vendredi 24 mai 2013

Galaxies Fed by Funnels of Fuel

Astrophysics / Exobiology.

May 24, 2013

 Cosmic Swirly Straws Feed Galaxy

Created with the help of supercomputers, this simulation shows the formation of a massive galaxy during the first 2 billion years of the universe. Hydrogen gas is gray, young stars appear blue, and older stars are red. The simulation reveals that gas flows into galaxies along filaments akin to cosmic bendy, or swirly, straws.

Computer simulations of galaxies growing over billions of years have revealed a likely scenario for how they feed: a cosmic version of swirly straws.

The results show that cold gas -- fuel for stars -- spirals into the cores of galaxies along filaments, rapidly making its way to their "guts." Once there, the gas is converted into new stars, and the galaxies bulk up in mass.

"Galaxy formation is really chaotic," said Kyle Stewart, lead author of the new study appearing in the May 20th issue of the Astrophysical Journal. "It took us several hundred computer processors, over months of time, to simulate and learn more about how this process works." Stewart, who is now at the California Baptist University in Riverside, Calif., completed the majority of this work while at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

In the early universe, galaxies formed out of clumps of matter, connected by filaments in a giant cosmic web. Within the galaxies, nuggets of gas cooled and condensed, becoming dense enough to trigger the birth of stars. Our Milky Way spiral galaxy and its billions of stars took shape in this way.

The previous, standard model of galaxy formation held that hot gas sank into the centers of burgeoning galaxies from all directions. Gas clouds were thought to collide into each other, sending out shock waves, which then heated up the gas. The process is similar to jets creating sonic booms, only in the case of galaxies, the in-falling gas travels faster than the speed of sound, piling up into waves. Eventually, the gas cools and sinks to the galactic center. This process was theorized to be slow, taking up to 8 billion years.

Recent research has contradicted this scenario in smaller galaxies, showing that the gas is not heated. An alternate "cold-mode" theory of galaxy formation was proposed instead, suggesting the cold gas might funnel along filaments into galaxy centers. Stewart and his colleagues set out to test this theory and address the mysteries about how the cold gas gets into galaxies, as well as the rate at which it spirals in.

Since it would take billions of years to watch a galaxy grow, the team simulated the process using supercomputers at JPL; NASA's Ames Research Center, Moffett Field, Calif.; and the University of California, Irvine. They ran four different simulations of the formation of a galaxy like our Milky Way, starting from just 57 million years after the big bang until present day.

Image above: This still from a supercomputer simulation reveals that cool gas flows into the centers of galaxies along filaments. Image credit: Video courtesy of the N-Body Shop at University of Washington.

The simulations began with the starting ingredients for galaxies -- hydrogen, helium and dark matter -- and then let the laws of physics take over to create their galactic masterpieces. Supercomputers are needed due to the enormous number of interactions.

"The simulations are like a gigantic game of chess," said Alyson Brooks, a co-author of the paper and expert in galaxy simulations at the University of Wisconsin, Madison. "For each point in time, we have to figure out how a given particle -- our chess piece -- should move based on the positions of all of the other particles. There are tens of millions of particles in the simulation, so figuring out how the gravitational forces affect each particle is time-consuming."

When the galaxy concoctions were ready, the researchers inspected the data, finding new clues about how cold gas sinks into the galaxy centers. The new results confirm that cold gas flows along filaments and show, for the first time, that the gas is spinning around faster than previously believed. The simulations also revealed that the gas is making its way down to the centers of galaxies more quickly than what occurs in the "hot-mode" of galaxy formation, in about 1 billion years.

"We have found that the filamentary structures that galaxies are built on are key to how they build up over time, by threading gas into them efficiently," said Leonidas Moustakas, a co-author at JPL.

The researchers looked at dark matter too -- an invisible substance making up about 85 percent of matter in the universe. Galaxies form out of lumps of regular matter, so-called baryonic matter that is composed of atoms, and dark matter. The simulations showed that dark matter is also spinning at a faster rate along the filaments, spiraling into the galaxy centers.

The results help answer a riddle in astronomy about galaxies with large extended disks of material spinning around them, far from their centers. Researchers didn't understand how the outer material could be spinning so fast. The cold-mode allows for this rapid spinning, fitting another jigsaw piece into the puzzle of how galaxies grow.

