vendredi 1 juillet 2011

NASA'S Spitzer Finds Distant Galaxies Grazed On Gas








NASA - SPITZER Space Telescope logo.

July 1, 2011

Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA's Spitzer Space Telescope.

Astronomers have discovered that galaxies in the distant universe continuously ingested their star-making fuel over long periods of time. This goes against previous theories that galaxies devoured their fuel in quick bursts after run-ins with other galaxies.

"Our study shows the merging of massive galaxies was not the dominant method of galaxy growth in the distant universe," said Ranga-Ram Chary of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena, Calif. "We're finding this type of galactic cannibalism was rare. Instead, we are seeing evidence for a mechanism of galaxy growth in which a typical galaxy fed itself through a steady stream of gas, making stars at a much faster rate than previously thought."

Chary is the principal investigator of the research appearing in the Aug. 1 issue of the Astrophysical Journal. According to his findings, these grazing galaxies fed steadily over periods of hundreds of millions of years and created an unusual amount of plump stars, up to 100 times the mass of our sun.

"This is the first time that we have identified galaxies that supersize themselves by grazing," said Hyunjin Shim, also of the Spitzer Science Center and lead author of the paper. "They have many more massive stars than our Milky Way galaxy."


Image above: This split view shows how a normal spiral galaxy around our local universe (left) might have looked back in the distant universe, when astronomers think galaxies would have been filled with larger populations of hot, bright stars (right). Image credit: NASA / JPL-Caltech / STScI.

Galaxies like our Milky Way are giant collections of stars, gas and dust. They grow in size by feeding off gas and converting it to new stars. A long-standing question in astronomy is: Where did distant galaxies that formed billions of years ago acquire this stellar fuel?

The most favored theory was that galaxies grew by merging with other galaxies, feeding off gas stirred up in the collisions.

Chary and his team addressed this question by using Spitzer to survey more than 70 remote galaxies that existed 1 to 2 billion years after the big bang (our universe is approximately 13.7 billion years old). To the surprise of the astronomers, these galaxies were blazing with what is called H alpha, radiation from hydrogen gas that has been hit with ultraviolet light from stars. High levels of H alpha indicate stars are forming vigorously. Seventy percent of the surveyed galaxies show strong signs of H alpha. By contrast, only 0.1 percent of galaxies in our local universe possess the signature.

SPITZER Space Telescope

Previous studies using ultraviolet-light telescopes found about six times less star formation than Spitzer, which sees infrared light.

Scientists think this may be due to large amounts of obscuring dust, through which infrared light can sneak. Spitzer opened a new window onto the galaxies by taking very long-exposure infrared images of a patch of sky called the GOODS fields, for Great Observatories Origins Deep Survey.

NASA's Jet Propulsion Laboratory in Pasadena manages the Spitzer Space Telescope mission for the agency's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center. Caltech manages JPL for NASA. For more information about Spitzer, visit: http://www.nasa.gov/spitzer and http://spitzer.caltech.edu/

Images, Text, Credits: NASA / JPL-Caltech / STScI.

Best regards, Orbiter.ch

jeudi 30 juin 2011

Integral challenges physics beyond Einstein












ESA - Integral Mission patch.

30 June 2011

ESA’s Integral gamma-ray observatory has provided results that will dramatically affect the search for physics beyond Einstein. It has shown that any underlying quantum ‘graininess’ of space must be at much smaller scales than previously predicted.

Einstein’s General Theory of Relativity describes the properties of gravity and assumes that space is a smooth, continuous fabric. Yet quantum theory suggests that space should be grainy at the smallest scales, like sand on a beach.

One of the great concerns of modern physics is to marry these two concepts into a single theory of quantum gravity.

Gamma-ray burst

Now, Integral has placed stringent new limits on the size of these quantum ‘grains’ in space, showing them to be much smaller than some quantum gravity ideas would suggest.

