vendredi 6 mars 2015

CERN - LHC injector tests to begin












CERN - European Organization for Nuclear Research logo.

March 6, 2015

With the Large Hadron Collider (LHC) due to start up again at the end of this month, the team in the LHC Control Centre are busy testing the systems that deliver the beams.


Image above: A "splash event" in the LHCb detector, recorded during an injection test in 2009 (Image: LHCb).

At CERN, a series of accelerators boosts protons or ions to successively higher energies until they are injected into the LHC. The LHC then further accelerates the particles before delivering collisions to the four detectors ALICE, ATLAS, CMS and LHCb. The penultimate accelerator in the chain is the Super Proton Synchrotron (SPS), a machine nearly 7 kilometres in circumference, which receives particles from the Proton Synchrotron at 26 GeV, and boosts them to the 450 GeV needed for injection to the LHC.

Now, the LHC control team is testing the injection systems to ensure that the upcoming startup of the accelerator runs as smoothly as possible. Though particles will be injected into parts of the LHC this weekend, there will be no fully circulating beams until the planned startup at the end of this month.

"We will do two tests," says Ronaldus Suykerbuyk of the LHC operation team. "Beam 1 will pass through the ALICE detector up to point 3, where we will dump the beam on a collimator, and for Beam 2 we will go through the LHCb detector up to the beam dump at point 6." A screen placed in the beam pipe will register a successful pass as a bright dot. The team will also record other parameters, including the timings of the injection kickers – fast pulsing dipole magnets that "kick" the beam into the accelerator – and the beam trajectory in the injection lines and LHC beam pipe.


Image above: Beams will not circulate all the way around the LHC, but rather reach point 3 and point 6 during the tests (Image: Leonard Rimensberger/CERN).

"This test really is a massive debugging exercise," says Mike Lamont, head of the operations team. "We've already pre-tested all the control systems without beam. If the beam goes around we’ll be happy!"

The ALICE and LHCb experiments are preparing their detectors to receive the pulses of particles. "ALICE will receive muons originating from the SPS beam dump," says ALICE physicist Despina Hatzifotiadou, "They will be used for trigger timing studies and to align the muon spectrometer".

LHCb will also be taking data. "These tests create an excellent opportunity for us to commission the LHCb detector and data-acquisition system. The collected data are also invaluable for detector studies and alignment purposes, that is, determining the relative geometrical locations of the different sub-detectors with respect to each other," says Patrick Robbe of LHCb. "It's exciting because the tests show that we are getting closer and closer to the restart!"

But there is still much work to do before first circulating beams, says Suykerbuyk. "We have to finish all the powering tests and magnet training as well as test all the other hardware and beam-diagnostic systems." It's going to be a busy few weeks for all concerned.

Note:

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 22 Member States.

Related links:

Timelapse: LHC experiments prepare for restart: http://orbiterchspacenews.blogspot.ch/2015/02/timelapse-lhc-experiments-prepare-for.html

CERN's two-year shutdown drawing to a close: http://orbiterchspacenews.blogspot.ch/2015/02/cerns-two-year-shutdown-drawing-to-close.html

Large Hadron Collider (LHC): http://home.web.cern.ch/topics/large-hadron-collider

ALICE: http://home.web.cern.ch/about/experiments/alice

ATLAS: http://home.web.cern.ch/about/experiments/atlas

CMS: http://home.web.cern.ch/about/experiments/cms

LHCb: http://home.web.cern.ch/about/experiments/lhcb

Super Proton Synchrotron (SPS): http://home.web.cern.ch/about/accelerators/super-proton-synchrotron

For more information about the European Organization for Nuclear Research (CERN), visit: http://home.web.cern.ch/

Image and Graphic (mentioned), Text, Credits: CERN/Cian O'Luanaigh.

Best regards, Orbiter.ch

Use of Rover Arm Expected to Resume in a Few Days












NASA - Mars Science Laboratory (MSL) patch.

March 6, 2015

Mission Status Report

Managers of NASA's Curiosity Mars rover mission expect to approve resumption of rover arm movements as early as next week while continuing analysis of what appears to be an intermittent short circuit in the drill.

A fluctuation in current on Feb. 27 triggered a fault-protection response that immediately halted action by the rover during the mission's 911th Martian day, or sol. Since then, the rover team has avoided driving Curiosity or moving the rover's arm, while engineers have focused on diagnostic tests. Science observations with instruments on the rover's mast have continued, along with environmental monitoring by its weather station.

"Diagnostic testing this week has been productive in narrowing the possible sources of the transient short circuit," said Curiosity Project Manager Jim Erickson of NASA's Jet Propulsion Laboratory, Pasadena, California. "The most likely cause is an intermittent short in the percussion mechanism of the drill. After further analysis to confirm that diagnosis, we will be analyzing how to adjust for that in future drilling."


Image above: This March 4, 2015, image from the Navcam on NASA's Curiosity Mars rover shows the position in which the rover held its arm for several days after a transient short circuit triggered onboard fault-protection programming to halt arm activities on Feb. 27. Image Credit: NASA/JPL-Caltech/MSSS.

The sample-collection drill on Curiosity's robotic arm uses both rotation and hammering, or percussion, to penetrate into Martian rocks and collect pulverized rock material for delivery to analytical instruments inside the rover.

The short on Sol 911 occurred while the rover was transferring rock-powder sample from the grooves of the drill into a mechanism that sieves and portions the powder. The percussion action was in use, to shake the powder loose from the drill.

Engineers received results Thursday, March 5, from a test on Curiosity that similarly used the drill's percussion action. During the third out of 180 up-and-down repeats of the action, an apparent short circuit occurred for less than one one-hundredth of a second.  Though small and fleeting, it would have been enough to trigger the fault protection that was active on Sol 911 under the parameters that were in place then.

The rover team plans further testing to characterize the intermittent short before the arm is moved from its present position, in case the short does not appear when the orientation is different.

After those tests, the team expects to finish processing the sample powder that the arm currently holds and then to deliver portions of the sample to onboard laboratory instruments. Next, Curiosity will resume climbing Mount Sharp.

Mars Science Laboratory(MSL) rover "Curiosity". 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.  JPL, a division of the California Institute of Technology in Pasadena, built the rover and manages the project for NASA's Science Mission Directorate in Washington.  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 and Twitter at: http://www.facebook.com/marscuriosity and http://www.twitter.com/marscuriosity

Images (mentioned), Text, Credits: NASA/JPL/Guy Webster.

Best regards, Orbiter.ch

Hubble Sees a Young Star Take Center Stage











NASA - Hubble Space Telescope patch.

March 6, 2015


With its helical appearance resembling a snail’s shell, this reflection nebula seems to spiral out from a luminous central star in this NASA/ESA Hubble Space Telescope image.

