 km.
Only low-frequency sound – infrasound – reaches these heights. It causes vertical movements that expand and contract the atmosphere by accelerating air particles.
On Monday, Japan remembers the 20 000 people who died in the earthquake and tsunami that devastated its northeastern coast two years ago. New studies have revealed that this massive quake was also felt in space by ESA’s GOCE satellite.
Since it was launched in 2009, GOCE has been mapping Earth’s gravity with unrivalled precision, orbiting at the lowest altitude of any observation satellite. But at less than 270 km up, it has to cope with air drag as it cuts through the remnants of the atmosphere.
The cleverly designed satellite carries an innovative ion engine that instantly compensates for any drag by generating carefully calculated thrusts. These measurements are provided by very precise accelerometers.
While the measurements ensure that GOCE remains ultra-stable in its low orbit to collect ultra-precise measurements of Earth’s gravity, atmospheric density and vertical winds along its path can be inferred from the thruster and accelerometer data.
ESA’s GOCE spacecraft
Exploiting GOCE data to the maximum, scientists from the Research Institute in Astrophysics and Planetology in France, the French space agency CNES, the Institute of Earth Physics of Paris and Delft University of Technology in the Netherlands, supported by ESA’s Earth Observation Support to Science Element, have been studying past measurements.
They discovered that GOCE detected sound waves from the massive earthquake that hit Japan on 11 March 2011.
When GOCE passed through these waves, its accelerometers sensed the vertical displacements of the surrounding atmosphere in a way similar to seismometers on the surface of Earth. Wave-like variations in air density were also observed.
Earthquake felt by GOCE
When GOCE passed through these waves, its accelerometers sensed the vertical displacements of the surrounding atmosphere in a way similar to seismometers on the surface of Earth. Wave-like variations in air density were also observed.
Raphael Garcia from the Research Institute in Astrophysics and Planetology said, “Seismologists are particularly excited by this discovery because they were virtually the only Earth scientists without a space-based instrument directly comparable to those deployed on the ground.
“With this new tool they can start to look up into space to understand what is going on under their feet.”
Research Institute in Astrophysics and Planetology: http://www.irap.omp.eu/index.php/eng
Institute of Earth Physics of Paris: http://www.ipgp.fr/index2.php?langue=1
TU Delft–Astrodynamics and Space Missions: http://www.lr.tudelft.nl/en/organisation/departments-and-chairs/space-engineering/astrodynamics-and-space-missions/
Hypersonic Technology Goettingen: http://www.htg-hst.de/index.htm
Support to Science Element: http://due.esrin.esa.int/stse/
Wiley: GOCE the first seismometer in orbit around the Earth: http://onlinelibrary.wiley.com/doi/10.1002/grl.50205/abstract
Gravity's grip: http://www.esa.int/Our_Activities/Observing_the_Earth/GOCE/Highlights/Gravity_s_grip
Images, Videos, Text, Credits: ESA / IRAP / CNES / TU Delft / HTG / Planetary Visions / AOES Medialab.
Publié par Orbiter.ch à 12:49
NASA - Mars Reconnaissance Orbiter (MRO) patch.
March 8, 2013
NASA's Mars Reconnaissance Orbiter (MRO) has provided images allowing scientists for the first time to create a 3-D reconstruction of ancient water channels below the Martian surface.
The spacecraft took numerous images during the past few years that showed channels attributed to catastrophic flooding in the last 500 million years. Mars during this period had been considered cold and dry. These channels are essential to understanding the extent to which recent hydrologic activity prevailed during such arid conditions. They also help scientists determine whether the floods could have induced episodes of climate change.
PIA16767: Visualization of Buried Marte Vallis Channels
The estimated size of the flooding appears to be comparable to the ancient mega flood that created the Channeled Scablands in the Pacific Northwest region of the United States in eastern Washington.
The findings are reported in the March 7 issue of Science Express by a team of scientists from NASA, the Smithsonian Institution, and the Southwest Research Institute in Houston.
"Our findings show the scale of erosion that created the channels previously was underestimated and the channel depth was at least twice that of previous approximations," said Gareth Morgan, a geologist at the National Air and Space Museum's Center for Earth and Planetary Studies in Washington and lead author on the paper. "This work demonstrates the importance of orbital sounding radar in understanding how water has shaped the surface of Mars."
The channels lie in Elysium Planitia, an expanse of plains along the Martian equator and the youngest volcanic region on the planet. Extensive volcanism throughout the last several hundred million years covered most of the surface of Elysium Planitia, and this buried evidence of Mars' older geologic history, including the source and most of the length of the 620-mile-long (1000-kilometer-long) Marte Vallis channel system. To probe the length, width and depth of these underground channels, the researchers used MRO's Shallow Radar (SHARAD).
Image above: Massive floodwaters on Mars gouged a channel more than 600 miles (1,000 kilometers) long, making a trench that was hidden to scientists until now because volcanic flows buried it underground. Erupting groundwater, perhaps triggered by a volcano or an earthquake, forced water across the surface during the past 500 million years.