"The goal of simulating galaxies is to compare them to what telescopes observe and see if we really understand how to build a galaxy," said Stewart. "It helps us makes sense of the real universe."

Other authors of the paper are: James Bullock of the University of California, Irvine; Ariyeh Maller of the New York City College of Technology, Brooklyn, N.Y., Jürg Diemand of the University of Zurich, Switzerland; and James Wadsley of the McMaster University, Hamilton, Ontario, Canada.

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

Image, Video, Text, Credit: courtesy of the N-Body Shop at University of Washington / NASA / JPL / Whitney Clavin.


Magnetar SGR 0418

NASA - Chandra X-ray Observatory patch.

May 24, 2013

This graphic shows an exotic object in our galaxy called SGR 0418+5729 (SGR 0418 for short). As described in our press release, SGR 0418 is a magnetar, a type of neutron star that has a relatively slow spin rate and generates occasional large blasts of X-rays.

The only plausible source for the energy emitted in these outbursts is the magnetic energy stored in the star. Most magnetars have extremely high magnetic fields on their surface that are ten to a thousand times stronger than for the average neutron star. New data shows that SGR 0418 doesn’t fit that pattern. It has a surface magnetic field similar to that of mainstream neutron stars.

In the image on the left, data from NASA’s Chandra X-ray Observatory shows SGR 0418 as a pink source in the middle. Optical data from the William Herschel telescope in La Palma and infrared data from NASA’s Spitzer Space Telescope are shown in red, green and blue.

On the right is an artist’s impression showing a close-up view of SGR 0418. This illustration highlights the weak surface magnetic field of the magnetar, and the relatively strong, wound-up magnetic field lurking in the hotter interior of the star. The X-ray emission seen with Chandra comes from a small hot spot, not shown in the illustration. At the end of the outburst this spot has a radius of only about 160 meters, compared with a radius for the whole star of about 12 km.

The researchers monitored SGR 0418 for over three years using Chandra, ESA's XMM-Newton as well as NASA's Swift and RXTE satellites. They were able to make an accurate estimate of the strength of the external magnetic field by measuring how its rotation speed changes during an X-ray outburst. These outbursts are likely caused by fractures in the crust of the neutron star precipitated by the buildup of stress in the stronger magnetic field lying below the surface.

Chandra X-ray Observatory. Image credit: NASA/JPL-Caltech

By modeling the evolution of the cooling of the neutron star and its crust, as well as the gradual decay of its magnetic field, the researchers estimated that SGR 0418 is about 550,000 years old. This makes SGR 0418 older than most other magnetars, and this extended lifetime has probably allowed the surface magnetic field strength to decline over time. Because the crust weakened and the interior magnetic field is relatively strong, outbursts could still occur.

The implications of this result for understanding supernova explosions and the number and evolution of magnetars is discussed in the press release.

SGR 0418 is located in the Milky Way galaxy at a distance of about 6,500 light years from Earth. These new results on SGR 0418 appear online and will be published in the June 10, 2013 issue of The Astrophysical Journal. 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.

Press release:

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Images, Text, Credits: X-ray: NASA/CXC/CSIC-IEEC/N.Rea et al; Optical: Isaac Newton Group of Telescopes, La Palma/WHT; Infrared: NASA/JPL-Caltech.

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jeudi 23 mai 2013

Hubble reveals the Ring Nebula’s true shape

NASA - Hubble Space Telescope patch.

May 23, 2013

In this composite image, visible-light observations by NASA’s Hubble Space Telescope are combined with infrared data from the ground-based Large Binocular Telescope in Arizona to assemble a dramatic view of the well-known Ring Nebula. Credit: NASA, ESA, C.R. Robert O’Dell (Vanderbilt University), G.J. Ferland (University of Kentucky), W.J. Henney and M. Peimbert (National Autonomous University of Mexico). Credit for Large Binocular Telescope data: David Thompson (University of Arizona).

The Ring Nebula's distinctive shape makes it a popular illustration for astronomy books. But new observations by NASA's Hubble Space Telescope of the glowing gas shroud around an old, dying, sun-like star reveal a new twist.

"The nebula is not like a bagel, but rather, it's like a jelly doughnut, because it's filled with material in the middle," said C. Robert O'Dell of Vanderbilt University in Nashville, Tenn. He leads a research team that used Hubble and several ground-based telescopes to obtain the best view yet of the iconic nebula. The images show a more complex structure than astronomers once thought and have allowed them to construct the most precise 3-D model of the nebula.

