vendredi 5 avril 2013

Mapping the Chemistry Needed for Life at Europa












NASA - Galileo Mission patch.

April 5, 2013

A new paper led by a NASA researcher shows that hydrogen peroxide is abundant across much of the surface of Jupiter's moon Europa. The authors argue that if the peroxide on the surface of Europa mixes into the ocean below, it could be an important energy supply for simple forms of life, if life were to exist there. The paper was published online recently in the Astrophysical Journal Letters.

"Life as we know it needs liquid water, elements like carbon, nitrogen, phosphorus and sulfur, and it needs some form of chemical or light energy to get the business of life done," said Kevin Hand, the paper's lead author, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Europa has the liquid water and elements, and we think that compounds like peroxide might be an important part of the energy requirement. The availability of oxidants like peroxide on Earth was a critical part of the rise of complex, multicellular life."

The paper, co-authored by Mike Brown of the California Institute of Technology in Pasadena, analyzed data in the near-infrared range of light from Europa, using the Keck II Telescope on Mauna Kea, Hawaii, over four nights in September 2011. The highest concentration of peroxide found was on the side of Europa that always leads in its orbit around Jupiter, with a peroxide abundance of 0.12 percent relative to water. (For perspective, this is roughly 20 times more diluted than the hydrogen peroxide mixture available at drug stores.) The concentration of peroxide in Europa's ice then drops off to nearly zero on the hemisphere of Europa that faces backward in its orbit.


This color composite view combines violet, green, and infrared images of Jupiter's intriguing moon, Europa, for a view of the moon in natural color (left) and in enhanced color designed to bring out subtle color differences in the surface (right). Image credit: NASA/JPL-Caltech/University of Arizona.

Hydrogen peroxide was first detected on Europa by NASA's Galileo mission, which explored the Jupiter system from 1995 to 2003, but Galileo observations were of a limited region. The new results show that peroxide is widespread across much of the surface of Europa, and the highest concentrations are reached in regions where Europa's ice is nearly pure water with very little sulfur contamination. The peroxide is created by the intense radiation processing of Europa's surface ice that comes from the moon's location within Jupiter's strong magnetic field.

"The Galileo measurements gave us tantalizing hints of what might be happening all over the surface of Europa, and we've now been able to quantify that with our Keck telescope observations," Brown said. "What we still don't know is how the surface and the ocean mix, which would provide a mechanism for any life to use the peroxide."

NASA's Galileo spacecraft. Credit: NASA

The scientists think hydrogen peroxide is an important factor for the habitability of the global liquid water ocean under Europa's icy crust because hydrogen peroxide decays to oxygen when mixed into liquid water. "At Europa, abundant compounds like peroxide could help to satisfy the chemical energy requirement needed for life within the ocean, if the peroxide is mixed into the ocean," said Hand.

The study was funded in part by the NASA Astrobiology Institute through the Icy Worlds team based at JPL, a division of Caltech. The NASA Astrobiology Institute, based at NASA's Ames Research Center, Moffett Field, Calif., is a partnership among NASA, 15 U.S. teams and 13 international consortia. The Institute is part of NASA's astrobiology program, which supports research into the origin, evolution, distribution and future of life on Earth and the potential for life elsewhere.

NASA's Galileo mission: http://science.nasa.gov/missions/galileo/

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

Cheers, Orbiter.ch

NASA Celebrates Four Decades of Plucky Pioneer 11












NASA - Pioneer Mission patch.

April 5, 2013

 (Click image for full resolution)

Image above: An artist's impression of the encounter between Pioneer 11 and Saturn. Image credit: NASA Ames.
 
Forty years ago, on April 5, 1973, a small, ambitious spacecraft launched from Cape Canaveral, heading towards the third-brightest point of light in the night sky. Following in the footsteps of its sister craft, Pioneer 10, Pioneer 11 was intended as a backup for the dangerous mission. A single additional instrument, a Flux-Gate Magnetometer, was the only difference between Pioneer 11 and the craft that had already become the first human-made object to leave the inner solar system and was well on its journey to the first and most massive of the gas giant planets, Jupiter.


Image above: The planet Jupiter as seen from above its north pole by Pioneer 11. The pole itself is roughly on the line of the terminator (boundary between Jovian day and night) across the top of the planet. Image credit: NASA Ames.

By the beginning of 1974, Pioneer 10’s journey to Jupiter had proved to be an unmitigated success - the craft had sustained no damage through the asteroid belt, little lasting radiation damage during it’s encounter with Jupiter and had returned far greater volumes of scientific data than expected. After Pioneer 10 successfully survived the Jovian encounter, Pioneer 11 was retargeted mid-flight to include another planetary encounter. The science team at NASA's Ames Research Center in California decided not simply to duplicate Pioneer 10’s mission, but to build upon it, directing the small craft to use Jupiter’s massive gravitational pull as a slingshot to propel the craft at a significantly increased velocity (just as had been done to propel Pioneer 10 out the solar system) to the next – and arguably most beautiful – planet in our system, Saturn.


Image above: Legendary space scientist James van Allen is seen smoking a pipe alongside physicist Edward Smith at a Pioneer 11 press conference in 1974. Image credit: NASA Ames.

After some pressure from the Voyager team at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who wanted Pioneer to test the path that Voyager would follow several years later, a decision was made to travel much closer to Jupiter than Pioneer 10. This more risky path was opposed by some of the Pioneer team, but on December 2, 1974, Pioneer 11 passed only 42,000 km (compared to Pioneer 10’s 200,000 km) above Jupiter’s cloud tops. Pioneer 11’s route took the spacecraft over the poles of the planet to avoid the intense radiation belts around Jupiter’s equator. This allowed the first mapping of the planet’s polar regions and sent the craft hurtling through space at a record speed of 172,800 km/h. During its encounter, Pioneer 11 managed to take the most detailed images of the Great Red Spot and calculated the mass of the moon Calisto.


Image above: An artist's impression of a Pioneer spacecraft on its way to interstellar space. Image credit: NASA Ames.

Because of Pioneer 11’s ambiguous status as a combination science and engineering demonstration mission, a heated debate broke out in the NASA community about what route it would take past Saturn. The famous Voyager missions were launched a full two years before Pioneer 11 reached Saturn and were already heading towards Jupiter through what was now known to be virtually risk-free asteroid belt. The Voyager spacecraft were much more sophisticated and cost many times more than the relatively simple Pioneer probes. Voyager 2’s “Grand Tour” of the Solar System (which involved visiting Jupiter, Saturn, Uranus and Neptune) required that the spacecraft travel through Saturn’s outer A ring in order to get close enough to use gravitational assist to propel it to Uranus.