Marte Vallis' morphology is similar to more ancient channel systems on Mars, especially those of the Chryse basin. Many scientists think the Chryse channels likely were formed by the catastrophic release of ground water, although others suggest lava can produce many of the same features. In comparison, little is known about Marte Vallis.
With the SHARAD radar, the team was able to map the buried channels in three dimensions with enough detail to see evidence suggesting two different phases of channel formation. One phase etched a series of smaller branching, or "anastomosing," channels that are now on a raised "bench" next to the main channel. These smaller channels flowed around four streamlined islands. A second phase carved the deep, wide channels.
Mars Reconnaissance Orbiter (MRO)
"In this region, the radar picked up multiple 'reflectors,' which are surfaces or boundaries that reflect radio waves, so it was possible to see multiple layers, " said Lynn Carter, the paper's co-author from NASA's Goddard Space Flight Center in Greenbelt, Md. "We have rarely seen that in SHARAD data outside of the polar ice regions of Mars."
The mapping also provided sufficient information to establish the floods that carved the channels originated from a now-buried portion of the Cerberus Fossae fracture system. The water could have accumulated in an underground reservoir and been released by tectonic or volcanic activity.
"While the radar was probing thick layers of dry, solid rock, it provided us with unique information about the recent history of water in a key region of Mars," said co-author Jeffrey Plaut of NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif.
The Italian Space Agency provided the SHARAD instrument on MRO and Sapienza University of Rome leads its operations. JPL manages MRO for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems of Denver built the orbiter and supports its operations.
The 3-D image can be viewed online at: http://photojournal.jpl.nasa.gov/catalog/PIA16767
For more about NASA's MRO mission, visit: http://www.nasa.gov/mro
Images, Text, Credit: NASA / JPL-Caltech / Sapienza University of Rome/Smithsonian Institution / USGS.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 05:10
jeudi 7 mars 2013
ISS - International Space Station patch / SpaceX - Commercial Resupply Serves SpX-2 patch.
March 7, 2013
A SpaceX Dragon spacecraft has delivered a "goody bag" to the crew aboard the International Space Station. But it's not filled with treats. This goody bag -- called the Wet Lab Kit -- is loaded with supplies to make it easier for crews to collect and process various types of samples in orbit, increasing scientific research and analysis more than ever before.
Launched on the second Commercial Resupply Mission March 1, this kit is part of the Wetlab 1 project. Wetlab 1 consists of the Wet Lab Kit, developed by NASA's Johnson Space Center in Houston, and a Plate Reader, developed by NanoRacks of Houston. Both items are funded by the International Space Station National Laboratory Office.
Image above: Frequently used tools and supplies are packed into the Wet Lab Kit, a soft goods bag that measures 19.5 inches by 16.75 inches by 9.5 inches when full. The kit, a part of Wetlab 1, is available for those who have experiments onboard the International Space Station. (NASA).
"With the arrival of Wetlab 1 to station, we are accelerating support for the research community's sample processing needs," said Bert Magh, project manager of Wetlab 1 at Johnson. "We think of it like a supply pantry for experiments. The Wet Lab Kit enhances the capabilities of the space station as a U.S. National Laboratory by providing frequently used supplies needed to complete the work there. Some investigators will benefit from being able to get analysis quicker rather than waiting for samples to return to Earth."
The kit is a 19.5-inch-by-16.75-inch-by-9.5-inch soft goods bag filled with flight-certified experiment tools and supplies. Contents include syringes, needles, absorbent pads, gloves, tape, labels, scissors, tubes, forceps, wipes, gauze, cable ties, bubble wrap and vials, among other things. These supplies allow a broad range of samples -- such as blood, urine, saliva, tissues, plants and specimens -- to be processed in orbit. Subsequent launches will resupply items in the kit as needed.
Image above: A Biological Research in Canisters experiment package with five Petri dish fixation units (PDFU) installed. The PDFUs each contain a Petri dish with the biological sample to be flown in space. (NASA).
The kit also contains a custom Disposable Glove Bag, which is an unpressurized enclosure that keeps liquids and particles from escaping into the station's cabin. It is made of clear Teflon and has two integral inward-protruding gloves. The seams are heat-sealed, and the gloves are attached with Teflon-coated fiberglass cloth tape. The bag inflates to become 16 inches tall, 25 inches deep and 34 inches wide. The bag then can be attached to a collapsible frame. Small, half-inch Velcro coins are inside the glove bag to hold experiment materials in place.
"In the past, crew members had to process their samples in the Microgravity Science Glovebox (MSG), which is needed for experiments that require stricter containment controls," Magh explained. "Now the crew won't have to interrupt MSG experiments. Instead, they can easily unfold the glove bag, perform their experiment and then deflate and trash it when completed."
Image above: The NanoRacks Plate Reader allows for in-orbit microbiological analysis, increasing life science and biological research. (NASA).
Should a spill occur, cleaning wipes are used inside the bag to clean and absorb any liquids before deflating the bag. To do this cleanup, the crew member uses the station's wet/dry vacuum through the bag's filter to prevent the release of any remaining particles or droplets.