According to calculations, the tiny grains would affect the way that gamma rays travel through space. The grains should ‘twist’ the light rays, changing the direction in which they oscillate, a property called polarisation.

High-energy gamma rays should be twisted more than the lower energy ones, and the difference in the polarisation can be used to estimate the size of the grains.

Philippe Laurent of CEA Saclay and his collaborators used data from Integral’s IBIS instrument to search for the difference in polarisation between high- and low-energy gamma rays emitted during one of the most powerful gamma-ray bursts (GRBs) ever seen.

Integral: gamma-ray observatory

GRBs come from some of the most energetic explosions known in the Universe. Most are thought to occur when very massive stars collapse into neutron stars or black holes during a supernova, leading to a huge pulse of gamma rays lasting just seconds or minutes, but briefly outshining entire galaxies.

GRB 041219A took place on 19 December 2004 and was immediately recognised as being in the top 1% of GRBs for brightness. It was so bright that Integral was able to measure the polarisation of its gamma rays accurately.

Dr Laurent and colleagues searched for differences in the polarisation at different energies, but found none to the accuracy limits of the data.

Some theories suggest that the quantum nature of space should manifest itself at the ‘Planck scale’: the minuscule 10-35 of a metre, where a millimetre is 10-3 m.

However, Integral’s observations are about 10 000 times more accurate than any previous and show that any quantum graininess must be at a level of 10-48 m or smaller.

video
ESA'S Integral - The Gamma Ray Burst

“This is a very important result in fundamental physics and will rule out some string theories and quantum loop gravity theories,” says Dr Laurent.

Integral made a similar observation in 2006, when it detected polarised emission from the Crab Nebula, the remnant of a supernova explosion just 6500 light years from Earth in our own galaxy.

This new observation is much more stringent, however, because GRB 041219A was at a distance estimated to be at least 300 million light years.

In principle, the tiny twisting effect due to the quantum grains should have accumulated over the very large distance into a detectable signal. Because nothing was seen, the grains must be even smaller than previously suspected.

“Fundamental physics is a less obvious application for the gamma-ray observatory, Integral,” notes Christoph Winkler, ESA’s Integral Project Scientist. “Nevertheless, it has allowed us to take a big step forward in investigating the nature of space itself.”

Now it’s over to the theoreticians, who must re-examine their theories in the light of this new result.

Related Link:

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

Related ESA publications:
Integral results leaflet (pdf): http://esamultimedia.esa.int/docs/Integral_2007web.pdf

Integral mission brochure (pdf): http://esamultimedia.esa.int/docs/science/media/integral_brochure.pdf

Images, Video, Text, Credits: ESA / Medialab / SPI Team / ECF.

Greetings, Orbiter.ch

'Dirty hack' restores Cluster mission from near loss












ESA - Cluster II Mission patch.

30 June 2011

Using ingenuity and an unorthodox 'dirty hack', ESA has recovered the four-satellite Cluster mission from near loss. The drama began in March, when a crucial science package stopped responding to commands – one of a mission controller's worst fears.

Since a pair of spectacular dual launches in 2000, the four Cluster satellites have been orbiting Earth in tightly controlled formation. Each of the 550 kg satellites carries an identical payload to investigate Earth's space environment and its interaction with the solar wind – the stream of charged particles pouring out from the Sun.

Cluster satellites study the effects of solar wind

Among each satellite's 11 instruments, five comprise the Wave Experiment Consortium (WEC), which makes important measurements of electrical and magnetic fields. All four sensors must work together to make carefully orchestrated observations – the loss of any one could seriously affect the unique 'four-satellite science' delivered by the mission.

On 5 March, the WEC package on Cluster's number 3 satellite, Samba, failed to switch on. Ground controllers at ESA's European Space Operations Centre, in Darmstadt, Germany, immediately triggered a series of standard recovery procedures, none of which succeeded.

Even worse, no status information could be coaxed out of the instruments.