"With Hubble's detail, we see a completely different shape than what's been thought about historically for this classic nebula," O'Dell said. "The new Hubble observations show the nebula in much clearer detail, and we see things are not as simple as we previously thought."

The Ring Nebula is about 2,000 light-years from Earth and measures roughly 1 light-year across. Located in the constellation Lyra, the nebula is a popular target for amateur astronomers.

This planetary nebula's simple, graceful appearance is thought to be due to perspective: our view from Earth looking straight into what is actually a barrel-shaped cloud of gas shrugged off by a dying central star. Hot blue gas near the energizing central star gives way to progressively cooler green and yellow gas at greater distances with the coolest red gas along the outer boundary. Credit: NASA/Hubble Heritage Team.

Previous observations by several telescopes had detected the gaseous material in the ring's central region. But the new view by Hubble's sharp-eyed Wide Field Camera 3 shows the nebula's structure in more detail. O'Dell's team suggests the ring wraps around a blue, football-shaped structure. Each end of the structure protrudes out of opposite sides of the ring.

The nebula is tilted toward Earth so that astronomers see the ring face-on. In the Hubble image, the blue structure is the glow of helium. Radiation from the white dwarf star, the white dot in the center of the ring, is exciting the helium to glow. The white dwarf is the stellar remnant of a sun-like star that has exhausted its hydrogen fuel and has shed its outer layers of gas to gravitationally collapse to a compact object.

O'Dell's team was surprised at the detailed Hubble views of the dark, irregular knots of dense gas embedded along the inner rim of the ring, which look like spokes in a bicycle wheel. These gaseous tentacles formed when expanding hot gas pushed into cool gas ejected previously by the doomed star. The knots are more resistant to erosion by the wave of ultraviolet light unleashed by the star. The Hubble images have allowed the team to match up the knots with the spikes of light around the bright, main ring, which are a shadow effect. Astronomers have found similar knots in other planetary nebulae.

Hubble in orbit. Image credit: NASA / ESA.

All of this gas was expelled by the central star about 4,000 years ago. The original star was several times more massive than our sun. After billions of years converting hydrogen to helium in its core, the star began to run out of fuel. It then ballooned in size, becoming a red giant. During this phase, the star shed its outer gaseous layers into space and began to collapse as fusion reactions began to die out. A gusher of ultraviolet light from the dying star energized the gas, making it glow.

The outer rings were formed when faster-moving gas slammed into slower-moving material. The nebula is expanding at more than 43,000 miles an hour, but the center is moving faster than the expansion of the main ring. O'Dell's team measured the nebula's expansion by comparing the new Hubble observations with Hubble studies made in 1998.

The Ring Nebula will continue to expand for another 10,000 years, a short phase in the lifetime of the star. The nebula will become fainter and fainter until it merges with the interstellar medium.

Studying the Ring Nebula's fate will provide insight into the sun's demise in another 6 billion years. The sun is less massive than the Ring Nebula's progenitor star, so it will not have an opulent ending.

"When the sun becomes a white dwarf, it will heat more slowly after it ejects its outer gaseous layers," O'Dell said. "The material will be farther away once it becomes hot enough to illuminate the gas. This larger distance means the sun's nebula will be fainter because it is more extended."

In the analysis, the research team also obtained images from the Large Binocular Telescope at the Mount Graham International Observatory in Arizona and spectroscopic data from the San Pedro Martir Observatory in Baja California, Mexico.


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

For more information about the Hubble Space Telescope, visit: and and

Images (mentioned), Text, Credit: NASA.


Solar Impulse Across America 2013: Landing in Dallas

Solar Impulse - Across America 2013 patch.

May 23, 2013

Across America 2013: 2nd leg from Phoenix Sky Harbor to Dallas Forth Worth. Landing. Image credits: Solar Impulse |Revillard|

Flight Phoenix KPHX - Dallas KDFW

- Pilot: André Borschberg, Co-Founder and CEO

- Take off time: May 22nd 04:47AM MST (UTC-7)

- Landing time: May 23rd 01:08AM CDT (UTC-5)

- Flight duration: 18h21min

- Average ground speed: 84 km/h ( 45,3 kt)

- Highest altitude reached: 27 000 ft

- Flight Distance: 1541 km (~832 NM)

Across America 2013: 2nd leg from Phoenix Sky Harbor to Dallas Forth Worth. Landing. Image credits: Solar Impulse / Revillard /

Who said surfing was only possible in California?