Scientists at the time were unsure of the makeup of the rings and were worried, as they were for Pioneer 10’s journey through the asteroid belt, that the spacecraft might be impacted and destroyed by objects in the ring. The material in the rings (now known to be mainly comprised of water ice) needed, on average, to be smaller than 1 mm, in which case they would be unlikely to damage the spacecraft, or larger than 1 cm so that they would be spaced far enough apart to allow a spacecraft to pass through them. If they fell between these two sizes, then a lethal impact was nearly inevitable.

video
Pioneer 11 Animation and Archive Footage

This video from the NASA archive shows animation of Pioneer's planned journey, launch footage, operations and artist conceptions of its science operations. (The red laser beams illustrate the method Pioneer used to take pictures since it was spin-stabilized).

Having already got more than they bargained for, the Pioneer team was ready to go out with a bang. They opted to risk their trusty spacecraft by sending it on a much more dangerous route through Saturn’s mysterious inner rings. This would maximize the scientific effectiveness of the mission and would prove the existence of the suspected D ring between the readily visible C ring and the planet’s upper atmosphere. The team was willing to take the more treacherous, unknown path for the sake of science. The Voyager team, however, had always seen Pioneer as a prelude to their more advanced mission and were adamant that the craft should test the route that Voyager 2 would take through the outer E ring two years later en route to Uranus.


Image above: Saturn and its moon Titan. The irregularities in ring silhouette and shadow are due to technical anomalies in the preliminary data later corrected. At the time this image was taken Pioneer was, at that time, 2,846,000 km (1,768,422 miles) from Saturn. Image credit: NASA Ames.

There were convincing arguments on both sides: the Pioneer team argued that the outer path would be too far away from Saturn for either spacecraft to take the measurements the scientists were interested in, while the Voyager team insisted that they could not risk passing through the rings without Pioneer testing them first.

Ultimately, it was decided by NASA Headquarters that Voyager 2’s safe passage to Uranus and Neptune would yield more scientific discovery than Pioneer’s path through the inner rings of Saturn and, to the sound of much booing from the Pioneer team, NASA director of Planetary Programs Tom Young announced Pioneer 11’s trajectory would be to the planet’s outer rings.


A drawing showing the trajectories of Pioneer 10 and 11 as well as Voyager 1 and 2 on their varied routes out of the Solar System. Image credit: NASA.

Certainly the decision to change Pioneer from a trailblazer into guinea pig, as some saw it, upset a number of the mission’s strongest supporters - especially the scientists who were hoping for another chance to use their instruments fully - but as time has passed, many people have changed their opinion of the contentious verdict.

“It was a controversial decision at the time,” mused Pioneer’s last project manager, Larry Lasher. “But with the brave path it forged, Pioneer 11 was proud to contribute to the success of Voyager 2 in its completion of the “Grand Tour,” and the exploration of two of the outermost planets in our Solar System.”

Despite its altered trajectory, which took it within 21,000 km of the Saturn, Pioneer 11 discovered two new moons (almost smacking into one of them in September 1979) and a new “F” ring. The spacecraft also discovered and charted the planet's magnetic field and magnetosphere, and mapped the general structure of Saturn's interior. The spacecraft's instruments measured the heat radiation from Saturn's interior and found that its planet-sized moon, Titan, was too cold to support life.


Image above: The golden plaque was the brainchild of Carl Sagan who wanted any alien civilization who might encounter the craft to know who made it and how to contact them. It gives our location in the Galaxy and depicts a naked man and woman drawn in relation to the spacecraft. Image credit: NASA.

Pioneer 11’s mission was only planned to last 21 months – just long enough to reach Jupiter – but in reality, the spacecraft continued functioning for decades after the end of its nominal mission. Pioneer 11’s most important milestone - the first encounter with Saturn - occurred eight months after its projected lifespan, while it became the fourth (Voyagers 1 and 2 had, by this time, overtaken it) human-made object to leave the planetary solar system almost 17 years after its launch on Feb 23, 1990. Thanks to the leadership of its legendary first project manager, Charles Hall, Pioneer could be seen as the prototype for cheaper, better, faster missions that followed in the 1990s.

Pioneer 11, ended its mission on Sept. 30, 1995, when the last transmission from the spacecraft was received. At that time, it took a full 12 hours for a radio signal (traveling at the speed of light) to reach the spacecraft. Currently, it is approximately 13 billion km from the sun and traveling in the direction of the constellation Scutum.

For more information about the Pioneer missions visit, http://www.nasa.gov/mission_pages/pioneer/

For more information about NASA Ames visit: http://www.nasa.gov/ames

Images (mentioned), Video, Text, Credits: NASA / Ames Research Center / James Schalkwyk.

Best regards, Orbiter.ch

jeudi 4 avril 2013

Scientists to Io: Your Volcanoes Are in the Wrong Place

 













NASA - New Horizons Mission patch / NASA - Galileo Mission patch.

April 4, 2013

Jupiter's moon Io is the most volcanically active world in the Solar System, with hundreds of volcanoes, some erupting lava fountains up to 250 miles high. However, concentrations of volcanic activity are significantly displaced from where they are expected to be based on models that predict how the moon's interior is heated, according to NASA and European Space Agency researchers.


Image above: This five-frame sequence of images from NASA's New Horizons mission captures the giant plume from Io's Tvashtar volcano. Snapped by the probe's Long Range Reconnaissance Imager (LORRI) as the spacecraft flew past Jupiter in 2007, this first-ever movie of an Io plume clearly shows motion in the cloud of volcanic debris, which extends 330 km (205 miles) above the moon's surface. Only the upper part of the plume is visible from this vantage point. The plume's source is 130 km (80 miles) below the edge of Io's disk, on the far side of the moon. Io's hyperactive nature is emphasized by the fact that two other volcanic plumes are also visible off the edge of Io's disk: Masubi at the 7 o'clock position, and a very faint plume, possibly from the volcano Zal, at the 10 o'clock position. Jupiter illuminates the night side of Io, and the most prominent feature visible on the disk is the dark horseshoe shape of the volcano Loki, likely an enormous lava lake. Boosaule Mons, which at 18 km (11 miles) is the highest mountain on Io and one of the highest mountains in the solar system, pokes above the edge of the disk on the right side. The five images were obtained over an 8-minute span, with two minutes between frames, from 23:50 to 23:58 Universal Time on 1 March 2007. Io was 3.8 million km (2.4 million miles) from New Horizons. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

Io is caught in a tug-of-war between Jupiter's massive gravity and the smaller but precisely timed pulls from two neighboring moons that orbit further from Jupiter – Europa and Ganymede. Io orbits faster than these other moons, completing two orbits every time Europa finishes one, and four orbits for each one Ganymede makes. This regular timing means that Io feels the strongest gravitational pull from its neighboring moons in the same orbital location, which distorts Io's orbit into an oval shape. This in turn causes Io to flex as it moves around Jupiter

NASA's New Horizons probe. Credit: NASA

For example, as Io gets closer to Jupiter, the giant planet's powerful gravity deforms the moon toward it and then, as Io moves farther away, the gravitational pull decreases and the moon relaxes. The flexing from gravity causes tidal heating -- in the same way that you can heat up a spot on a wire coat hanger by repeatedly bending it, the flexing creates friction in Io's interior, which generates the tremendous heat that powers the moon's extreme volcanism.