Dangerous scenario for orbiting satellite

"With no status data and no response from the instrument, we suspected either that the device's five power switches were locked closed or a failure caused by an electrical short circuit, one of the most dangerous faults on any satellite," said ESA's Jürgen Volpp, Cluster operations manager.

Engineers working in Cluster control room

Over the next several weeks, working closely with the satellites' builder, the WEC scientists and manufacturer, and other ESA teams, the Cluster control team diagnosed the problem, eventually making use of some onboard software that had been dormant since just after launch over 10 years ago.

The result ruled out a short circuit and pointed an accusing finger at the five power switches being locked in the 'closed' position.

Tests in 1995 had simulated what might happen if three of the five switches locked close, but no one ever considered how to recover from all five being locked – such a situation had not been deemed possible.

Five instruments in the WEC package on each Cluster satellite

Armed with this information and a great deal of ingenuity, the team painstakingly designed a recovery procedure and tested it on one of Samba's functioning sister satellites.

Solution based on a 'dirty hack'

"The solution was based on a 'dirty hack' – jargon referring to any non-standard procedure – but we really had no other option," said Jürgen.

Finally, on 1 June, in a very tense mission control room, a series of commands was radioed up. To immense relief, these flipped the power switches to 'on and the recalcitrant WEC came back to life.

“When unexpected trouble occurs, you really want to have an experienced and talented team on hand to solve the problem.”

Cluster has since returned to normal operation and measures are being taken to prevent this failure from happening again.

video

Video above: The four Cluster satellites were lauched in 2000 and been flying in formation around the Earth ever since. Their obits have changed over time as seen in this movie. The blue lines show the orbits of the Cluster satellites. Credit: UCL-MSSL / Chris Arridge.

"When everything goes as planned, flying a mission can be routine," said ESA's Manfred Warhaut, Head of Mission Operations. "But when unexpected trouble occurs, and there's nothing in the manuals, you really want to have an experienced and talented team on hand to solve the problem."

Related Links:

Exploring the Sun-Earth connection: http://www.esa.int/SPECIALS/Cluster/

Space Operations & Situational Awareness: http://www.esa.int/SPECIALS/Operations/index.html

Cluster overview: http://www.esa.int/esaSC/120383_index_0_m.html

Cluster II operations: http://www.esa.int/SPECIALS/Operations/SEMYSMQJNVE_0.html

Images, Video (mentioned), Text, Credits: ESA / J. Mai.

Greetings, Orbiter.ch

mercredi 29 juin 2011

Expert’s reentry flap endures hot baptism










ESA’s Expert – the European Experimental Reentry Testbed logo.

29 June 2011

A spacecraft control flap designed for the super-heated hypersonic fall through Earth’s atmosphere has come through testing in the world’s largest plasma wind tunnel to be ready for its first flight next year.

This flap and its advanced sensors are destined to fly on ESA’s Expert – the European Experimental Reentry Testbed – a blunt-nosed capsule being shot up to the edge of space next spring on a Russian Volna rocket to gather data on atmospheric reentry at 5 km/s.

video
Side view of testing

Expert carries experimental side flaps to help show that they can steer larger ESA reentry vehicles such as the IXV Intermediate eXperimental Vehicle in 2013.

“This flap is fitted with a variety of instruments, including cameras, pressure monitors and an ultraviolet spectrometer to gather data during the hottest two minutes of Expert’s 15-minute flight,” explained Jan Thoemel, Expert Project Scientist.

“We needed to prove this instrumentation will indeed function as planned, and check our mathematical modelling was accurate. “This meant recreating the extreme environment of atmospheric reentry down on the ground.”

Expert during reentry

Italy’s Scirocco plasma wind tunnel in Capua, near Naples, is one of the few sites worldwide where such testing is possible.

Named for the hot Mediterranean wind and operated by the CIRA aerospace research centre, Scirocco runs vast amounts of power through an arc heater, heating up air into a blowtorch-like plasma that jets through its 2 m-diameter tunnel.