The star in the center, known as V1331 Cyg and located in the dark cloud LDN 981 — or, more commonly, Lynds 981 — had previously been defined as a T Tauri star. A T Tauri is a young star — or Young Stellar Object — that is starting to contract to become a main sequence star similar to the sun.

What makes V1331Cyg special is the fact that we look almost exactly at one of its poles. Usually, the view of a young star is obscured by the dust from the circumstellar disc and the envelope that surround it. However, with V1331Cyg we are actually looking in the exact direction of a jet driven by the star that is clearing the dust and giving us this magnificent view.

video
Hubble orbiting Earth

This view provides an almost undisturbed view of the star and its immediate surroundings allowing astronomers to study it in greater detail and look for features that might suggest the formation of a very low-mass object in the outer circumstellar disk.

For more information and images from Hubble Space Telescope, visit: http://www.spacetelescope.org and http://hubblesite.org

Image, Video, Text, Credits: ESA/Hubble, NASA/Karl Stapelfeldt (GSFC), B. Stecklum and A. Choudhary (Thüringer Landessternwarte Tautenburg, Germany).

Greetings, Orbiter.ch

Hayabusa2 Moving to Cruising Phase while heading to Asteroid 1999 JU3











JAXA - Hayabusa2 Asteroid 1999JU3 Explorer logo.

March 6, 2015

The Asteroid Explorer "Hayabusa2" completed its initial functional confirmation period on March 2, 2015, as all scheduled checkout and evaluation of acquired data were completed. The explorer has been under inspection for about three months after its launch on Dec. 3, 2014.

Relative locations of Hayabusa2, Earth, Sun and 1999 JU3 (Schematic drawing)

The Hayabusa2 is moving to the cruising phase while heading to the asteroid "1999 JU3" on March 3. It will be under preparatory operation for an Earth swing-by scheduled in Nov. or Dec., 2015.

We plan to increase the cruising speed of the explorer (60 m/sec.) by operating two ion engines twice (in total about 600 hours or 25 days) until the Earth swing-by. For the first operation, we will gradually increase the time duration of continuous ion-engine operation from March 3, and will operate the engines for about 400 hours within March. The second operation is scheduled in early June.

Hayabusa2 direction viewed from the Earth

* Please refer to the attached mission schedule: http://global.jaxa.jp/press/2015/03/20150303_hayabusa2.html#at

The Hayabusa2 is in good health.

We would like to express our profound appreciation to all pertinent parties who have supported and cooperated with our initial functional confirmation operation. Your further and continued support will be highly appreciated for this long-term space exploration mission of the Hayabusa2.

* For more information about the Hayabusa2, please refer to the following JAXA website "Hayabusa2 project page." (Link bellow).

Mission Schedule: 


Hayabusa2 Cruising Phase Status:



Reference:

Asteroid Explorer "Hayabusa2": http://global.jaxa.jp/projects/sat/hayabusa2/

JAXA Press Release: http://global.jaxa.jp/press/2015/03/20150303_hayabusa2.html

Images, Graphics, Text, Credit: Japan Aerospace Exploration Agency (JAXA).

Best regards, Orbiter.ch

NASA Spacecraft Becomes First to Orbit a Dwarf Planet












NASA - Dawn Mission patch.

March 6, 2015

NASA's Dawn spacecraft has become the first mission to achieve orbit around a dwarf planet. The spacecraft was approximately 38,000 miles (61,000 kilometers) from Ceres when it was captured by the dwarf planet’s gravity at about 4:39 a.m. PST (7:39 a.m. EST) Friday.

Mission controllers at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California received a signal from the spacecraft at 5:36 a.m. PST (8:36 a.m. EST) that Dawn was healthy and thrusting with its ion engine, the indicator Dawn had entered orbit as planned.

"Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet," said Marc Rayman, Dawn chief engineer and mission director at JPL. "Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres, home."


Image above: Ceres is seen from NASA's Dawn spacecraft on March 1, just a few days before the mission achieved orbit around the previously unexplored dwarf planet. The image was taken at a distance of about 30,000 miles (about 48,000 kilometers). Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

In addition to being the first spacecraft to visit a dwarf planet, Dawn also has the distinction of being the first mission to orbit two extraterrestrial targets. From 2011 to 2012, the spacecraft explored the giant asteroid Vesta, delivering new insights and thousands of images from that distant world. Ceres and Vesta are the two most massive residents of our solar system’s main asteroid belt between Mars and Jupiter.

The most recent images received from the spacecraft, taken on March 1 show Ceres as a crescent, mostly in shadow because the spacecraft's trajectory put it on a side of Ceres that faces away from the sun until mid-April. When Dawn emerges from Ceres' dark side, it will deliver ever-sharper images as it spirals to lower orbits around the planet.

"We feel exhilarated," said Chris Russell, principal investigator of the Dawn mission at the University of California, Los Angeles (UCLA). "We have much to do over the next year and a half, but we are now on station with ample reserves, and a robust plan to obtain our science objectives."

Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team.

For a complete list of mission participants, visit: http://dawn.jpl.nasa.gov/mission

For more information about Dawn, visit: http://www.nasa.gov/dawn

Image (mentioned), Text, Credits: NASA/Dwayne Brown.

Greetings, Orbiter.ch

jeudi 5 mars 2015

Satellite Movie Shows Winter Storm Sweep Over U.S. East Coast












NOAA / NASA - GOES Mission logo.

March 5, 2015

video
GOES Video of the Winter Storm of March 3-5, 2015

Video above: This GOES-East animation from March 3 to March 5 at 17:45 UTC (12:45 p.m. EST) shows clouds associated with a cold front push east and south that brought winter weather to the U.S. East Coast. Video Credit: NASA/NOAA GOES Project.

A winter storm was bringing snow, sleet and freezing rain from lower Mississippi Valley to Northeastern U.S. on Thursday, March 5, 2015. A new NASA animation of NOAA's GOES-East satellite imagery showed the progression of the clouds associated with the storm system that triggered winter storm warnings and winter weather advisories from the southern Plains eastward through the Mid-Atlantic and southern New England coast. The system also triggered flood warnings along and to the west of the central Appalachians.

An animation of GOES satellite visible and infrared imagery from March 3 through March 5 showed clouds associated with a cold front push over U.S. East coast. Behind the front, Arctic air is expected to drop low temperatures into the single numbers from Washington, D.C. to Minnesota overnight. Temperatures in the Carolinas and Tennessee are expected to drop to the low 20s.

NOAA's National Weather Service Weather Prediction Center (NWS NPC) in College Park, Maryland noted "a strong cold front moving across the eastern U.S. will bring heavy snow from parts of the Ohio Valley to the Northeast today (March 5) with rain, freezing rain and sleet possible from parts of the lower Mississippi Valley across the Southeast to the southern Mid-Atlantic. Snowfall totals of 5 to 10 inches are possible for some areas. Winter Storm Warnings remain in effect from Texas to Nantucket."