The question remains regarding exactly how this tidal heating affects the moon's interior. Some propose it heats up the deep interior, but the prevailing view is that most of the heating occurs within a relatively shallow layer under the crust, called the asthenosphere. The asthenosphere is where rock behaves like putty, slowly deforming under heat and pressure.


Image above: This is a map of the predicted heat flow at the surface of Io from different tidal heating models. Red areas are where more heat is expected at the surface while blue areas are where less heat is expected. Figure A shows the expected distribution of heat on Io's surface if tidal heating occurred primarily within the deep mantle, and figure B is the surface heat flow pattern expected if heating occurs primarily within the asthenosphere. In the deep mantle scenario, surface heat flow concentrates primarily at the poles, whereas in the asthenospheric heating scenario, surface heat flow concentrates near the equator. Credit: NASA/Christopher Hamilton.

"Our analysis supports the prevailing view that most of the heat is generated in the asthenosphere, but we found that volcanic activity is located 30 to 60 degrees East from where we expect it to be," said Christopher Hamilton of the University of Maryland, College Park. Hamilton, who is stationed at NASA's Goddard Space Flight Center in Greenbelt, Md., is lead author of a paper about this research published January 1 in Earth and Planetary Science Letters.

Galileo spacecraft. Credit: NASA

Hamilton and his team performed the spatial analysis using the a new, global geologic map of Io, produced by David Williams of Arizona State University, Tempe, Ariz., and his colleagues using data from NASA spacecraft. The map provides the most comprehensive inventory of Io's volcanoes to date, thereby enabling patterns of volcanism to be explored in unprecedented detail. Assuming that the volcanoes are located above where the most internal heating occurs, the team tested a range of interior models by comparing observed locations of volcanic activity to predicted tidal heating patterns.

"We performed the first rigorous statistical analysis of the distribution of volcanoes in the new global geologic map of Io," says Hamilton. "We found a systematic eastward offset between observed and predicted volcano locations that can't be reconciled with any existing solid body tidal heating models."

Possibilities to explain the offset include a faster than expected rotation for Io, an interior structure that permits magma to travel significant distances from where the most heating occurs to the points where it is able erupt on the surface, or a missing component in existing tidal heating models, like fluid tides from an underground magma ocean, according to the team.


Image above: This is a composite image of Io and Europa taken March 2, 2007 with the New Horizons spacecraft. Here Io (top) steals the show with its beautiful display of volcanic activity. Three volcanic plumes are visible. Most conspicuous is the enormous 300-kilometer (190-mile) high plume from the Tvashtar volcano at the 11 o'clock position on Io's disk. Two much smaller plumes are also visible: that from the volcano Prometheus, at the 9 o'clock position on the edge of Io's disk, and from the volcano Amirani, seen between Prometheus and Tvashtar along Io's terminator (the line dividing day and night). The Tvashtar plume appears blue because of the scattering of light by tiny dust particles ejected by the volcanoes, similar to the blue appearance of smoke. In addition, the contrasting red glow of hot lava can be seen at the source of the Tvashtar plume. This image was taken from a range of 4.6 million kilometers (2.8 million miles) from Io and 3.8 million kilometers (2.4 million miles) from Europa. Although the moons appear close together in this view, a gulf of 790,000 kilometers (490,000 miles) separates them. Io's night side is lit up by light reflected from Jupiter, which is off the frame to the right. Europa's night side is dark, in contrast to Io, because this side of Europa faces away from Jupiter. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

The magnetometer instrument on NASA's Galileo mission detected a magnetic field around Io, suggesting the presence of a global subsurface magma ocean. As Io orbits Jupiter, it moves inside the planet's vast magnetic field. Researchers think this could induce a magnetic field in Io if it had a global ocean of electrically conducting magma.

"Our analysis supports a global subsurface magma ocean scenario as one possible explanation for the offset between predicted and observed volcano locations on Io," says Hamilton. "However, Io's magma ocean would not be like the oceans on Earth. Instead of being a completely fluid layer, Io's magma ocean would probably be more like a sponge with at least 20 percent silicate melt within a matrix of slowly deformable rock."

Tidal heating is also thought to be responsible for oceans of liquid water likely to exist beneath the icy crusts of Europa and Saturn's moon Enceladus. Since liquid water is a necessary ingredient for life, some researchers propose that life might exist in these subsurface seas if a useable energy source and a supply of raw materials are present as well. These worlds are far too cold to support liquid water on their surfaces, so a better understanding of how tidal heating works may reveal how it could sustain life in otherwise inhospitable places throughout the Universe.


Image above: This is a montage of New Horizons images of Jupiter and its volcanic moon Io, taken during the spacecraft's Jupiter flyby in early 2007. The image shows a major eruption in progress on Io's night side, at the northern volcano Tvashtar. Incandescent lava glows red beneath a 330-kilometer (205-mile-high) volcanic plume, whose uppermost portions are illuminated by sunlight. The plume appears blue due to scattering of light by small particles in the plume. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Goddard Space Flight Center.

"The unexpected eastward offset of the volcano locations is a clue that something is missing in our understanding of Io," says Hamilton. "In a way, that's our most important result. Our understanding of tidal heat production and its relationship to surface volcanism is incomplete. The interpretation for why we have the offset and other statistical patterns we observed is open, but I think we've enabled a lot of new questions, which is good."

Io's volcanism is so extensive that it gets completely resurfaced about once every million years or so, actually quite fast compared to the 4.5-billion-year age of the solar system. So in order to know more about Io's past, we have to understand its interior structure better, because its surface is too young to record its full history, according to Hamilton.

The research was funded by NASA, the NASA Postdoctoral Program, administered by Oak Ridge Associated Universities, and the European Space Agency.

Related links:

NASA's New Horizons mission: http://www.nasa.gov/mission_pages/newhorizons/main/index.html

NASA's Galileo mission: http://science.nasa.gov/missions/galileo/

Images (mentioned), Text, Credit: NASA's Goddard Space Flight Center / Nancy Neal-Jones / Bill Steigerwald.