After completing the longest distance flight in the history of the project, landing at 01:08AM CDT (UTC-5) on Thursday May 23nd at Dallas Fort Worth International Airport, André expressed two wishes. The first was to stretch his long legs as it can get quite cramped when you’re over 6’2’’ (190 cm) tall in the meager 46 ft³ (1.3 m³) cockpit. The second one proved, once again, André’s pride in his family name; Borschberg: the good living. He articulated the wish to enjoy Texas’ world-renowned steak and even asked Dallas residents to send him names of the best spots in town. Ideas; anybody?

Jokes aside, it was a unique but challenging journey. The pre-flight preparations were intense because of the specific wind conditions, manifest after sunset. This allowed André to live a true “sky surfing” experience. Because of the lightness and slow speed of the solar airplane, it literally rode the updraft and downdraft of the mountain winds. This is clearly visible on the flight profile, a phenomenon that caused the plane to rise and fall, riding the wind waves.

Across America 2013: 2nd leg from Phoenix Sky Harbor to Dallas Forth Worth. B. Piccard and A. Borschberg with the Clean Generation Flag. Image credits: Solar Impulse / Revillard /

The flight was a perfect training experience for both the pilot and the team in the Mission Control Center. It has reconfirmed the need to remain flexible and try to request, when possible, permission to fly at different altitudes to local Air Traffic Controllers. Having options can help avoid being stuck in a segment that’s experiencing unique winds – but it’s not always possible due to dense air traffic flying below the solar airplane.

Across America 2013: Landing in Dallas Forth Worth

Texan skies have certainly challenged the top ranking of California’s surfing, but now that André’s safely back on the ground, he can indulge in a good pair of cowboy boots and other more traditionally Texan sports.

For more information about Solar Impulse:

Images (mentioned), Video. Text, Credit: Solar Impulse.


ESO's Very Large Telescope Celebrates 15 Years of Success

ESO - European Southern Observatory logo.

23 May 2013

 The Very Large Telescope Snaps a Stellar Nursery and Celebrates Fifteen Years of Operations

With this new view of a spectacular stellar nursery ESO is celebrating 15 years of the Very Large Telescope — the world's most advanced optical instrument. This picture reveals thick clumps of dust silhouetted against the pink glowing gas cloud known to astronomers as IC 2944. These opaque blobs resemble drops of ink floating in a strawberry cocktail, their whimsical shapes sculpted by powerful radiation coming from the nearby brilliant young stars.

This new picture celebrates an important anniversary for the Very Large Telescope – it is fifteen years since the first light on the first of its four Unit Telescopes, on 25 May 1998. Since then the four original giant telescopes have been joined by the four small Auxiliary Telescopes that form part of the VLT Interferometer (VLTI). The VLT is one of the most powerful and productive ground-based astronomical facilities in existence. In 2012 more than 600 refereed scientific papers based on data from the VLT and VLTI were published (ann13009).

Fifteen years of the Very Large Telescope

Interstellar clouds of dust and gas are the nurseries where new stars are born and grow. The new picture shows one of them, IC 2944, which appears as the softly glowing pink background [1]. This image is the sharpest view of the object ever taken from the ground [2]. The cloud lies about 6500 light-years away in the southern constellation of Centaurus (The Centaur). This part of the sky is home to many other similar nebulae that are scrutinised by astronomers to study the mechanisms of star formation.

Emission nebulae like IC 2944 are composed mostly of hydrogen gas that glows in a distinctive shade of red, due to the intense radiation from the many brilliant newborn stars. Clearly revealed against this bright backdrop are mysterious dark clots of opaque dust, cold clouds known as Bok globules. They are named after the Dutch-American astronomer Bart Bok, who first drew attention to them in the 1940s as possible sites of star formation. This particular set is nicknamed the Thackeray Globules [3].

The stellar nursery IC 2944 in the constellation of Centaurus

Larger Bok globules in quieter locations often collapse to form new stars but the ones in this picture are under fierce bombardment from the ultraviolet radiation from nearby hot young stars. They are both being eroded away and also fragmenting, rather like lumps of butter dropped into a hot frying pan. It is likely that Thackeray’s Globules will be destroyed before they can collapse and form stars.