Wetlab 2 is in the development stage and is targeted for launch in 2014. This project will provide hardware that will allow in-orbit gene expression analysis. The instrument will be capable of taking a sample grown in orbit, extracting the ribonucleic acid and setting up reactions that read and record real-time gene expression information. That information will be transmitted to Earth.
Image above: NASA astronaut Nicole Stott working on the Cell Biology Experiment Facility (CBEF) SPACE SEED experiment in the Kibo JEM Pressurized Module (JPM) during Expedition 21. The Wet Lab Kit will make it easier for sample collection like this aboard the International Space Station. (NASA).
Also for use alongside the Web Lab Kit is the NanoRacks Plate Reader, which was launched to the station July 27, 2012, aboard the Japanese H-II Transfer Vehicle-3 resupply spacecraft. This instrument allows for in-orbit microbiological analysis, increasing life science and biological research on the station.
"Because of Wetlab 1, station users don't have to send their own supplies," said Magh. "The Wet Lab Kit is ready for them to use now. It is prepared for our customers with the tools and supplies they request from our Wet Lab Kit catalog for processing their experiment samples. The Plate Reader makes it possible to instantly analyze samples and send the data to scientists on Earth."
Image above: This cutaway view of an artist's rendering of the International Space Station shows a very busy crew inside and outside the orbital lab. The station's current six-person crew size. (NASA).
Not having to certify the equipment provided in the Wet Lab Kit for spaceflight may save time and money for future researchers. Investigators interested in flying their experiments on the orbiting laboratory can visit the Opportunities for International Space Station Research website: http://www.nasa.gov/mission_pages/station/research/ops/index.html
For more information about International Space Station (ISS), visit: http://www.nasa.gov/mission_pages/station/main/index.html
Images (mentioned), Text, Credit: NASA's Marshall Space Flight Center / Jessica Eagan.
Publié par Orbiter.ch à 14:42
NASA - Solar Dynamics Observatory (SDO) patch.
March 7, 2013
A Quiet Interlude in Solar Max
Something unexpected is happening on the Sun. 2013 was supposed to be the year of “solar maximum,” the peak of the 11-year sunspot cycle. Yet 2013 has arrived and solar activity is relatively low. Sunspot numbers are well below their values from 2011, and strong solar flares have been infrequent. The quiet has led some observers to wonder if forecasters missed the mark.
Solar physicist Dean Pesnell of NASA’s Goddard Space Flight Center has a different explanation. “This is solar maximum,” he says. “But it looks different from what we expected because it is double-peaked.”
Conventional wisdom holds that solar activity swings back and forth like a simple pendulum. At one end of the cycle, there is a quiet time with few sunspots and flares. At the other end, solar max brings high sunspot numbers and frequent solar storms. It’s a regular rhythm that repeats every 11 years.
Reality is more complicated. Astronomers have been counting sunspots for centuries, and they have seen that the solar cycle is not perfectly regular. The back-and-forth swing in sunspot counts can take anywhere from 10 to 13 years to complete. Also, the amplitude of the cycle varies; some solar maxima are very weak, others very strong.
The top image above shows the Earth-facing surface of the Sun on February 28, 2013, as observed by the Helioseismic and Magnetic Imager (HMI) on NASA’s Solar Dynamics Observatory. HMI observes the solar disk at 6173 Ångstroms, a wavelength designed to study surface oscillations and the magnetic field. HMI observed just a few small sunspots on an otherwise clean face, which is usually riddled with many spots during peak solar activity. The video below shows a full solar rotation observed by HMI from February 1-28, 2013. (Download the animation from the links below the image.)
Solar Max Sunspots from the Solar Dynamics Observatory
Pesnell notes yet another complication in the solar cycle: “The last two solar maxima, around 1989 and 2001, had not one but two peaks.” Solar activity went up, dipped, then rose again, performing a mini-cycle that lasted about two years. The same thing could be happening now, as sunspot counts jumped in 2011 and dipped in 2012. Pesnell expects them to rebound in 2013: “I am comfortable in saying that another peak will happen in 2013 and possibly last into 2014,”
The second image above plots monthly sunspot numbers for solar cycle 24 (the current one), cycle 23, and cycle 21, the last one with one, normal peak.
Another curiosity of the solar cycle is that the Sun's hemispheres do not always peak at the same time. In the current cycle, the south has been lagging behind the north. The second peak, if it occurs, will likely feature the southern hemisphere playing catch-up, with a surge in activity south of the Sun's equator.
NASA's Solar Dynamics Observatory (SDO)
Pesnell is a member of the NOAA/NASA Solar Cycle Prediction Panel, which last assembled in 2008 to forecast the next solar maximum. The panel declared: “The next solar cycle (Cycle 24) will be below average in intensity, with a maximum sunspot number of 90. Given the date of solar minimum and the predicted maximum intensity, solar maximum is now expected to occur in May 2013.”
Given the tepid state of solar activity now, a maximum in May seems unlikely. “We may be seeing what happens when you predict a single amplitude and the Sun responds with a double peak,” says Pesnell. He notes a similarity between Solar Cycle 24 and Solar Cycle 14, which had a double-peak during the first decade of the 20th century. If the two cycles are twins, “it would mean one peak in late 2013 and another in 2015.”