Best regards, Orbiter.ch

Gravity-Bending Find Leads to Kepler Meeting Einstein












NASA - Kepler Mission patch.

April 4, 2013

video
 Dead Star Warps Light of Red Star

Video above: This artist's animation depicts an ultra-dense dead star, called a white dwarf, passing in front of a small red star. As the white dwarf crosses in front, its gravity is so great that it bends and magnifies the light of the red star.

NASA's Kepler space telescope has witnessed the effects of a dead star bending the light of its companion star. The findings are among the first detections of this phenomenon -- a result of Einstein's general theory of relativity -- in binary, or double, star systems.

The dead star, called a white dwarf, is the burnt-out core of what used to be a star like our sun. It is locked in an orbiting dance with its partner, a small "red dwarf" star. While the tiny white dwarf is physically smaller than the red dwarf, it is more massive.

"This white dwarf is about the size of Earth but has the mass of the sun," said Phil Muirhead of the California Institute of Technology, Pasadena, lead author of the findings to be published April 20 in the Astrophysical Journal. "It's so hefty that the red dwarf, though larger in physical size, is circling around the white dwarf."

Kepler's primary job is to scan stars in search of orbiting planets. As the planets pass by, they block the starlight by miniscule amounts, which Kepler's sensitive detectors can see.


Image above: This artist's concept depicts a dense, dead star called a white dwarf crossing in front of a small, red star. Image credit: NASA/JPL-Caltech.

"The technique is equivalent to spotting a flea on a light bulb 3,000 miles away, roughly the distance from Los Angeles to New York City," said Avi Shporer, co-author of the study, also of Caltech.

Muirhead and his colleagues regularly use public Kepler data to search for and confirm planets around smaller stars, the red dwarfs, also known as M dwarfs. These stars are cooler and redder than our yellow sun. When the team first looked at the Kepler data for a target called KOI-256, they thought they were looking at a huge gas giant planet eclipsing the red dwarf.

"We saw what appeared to be huge dips in the light from the star, and suspected it was from a giant planet, roughly the size of Jupiter, passing in front," said Muirhead.

To learn more about the star system, Muirhead and his colleagues turned to the Hale Telescope at Palomar Observatory near San Diego. Using a technique called radial velocity, they discovered that the red dwarf was wobbling around like a spinning top. The wobble was far too big to be caused by the tug of a planet. That is when they knew they were looking at a massive white dwarf passing behind the red dwarf, rather than a gas giant passing in front.

NASA's Kepler space telescope. Image credit: NASA/JPL-Caltech

The team also incorporated ultraviolet measurements of KOI-256 taken by the Galaxy Evolution Explorer (GALEX), a NASA space telescope now operated by the California Institute of Technology in Pasadena. The GALEX observations, led by Cornell University, Ithaca, N.Y., are part of an ongoing program to measure ultraviolet activity in all the stars in Kepler field of view, an indicator of potential habitability for planets in the systems. These data revealed the red dwarf is very active, consistent with being "spun-up" by the orbit of the more massive white dwarf.

The astronomers then went back to the Kepler data and were surprised by what they saw. When the white dwarf passed in front of its star, its gravity caused the starlight to bend and brighten by measurable effects.

"Only Kepler could detect this tiny, tiny effect," said Doug Hudgins, the Kepler program scientist at NASA Headquarters, Washington. "But with this detection, we are witnessing Einstein's general theory of relativity at play in a far-flung star system."

One of the consequences of Einstein's general theory of relativity is that gravity bends light. Astronomers regularly observe this phenomenon, often called gravitational lensing, in our galaxy and beyond. For example, the light from a distant galaxy can be bent and magnified by matter in front of it. This reveals new information about dark matter and dark energy, two mysterious ingredients in our universe.


Images above: This chart shows data from NASA's Kepler space telescope, which looks for planets by monitoring changes in the brightness of stars. Image credit: NASA/Ames/JPL-Caltech.

Gravitational lensing has also been used to discover new planets and hunt for free-floating planets.

In the new Kepler study, scientists used the gravitational lensing to determine the mass of the white dwarf. By combining this information with all the data they acquired, the scientists were also able to measure accurately the mass of the red dwarf and the physical sizes of both stars. Kepler's data and Einstein's theory of relativity have together led to a better understanding of how binary stars evolve.

Other authors include Andrew Vanderburg of the University of California, Berkeley; Avi Shporer, Juliette Becker, Jonathan J. Swift, Sasha Hinkley, J. Sebastian Pineda, Michael Bottom, Christoph Baranec, Reed Riddle, Shriharsh P. Tendulkar, Khanh Bui, Richard Dekany and John Asher Johnson of Caltech; James P. Lloyd and Jim Fuller of Cornell University; Ming Zhao of The Pennsylvania State University, University Park; Andrew W. Howard of University of Hawaii, Hilo; Kaspar von Braun of the Max Planck Institute for Astronomy, Germany; Tabetha S. Boyajian of Yale University, New Haven, Conn.; Nicholas Law of the University of Toronto, Canada; A. N. Ramaprakash, Mahesh Burse, Pravin Chordia, Hillol Das and Sujit Punnadi of the Inter-University Centre for Astronomy & Astrophysics, India.

NASA Ames manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development. Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with JPL at the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters. JPL is a division of Caltech.

For more information about the Kepler mission, visit: http://www.nasa.gov/kepler

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

Greetings, Orbiter.ch

Hubble breaks record for furthest supernova












NASA - Hubble Space Telescope patch.

4 April 2013

 Record-breaking supernova in the CANDELS Ultra Deep Survey

The NASA/ESA Hubble Space Telescope has broken the record in the quest to find the furthest supernova of the type used to measure cosmic distances. This supernova exploded more than 10 billion years ago (redshift 1.914), at a time the Universe was in its early formative years and stars were being born at a rapid rate.

The supernova, designated SN UDS10Wil [1], belongs to a special class of exploding stars known as Type Ia supernovae. These bright beacons are prized by astronomers because they can be used as a yardstick for measuring cosmic distances, thereby yielding clues to the nature of dark energy, the mysterious force accelerating the rate of expansion of the Universe.

Record-breaking supernova in the CANDELS Ultra Deep Survey (compass and scale)

“This new distance record holder opens a window into the early Universe, offering important new insights into how these supernovae form,” said astronomer David O. Jones of The Johns Hopkins University in Baltimore, Md., lead author on the science paper detailing the discovery. “At that epoch, we can test theories about how reliable these detonations are for understanding the evolution of the Universe and its expansion.”