Image above: This GOES-East image from March 5 at 17:30 UTC (12:30 p.m. EST) shows clouds associated with a cold front push east and south that brought winter weather to the U.S. East Coast. Image Credit: NASA/NOAA GOES Project.

The animation ends at 17:45 UTC (12:45 p.m. EST). Before the end of the animation, the low pressure center along an arctic frontal boundary was nearly stationary over western North Carolina at 9 a.m. EST on March 5, according to the NWS NPC. NWS radar and surface observations indicated an extended swath of precipitation from near the Texas Gulf Coast through the interior eastern U.S. into southern New England. NPC's storm summary noted at that time "rain was changing to sleet/freezing rain and to all snow along a band within this swath as colder air continues to filter in from the north.  Some areas in Tennessee, the northern mid-Atlantic and southern New England were reporting moderate to heavy snow."

To create the video and imagery, NASA/NOAA's GOES Project takes the cloud data from NOAA's GOES-East satellite and overlays it on a true-color image of land and ocean created by data from the Moderate Resolution Imaging Spectroradiometer, or MODIS, instrument that flies aboard NASA's Aqua and Terra satellites. Together, those data created the entire picture of the storm and show its movement. After the storm system passes, the snow on the ground becomes visible.

GOES satellites provide the kind of continuous monitoring necessary for intensive data analysis. Geostationary describes an orbit in which a satellite is always in the same position with respect to the rotating Earth. This allows GOES to hover continuously over one position on Earth's surface, appearing stationary.

For updated information about the storm system, visit NOAA's NWS website: http://www.weather.gov

For more information about GOES satellites, visit: http://www.goes.noaa.gov/ or http://goes.gsfc.nasa.gov/

Image (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Rob Gutro.

Greetings, Orbiter.ch

Mars: The Planet that Lost an Ocean’s Worth of Water












ESO - European Southern Observatory logo.

5 March 2015

Artist’s impression of Mars four billion years ago

A primitive ocean on Mars held more water than Earth’s Arctic Ocean, and covered a greater portion of the planet’s surface than the Atlantic Ocean does on Earth, according to new results published today. An international team of scientists used ESO’s Very Large Telescope, along with instruments at the W. M. Keck Observatory and the NASA Infrared Telescope Facility, to monitor the atmosphere of the planet and map out the properties of the water in different parts of Mars’s atmosphere over a six-year period. These new maps are the first of their kind. The results appear online in the journal Science today.

About four billion years ago, the young planet would have had enough water to cover its entire surface in a liquid layer about 140 metres deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars’s northern hemisphere, and in some regions reaching depths greater than 1.6 kilometres.

Artist’s impression of Mars four billion years ago

“Our study provides a solid estimate of how much water Mars once had, by determining how much water was lost to space,” said Geronimo Villanueva, a scientist working at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, USA, and lead author of the new paper. “With this work, we can better understand the history of water on Mars.”

The new estimate is based on detailed observations of two slightly different forms of water in Mars’s atmosphere. One is the familiar form of water, made with two hydrogen atoms and one oxygen, H2O. The other is HDO, or semi-heavy water, a naturally occurring variation in which one hydrogen atom is replaced by a heavier form, called deuterium.

video
Artist’s impression of Mars four billion years ago

As the deuterated form is heavier than normal water, it is less easily lost into space through evaporation. So, the greater the water loss from the planet, the greater the ratio of HDO to H2O in the water that remains [1].

The researchers distinguished the chemical signatures of the two types of water using ESO’s Very Large Telescope in Chile, along with instruments at the W. M. Keck Observatory and the NASA Infrared Telescope Facility in Hawaii [2]. By comparing the ratio of HDO to H2O, scientists can measure by how much the fraction of HDO has increased and thus determine how much water has escaped into space. This in turn allows the amount of water on Mars at earlier times to be estimated.

video
Artist’s impression of Mars four billion years ago

In the study, the team mapped the distribution of H2O and HDO repeatedly over nearly six Earth years — equal to about three Mars years — producing global snapshots of each, as well as their ratio. The maps reveal seasonal changes and microclimates, even though modern Mars is essentially a desert.

Ulli Kaeufl of ESO, who was responsible for building one of the instruments used in this study and is a co-author of the new paper, adds: "I am again overwhelmed by how much power there is in remote sensing on other planets using astronomical telescopes: we found an ancient ocean more than 100 million kilometres away!"

The team was especially interested in regions near the north and south poles, because the polar ice caps are the planet’s largest known reservoir of water. The water stored there is thought to document the evolution of Mars’s water from the wet Noachian period, which ended about 3.7 billion years ago, to the present.

video
Mars: the planet that lost an ocean's worth of water

The new results show that atmospheric water in the near-polar region was enriched in HDO by a factor of seven relative to Earth’s ocean water, implying that water in Mars’s permanent ice caps is enriched eight-fold. Mars must have lost a volume of water 6.5 times larger than the present polar caps to provide such a high level of enrichment. The volume of Mars’s early ocean must have been at least 20 million cubic kilometres.

Based on the surface of Mars today, a likely location for this water would be the Northern Plains, which have long been considered a good candidate because of their low-lying ground. An ancient ocean there would have covered 19% of the planet’s surface — by comparison, the Atlantic Ocean occupies 17% of the Earth’s surface.

“With Mars losing that much water, the planet was very likely wet for a longer period of time than previously thought, suggesting the planet might have been habitable for longer,” said Michael Mumma, a senior scientist at Goddard and the second author on the paper.

It is possible that Mars once had even more water, some of which may have been deposited below the surface. Because the new maps reveal microclimates and changes in the atmospheric water content over time, they may also prove to be useful in the continuing search for underground water.

Notes:

[1] In oceans on Earth there are about 3200 molecules of H2O for each HDO molecule.

[2] Although probes on the Martian surface and orbiting the planet can provide much more detailed in situ measurements, they are not suitable for monitoring the properties of the whole Martian atmosphere. This is best done using infrared spectrographs on large telescopes back on Earth.

More information:

This research was presented in a paper entitled “Strong water isotopic anomalies in the Martian atmosphere: probing current and ancient reservoirs”, by G. VIllanueva et al., to appear online in Science on 5 March 2015.

The team is composed of G.L. Villanueva (NASA Goddard Space Flight Center, Greenbelt, USA; Catholic University of America, Washington, D.C., USA), M.J. Mumma (NASA Goddard Space Flight Center), R.E. Novak (Iona College, New York, USA), H.U. Käufl (ESO, Garching, Germany), P. Hartogh (Max Planck Institute for Solar System Research, Göttingen, Germany), T. Encrenaz (CNRS — Observatoire de Paris-Meudon, Paris, France), A. Tokunaga (University of Hawaii-Manoa, Hawaii, USA), A. Khayat (University of Hawaii-Manoa) and M. D. Smith (NASA Goddard Space Flight Center).