Fifteen years of the Very Large Telescope

Bok globules are not easy to study. As they are opaque to visible light it is difficult for astronomers to observe their inner workings, and so other tools are needed to unveil their secrets — observations in the infrared or in the submillimetre parts of the spectrum, for example, where the dust clouds, only a few degrees over absolute zero, appear bright. Such studies of the Thackeray globules have confirmed that there is no current star formation within them.

Zooming in on the stellar nursery IC 2944 and Thackeray's Globules

This region of sky has also been imaged in the past by the NASA/ESA Hubble Space Telescope (opo0201a). This new view from the FORS instrument on ESO’s Very Large Telescope at the Paranal Observatory in northern Chile [4] covers a wider patch of sky than Hubble and shows a broader landscape of star formation.

A close-up look at the stellar nursery IC 2944 and Thackeray's Globules


[1] The nebula IC 2944 is associated with the bright star cluster IC 2948 and both of these names are also sometimes associated with the whole region. Many of the bright cluster stars appear in this picture.

[2] The seeing of the blue image in this colour combination was better than 0.5 arcseconds, exceptionally good for a ground-based telescope.

[3] They were discovered from South Africa by the English astronomer A. David Thackeray in 1950.

[4] This picture comes from the ESO Cosmic Gems programme, an outreach initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. All data collected may also be suitable for scientific purposes, and are made available to astronomers through ESO’s science archive.

More information:

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”.

ESOcast 57: ESO´s VLT Celebrates 15 Years of Success:


ESO Cosmic Gems programme:

Photos of the Very Large Telescope:

Photos from the Very Large Telescope:

ESO Cosmic Gems programme:

Images, Text, Credits: ESO/P.D. Barthel/M. McCaughrean/M. Andersen/S. Gillessen et al./Y. Beletsky/R. Chini/T. Preibisch/IAU and Sky & Telescope/Videos: ESO/Nick Risinger ( Music: John Dyson (from the album Moonwind).

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mercredi 22 mai 2013

Forecast for Titan: Wild Weather Could Be Ahead

NASA / ESA - Cassini Mission to Saturn patch.

May 22, 2013

 Vast Ligeia Mare in False Color

Image above: Ligeia Mare, shown here in data obtained by NASA's Cassini spacecraft, is the second largest known body of liquid on Saturn's moon Titan. Image credit: NASA/JPL-Caltech/ASI/Cornell.

Saturn's moon Titan might be in for some wild weather as it heads into its spring and summer, if two new models are correct. Scientists think that as the seasons change in Titan's northern hemisphere, waves could ripple across the moon's hydrocarbon seas, and hurricanes could begin to swirl over these areas, too. The model predicting waves tries to explain data from the moon obtained so far by NASA's Cassini spacecraft. Both models help mission team members plan when and where to look for unusual atmospheric disturbances as Titan summer approaches.

"If you think being a weather forecaster on Earth is difficult, it can be even more challenging at Titan," said Scott Edgington, Cassini's deputy project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We know there are weather processes similar to Earth's at work on this strange world, but differences arise due to the presence of unfamiliar liquids like methane. We can't wait for Cassini to tell us whether our forecasts are right as it continues its tour through Titan spring into the start of northern summer."

Titan's north polar region, which is bejeweled with sprawling hydrocarbon seas and lakes, was dark when Cassini first arrived at the Saturn system in 2004. But sunlight has been creeping up Titan's northern hemisphere since August 2009, when the sun's light crossed the equatorial plane at equinox. Titan's seasons take about seven Earth years to change. By 2017, the end of Cassini's mission, Titan will be approaching northern solstice, the height of summer.

Reflection of Sunlight off Titan Lake

Image above: This image shows the first flash of sunlight reflected off a lake on Saturn's moon Titan. Image credit: NASA/JPL/University of Arizona/DLR.

Given the wind-sculpted dunes Cassini has seen on Titan, scientists were baffled about why they hadn't yet seen wind-driven waves on the lakes and seas. A team led by Alex Hayes, a member of Cassini's radar team who is based at Cornell University, Ithaca, N.Y., set out to look for how much wind would be required to generate waves. Their new model, just published in the journal Icarus, improves upon previous ones by simultaneously accounting for Titan's gravity; the viscosity and surface tension of the hydrocarbon liquid in the lakes; and the air-to-liquid density ratio.