One of the debates surrounding Type Ia supernovae is the nature of the fuse that ignites them. This latest discovery adds credence to one of two competing theories of how they explode. Although preliminary, the evidence favours the explosive merger of two burned out stars — small, dim, and dense stars known as white dwarfs, the final state for stars like our Sun.

The CANDELS Ultra Deep Survey (UDS)

The discovery was part of a three-year Hubble program called the CANDELS+CLASH Supernova Project, begun in 2010 [2]. This program aimed to survey faraway Type Ia supernovae to determine their distances and see if their behaviour has changed over the 13.8 billion years since the Big Bang, using the sharpness and versatility of Hubble’s Wide Field Camera 3.

So far, CANDELS+CLASH has uncovered more than 100 supernovae of all types that exploded from 2.4 to over 10 billion years ago. The team has identified eight of these discoveries as Type Ia supernovae that exploded more than 9 billion years ago — including this new record-breaker, which, although only four percent older than the previous record holder, pushes the record roughly 350 million years further back in time [3].

Record-breaking supernova in the CANDELS Ultra Deep Survey: before, after, and difference

The supernova team’s search technique involved taking multiple near-infrared images spaced roughly 50 days apart over the span of three years, looking for a supernova’s faint glow. After spotting SN UDS10Wil in December 2010, the CANDELS team then used the spectrometer on Hubble’s Wide Field Camera 3, along with the European Southern Observatory’s Very Large Telescope, to verify the supernova’s distance and to decode its light, hoping to find the unique signature of a Type Ia supernova.

Finding remote supernovae opens up the possibility to measure the Universe’s accelerating expansion due to dark energy [4]. However, this is an area that is not fully understood — and nor are the origins of Type Ia supernovae. “This new result is a really exciting step forward in our study of supernovae and the distant Universe,” said team member Jens Hjorth of the Dark Cosmology Centre at the Niels Bohr Institute, University of Copenhagen. “We can begin to explore and understand the stars that cause these violent explosions.”

After view of the record-breaking supernova in the CANDELS Ultra Deep Survey

The team’s preliminary evidence shows a sharp decline in the rate of Type Ia supernova blasts between roughly 7.5 billion years ago and more than 10 billion years ago. This, combined with the discovery of such Type Ia supernovae so early in the Universe, suggests that the explosion mechanism is a merger between two white dwarfs.

In the single white dwarf scenario — a pathway in which a white dwarf gradually feeds off a partnering normal star and explodes when it accretes too much mass — the rate of supernovae can be relatively high in the early Universe, because some of these systems can reach the point of explosion very quickly. The steep drop-off favours the double white dwarf mechanism, because it predicts that most stars in the early Universe are too young to become Type Ia supernovae.

Hubble in orbit

Knowing what triggers Type Ia supernovae will also show how quickly the Universe enriched itself with heavier elements, such as iron. These exploding stars produce about half of the iron in the Universe, the raw material for building planets, and life.

The team’s results will appear in the 10 May 2013 issue of The Astrophysical Journal.

Notes:

[1] The supernova has been catalogued as SN UDS10Wil in the CANDEL-CLASH list. It has also been nicknamed SN Wilson, after the 28th U.S. president Woodrow Wilson.

[2] This project searches for supernovae in near-infrared light and verifies their distances with spectroscopy. The supernova search draws on two large Hubble programs studying distant galaxies and galaxy clusters: the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) and the Cluster Lensing and Supernova Survey with Hubble (CLASH).

[3] The previous record holder was recently announced by a team that identified a supernova that exploded around 9 billion years ago (redshift 1.7). The paper was published in The Astrophysical Journal, available here: http://iopscience.iop.org/0004-637X/763/1/35

[4] It has been known since the late 1920s that distant galaxies appear to be moving away from us with a speed that is proportional to their distance. Edwin Hubble and Georges Lemaître were the first to infer that this implied the whole Universe is expanding. In 2011, the Nobel Prize in Physics was awarded to the teams of astronomers that discovered, using Type Ia supernovae, that this expansion is actually accelerating (ann11069) — Adam Riess of Johns Hopkins University, Saul Perlmutter of the University of California at Berkeley, and Brian Schmidt of the Australian National University in Canberra. This acceleration is attributed to dark energy, whose nature is unknown.

Notes for editors:

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

The research is presented in a paper entitled “The Discovery of the Most Distant Known Type Ia Supernova at Redshift 1.914”, accepted for publication in 10 May 2013 issue of The Astrophysical Journal.

The international team of astronomers in this study consists of:

D. O. Jones (Johns Hopkins University, USA), S. A. Rodney (Johns Hopkins University, USA; Hubble Fellow), A. G. Riess (Johns Hopkins University, USA; Space Telescope Science Institute, USA), B. Mobasher (University of California, USA), T. Dahlen (Space Telescope Science Institute, USA), C. McCully (The State University of New Jersey, USA), T. F. Frederiksen (University of Copenhagen, Denmark), S. Casertano (Space Telescope Science Institute, USA), J. Hjorth (University of Copenhagen, Denmark), C. R. Keeton (The State University of New Jersey, USA), A. Koekemoer (Space Telescope Science Institute, USA), L. Strolger (Western Kentucky University, USA), T. G. Wiklind (Joint ALMA Observatory, ESO, Chile), P. Challis (Harvard/Smithsonian Center for Astrophysics, USA), O. Graur (Tel-Aviv University, Israel;  American Museum of Natural History, USA), B. Hayden (University of Notre Dame, USA), B. Patel (The State University of New Jersey, USA), B. J. Weiner (University of Arizona, USA), A. V. Filippenko (University of California, USA), P. Garnavich (University of Notre Dame, USA), S. W. Jha (The State University of New Jersey, USA), R. P. Kirshner (Harvard/Smithsonian Center for Astrophysics, USA), S. M. Faber (University of California, USA), H. C. Ferguson (Space Telescope Science Institute, USA), N. A. Grogin (Space Telescope Science Institute, USA), and D. Kocevski (Harvard/Smithsonian Center for Astrophysics, USA).

Links:

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

NASA press release: http://hubblesite.org/newscenter/archive/releases/2013/11/

CANDELS survey: http://candels.ucolick.org/

CLASH collaboration: http://www.stsci.edu/~postman/CLASH/

Research paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1306.pdf

Images, Text, Credits: NASA, ESA, A. Riess, Z. Levay (STScI and JHU), and D. Jones and S. Rodney (JHU) / S. Faber (University of California, Santa Cruz), H. Ferguson (STScI), and the CANDELS team.

Greetings, Orbiter.ch

mercredi 3 avril 2013

NASA Team Investigates Complex Chemistry at Titan












NASA / ESA - Cassini-Huygens Mission to Saturn & Titan patch.