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 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. 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 a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Four programmes at NASA Headquarters in Washington, D.C., supported this work: Mars Fundamental Research, Planetary Astronomy, Planetary Atmospheres, and NASA Astrobiology.

Link:

Photos of the ESO Very Large Telescope: http://www.eso.org/public/images/archive/category/paranal/

Related links:


W. M. Keck Observatory: http://en.wikipedia.org/wiki/W._M._Keck_Observatory

NASA Infrared Telescope Facility: http://en.wikipedia.org/wiki/NASA_Infrared_Telescope_Facility

Images, Text, Credits: ESO/M. Kornmesser/N. Risinger (skysurvey.org)/Videos: ESO/M. Kornmesser.

Greetings, Orbiter.ch

Hubble sees multiple images of a supernova for the very first time












ESA - Hubble Space Telescope logo.

5 March 2015

An explosive quartet

Galaxy cluster MACS j1149.5+223 and a supernova four times over

Astronomers using the NASA/ESA Hubble Space Telescope have, for the first time, spotted four images of a distant exploding star. The images are arranged in a cross-shaped pattern by the powerful gravity of a foreground galaxy embedded in a massive cluster of galaxies. The supernova discovery paper will appear on 6 March 2015 in a special issue of Science celebrating the centenary of Albert Einstein’s theory of general relativity.

Whilst looking closely at a massive elliptical galaxy and its associated galaxy cluster MACS J1149+2223 — whose light took over 5 billion years to reach us — astronomers have spotted a strange and rare sight. The huge mass of the galaxy and the cluster is bending the light from a much more distant supernova behind them and creating four separate images of it. The light has been magnified and distorted due to gravitational lensing [1] and as a result the images are arranged around the elliptical galaxy in a formation known as an Einstein cross.

Galaxy cluster MACS j1149.5+223

Although astronomers have discovered dozens of multiply imaged galaxies and quasars, they have never before seen multiple images of a stellar explosion.

“It really threw me for a loop when I spotted the four images surrounding the galaxy — it was a complete surprise,” said Patrick Kelly of the University of California Berkeley, USA, a member of the Grism Lens Amplified Survey from Space (GLASS) collaboration and lead author on the supernova discovery paper. He discovered the supernova during a routine search of the GLASS team’s data, finding what the GLASS group and the Frontier Fields Supernova team have been searching for since 2013 [2]. The teams are now working together to analyse the images of the supernova, whose light took over 9 billion years to reach us [3].

Four supernova images in an Einstein cross

“The supernova appears about 20 times brighter than its natural brightness,” explains the paper’s co-author Jens Hjorth from the Dark Cosmology Centre, Denmark. “This is due to the combined effects of two overlapping lenses. The massive galaxy cluster focuses the supernova light along at least three separate paths, and then when one of those light paths happens to be precisely aligned with a single elliptical galaxy within the cluster, a secondary lensing effect occurs.” The dark matter associated with the elliptical galaxy bends and refocuses the light into four more paths, generating the rare Einstein cross pattern the team observed.

This unique observation will help astronomers refine their estimates of the amount and distribution of dark matter in the lensing galaxy and cluster. There is more dark matter in the Universe than visible matter, but it is extremely elusive and is only known to exist via its gravitational effects on the visible Universe, so the lensing effects of a galaxy or galaxy cluster are a big clue to the amount of dark matter it contains.

Illustration showing gravitational lensing producing four supernova images

When the four supernova images fade away as the explosion dies down, astronomers will have a rare chance to catch a rerun of the explosion. The supernova images do not arrive at the Earth at the same time because, for each image produced, the light takes a different route. Each route has a different layout of matter — both dark and visible — along its path. this causes bends in the road, and so for some routes the light takes longer to reach us than for others. Astronomers can use their model of how much dark matter is in the cluster, and where it is, to predict when the next image will appear as well as using the time delays they observe to make the mass models even more accurate [4].

“The four supernova images captured by Hubble appeared within a few days or weeks of each other and we found them after they had appeared,” explains Steve Rodney of Johns Hopkins University, USA, leader of the Frontier Fields Supernova team. “But we think the supernova may have appeared in a single image some 20 years ago elsewhere in the cluster field, and, even more excitingly, it is expected to reappear once more in the next one to five years — and at that time we hope to catch it in action.”

video
Animation showing how Hubble spotted four images of the same supernova

The supernova has been nicknamed Refsdal in honor of Norwegian astronomer Sjur Refsdal, who, in 1964, first proposed using time-delayed images from a lensed supernova to study the expansion of the Universe. “Astronomers have been looking to find one ever since,” said Tommaso Treu of the University of California Los Angeles, USA, the GLASS project’s principal investigator. “And now the long wait is over!”

Notes:

[1] Gravitational lensing was first predicted by Albert Einstein. This effect is similar to a glass lens bending light to magnify and distort the image of an object behind it.

[2] The Frontier Fields is a three-year programme that uses Hubble to observe six massive galaxy clusters to probe not only what is inside the clusters but also what is beyond them through gravitational lensing. The GLASS survey uses Hubble’s capabilities to study remote galaxies using ten massive galaxy clusters as gravitational lenses, including the six in the Frontier Fields.

[3] The team used the W. M. Keck Observatory on Mauna Kea, in Hawaii, to measure the redshift of the supernova’s host galaxy, which is a proxy to its distance.

[4] Measuring the time delays between images offers clues to the type of warped-space terrain the supernova’s light had to cover and will help the astronomers fine tune the models that map out the cluster’s mass.

Notes for editors:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of P. Kelly (University of California, Berkeley, USA); S. Rodney (The Johns Hopkins University, USA); T. Treu (University of California, Los Angeles, USA); R. Foley (University of Illinois at Urbana-Champaign, USA); G. Brammer (Space Telescope Science Institute, USA); K. Schmidt (University of California, Santa Barbara, USA); A. Zitrin (California Institute of Technology, USA); A. Sonnenfeld (University of California, Los Angeles, USA); L. Strolger (Space Telescope Science Institute, USA & Western Kentucky University, USA); O. Graur (New York University, USA), A. Filippenko (University of California, Berkeley, USA), S. Jha (Rutgers, USA); A. Riess (The Johns Hopkins University, USA & Space Telescope Science Institute, USA); M. Bradac (University of California, Davis, USA), B. Weiner (Steward Observatory, USA); D. Scolnic (The Johns Hopkins University, USA); M. Malkan (University of California, Los Angeles, USA); A. von der Linden (Dark Cosmology Centre, Denmark); M. Trenti (University of Melbourne, Australia); J. Hjorth (Dark Cosmology Centre, Denmark); R. Gavazzi (Institut d’Astrophysique de Paris, France); A. Fontana (INAF-OAR, Italy); J. Merten (California Institute of Technology, USA); C. McCully (University of California, Santa Barbara,, USA); T. Jones (University of California, Santa Barbara,, USA); M. Postman (Space Telescope Science Institute, USA); A. Dressler (Carnegie Observatories, USA), B. Patel (Rutgers, USA), S. Cenko (NASA/Goddard Space Flight Center, USA); M. Graham (University of California, Berkeley, USA); and Bradley E. Tucker (University of California, Berkeley, USA).