“We now know that the wind speeds predicted during the times Cassini has observed Titan have been below the threshold necessary to generate waves," Hayes said. "What is exciting, however, is that the wind speeds predicted during northern spring and summer approach those necessary to generate wind waves in liquid ethane and/or methane. It may soon be possible to catch a wave in one of the solar system’s most exotic locations.”

The new model found that winds of 1 to 2 mph (2 to 3 kilometers per hour) are needed to generate waves on Titan lakes, a speed that has not yet been reached during Titan's currently calm period. But as Titan's northern hemisphere approaches spring and summer, other models predict the winds may increase to 2 mph (3 kilometers per hour) or faster. Depending on the composition of the lakes, winds of that speed could be enough to produce waves 0.5 foot (0.15 meter) high.

Cassini spacecraft Titan fly-by. Image credit: NASA/JPL

The other model about hurricanes, recently published in Icarus, predicts that the warming of the northern hemisphere could also bring hurricanes, also known as tropical cyclones. Tropical cyclones on Earth gain their energy from the build-up of heat from seawater evaporation and miniature versions have been seen over big lakes such as Lake Huron. The new modeling work, led by Tetsuya Tokano of the University of Cologne, Germany, shows that the same processes could be at work on Titan as well, except that it is methane rather than water that evaporates from the seas. The most likely season for these hurricanes would be Titan's northern summer solstice, when the sea surface gets warmer and the flow of the air near the surface becomes more turbulent. The humid air would swirl in a counterclockwise direction over the surface of one of the northern seas and increase the surface wind over the seas to possibly 45 mph (about 70 kilometers per hour).

"For these hurricanes to develop at Titan, there needs to be the right mix of hydrocarbons in these seas, and we still don't know their exact composition," Tokano said. "If we see hurricanes, that would be one good indicator that there is enough methane in these lakes to support this kind of activity. So far, scientists haven't yet been able to detect methane directly."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate, Washington. JPL is a division of the California Institute of Technology in Pasadena, Calif.

For more information about Cassini and its mission, visit: and and

Images (mentioned), Text, Credits: NASA / JPL / Jia-Rui Cook.


Rare merger reveals secrets of galaxy evolution

ESA / NASA - Herschel Mission patch.

22 May 2013

A rare encounter between two gas-rich galaxies spotted by ESA’s Herschel space observatory indicates a solution to an outstanding problem: how did massive, passive galaxies form in the early Universe?

Most large galaxies fall into one of two major categories: spirals like our own Milky Way that are full of gas and actively forming stars, or gas-poor ellipticals, populated by old cool red stars and showing few signs of ongoing star formation.

Massive galaxy merger caught in the act

It was long assumed that the large elliptical galaxies seen in the Universe today built up gradually over time via the gravitational acquisition of many small dwarf galaxies. The theory held that the gas in those galaxies would gradually be converted into cool, low-mass stars, so that by today they would have exhausted all of their star-forming material, leaving them ‘red and dead’.

So the discovery in the last decade that very massive elliptical galaxies had managed to form during just the first 3–4 billion years of the Universe’s history posed something of a conundrum. Somehow, on short cosmological timescales, these galaxies had rapidly assembled vast quantities of stars and then ‘switched off’.

One idea is that two spiral galaxies might collide and merge to produce a vast elliptical galaxy, with the collision triggering such a massive burst of star formation that it would rapidly deplete the gas reservoir. In a new study using Herschel data, astronomers have captured the onset of this process between two massive galaxies, seen when the Universe was just 3 billion years old.

The galaxy pair was initially identified in the Herschel data as a single bright source, named HXMM01. Follow-up observations showed that it is in fact two galaxies, each boasting a stellar mass equal to about 100 billion Suns and an equivalent amount of gas.

The galaxies are linked by bridge of gas, indicating that they are merging.

 Mega Galaxy Merger

“This monster system of interacting galaxies is the most efficient star-forming factory ever found in the Universe at a time when it was only 3 billion years old,” says Hai Fu from University of California, Irvine, USA, who led the study published in Nature.

“The HXMM01 system is unusual not only because of its high mass and intense star-forming activity, but also because it exposes a crucial, intermediate step of the merging process, providing valuable insight that will help us constrain models for the formation and evolution of galaxies,” adds co-author Asantha Cooray, also from University of California, Irvine.