NASA images courtesy Solar Dynamics Observatory and Helioseismic and Magnetic Imager science teams. Sunspot number data from the NOAA National Geophysical Data Center. NASA animation by Robert Simmon. Caption adapted from a story by Tony Phillips, Science@NASA.
Solar Dynamics Observatory (SDO): http://sdo.gsfc.nasa.gov/
Helioseismic and Magnetic Imager science teams: http://hmi.stanford.edu/
Sunspot number data from the NOAA National Geophysical Data Center: http://www.ngdc.noaa.gov/stp/solar/ssndata.html
Images, Video, Text, Credits: NASA / SDO.
Publié par Orbiter.ch à 10:10
Asteroid & Comet Watch.
March 7, 2013
Image above: Comet 2013 A1 (Siding Spring) will make a very close approach to Mars in October 2014. Photo-montage credit: Orbiter.ch Aerospace.
The latest trajectory of comet 2013 A1 (Siding Spring) generated by the Near-Earth Object Program Office at NASA's Jet Propulsion Laboratory in Pasadena, Calif., indicates the comet will pass within 186,000 miles (300,000 kilometers) of Mars and there is a strong possibility that it might pass much closer. The NEO Program Office's current estimate based on observations through March 1, 2013, has it passing about 31,000 miles (50,000 kilometers) from the Red Planet's surface. That distance is about two-and-a-half times that of the orbit of outermost moon, Deimos.
Scientists generated the trajectory for comet Siding Spring based on the data obtained by observations since October 2012. Further refinement to its orbit is expected as more observational data is obtained. At present, Mars lies within the range of possible paths for the comet and the possibility of an impact cannot be excluded. However, since the impact probability is currently less than one in 600, future observations are expected to provide data that will completely rule out a Mars impact.
This computer graphic (above) depicts the orbit of comet 2013 A1 (Siding Spring) through the inner solar system. On Oct. 19, 2014, it is expected to pass within 186,000 miles (300,000 kilometers) of Mars. Image credit: NASA/JPL-Caltech.
During the close Mars approach the comet will likely achieve a total visual magnitude of zero or brighter, as seen from Mars-based assets. From Earth, the comet is not expected to reach naked eye brightness, but it may become bright enough (about magnitude 8) that it could be viewed from the southern hemisphere in mid-September 2014, using binoculars, or small telescopes.
Scientists at the Near-Earth Object Program Office estimate that comet Siding Spring has been on a more than a million-year journey, arriving from our solar system's distant Oort cloud. The comet could be complete with the volatile gases that short period comets often lack due to their frequent returns to the sun's neighborhood.
Mars. Image credit: NASA.
Rob McNaught discovered comet 2013 A1 Siding Spring on Jan. 3, 2013, at Siding Spring Observatory in Australia. A study of germane archival observations has unearthed more images of the comet, extending the observation interval back to Oct. 4, 2012.
NASA detects, tracks and characterizes asteroids and comets passing close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them, and plots their orbits to determine if any could be potentially hazardous to our planet.
JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.
More information about asteroids and near-Earth objects is at: http://www.jpl.nasa.gov/asteroidwatch . More information about asteroid radar research is at: http://echo.jpl.nasa.gov/ . More information about the Deep Space Network is at: http://deepspace.jpl.nasa.gov/dsn .
Images (mentioned), Text, Credits: NASA / Dwayne Brown / Jet Propulsion Laboratory (JPL) / DC Agle.
Publié par Orbiter.ch à 09:36
NASA - Chandra X-ray Observatory patch / ESA - XMM-Newton Mission patch.
March 7, 2013
Globular Cluster 47 Tucanae
Neutron stars, the ultra-dense cores left behind after massive stars collapse, contain the densest matter known in the Universe outside of a black hole. New results from Chandra and other X-ray telescopes have provided one of the most reliable determinations yet of the relation between the radius of a neutron star and its mass. These results constrain how nuclear matter – protons and neutrons, and their constituent quarks – interact under the extreme conditions found in neutron stars.
Three telescopes – Chandra, ESA's XMM-Newton, and NASA's Rossi X-ray Timing Explorer (RXTE) – were used to observe 8 different neutron stars, including one in 47 Tucanae, a globular cluster located about 15,000 light years away in the outskirts of the Milky Way. The image shown here was constructed from a long Chandra observation of 47 Tucanae. Lower-energy X-rays are red, X-rays with intermediate energies are green, and the highest-energy X-rays are shown in blue.
In the image, the double, or binary, star system labeled as X7 contains a neutron star slowly pulling gas away from a companion star with a mass much lower than the Sun. In 2006, researchers used observations of the amount of X-rays from X7 at different energies together with theoretical models to determine a relationship between the mass and the radius of the neutron star. A similar procedure was used for Chandra observations of a neutron star in another globular cluster, NGC 6397, and for two other neutron stars in clusters observed by ESA’s XMM-Newton.
ESA's XMM-Newton. Image Credit: ESA
Four other neutron stars were observed with RXTE to undergo bursts of X-rays that cause the atmosphere of the neutron star to expand. By following the cooling of the star, its surface area can be calculated. Then, by folding in independent estimates of the distance to the neutron star, scientists were able to gather more information on the relationships between the masses and radii of these neutron stars.