Links:

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

The Grism Lens Amplified Survey from Space (GLASS) collaboration: http://glass.physics.ucsb.edu/

Frontier Fields: http://frontierfields.org/

NASA release: http://hubblesite.org/newscenter/archive/releases/2015/08

Link to science paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1505a.pdf

Images, Video, Tex, Credits: NASA, ESA, S. Rodney (John Hopkins University, USA) and the FrontierSN team; T. Treu (University of California Los Angeles, USA), P. Kelly (University of California Berkeley, USA) and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI).

Best regards, Orbiter.ch

Single Site on Mars Advanced for 2016 NASA Lander












NASA - InSight Mission logo.

March 5, 2015

THINGS TO KNOW:

- Launch period -- the first Mars launch from California -- opens March 4, 2016

- The mission will examine Mars' interior to learn how Earth-like planets form and evolve

- Landing-site evaluation has narrowed to one site in Mars' Elysium Planitia


NASA's next mission to Mars, scheduled to launch one year from today to examine the Red Planet's deep interior and investigate how rocky planets like Earth evolved, now has one specific site under evaluation as the best place to land and deploy its science instruments.


Image above: In the weeks after NASA's InSight mission reaches Mars in September 2016, the lander's arm will lift two science instruments off the deck and place them onto the ground. Image credit: NASA/JPL-Caltech.

The mission called InSight -- an acronym for "Interior Exploration using Seismic Investigations, Geodesy and Heat Transport" -- is scheduled to launch from Vandenberg Air Force Base, California. The launch period runs from March 4 to March 30, 2016, and will mark the first California launch of an interplanetary mission. Installation of science-instrument hardware onto the spacecraft has begun and a key review has given thumbs up to integration and testing of the mission's component systems from several nations participating in the international project.

The landing-site selection process evaluated four candidate locations selected in 2014. The quartet is within the flat-lying "Elysium Planitia," less than five degrees north of the equator, and all four appear safe for InSight's landing. The single site will continue to be analyzed in coming months for final selection later this year. If unexpected problems with this site are found, one of the others would be imaged and could be selected. The favored site is centered at about four degrees north latitude and 136 degrees east longitude.

"This is wondrous terrain, exactly what we want to land on because it is smooth, flat, with very few rocks in the highest-resolution images," said InSight's site-selection leader, Matt Golombek of NASA's Jet Propulsion Laboratory, Pasadena, California.

Mars orbiters have provided detailed information about the candidate sites, which are mapped as landing ellipses about 81 miles (130 kilometers) west-to-east by about 17 miles (27 kilometers) north-to-south. An ellipse covers the area within which InSight has odds of about 99 percent of landing, if targeted for the ellipse center. Several types of terrain, such as "cratered," "etched" and "smooth" were mapped in each ellipse. The one chosen for final evaluations has highest proportion in the smooth category.

After InSight reaches Mars on Sept. 28, 2016, the mission will assess properties of the planet's crust, mantle and core. The interior of Mars has not been churned as much as Earth's because Mars lacks the tectonic activity that recycles Earth's crustal plates back into the mantle. Thus, Mars offers an opportunity to find clues no longer present on Earth about how rocky planets such as Earth, Mars, Venus and Mercury formed and evolved.

InSight's primary science will study the planet's interior, not surface features. Besides safety for the landing, the main site-selection criterion is for the ground within reach of the lander's robotic arm to be penetrable for a heat-flow probe designed to hammer itself into the soil to a depth three to five yards, or meters.


Image above: This map shows the single area under continuing evaluation as the InSight mission's Mars landing site, as of a year before the mission's May 2016 launch. Image credit: NASA/JPL-Caltech.

Evidence that the ground will be suitable for the probe, rather than rock solid, comes from assessment by the Thermal Imaging System on NASA's Mars Odyssey orbiter of how quickly the ground cools at night or warms in sunlight, and evaluation of images from the High Resolution Imaging Science Experiment on NASA's Mars Reconnaissance Orbiter.

The heat-flow probe is a key part of InSight's Heat Flow and Physical Properties Package (HP3) provided by the German Aerospace Center (DLR). Electronics for that instrument were the first hardware from the science payload put onto the InSight spacecraft being assembled and tested at Lockheed Martin Space Systems, Denver.

"As flight components such as the HP3 electronics become available, our team continues to integrate them on the spacecraft and test their functionality," said Stu Spath, InSight spacecraft program manager at Lockheed Martin. "We're steadily marching toward the start of spacecraft environmental testing this spring."

InSight's robotic arm will also place another science instrument onto the ground. This is the Seismic Experiment for Interior Structure, or SEIS, from the French Space Agency (CNES), with components from Germany, Switzerland, the United Kingdom and the United States.

A third experiment will use the radio link between InSight and NASA's Deep Space Network antennas on Earth to measure precisely a wobble in Mars' rotation that could reveal whether the planet has a molten or solid core. Wind and temperature sensors from Spain's Center for Astrobiology and a pressure sensor will monitor weather, and a magnetometer will measure magnetic disturbances.


Artist rendition of the proposed InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) Lander. Image credit: NASA/JPL-Caltech.

The project passed its System Integration Review in February. "A panel of experts from outside the project reviewed the system-level integration and test program," said InSight Project Manager Tom Hoffman, of JPL. "For Insight, there are multiple systems being brought together from several countries for final integration and testing in Denver."

InSight and other NASA current and future projects will help inform the journey to Mars, an agency priority to send humans to the Red Planet in the 2030s.

JPL manages InSight for NASA's Science Mission Directorate in Washington. InSight is part of NASA's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama.

Related article (Mars Elysium Planitia):

NASA Mission Helps Craft 3-D Image Of Buried Mars Flood Channels: http://orbiterchspacenews.blogspot.ch/2013/03/nasa-mission-helps-craft-3-d-image-of.html

For more information about InSight, visit: http://insight.jpl.nasa.gov

Additional information on the Discovery Program is available at: http://discovery.nasa.gov

You can follow the mission on Facebook and Twitter at: http://www.facebook.com/NASAInSight and http://twitter.com/nasainsight

Images (mentioned), Text, Credits: NASA/JPL/Guy Webster.

Greetings, Orbiter.ch

mercredi 4 mars 2015

Testing to Diagnose Power Event in Mars Rover










NASA - Mars Science Laboratory (MSL) logo.