April 3, 2013


Image above: The colorful globe of Saturn's largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA's Cassini spacecraft.Image credit: NASA/JPL-Caltech/Space Science Institute.

A laboratory experiment at NASA's Jet Propulsion Laboratory, Pasadena, Calif., simulating the atmosphere of Saturn's moon Titan suggests complex organic chemistry that could eventually lead to the building blocks of life extends lower in the atmosphere than previously thought. The results now point out another region on the moon that could brew up prebiotic materials. The paper was published in Nature Communications this week.

Huygens probe jettison from the Cassini spacecraft. Image credit: ESA

"Scientists previously thought that as we got closer to the surface of Titan, the moon's atmospheric chemistry was basically inert and dull," said Murthy Gudipati, the paper's lead author at JPL. "Our experiment shows that's not true. The same kind of light that drives biological chemistry on Earth's surface could also drive chemistry on Titan, even though Titan receives far less light from the sun and is much colder. Titan is not a sleeping giant in the lower atmosphere, but at least half awake in its chemical activity."


In this picture, molecules of dicyanoacetylene are seen on a special film on a sapphire window. Image credit: NASA/JPL-Caltech.

Scientists have known since NASA's Voyager mission flew by the Saturn system in the early 1980s that Titan, Saturn's largest moon, has a thick, hazy atmosphere with hydrocarbons, including methane and ethane. These simple organic molecules can develop into smog-like, airborne molecules with carbon-nitrogen-hydrogen bonds, which astronomer Carl Sagan called "tholins."

"We've known that Titan's upper atmosphere is hospitable to the formation of complex organic molecules," said co-author Mark Allen, principal investigator of the JPL Titan team that is a part of the NASA Astrobiology Institute, headquartered at Ames Research Center, Moffett Field, Calif. "Now we know that sunlight in the Titan lower atmosphere can kick-start more complex organic chemistry in liquids and solids rather than just in gases."

The team examined an ice form of dicyanoacetylene -- a molecule detected on Titan that is related to a compound that turned brown after being exposed to ambient light in Allen’s lab 40 years ago.

In this latest experiment, dicyanoacetylene was exposed to laser light at wavelengths as long as 355 nanometers. Light of that wavelength can filter down to Titan's lower atmosphere at a modest intensity, somewhat like the amount of light that comes through protective glasses when Earthlings view a solar eclipse, Gudipati said. The result was the formation of a brownish haze between the two panes of glass containing the experiment, confirming that organic-ice photochemistry at conditions like Titan's lower atmosphere could produce tholins.


This still image was captured by the European Space Agency's Huygens probe as it plunged through Titan's thick, orange-brown atmosphere on Jan. 14, 2005. Image credit: ESA/NASA/JPL-Caltech/University of Arizona.

The complex organics could coat the "rocks" of water ice at Titan's surface and they could possibly seep through the crust, to a liquid water layer under Titan's surface. In previous laboratory experiments, tholins like these were exposed to liquid water over time and developed into biologically significant molecules, such as amino acids and the nucleotide bases that form RNA.

Artist's view of the Huygens probe landed. Image credit: ESA

"These results suggest that the volume of Titan's atmosphere involved in the production of more complex organic chemicals is much larger than previously believed," said Edward Goolish, acting director of NASA's Astrobiology Institute. "This new information makes Titan an even more interesting environment for astrobiological study."

video
Animation PIA08118: A View from Huygens - Jan. 14, 2005

The team included Isabelle Couturier of the University of Provence, Marseille, France; Ronen Jacovi, a NASA postdoctoral fellow from Israel; and Antti Lignell, a Finnish Academy of Science postdoctoral fellow from Helsinki at JPL.

Founded in 1998, the NASA Astrobiology Institute is a partnership between NASA, 15 U.S. teams and 13 international consortia. It is based at NASA Ames Research Center, Moffett Field, Calif. The Institute's goals are to promote, conduct and lead interdisciplinary astrobiology research, train a new generation of astrobiology researchers, and share the excitement of astrobiology with learners of all ages. The NAI is part of NASA's Astrobiology program, which supports research into the origin, evolution, distribution and future of life on Earth and the potential for life elsewhere. For more information, visit http://astrobiology.nasa.gov/.

JPL is a division of the California Institute of Technology, Pasadena.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington.

For more information on Cassini, visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov and http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Images (mentioned), Text, Credits: NASA / JPL / Jia-Rui Cook / Ames Research Center / James Schalkwyk / Video: ESA/NASA/JPL/University of Arizona.

Greetings, Orbiter.ch

Used Parachute on Mars Flaps in the Wind












NASA - Mars Reconnaissance Orbiter (MRO) patch.

April 3, 2013

Photos from NASA's Mars Reconnaissance Orbiter show how the parachute that helped NASA's Curiosity rover land on Mars last summer has subsequently changed its shape on the ground.

The images were obtained by the High Resolution Imaging Science Experiment (HiRISE) camera on Mars Reconnaissance Orbiter.

Seven images taken by HiRISE between Aug. 12, 2012, and Jan. 13, 2013, show the used parachute shifting its shape at least twice in response to wind.


This sequence of seven images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter shows wind-caused changes in the parachute of NASA's Mars Science Laboratory spacecraft as the chute lay on the Martian ground during months after its use in safe landing of the Curiosity rover. Image credit: NASA/JPL-Caltech/Univ. of Arizona.

The images in the sequence of photos are available online at http://uahirise.org/releases/msl-chute.php and at http://www.nasa.gov/mission_pages/MRO/multimedia/pia16813.html .

Researchers have used HiRISE to study many types of changes on Mars. Its first image of Curiosity's parachute, not included in this series, caught the spacecraft suspended from the chute during descent through the Martian atmosphere.

Descent of the Phoenix Lander (click on the image for enlarge)

Image above: MRO's HiRISE camera acquired this dramatic oblique image of Phoenix descending on its parachute. Shown here is a a wider view of the full image, showing a 10 kilometer diameter crater informally called "Heimdall" and an improved full-resolution image of the parachute and lander. Image credit: NASA/JPL/University of Arizona.

Although it appears that Phoenix is descending into the crater, it is actually about 20 kilometers in front of the crater. It is difficult to believe that it is in front of the crater because it is so much smaller, but in reality it is, and that's a good thing because landing on the steep rocky slopes of the crater would have been far too exciting (or risky).

Images from the lander clearly show that it sits on a flat plain, although the rim of Heimdall may be visible on the horizon. Given the position and pointing angle of MRO, Phoenix is at about 13 kilometers above the surface, just a few seconds after the parachute opened. This improved image shows some details of the parachute, including the gap between upper and lower sections. At the time of this observation, MRO had an orbital altitude of 310 kilometers, traveling at a ground velocity of 3.4 kilometers/second, and a distance of 760 kilometers to the Phoenix lander.