Because the mass and radius of a neutron star is directly related to interactions between the particles in the interior of the star, the latest results give scientists new information about the inner workings of neutron stars.
The researchers used a wide range of different models for the structure of these collapsed objects and determined that the radius of a neutron star with a mass that is 1.4 times the mass of the Sun is between 10.4 and 12.9 km (6.5 to 8.0 miles). They also estimated the density at the center of a neutron star was about 8 times that of nuclear matter found in Earth-like conditions. This translates into a pressure that is over ten trillion trillion times the pressure required for diamonds to form inside the Earth.
The results apply whether the entire set of bursting sources, or the most extreme of the other sources, are removed from the sample. Previous studies have used smaller samples of neutron stars or have not accounted for as many uncertainties in using the models.
NASA's Chandra X-ray Observatory & RXTE. Image Credit: NASA
The new values for the neutron star's structure should hold true even if matter composed of free quarks exists in the core of the star. Quarks are fundamental particles that combine to form protons and neutrons and are not usually found in isolation. It has been postulated that free quarks may exist inside the centers of neutron stars, but no firm evidence for this has ever been found.
The researchers also made an estimate of the distances between neutrons and protons in atomic nuclei here on earth. A larger neutron star radius naturally implies that, on average, neutrons and protons in a heavy nucleus are farther apart. Their estimate is being compared with values from terrestrial experiments.
The neutron star observations also provided new information about the so-called "symmetry energy" for nuclear matter, which is the energy cost required to create a system with a different number of protons than neutrons. The symmetry energy is important for neutron stars because they contain almost ten times as many neutrons as protons. It is also important for heavy atoms on Earth, like Uranium, because they often have more neutrons than protons. The results show that the symmetry energy does not change much with density.
These results will be published in a paper in the March 1st, 2013 issue of The Astrophysical Journal Letters. The authors are Andrew Steiner, from the Institute for Nuclear Theory at the University of Washington, James Lattimer from Stony Brook University in New York and Edward Brown from Michigan State University.
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.
Read more/access all images: http://chandra.harvard.edu/photo/2013/47tuc/
Chandra's Flickr photoset: http://www.flickr.com/photos/nasamarshall/sets/72157606205297786/
Images, Text, Credits: NASA/CXC/Michigan State/A.Steiner et al. / ESA / NASA / J.D. Harrington / Marshall Space Flight Center / Janet Anderson / Chandra X-ray Center / Megan Watzke.
Publié par Orbiter.ch à 06:25
mercredi 6 mars 2013
NASA - Galileo Mission patch.
March 6, 2013
This illustration of Europa (foreground), Jupiter (right) and Io (middle) is an artist's concept. Image credit: NASA/JPL-Caltech.
If you could lick the surface of Jupiter's icy moon Europa, you would actually be sampling a bit of the ocean beneath. A new paper by Mike Brown, an astronomer at the California Institute of Technology in Pasadena, Calif., and Kevin Hand from NASA's Jet Propulsion Laboratory, also in Pasadena, details the strongest evidence yet that salty water from the vast liquid ocean beneath Europa's frozen exterior actually makes its way to the surface.
The finding, based on some of the best data of its kind since NASA's Galileo mission (1989 to 2003) to study Jupiter and its moons, suggests there is a chemical exchange between the ocean and surface, making the ocean a richer chemical environment. The work is described in a paper that has been accepted for publication in the Astronomical Journal.
The exchange between the ocean and the surface, Brown said, "means that energy might be going into the ocean, which is important in terms of the possibilities for life there. It also means that if you'd like to know what's in the ocean, you can just go to the surface and scrape some off."
This view of Jupiter’s moon Europa features several regional-resolution mosaics overlaid on a lower resolution global view for context. Image credit: NASA/JPL-Caltech/University of Arizona.
Europa's ocean is thought to cover the moon's whole globe and is about 60 miles (100 kilometers) thick under a thin ice shell. Since the days of NASA's Voyager and Galileo missions, scientists have debated the composition of Europa's surface. The infrared spectrometer aboard Galileo was not capable of providing the detail needed to identify definitively some of the materials present on the surface. Now, using the Keck II Telescope on Mauna Kea, Hawaii, and its OSIRIS spectrometer, Brown and Hand have identified a spectroscopic feature on Europa's surface that indicates the presence of a magnesium sulfate salt, a mineral called epsomite, that could have formed by oxidation of a mineral likely originating from the ocean below.
Brown and Hand started by mapping the distribution of pure water ice versus anything else. The spectra showed that even Europa's leading hemisphere contains significant amounts of non-water ice. Then, at low latitudes on the trailing hemisphere—the area with the greatest concentration of the non-water ice material—they found a tiny, never-before-detected dip in the spectrum.
The two researchers tested everything from sodium chloride to Drano in Hand's lab at JPL, where he tries to simulate the environments found on various icy worlds. At the end of the day, the signature of magnesium sulfate persisted.