March 4, 2015

Mars Science Laboratory Mission Status Report

NASA's Curiosity Mars rover is expected to remain stationary for several days of engineering analysis following an onboard fault-protection action on Feb. 27 that halted a process of transferring sample material between devices on the rover's robotic arm.

Telemetry received from the rover indicated that a transient short circuit occurred and the vehicle followed its programmed response, stopping the arm activity underway at the time of the irregularity in the electric current.

"We are running tests on the vehicle in its present configuration before we move the arm or drive," said Curiosity Project Manager Jim Erickson, of NASA's Jet Propulsion Laboratory in Pasadena, California. "This gives us the best opportunity to determine where the short is."

A transient short in some systems on the rover would have little effect on rover operations. In others, it could prompt the rover team to restrict use of a mechanism.


Image above: his raw-color view from Curiosity's Mastcam shows the rover's drill just after finishing a drilling operation at "Telegraph Peak" on Feb. 24, 2015. Image Credit: NASA/JPL-Caltech/MSSS.

When the fault occurred, the rover was conducting an early step in the transfer of rock powder collected by the drill on the arm to laboratory instruments inside the rover. With the drill bit pointed up and the drill's percussion mechanism turned on, the rock powder was descending from collection grooves in the bit assembly into a chamber in the mechanism that sieves and portions the sample powder. The sample powder is from a rock target called "Telegraph Peak."  The same transfer process was completed smoothly with samples from five previous drilling targets in 2013 and 2014.

NASA's Mars Science Laboratory Project is using Curiosity to assess ancient habitable environments and major changes in Martian environmental conditions.  JPL, a division of the California Institute of Technology in Pasadena, built the rover and manages the project for NASA's Science Mission Directorate in Washington.  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 and Twitter at: http://www.facebook.com/marscuriosity and http://www.twitter.com/marscuriosity

Image (mentioned), Text, Credits: NASA/JPL/Guy Webster.

Best regards. Orbiter.ch

Planet 'Reared' by Four Parent Stars












Palomar Observatory logo.

March 4, 2015


Image above: This artist's conception shows the 30 Ari system, which includes four stars and a planet. Image Credit: Karen Teramura, UH IfA.

Growing up as a planet with more than one parent star has its challenges. Though the planets in our solar system circle just one star -- our sun -- other more distant planets, called exoplanets, can be reared in families with two or more stars. Researchers wanting to know more about the complex influences of multiple stars on planets have come up with two new case studies: a planet found to have three parents, and another with four.

The discoveries were made using instruments fitted to telescopes at the Palomar Observatory in San Diego: the Robo-AO adaptive optics system, developed by the Inter-University Center for Astronomy and Astrophysics in India and the California Institute of Technology in Pasadena, and the PALM-3000 adaptive optics system, partially funded by NASA and developed by NASA's Jet Propulsion Laboratory in Pasadena, California, and Caltech.

This is only the second time a planet has been identified in a quadruple star system. While the planet was known before, it was thought to have only three stars, not four. The first four-star planet, KIC 4862625, was discovered in 2013 by citizen scientists using public data from NASA's Kepler mission.

The latest discovery suggests that planets in quadruple star systems might be less rare than once thought. In fact, recent research has shown that this type of star system, which usually consists of two pairs of twin stars slowly circling each other at great distances, is itself more common than previously believed.


Image above: The four stars and one planet of the 30 Ari system are illustrated in this diagram. Image Credit: NASA/JPL-Caltech.

"About four percent of solar-type stars are in quadruple systems, which is up from previous estimates because observational techniques are steadily improving," said co-author Andrei Tokovinin of the Cerro Tololo Inter-American Observatory in Chile.

The newfound four-star planetary system, called 30 Ari, is located 136 light-years away in the constellation Aries. The system's gaseous planet is enormous, with 10 times the mass of Jupiter, and it orbits its primary star every 335 days. The primary star has a relatively close partner star, which the planet does not orbit. This pair, in turn, is locked in a long-distance orbit with another pair of stars about 1,670 astronomical units away (an astronomical unit is the distance between Earth and the sun). Astronomers think it's highly unlikely that this planet, or any moons that might circle it, could sustain life.

Were it possible to see the skies from this world, the four parent stars would look like one small sun and two very bright stars that would be visible in daylight. One of those stars, if viewed with a large enough telescope, would be revealed to be a binary system, or two stars orbiting each other.

In recent years, dozens of planets with two or three parent stars have been found, including those with "Tatooine" sunsets reminiscent of the Star Wars movies. Finding planets with multiple parents isn't too much of a surprise, considering that binary stars are more common in our galaxy than single stars.

"Star systems come in myriad forms. There can be single stars, binary stars, triple stars, even quintuple star systems," said Lewis Roberts of JPL, lead author of the new findings appearing in the journal Astronomical Journal. "It’s amazing the way nature puts these things together."

Roberts and his colleagues want to understand the effects that multiple parent stars can have on their developing youthful planets. Evidence suggests that stellar companions can influence the fate of planets by changing the planets' orbits and even triggering some to grow more massive. For example, the "hot Jupiters" -- planets around the mass of Jupiter that whip closely around their stars in just days -- might be gently nudged closer to their primary parent star by the gravitational hand of a stellar companion.

Palomar Observatory. Image Credit: Wikimedia

In the new study, the researchers describe using the automated Robo-AO system on Palomar Observatory to scan the night skies, searching hundreds of stars each night for signs of stellar companions. They found two candidates hosting exoplanets: the four-star system 30 Ari, and a triple-star planetary system called HD 2638. The findings were confirmed using the higher-resolution PALM-3000 instrument, also at Palomar Observatory.

The new planet with a trio of stars is a hot Jupiter that circles its primary star tightly, completing one lap every three days. Scientists already knew this primary star was locked in a gravitational tango with another star, about 0.7 light-years away, or 44,000 astronomical units. That's relatively far apart for a pair of stellar companions. The latest discovery is of a third star in the system, which orbits the primary star from a distance of 28 astronomical units -- close enough to have influenced the hot Jupiter's development and final orbit.

"This result strengthens the connection between multiple star systems and massive planets," said Roberts.

In the case of Ari 30, the discovery brought the number of known stars in the system from three to four. The fourth star lies at a distance of 23 astronomical units from the planet. While this stellar companion and its planet are closer to each other than those in the HD 2638 system, the newfound star does not appear to have impacted the orbit of the planet. The exact reason for this is uncertain, so the team is planning further observations to better understand the orbit of the star and its complicated family dynamics.

JPL is managed for NASA by the California Institute of Technology in Pasadena.

For more information about the Palomar Observatory, visit: http://www.astro.caltech.edu/palomar/homepage.html

Images (mentioned), Text, Credits: NASA/JPL/Whitney Clavin.