Its arc heater was taken up to 10 000ºC with 38 MW of electricity, creating a plasma flow seven times the speed of sound and bringing the temperature of the flap up to 1200ºC.

Identical to the flight version, the test flap is made from heat-resistant ceramics. Its instruments include a miniature infrared camera provided by RUAG Space Switzerland and pressure and high-temperature sensors developed by the German Aerospace Center DLR and CIRA.

video
Infrared view of testing

“After years of preparation we performed four test runs on 13 April, comfortably exceeding the heat loads we anticipate the flap will encounter during its spaceflight aboard Expert,” explained Jan.

“Each test reached 1.75 times the flight heat load, amounting to seven times the flight heat load overall.

“Despite this, our instrumentation performed excellently, validating it for actual flight.

“In the months that followed we’ve been comparing the test results to our software models to highlight any discrepancies, as a way of improving the computational fluid dynamics design tools used for Expert.”

Scirocco plasma wind tunnel

Running on the equivalent energy consumption of a small town, Scirocco’s construction was co-funded by ESA and the Italian Ministry for University and Research, with ‘wind-on’ occurring in March 2001.

The facility serves a wide variety of customers worldwide. Its operator CIRA is playing a wider role in preparing for Expert’s flight.

Expert vehicle

“This test campaign represented a particular challenge because it was approaching the limits of the facility’s capabilities,” explained Giulano Marino of CIRA.

“Many new components had to be installed first, requiring extensive testing, but the results speak for themselves.”

video
Expert will be launched by submarine

The Scirocco testing was funded through ESA’s Basic Technology Research Programme, which supports new technology development.

The Expert capsule, studded with around 150 different sensors, is due to fly in spring 2012, sea-launched from a Russian submarine for recovery on Russia’s Kamchatka peninsula.

Related links:

Expert: http://www.esa.int/SPECIALS/EXPERT/index.html

Scirocco Plasma Wind Tunnel: http://www.cira.it/html/inglese/laboratori/scheda.asp?titolo=PWT

CIRA: http://www.cira.it/en

RUAG Space Switzerland: http://www.ruag.com/space/RUAG_Space_Switzerland

DLR: http://www.dlr.de/en/desktopdefault.aspx

Images, Videos, Text, Credits: ESA / CIRA.

Best regards, Orbiter.ch

Most Distant Quasar Found












ESO - European Southern Observatory logo.

29 June 2011

 An artist’s rendering of the most distant quasar

A team of European astronomers has used ESO’s Very Large Telescope and a host of other telescopes to discover and study the most distant quasar found to date. This brilliant beacon, powered by a black hole with a mass two billion times that of the Sun, is by far the brightest object yet discovered in the early Universe. The results will appear in the 30 June 2011 issue of the journal Nature.

“This quasar is a vital probe of the early Universe. It is a very rare object that will help us to understand how supermassive black holes grew a few hundred million years after the Big Bang,” says Stephen Warren, the study’s team leader.

The most distant quasar

Quasars are very bright, distant galaxies that are believed to be powered by supermassive black holes at their centres. Their brilliance makes them powerful beacons that may help to probe the era when the first stars and galaxies were forming. The newly discovered quasar is so far away that its light probes the last part of the reionisation era [1].

Wide-field view of the sky around the most remote quasar

The quasar that has just been found, named ULAS J1120+0641 [2], is seen as it was only 770 million years after the Big Bang (redshift 7.1, [3]). It took 12.9 billion years for its light to reach us.