Mars Phoenix Lander. Image credit: NASA / JPL-Caltech

The image was rotated to a position that seems approximately parallel to the horizon based on the elongation of Heimdall Crater, but this is not exact. Thus, although Phoenix appears to hang from the parachute at an angle, as if swaying in the wind, the exact geometry has not yet been determined. The parachute image is very sharp as its apparent motion was straight down the HiRISE TDI (time delay integration) columns. However, the surface of Mars was moving at an angle to the TDI columns, and thus is smeared by a few pixels, although the smear is not apparent at the reduced scale of the image shown here.

HiRISE is operated by the University of Arizona, Tucson. The instrument was built by Ball Aerospace & Technologies Corp., Boulder, Colo. The Mars Reconnaissance Orbiter Project and Curiosity are managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate, Washington. JPL is a division of the California Institute of Technology in Pasadena.

For more information about the Mars Reconnaissance Orbiter, which has been studying Mars from orbit since 2006, visit http://www.nasa.gov/mro

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

Cheers, Orbiter.ch

Shining light on elusive dark matter‏


















NASA - Alpha Magnetic Spectrometer (AMS-02) patch.


3 April 2013

 Localization of the AMS-02 (red circle) on ISS

The antimatter hunter AMS-02 on the International Space Station is searching for the missing pieces of our Universe. The project’s first results published today are hinting at a new phenomenon and revealing more about the invisible ‘dark matter’.

AMS-02, the Alpha Magnetic Spectrometer, consists of seven instruments that monitor cosmic rays from space. Unprotected by Earth’s atmosphere the instruments receive a constant barrage of high-energy particles. As these particles pass through AMS-02, the instruments record their speed, energy and direction.

Space Station after AMS-02 installation

The project is one of the largest scientific collaborations of all time involving 56 institutes from 16 countries. The instrument was tested at ESA’s technical facility ESTEC in the Netherlands before being shipped to the US for launch on Space Shuttle Endeavour. As part of his DAMA mission, ESA astronaut Roberto Vittori controlled the Shuttle’s robotic arm that transferred the 6918 kg instrument to the International Space Station in 2011.

Scientists have collected data on over 400 000 electrons together with their antimatter twins, the positrons. Data released today show how the ratio of positrons compared to electrons passing through AMS-02 changes depending on their energy, confirming data from previous instruments.

AMS-02 testing at ESTEC

The findings hint at a new phenomenon but it is unknown whether the positron ratio comes from dark energy particles colliding with each other or from pulsating stars in our galaxy that produce antimatter.

Shine a torch in a completely dark room, and you will see only what the torch illuminates. That does not mean that the room around you does not exist. Similarly we know dark matter exists but have never observed it directly.

New cosmic recipe

ESA’s Planck satellite refined our knowledge of what makes up our Universe, showing last month that it is made of 26.8% dark matter. AMS-02 and the operators controlling it are working day and night to investigate the individual particles that make up dark matter.

Despite recording over 30 billion cosmic rays since AMS-2 was installed on the International Space Station in 2011, the findings presented today are based on only 10% of the readings the instrument will deliver over its lifetime.

video
AMS-02 / How Long

Video above: Building AMS-02: 16 years in three minutes. Credits: Widlab / CERN.

Scientists are confident that AMS-02 will deliver the data needed to solve the riddle of where the changes in positron ratio come from in the near future.

“Over the coming months, AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin.” says Professor Samuel Ting, the project's lead investigator.

Related links:

DAMA Mission: http://www.esa.int/Our_Activities/Human_Spaceflight/DAMA_mission

STS-134 mission: http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html

AMS-02 homepage: http://www.ams02.org/

Images, Video, Text, Credits: ESA and the Planck Collaboration / Widlab / CERN / NASA.

Best regards, Orbiter.ch

Stars in NGC 602a












NASA - Chandra X-ray Observatory patch,

April 3, 3013

NGC 602a

The Small Magellanic Cloud (SMC) is one of the Milky Way's closest galactic neighbors. Even though it is a small, or so-called dwarf galaxy, the SMC is so bright that it is visible to the unaided eye from the Southern Hemisphere and near the equator. Many navigators, including Ferdinand Magellan who lends his name to the SMC, used it to help find their way across the oceans.

Modern astronomers are also interested in studying the SMC (and its cousin, the Large Magellanic Cloud), but for very different reasons. Because the SMC is so close and bright, it offers an opportunity to study phenomena that are difficult to examine in more distant galaxies.

New Chandra data of the SMC have provided one such discovery: the first detection of X-ray emission from young stars with masses similar to our Sun outside our Milky Way galaxy. The new Chandra observations of these low-mass stars were made of the region known as the "Wing" of the SMC. In this composite image of the Wing the Chandra data is shown in purple, optical data from the Hubble Space Telescope is shown in red, green and blue and infrared data from the Spitzer Space Telescope is shown in red.

Astronomers call all elements heavier than hydrogen and helium -- that is, with more than two protons in the atom's nucleus -- "metals." The Wing is a region known to have fewer metals compared to most areas within the Milky Way. There are also relatively lower amounts of gas, dust, and stars in the Wing compared to the Milky Way.

Taken together, these properties make the Wing an excellent location to study the life cycle of stars and the gas lying in between them. Not only are these conditions typical for dwarf irregular galaxies like the SMC, they also mimic ones that would have existed in the early Universe.

Most star formation near the tip of the Wing is occurring in a small region known as NGC 602, which contains a collection of at least three star clusters. One of them, NGC 602a, is similar in age, mass, and size to the famous Orion Nebula Cluster. Researchers have studied NGC 602a to see if young stars -- that is, those only a few million years old -- have different properties when they have low levels of metals, like the ones found in NGC 602a.

Using Chandra, astronomers discovered extended X-ray emission, from the two most densely populated regions in NGC 602a. The extended X-ray cloud likely comes from the population of young, low-mass stars in the cluster, which have previously been picked out by infrared and optical surveys, using Spitzer and Hubble respectively. This emission is not likely to be hot gas blown away by massive stars, because the low metal content of stars in NGC 602a implies that these stars should have weak winds. The failure to detect X-ray emission from the most massive star in NGC 602a supports this conclusion, because X-ray emission is an indicator of the strength of winds from massive stars. No individual low-mass stars are detected, but the overlapping emission from several thousand stars is bright enough to be observed.