Best regards, Orbiter.ch

NASA’s Chandra Observatory Finds Cosmic Showers Halt Galaxy Growth












NASA - Chandra X-ray Observatory patch.

March 4, 2015


Using NASA’s Chandra X-ray Observatory, astronomers have found that the growth of galaxies containing supermassive black holes can be slowed down by a phenomenon referred to as cosmic precipitation.

Cosmic precipitation is not a weather event, as we commonly associate the word -- rain, sleet, or snow. Rather, it is a mechanism that allows hot gas to produce showers of cool gas clouds that fall into a galaxy. Researchers have analyzed X-rays from more than 200 galaxy clusters, and believe that this gaseous precipitation is key to understanding how giant black holes affect the growth of galaxies.

“We know that precipitation can slow us down on our way to work,” said Mark Voit of Michigan State University (MSU) in East Lansing, lead author of the paper that appears in the latest issue of Nature. “Now we have evidence that it can also slow down star formation in galaxies with huge black holes.”


Image above: A study of over 200 galaxy clusters, including Abell 2597 shown here, with NASA’s Chandra X-ray Observatory has revealed how an unusual form of cosmic precipitation stifles star formation. Image Credit: NASA/CXC/DSS/Magellan.

Astronomers have long pursued the quest to understand how supermassive black holes, which can be millions or even billions of times the mass of the sun, affect their host galaxies.

“We’ve known for quite some time that supermassive black holes influence the growth of their host galaxies, but we haven’t yet figured out all of the details,” said co-author Megan Donahue, also of MSU. “These results get us a step closer.”

The study looked at some of the largest known galaxies lying in the middle of galaxy clusters. These galaxies are embedded in enormous atmospheres of hot gas. This hot gas should cool and many stars should then form. However, observations show that something is hindering the star birth.

The answer appears to lie with the supermassive black holes at the centers of the large galaxies. Under specific conditions, clumps of gas can radiate away their energy and form cool clouds that mix with surrounding hot gas. Some of these clouds form stars, but others rain onto the supermassive black hole, triggering jets of energetic particles that push against the falling gas and reheat it, preventing more stars from forming. This cycle of cooling and heating creates a feedback loop that regulates the growth of the galaxies.

“We can say that a typical weather forecast for the center of a massive galaxy is this: cloudy with a chance of heat from a huge black hole,” said co-author Greg Bryan of Columbia University in New York.

Voit and his colleagues used Chandra data to estimate how long it should take for the gas to cool at different distances from the black holes in the study. Using that information, they were able to accurately predict the “weather” around each of the black holes.

They found that the precipitation feedback loop driven by energy produced by the black hole jets prevents the showers of cold clouds from getting too strong. The Chandra data indicate the regulation of this precipitation has been going on for the last 7 billion years or more.

“Without these black holes and their jets, the central galaxies of galaxy clusters would have many more stars than they do today,” said co-author Michael McDonald of the Massachusetts Institute of Technology in Cambridge.

While a rain of cool clouds appears to play a key role in regulating the growth of some galaxies, the researchers have found other galaxies where the cosmic precipitation had shut off. The intense heat in these central galaxies, possibly from colliding with another galaxy cluster, likely “dried up” the precipitation around the black hole.

Chandra X-ray Observatory spacecraft. Image Credits: NASA/CXC

Future studies will test whether this precipitation-black hole feedback process also regulates star formation in smaller galaxies, including our own Milky Way galaxy.

A pre-print of the Nature study is available online. The study builds on work by Voit and Donahue that was published in the Jan. 20 issue of The Astrophysical Journal Letters and also is available online.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for the agency’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

An interactive image, podcast, and video about these findings are available at: http://chandra.si.edu

For more Chandra images, multimedia and related materials, visit: http://www.nasa.gov/chandra

Images (mentioned), Text, Credits: NASA/Felicia Chou/Marshall Space Flight Center/Janet Anderson/Chandra X-ray Center/Megan Watzke.

Greetings, Orbiter.ch

ESA experts assess risk from exploded satellite












ESA - Clean Space logo.

4 March 2015

After studying the recent explosive break-up of a US satellite, ESA space debris experts have concluded this event does not increase the collision risk to nearby ESA missions in any meaningful way.

The US Air Force’s Defense Meteorological Satellite Programme Flight 13 (DMSP-13) broke up into some 40 pieces on 3 February. The military weather satellite was in a low-Earth orbit – commonly used by Earth observation missions and some communication satellites – at more than 800 km altitude.

DMSP satellite

“The event is not considered major,” explained Holger Krag of ESA’s Space Debris Office. “Should the reported number of fragments stabilise at this level, we can consider it to be within the range of the past 250 on-orbit fragmentation events.

“For our missions – with CryoSat-2 being closest to the event altitude – we do not expect any meaningful risk due to the event.”

Based at ESA’s ESOC space operations centre in Darmstadt, Germany, the Space Debris Office receives space debris data from the US Joint Space Operations Center and performs analyses and simulations of the present and future debris environment, as well as working with missions to prepare ‘collision avoidance manoeuvres’.

Control room at ESOC

Satellite fragmentations are typically triggered by break-ups of tanks or batteries caused by remnant onboard energy sources under the influence of the harsh environment in space. 

The dispersion of the fragments associated with the DMSP-13 event is fairly large, however, and the largest concentration of fragments resides near the altitude in which the satellite operated. This is still about 100 km above ESA’s satellite constellation. The fragments will slowly decay over the years and decades to come.

ESA’s Clean Space initiative – tasked with reducing the environmental impacts of the space industry on both Earth and space – is looking into the technology to mitigate the debris levels in heavily-trafficked low-Earth orbits. At orbital velocities, even a 1 cm nut could hit a satellite with the force of a hand grenade.

Debris in low-Earth orbit

On 17–18 March, technical experts will meet at ESA’s ESTEC technical centre at Noordwijk, the Netherlands, to discuss debris mitigation technologies: methods to ensure that satellites can remove themselves from key low-Earth orbits well in advance of such a fragmentation event occurring, while also reducing the risk posed by reentering satellites.

“International regulations state that low-orbiting satellites are removed within 25 years of their mission end-of-life,” commented Luisa Innocenti, heading Clean Space. “Either they should end up at an altitude where atmospheric drag gradually induces reentry, or alternatively be despatched up to quieter ‘graveyard orbits’.

Space debris removal mission

“The challenge is to introduce these mandated mitigation methods while minimising the impact to the mission itself, especially for lower-mass satellites.”

But mitigation can only go so far. Projections show that the debris population will continue to grow through a chain reaction of collisions unless individual large items of debris – derelict satellites or launcher upper stages – are periodically retrieved.

ESA’s e.DeOrbit mission, currently undergoing preliminary Phase A/B design for launch in 2021, aims to demonstrate the feasibility of active debris removal.