The onset of the merger has sparked a star-formation frenzy, with the system spawning stars at a phenomenal rate equivalent to roughly 2000 stars like the Sun every year. By comparison, a galaxy like the Milky Way today only manages to produce the equivalent of one Sun-like star per year.

Furthermore, the efficiency with which gas is being converted into stars is around ten times higher than that seen in more normal galaxies, which form stars at much slower rates. 

Such a high star-formation rate is not sustainable, however, and the gas reservoir contained in the HXMM01 system will be quickly exhausted, quenching further star formation and leading to an aging population of low-mass, cool, red stars.

Herschel space observatory

Dr Fu’s team estimate that it will take about 200 million years to convert all the gas into stars, with the merging process completed within a billion years. The final product will be a massive red and dead elliptical galaxy of about 400 billion solar masses.

“We were very lucky to catch this extreme system in such a critical transitional phase. It shows that the merger of gas-rich and actively star-forming galaxies is a possible mechanism to form the most massive ellipticals that are observed in the young Universe,” says Seb Oliver from University of Sussex, UK, and Principal Investigator for the HerMES Key Programme, within which the data have been collected.

“This discovery highlights the importance of the vast sky-scanning surveys that were completed with Herschel. In this case, the exceptional source HXMM01 was revealed, which may point to a solution of the riddle of how very massive galaxies formed and evolved when the Universe was still young,” adds Göran Pilbratt, ESA’s Herschel Project Scientist.

“The rapid assembly of an elliptical galaxy of 400 billion solar masses at a redshift of 2.3,” by H. Fu, et al., is published in Nature 23 May 2013.

The study is based on observations performed as part of the Herschel Multi-tiered Extragalactic Survey (HerMES). HerMES is a Herschel Guaranteed Time Key Programme designed to probe galaxy evolution at high redshift.

The source HXMM01 was initially detected in observations performed with the Spectral and Photometric Imaging Receiver (SPIRE). Additional data from the Photodetector Array Camera and Spectrometer (PACS) were also used.

Follow-up observations were performed with the W. M. Keck Observatory and the Submillimeter Array (SMA) at Mauna Kea, Hawaii; NRAO’s Karl G. Jansky Very Large Array and Robert C. Byrd Green Bank Telescope; the NASA/ESA Hubble Space Telescope; the William Herschel Telescope at La Palma, Spain; the IRAM/Plateau de Bure Interferometer (PdBI); the Max-Planck Millimetre Bolometer 2 (MAMBO2) at the IRAM 30m telescope; the Combined Array for Research in Millimeter-wave Astronomy (CARMA).

The study was supplemented with archival data from a variety of spaceborne and ground facilities: ESA’s XMM-Newton X-ray observatory; NASA’s Galaxy Evolution Explorer (GALEX), Spitzer Space Telescope, and Wide-field Infrared Survey Explorer (WISE); the Canada Hawaii Telescope Legacy Survey (CFHTLS); the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey of NRAO’s Very Large Array (VLA).

Herschel was launched on 14 May 2009 and completed science observations on 29 April 2013.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

For more information about Herschel space observatory, visit:

Images, Text, Video, Credits: ESA / NASA / JPL-Caltech / UC Irvine / STScI / Keck / NRAO / SAO.


mardi 21 mai 2013

NASA Mars Rover Curiosity Drills Second Rock Target

NASA - Mars Science Laboratory (MSL) patch.

May 21, 2013

 Artist's view of Curiosity drilling. Image credit: NASA/JPL-Caltech

NASA's Mars rover Curiosity has used the drill on its robotic arm to collect a powdered sample from the interior of a rock called "Cumberland."

Plans call for delivering portions of the sample in coming days to laboratory instruments inside the rover. This is only the second time that a sample has been collected from inside a rock on Mars. The first was Curiosity's drilling at a target called "John Klein" three months ago. Cumberland resembles John Klein and lies about nine feet (2.75 meters) farther west. Both are within a shallow depression called "Yellowknife Bay."

Image above: NASA's Mars rover Curiosity drilled into this rock target, "Cumberland," during the 279th Martian day, or sol, of the rover's work on Mars (May 19, 2013) and collected a powdered sample of material from the rock's interior. Image credit: NASA/JPL-Caltech/MSSS.