Chandra spacectaft

The Chandra results imply that the young, metal-poor stars in NGC 602a produce X-rays in a manner similar to stars with much higher metal content found in the Orion cluster in our galaxy. The authors speculate that if the X-ray properties of young stars are similar in different environments, then other related properties -- including the formation and evolution of disks where planets form -- are also likely to be similar.

X-ray emission traces the magnetic activity of young stars and is related to how efficiently their magnetic dynamo operates. Magnetic dynamos generate magnetic fields in stars through a process involving the star's speed of rotation, and convection, the rising and falling of hot gas in the star's interior.

The combined X-ray, optical and infrared data also revealed, for the first time outside our Galaxy, objects representative of an even younger stage of evolution of a star. These so-called "young stellar objects" have ages of a few thousand years and are still embedded in the pillar of dust and gas from which stars form, as in the famous "Pillars of Creation" of the Eagle Nebula.

A paper describing these results was published online and in the March 1, 2013 issue of The Astrophysical Journal. The first author is Lidia Oskinova from the University of Potsdam in Germany and the co-authors are Wei Sun from Nanjing University, China; Chris Evans from the Royal Observatory Edinburgh, UK; Vincent Henault-Brunet from University of Edinburgh, UK; You-Hua Chu from the University of Illinois, Urbana, IL; John Gallagher III from the University of Wisconsin-Madison, Madison, WI; Martin Guerrero from the Instituto de Astrofísica de Andalucía, Spain; Robert Gruendl from the University of Illinois, Urbana, IL; Manuel Gudel from the University of Vienna, Austria; Sergey Silich from the Instituto Nacional de Astrofısica Optica y Electr´onica, Puebla, Mexico; Yang Chen from Nanjing University, China; Yael Naze from Universite de Liege, Liege, Belgium; Rainer Hainich from the University of Potsdam, Germany, and Jorge Reyes-Iturbide from the Universidade Estadual de Santa Cruz, Ilheus, Brazil.

Read more/access all images: http://chandra.harvard.edu/photo/2013/ngc602/

Chandra's Flickr photoset: http://www.flickr.com/photos/nasamarshall/sets/72157606205297786/

Images, Credits: X-ray: NASA/CXC/Univ.Potsdam/L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech /  Northrop Grumman / Text: NASA / J.D. Harrington / Marshall Space Flight Center / Janet Anderson / Chandra X-ray Center / Megan Watzke.

Greetings, Orbiter.ch

mardi 2 avril 2013

Black hole wakes up and has a light snack‏














ESA - Integral Mission patch / ESA - XMM-Newton Mission patch.

2 April 2013

Astronomers have watched as a black hole woke up from a decades-long slumber to feed on a low-mass object – either a brown dwarf or a giant planet – that strayed too close. A similar feeding event, albeit on a gas cloud, will soon happen at the black hole at the centre of our own Milky Way Galaxy.

Galaxy NGC 4845

The discovery in galaxy NGC 4845, 47 million light-years away, was made by ESA’s Integral space observatory, with follow-up observations from ESA’s XMM-Newton, NASA’s Swift and Japan’s MAXI X-ray monitor on the International Space Station.

JAXA’s MAXI X-ray monitor on the International Space Station

Astronomers were using Integral to study a different galaxy when they noticed a bright X-ray flare coming from another location in the same wide field-of-view. Using XMM-Newton, the origin was confirmed as NGC 4845, a galaxy never before detected at high energies.

Along with Swift and MAXI, the emission was traced from its maximum in January 2011, when the galaxy brightened by a factor of a thousand, and then as it subsided over the course of the year.

video
Black hole eats a super-Jupiter

“The observation was completely unexpected, from a galaxy that has been quiet for at least 20–30 years,” says Marek Nikolajuk of the University of Bialystok, Poland, lead author of the paper in Astronomy & Astrophysics.

By analysing the characteristics of the flare, the astronomers could determine that the emission came from a halo of material around the galaxy’s central black hole as it tore apart and fed on an object of 14–30 Jupiter masses. This size range corresponds to brown dwarfs, substellar objects that are not massive enough to fuse hydrogen in their core and ignite as stars.

NASA’s Swift

However, the authors note that it could have had an even lower mass, just a few times that of Jupiter, placing it in the range of gas-giant planets.

Recent studies have suggested that free-floating planetary-mass objects of this kind may occur in large numbers in galaxies, ejected from their parent solar systems by gravitational interactions.

The black hole in the centre of NGC 4845 is estimated to have a mass of around 300 000 times that of our own Sun. It also likes to play with its food: the way the emission brightened and decayed shows there was a delay of 2–3 months between the object being disrupted and the heating of the debris in the vicinity of the black hole.

“This is the first time where we have seen the disruption of a substellar object by a black hole,” adds co-author Roland Walter of the Observatory of Geneva, Switzerland.

ESA’s XMM-Newton

“We estimate that only its external layers were eaten by the black hole, amounting to about 10% of the object’s total mass, and that a denser core has been left orbiting the black hole.”

The flaring event in NGC 4845 can be seen as a warm-up act for a similar event expected in the supermassive black hole at the centre of our own Milky Way Galaxy, perhaps even this year.

While there are no brown dwarfs or planets on the menu this time, a compact cloud of gas amounting to just a few Earth masses has been seen spiralling towards the black hole and is predicted to meet its fate soon.

ESA’s Integral space observatory

Along with the object seen being eaten by the black hole in NGC 4845, these events will tell astronomers more about what happens to the demise of different types of objects as they encounter black holes of varying sizes.

“Estimates are that events like these may be detectable every few years in galaxies around us, and if we spot them, Integral, along with other high-energy space observatories, will be able to watch them play out just as it did with NGC 4845,” says Christoph Winkler, ESA’s Integral project scientist.

Notes for Editors:

“Tidal disruption of a super-Jupiter in NGC 4845,” by M. Nikolajuk and R. Walter is published in Astronomy & Astrophysics, April 2013.

More about... :

XMM-Newton overview: http://www.esa.int/Our_Activities/Space_Science/XMM-Newton_overview

XMM-Newton image gallery: http://xmm.esac.esa.int/external/xmm_science/gallery/public/index.php

XMM-Newton in-depth: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=23

Integral in depth: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=21

Related links:

NASA Swift: http://www.nasa.gov/mission_pages/swift/main/index.html

MAXI: http://www.nasa.gov/mission_pages/station/research/experiments/MAXI.html

Read the science paper: http://www.aanda.org/10.1051/0004-6361/201220664

Watch YouTube video about this research: https://www.youtube.com/watch?v=xiVECYf8uxk

Images, Video, Text, Credits: ESA / NASA / Orbiter.ch Aerospace.

Best regards, Orbiter.ch