The magnesium sulfate appears to be generated by the irradiation of sulfur ejected from the Jovian moon Io and, the authors deduce, magnesium chloride salt originating from Europa's ocean. Chlorides such as sodium and potassium chlorides, which are expected to be on the Europa surface, are in general not detectable because they have no clear infrared spectral features. But magnesium sulfate is detectable. The authors believe the composition of Europa's ocean may closely resemble the salty ocean of Earth.
NASA's Galileo spacecraft. Image credit: NASA/JPL-Caltech
Europa is considered a premier target in the search for life beyond Earth, Hand said. A NASA-funded study team led by JPL and the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., has been working with the scientific community to identify options to explore Europa further. "If we've learned anything about life on Earth, it's that where there's liquid water, there's generally life," Hand said. "And of course our ocean is a nice, salty ocean. Perhaps Europa's salty ocean is also a wonderful place for life."
The work was supported, in part, by the NASA Astrobiology Institute through the Icy Worlds team based at JPL, a division of Caltech. The NASA Astrobiology Institute, based at NASA's Ames Research Center, Moffett Field, Calif., is a partnership among NASA, 15 U.S. teams, and 13 international consortia. The NAI is part of NASA's Astrobiology program, which supports research into the origin, evolution, distribution and future of life on Earth and the potential for life elsewhere.
For more information about NASA's Galileo Mission, visit: http://science.nasa.gov/missions/galileo/
Images (mentioned), Text, Credits: NASA / Jet Propulsion Laboratory (JPL) / Jia-Rui Cook / California Institute of Technology (Caltech) / Brian Bell.
Publié par Orbiter.ch à 16:36
ESO - European Southern Observatory logo.
6 March 2013
New results pin down the distance to the galaxy next door
Artist’s impression of eclipsing binary
After nearly a decade of careful observations an international team of astronomers has measured the distance to our neighbouring galaxy, the Large Magellanic Cloud, more accurately than ever before. This new measurement also improves our knowledge of the rate of expansion of the Universe — the Hubble Constant — and is a crucial step towards understanding the nature of the mysterious dark energy that is causing the expansion to accelerate. The team used telescopes at ESO’s La Silla Observatory in Chile as well as others around the globe. These results appear in the 7 March 2013 issue of the journal Nature.
Astronomers survey the scale of the Universe by first measuring the distances to close-by objects and then using them as standard candles  to pin down distances further and further out into the cosmos. But this chain is only as accurate as its weakest link. Up to now finding an accurate distance to the Large Magellanic Cloud (LMC), one of the nearest galaxies to the Milky Way, has proved elusive. As stars in this galaxy are used to fix the distance scale for more remote galaxies, it is crucially important.
Explanation of eclipsing binaries
But careful observations of a rare class of double star have now allowed a team of astronomers to deduce a much more precise value for the LMC distance: 163 000 light-years.
“I am very excited because astronomers have been trying for a hundred years to accurately measure the distance to the Large Magellanic Cloud, and it has proved to be extremely difficult,” says Wolfgang Gieren (Universidad de Concepción, Chile) and one of the leaders of the team. “Now we have solved this problem by demonstrably having a result accurate to 2%.”
Map of the Large Magellanic Cloud
The improvement in the measurement of the distance to the Large Magellanic Cloud also gives better distances for many Cepheid variable stars . These bright pulsating stars are used as standard candles to measure distances out to more remote galaxies and to determine the expansion rate of the Universe — the Hubble Constant. This in turn is the basis for surveying the Universe out to the most distant galaxies that can be seen with current telescopes. So the more accurate distance to the Large Magellanic Cloud immediately reduces the inaccuracy in current measurements of cosmological distances.
The astronomers worked out the distance to the Large Magellanic Cloud by observing rare close pairs of stars, known as eclipsing binaries . As these stars orbit each other they pass in front of each other. When this happens, as seen from Earth, the total brightness drops, both when one star passes in front of the other and, by a different amount, when it passes behind .
Zooming in on an eclipsing binary in the Large Magellanic Cloud
By tracking these changes in brightness very carefully, and also measuring the stars’ orbital speeds, it is possible to work out how big the stars are, their masses and other information about their orbits. When this is combined with careful measurements of the total brightness and colours of the stars  remarkably accurate distances can be found.
This method has been used before, but with hot stars. However, certain assumptions have to be made in this case and such distances are not as accurate as is desirable. But now, for the first time, eight extremely rare eclipsing binaries where both stars are cooler red giant stars have been identified . These stars have been studied very carefully and yield much more accurate distance values — accurate to about 2%.
“ESO provided the perfect suite of telescopes and instruments for the observations needed for this project: HARPS for extremely accurate radial velocities of relatively faint stars, and SOFI for precise measurements of how bright the stars appeared in the infrared,” adds Grzegorz Pietrzyński (Universidad de Concepción, Chile and Warsaw University Observatory, Poland), lead author of the new paper in Nature.
Artist’s impression of eclipsing binary
“We are working to improve our method still further and hope to have a 1% LMC distance in a very few years from now. This has far-reaching consequences not only for cosmology, but for many fields of astrophysics,” concludes Dariusz Graczyk, the second author on the new Nature paper.