The hole that Curiosity drilled into Cumberland on May 19 is about 0.6 inch (1.6 centimeters) in diameter and about 2.6 inches (6.6 centimeters) deep.

The science team expects to use analysis of material from Cumberland to check findings from John Klein. Preliminary findings from analysis of John Klein rock powder by Curiosity's onboard laboratory instruments indicate that the location long ago had environmental conditions favorable for microbial life. The favorable conditions included the key elemental ingredients for life, an energy gradient that could be exploited by microbes, and water that was not harshly acidic or briny.

Animation above: This pair of images from the Mars Hand Lens Imager (MAHLI) on NASA's Mars rover Curiosity shows the rock target "Cumberland" before and after Curiosity drilled into it to collect a sample for analysis. The diameter of the drilled hole is about 0.6 inch (1.6 centimeters). Image credit: NASA/JPL-Caltech/MSSS.

NASA's Mars Science Laboratory Project is using Curiosity to assess the history of habitable environmental conditions inside Gale Crater. After a few more high-priority observations by the rover within and near Yellowknife Bay, the rover team plans to start Curiosity on a months-long trek to the base of a layered mound, Mount Sharp, at the middle of the crater. JPL, a division of the California Institute of Technology in Pasadena, manages the project for NASA's Science Mission Directorate in Washington.

More information about Curiosity is online at and . You can follow the mission on Facebook at: and on Twitter at: .

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

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Pilatus unveils new jet

Pilatus Aircraft logo.

May 21, 2013

 Pilatus PC-24

The Swiss aircraft manufacturer unveiled the PC-24, on Tuesday in Geneva, the world premiere at the EBACE.

The new aircraft can land on shorter distances and on all types of tracks and provide more space in the cabin and a rear door for easier loading.

The new aircraft can land on shorter distances and on all types of tracks

"This is another great moment in the history of our firm based in Stans since 1939," said Chairman of the Board of Directors of Pilatus, Oscar Schwenk, before a crowd of guests gathered at the first day of the annual fair aviation business EBACE, at Palexpo.

"The PC-24 brings together the traditional values ​​of flexibility, efficiency and accuracy in a Swiss business jet for the first time," he said.

It will also provide more space in the cabin and a rear door for easier loading

The new aircraft will reach a maximum speed of 787 km / h and a distance of 3610 km with four passengers. Production will begin in early 2014 and will be marketed in 2017.

The PC-24, dubbed the first "Super Versatile Jet" will be sold about nine million francs. It can be turned into a small freighter or medical.

Pilatus PC-24 description

For more information about Pilatus aircraft, visit:

Images, Text, Credits: Pilatus / ats / Translation: Aerospace.


dimanche 19 mai 2013

Spacecraft Bion-M № 1 returns to Earth

ROSCOSMOS - Bion M-1 Mission patch.


 Artistic representation of the Bion M-1 atmospheric return

May 19 in accordance with the planing, after a 30-day mission, in the Orenburg region held lander spacecraft landing Bion-M № 1.

SC Bion-M was created in the Federal State Unitary Enterprise SRP TsSKB-Progress (Samara) under the Federal Space Program for orbital flight in basic and applied research in space biology, physiology and biotechnology with the return of the results of experiments on Earth.

SC Bion-M № 1 description

After landing on Earth reentry vehicle with biological objects (animals, fish, insects, bacteria, etc.) on board, for their speedy recovery and carry out the initial evaluation, as well as preparation for the transportation and delivery of safe laboratory research institutions, was launched a special field laboratory . In workplaces, the necessary temperature and composition of the atmosphere for a comfortable pet friendly and the staff.

 The final installation of the SC Bion-M № 1 biological objects and animals

According to the specialists of the Institute of Biomedical Problems, Russian Academy of Sciences examination of the animals immediately after the flight produces a unique material that is required for the assessment and understanding of the processes taking place in the various systems of the body.

Russian scientific spacecraft Bion-M № 1 was launched on April 19, 2013 at 14 pm 00 minutes. MSK using ILV Soyuz-2.1a from Launch Complex 31, site Baikonur cosmodrome.

SC Bion-M № 1:

Roscosmos Press Release:

Images, Text, Credits: Press Service of the Russian Federal Space Agency (Roscosmos PAO) / ROSCOSMOS / Translation: Aerospace.

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