Related links:

ESA’s e.DeOrbit mission: http://www.esa.int/Our_Activities/Space_Engineering_Technology/Clean_Space/Readying_ESA_s_garbage_truck_Robin_Biesbroek_interview

Space Debris Office: http://www.esa.int/Our_Activities/Operations/Space_Debris

CleanSat: new satellite technologies for cleaner low orbits: http://orbiterchspacenews.blogspot.ch/2015/01/cleansat-new-satellite-technologies-for.html

Technical day on deorbiting strategies and CleanSat workshop: http://space-env.esa.int/indico/conferenceDisplay.py?confId=73

Images, Text, Credits: ESA/J. Mai/USAF.

Greetings, Orbiter.ch

mardi 3 mars 2015

NASA-Funded Study Finds Two Solar Wind Jets in the Heliosphere













NASA logo / NASA - IBEX Mission patch.

March 3, 2015

As the sun skims through the galaxy, it emits charged particles in a stream of plasma called the solar wind. The solar wind, in turn, creates a bubble known called the heliosphere that extends far beyond the planets of the solar system. For decades, scientists have visualized the heliosphere as shaped like a comet, with a very long tail extending some 464 billion miles, which is thousands of times as far as the distance from Earth to the sun.


Image above: A new simulation of the heliosphere – the magnetic bubble surrounding the sun – shows it to have two relatively short jets streaming away from the nose. Image Credit: M. Opher/Reproduced by permission of the AAS.

New NASA-funded research now suggests that the heliosphere is actually dominated by two giant jets of material shooting backwards over the north and south poles of the sun, which are confined by the interaction of the sun’s magnetic field with the interstellar magnetic field. These curve around in two—relatively short – tails toward the back. The end result is a heliosphere without that long tail; a heliosphere that looks a lot more like a crescent moon than a comet. What's more, the two jets are similar to other astrophysical jets seen in space, so studying them locally could open doors to understanding such jets throughout the universe. The research is described in a paper in Astrophysical Journal Letters, which appeared online on Feb. 19, 2015.

"Everyone's assumption has been that the shape of the heliosphere was molded by the flow of interstellar material passing around it," said Merav Opher, an astronomer at Boston University, who is lead author on the paper. "Scientists thought the solar wind flowing down the tail could easily pull the magnetic fields in the heliosphere along as it flowed by, creating this long tail. But it turns out the magnetic fields are strong enough to resist that pull – so instead they squeeze the solar wind and create these two jets."

Opher and her colleagues found the jets and determined the new shape when they adjusted simulations of the heliosphere based on observations collected from NASA's Voyager 1 spacecraft, which recently moved outside of the heliosphere into interstellar space. As the first man-made object outside of our solar system, Voyager provided our only glimpse so far of the interstellar medium and it provided one giant surprise: The magnetic fields out there were aligned pretty much the same as the ones in here, though it had long been expected they would be oriented in a different direction.


Images above: Scientists think the magnetic bubble around our sun may look more like the shortened one as seen in this image of the star BZ Cam (left), as opposed to the long one as seen around the star Mira (right). Image Credit: NASA/Casalegno/GALEX.

Opher -- along with space scientist Jim Drake at the University of Maryland in College Park who is a co-author on the paper – had previously created models based on computer code developed by space physicists at the University of Michigan of the heliosphere. Their previous work focused on the nose of the heliosphere, trying to understand the physics there as we hurtle through space. To see if they could replicate the unexpected Voyager results, the team created a higher resolution simulation.

The new simulation described a heliosphere unlike one considered before.

“The Voyagers had a flashlight in the kitchen, and nobody was looking in the attic,” she remarks. “We noticed, while studying the draping of the galaxy’s magnetic field around the nose, that the heliosphere was much shorter than we anticipated."

Instead of being dominated solely by the flow of the interstellar material to create a long tail, the shape of the heliosphere is also affected by the solar wind jets emanating from the sun, said Drake.

"If there were no interstellar flow, then the magnetic fields around the sun would shape the solar wind into two jets pointing straight north and south," said Drake. "The magnetic fields contract around these jets, shooting the solar wind out like squishing a tube of toothpaste."

In the presence of the interstellar flow, these jets are bowed backwards, creating a crescent shape, as seen from the side of the sun. The jets erode in the presence of the strong interstellar flow, leading to two attenuated, short tails. This leads to a much shorter heliosphere of only about 250 times the distance between Earth and the sun, or about 23 billion miles.


Image above: The yellow shape is the heliopause, the boundary between the heliosphere and the local interstellar medium. The sun sits at the center of this bubble, but is too small to be seen here. The gray lines are the solar magnetic field lines and the red lines are the interstellar magnetic field. Image Credit: M. Opher.

"Not only is the heliosphere's shape different from what people thought," said Drake. "But the mechanism for these jets is the same as in many astrophysical systems. Astrophysical jets elsewhere produce energetic particles, but they are remote and hard to diagnose. Our jets are nearby so we might be able to figure out how they produce the energetic particles measured in the heliosphere."

To support their heliosphere model, the scientists turned to additional observations of the tail. Both NASA's Cassini and Interstellar Boundary Explorer, or IBEX, have gathered information about the tail end of the heliosphere by looking at what's called energetic neutral atoms, or ENAs. ENAs are created by energetic particle collisions in space and conveniently travel in straight lines, unlike many other particles in space. Observing ENAs traveling in from a certain area, therefore, can be used to map that region.

"Cassini data showed a similar amount of ENAs from the tail and the nose," said Opher.  "Suggesting that the size of both sides was similar, which means a short tail."

An IBEX paper from 2013 also described as a two-lobed shape down the tail. Opher and Drake suggest that the lobes observed might actually have been the two jets with interstellar, non-heliospheric material in between. The paper on the IBEX results, however, interpreted the heliosphere as having a long tail.

With such previous results, Opher expects the new model to be controversial. “This is going to be heavily, heavily debated,” she said, pointing out that many scientists work from the traditional comet-shaped model of the heliosphere. But, said Opher, the out-of-the-box results coming from spacecraft observations demand a similarly unconventional explanation.

In the meantime, these newly postulated jets look like baby versions of the super-powered jets that exist around exotic objects like black holes and pulsars. They are also seen around proto-stars just being born.  Being able to study these jets in our own backyard provides a homegrown laboratory in which to study a structure that is seen everywhere in the universe.

“If we’re right about all of this, it gives us a local test bed for exploring some very important physics,” said Drake.

Related Links:

More on IBEX and the heliotail: http://www.nasa.gov/content/nasa-s-ibex-provides-first-view-of-the-solar-system-s-tail/

New View of the Solar System: Astrophysical Jets Driven by the Sun: https://cmns.umd.edu/news-events/features/2804

New Vision of the Final Frontier: http://www.bu.edu/research/articles/new-vision-of-the-final-frontier/

Images (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Karen C. Fox.

Greetings, Orbiter.ch