 Standard candles are objects of known brightness. By observing how bright such an object appears astronomers can work out the distance — more distant objects appear fainter. Examples of such standard candles are Cepheid variables  and Type Ia supernovae. The big difficulty is calibrating the distance scale by finding relatively close examples of such objects where the distance can be determined by other means.
 Cepheid variables are bright unstable stars that pulsate and vary in brightness. But there is a very clear relationship between how quickly they change and how bright they are. Cepheids that pulsate more quickly are fainter than those that pulsate more slowly. This period-luminosity relation allows them to be used as standard candles to measure the distances of nearby galaxies.
 This work is part of the long-term Araucaria Project to improve measurements of the distances to nearby galaxies.
 The exact light variations depend on the relative sizes of the stars, their temperatures and colours and the details of the orbit.
 The colours are measured by comparing the brightness of the stars at different near-infrared wavelengths.
 These stars were found by searching the 35 million LMC stars that were studied by the OGLE project.
This research was presented in a paper “An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent”, by G. Pietrzyński et al., to appear in the 7 March 2013 issue of the journal Nature.
The team is composed of G. Pietrzyński (Universidad de Concepción, Chile; Warsaw University Observatory, Poland), D. Graczyk (Universidad de Concepción), W. Gieren (Universidad de Concepción), I. B. Thompson (Carnegie Observatories, Pasadena, USA), B., Pilecki (Universidad de Concepción; Warsaw University Observatory), A. Udalski (Warsaw University Observatory), I. Soszyński (Warsaw University Observatory), S. Kozłowski (Warsaw University Observatory), P. Konorski (Warsaw University Observatory), K. Suchomska (Warsaw University Observatory), G. Bono (Università di Roma Tor Vergata, Rome, Italy; INAF-Osservatorio Astronomico di Roma, Italy), P. G. Prada Moroni (Università di Pisa, Italy; INFN, Pisa, Italy), S. Villanova (Universidad de Concepción ), N. Nardetto (Laboratoire Fizeau, UNS/OCA/CNRS, Nice, France), F. Bresolin (Institute for Astronomy, Hawaii, USA), R. P. Kudritzki (Institute for Astronomy, Hawaii, USA), J. Storm (Leibniz Institute for Astrophysics, Potsdam, Germany), A. Gallenne (Universidad de Concepción), R. Smolec (Nicolaus Copernicus Astronomical Centre, Warsaw, Poland), D. Minniti (Pontificia Universidad Católica de Chile, Santiago, Chile; Vatican Observatory, Italy), M. Kubiak (Warsaw University Observatory), M. Szymański (Warsaw University Observatory), R. Poleski (Warsaw University Observatory), Ł. Wyrzykowski (Warsaw University Observatory), K. Ulaczyk (Warsaw University Observatory), P. Pietrukowicz (Warsaw University Observatory), M. Górski (Warsaw University Observatory), P. Karczmarek (Warsaw University Observatory).
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 in Nature: http://www.eso.org/public/archives/releases/sciencepapers/eso1311/eso1311a.pdf
Photos of HARPS/3.6m: http://www.eso.org/public/images/?search=HARPS
Photos of NTT: http://www.eso.org/public/images/archive/search/?adv=&subject_name=New%20Technology%20Telescope
Photos taken using SOFI: http://www.eso.org/public/images/archive/search/?adv=&instrument=27
Images, Text, Credits: ESO / L. Calçada / R. Gendler / Videos: ESO / Nick Risinger (skysurvey.org) / R. Gendler / L. Calçada. Music: movetwo.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 14:50
mardi 5 mars 2013
Spektr-R / RadioAstron spacecraft
In the early part of the scientific program of the mission, RadioAstron studied three groups of space objects: quasars - nuclei of distant galaxies, pulsars - neutron stars in our galaxy, masers - region of star formation in our galaxy. In early 2013, obtained important new results.
RadioAstron and records
With the help of the RadioAstron managed to break all the world records on the angular resolution by implementing the most keen eye for history. Interference signals from distant galaxies, ultra-confident registered on the basis of Earth-Space to 20 diameters of the Earth! Specifically, it was possible to beat the record set in 2012, ground-based interferometers for observations at 1.3 mm wavelength. Achieved an angular resolution of 40 microseconds of arc.
Fig. 1: Record the detection of ultra compact active galactic nuclei in the project RadioAstron.
At the traditional diagram represents the value of the response as a function of delay (delay) and frequency interference (fringe rate).
Left - the quasar 3C273, the range of 18 cm, base diameter 13.5 interferometer Earth RadioAstron-Aresibo/SShA, January 20, 2013
In the center - the active galaxy BL Lacertae, a range of 6 cm, the base of the interferometer 19 diameters of the Earth, RadioAstron-Effelsberg / Germany, November 28, 2012
Right - the quasar 3C273, the range of 1.3 cm, the base of the interferometer 8 diameters of the Earth, RadioAstron-GBT/SShA, February 2, 2013.
RadioAstron and the interstellar medium
The modern theory of the interstellar plasma in our galaxy predicted that the long-wavelength radio emission from pulsars and quasars will be eroded and, as a result, RadioAstron can not register them signals on large ground-based and space bases for wavelengths of 18 and 92 cm results fully refuted this prediction (see Figures 1 and 2), broke up with the theory in 10100 times!
This discovery completely changes the current understanding of the structure of the interstellar plasma in our galaxy.
Fig. 2: Structure of the interference response distant pulsar V0329 +55, at a distance of 6000 light years.
For a source that is not subjected to the effects of scattering on the chart view to be a single peak. In fact, there is a tight band interference responses, each of which corresponds to the peaks of the interference of the rays passing through its combination of refraction in the plasma inhomogeneities.
RadioAstron and galactic water
Detected water maser emission from ultra cloud size 8 diameters of the Sun, in the formation of massive stars W3IRS5, located at a distance 5.5 thousand light years in the Perseus spiral arm of our galaxy (see Figures 3 and 4).
This result will allow scientists to better understand the formation of massive stars.
Fig. 3: Interference response from the star forming region W3IRS5 Observations RadioAstron with Spanish telescope Yebes.
On the vertical axis: amplitude of the correlated signal. Horizontal axis: the residual value of frequency interference and spectral frequency.
Fig. 4: The interference response of the star forming region W3IRS5 Observations RadioAstron with Polish telescope Torun.
Original text in Russian: http://www.federalspace.ru/main.php?id=2&nid=19935
Images, Graphics, Text, Credits: Press Service of the Russian Space Agency and ACC Physics Institute. Lebedev, Russian Academy of Sciences (ASC FIAN) / Translation: Orbiter.ch Aerospace.
Publié par Orbiter.ch à 14:14
ESA - Herschel Mission patch.
5 March 2013
ESA’s Herschel space observatory is expected to exhaust its supply of liquid helium coolant in the coming weeks after spending more than three exciting years studying the cool Universe.
Herschel was launched on 14 May 2009 and, with a main mirror 3.5 m across, it is the largest, most powerful infrared telescope ever flown in space.
Herschel and Rosette Nebula
A pioneering mission, it is the first to cover the entire wavelength range from the far-infrared to submillimetre, making it possible to study previously invisible cool regions of gas and dust in the cosmos, and providing new insights into the origin and evolution of stars and galaxies.
In order to make such sensitive far-infrared observations, the detectors of the three science instruments – two cameras/imaging spectrometers and a very high-resolution spectrometer – must be cooled to a frigid –271°C, close to absolute zero. They sit on top of a tank filled with superfluid liquid helium, inside a giant thermos flask known as a cryostat.
Herschel’s cryostat vacuum vessel
The superfluid helium evaporates over time, gradually emptying the tank and determining Herschel’s scientific life. At launch, the cryostat was filled to the brim with over 2300 litres of liquid helium, weighing 335 kg, for 3.5 years of operations in space.
Indeed, Herschel has made extraordinary discoveries across a wide range of topics, from starburst galaxies in the distant Universe to newly forming planetary systems orbiting nearby young stars.
However, all good things must come to an end and engineers believe that almost all of the liquid helium has now gone.
It is not possible to predict the exact day the helium will finally run out, but confirmation will come when Herschel begins its next daily 3-hour communication period with ground stations on Earth.
“It is no surprise that this will happen, and when it does we will see the temperatures of all the instruments rise by several degrees within just a few hours,” says Micha Schmidt, the Herschel Mission Operations Manager at ESA’s European Space Operations Centre in Darmstadt, Germany.
Integrating the instruments
The science observing programme was carefully planned to take full advantage of the lifetime of the mission, with all of the highest-priority observations already completed.
In addition, Herschel is performing numerous other interesting observations specifically chosen to exploit every last drop of helium.
“When observing comes to an end, we expect to have performed over 22 000 hours of science observations, 10% more than we had originally planned, so the mission has already exceeded expectations,” says Leo Metcalfe, the Herschel Science Operations and Mission Manager at ESA’s European Space Astronomy Centre in Madrid, Spain.
“We will finish observing soon, but Herschel data will enable a vast amount of exciting science to be done for many years to come,” says Göran Pilbratt, ESA’s Herschel Project Scientist at ESA’s European Space Research and Technology Centre in Noordwijk, the Netherlands.
“In fact, the peak of scientific productivity is still ahead of us, and the task now is to make the treasure trove of Herschel data as valuable as possible for now and for the future.”
Herschel will continue communicating with its ground stations for some time after the helium is exhausted, allowing a range of technical tests. Finally, in early May, it will be propelled into its long-term stable parking orbit around the Sun.
Related links / more about:
Herschel: ESA's giant infrared observatory: http://www.esa.int/Our_Activities/Space_Science/Herschel
Herschel overview: http://www.esa.int/Our_Activities/Space_Science/Herschel
Online Showcase of Herschel Images OSHI: http://oshi.esa.int/
Herschel operations: http://www.esa.int/Our_Activities/Operations/Herschel_operations
Herschel in depth: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=16
Herschel Science Centre: http://herschel.esac.esa.int/
Herschel postcard gallery: http://archives.esac.esa.int/hsa/aio/doc/postcardGallery.html
Images, Text, Credits: ESA / C. Carreau / Astrium.
Publié par Orbiter.ch à 10:24