Although more distant objects have been confirmed (such as a gamma-ray burst at redshift 8.2, eso0917, and a galaxy at redshift 8.6, eso1041), the newly discovered quasar is hundreds of times brighter than these. Amongst objects bright enough to be studied in detail, this is the most distant by a large margin.

video
Zooming in on the most distant quasar found so far

The next most-distant quasar is seen as it was 870 million years after the Big Bang (redshift 6.4). Similar objects further away cannot be found in visible-light surveys because their light, stretched by the expansion of the Universe, falls mostly in the infrared part of the spectrum by the time it gets to Earth. The European UKIRT Infrared Deep Sky Survey (UKIDSS) which uses the UK's dedicated infrared telescope [4] in Hawaii was designed to solve this problem. The team of astronomers hunted through millions of objects in the UKIDSS database to find those that could be the long-sought distant quasars, and eventually struck gold.

“It took us five years to find this object,” explains Bram Venemans, one of the authors of the study. “We were looking for a quasar with redshift higher than 6.5. Finding one that is this far away, at a redshift higher than 7, was an exciting surprise. By peering deep into the reionisation era, this quasar provides a unique opportunity to explore a 100-million-year window in the history of the cosmos that was previously out of reach.”

The distance to the quasar was determined from observations made with the FORS2 instrument on ESO’s Very Large Telescope (VLT) and instruments on the Gemini North Telescope [5]. Because the object is comparatively bright it is possible to take a spectrum of it (which involves splitting the light from the object into its component colours). This technique allowed the astronomers to find out quite a lot about the quasar.

video
A 3D animation of the most distant quasar

These observations showed that the mass of the black hole at the centre of ULAS J1120+0641 is about two billion times that of the Sun. This very high mass is hard to explain so early on after the Big Bang. Current theories for the growth of supermassive black holes predict a slow build-up in mass as the compact object pulls in matter from its surroundings.

“We think there are only about 100 bright quasars with redshift higher than 7 over the whole sky,” concludes Daniel Mortlock, the leading author of the paper. “Finding this object required a painstaking search, but it was worth the effort to be able to unravel some of the mysteries of the early Universe.”

Video ESOcast 32: Most Distant Quasar Found: http://www.eso.org/public/videos/eso1122a/

Notes:

[1] About 300 000 years after the Big Bang, which occurred 13.7 billion years ago, the Universe had cooled down enough to allow electrons and protons to combine into neutral hydrogen (a gas without electric charge). This cool dark gas permeated the Universe until the first stars started forming about 100 to 150 million years later. Their intense ultraviolet radiation slowly split the hydrogen atoms back into protons and electrons, a process called reionisation, making the Universe more transparent to ultraviolet light.  It is believe that this era occurred between about 150 million to 800 million years after the Big Bang.

[2] The object was found using data from the UKIDSS Large Area Survey, or ULAS. The numbers and prefix ‘J’ refer to the quasar’s position in the sky.

[3] Because light travels at a finite speed, astronomers look back in time as they look further away into the Universe. It took 12.9 billion years for the light from ULAS J1120+0641 to travel to telescopes on Earth so the quasar is seen as it was when the Universe was only 770 million years old. In those 12.9 billion years, the Universe expanded and the light from the object stretched as a result. The cosmological redshift, or simply redshift, is a measure of the total stretching the Universe underwent between the moment when the light was emitted and the time when it was received.

[4] UKIRT is the United Kingdom Infrared Telescope. It is owned by the UK’s Science and Technology Facilities Council and operated by the staff of the Joint Astronomy Centre in Hilo, Hawaii.

[5] FORS2 is the VLT’s FOcal Reducer and low dispersion Spectrograph. Other instruments used to split up the light of the object were the Gemini Multi-Object Spectrograph (GMOS) and the Gemini Near-Infrared Spectrograph (GNIRS). The Liverpool Telescope, the Isaac Newton Telescope and the UK Infrared Telescope (UKIRT) were also used to confirm survey measurements.

More information:

This research was presented in a paper to appear in the journal Nature on 30 June 2011.

The team is composed of Daniel J. Mortlock (Imperial College London [Imperial], UK), Stephen J. Warren (Imperial), Bram P. Venemans (ESO, Garching, Germany), Mitesh Patel (Imperial), Paul C. Hewett (Institute of Astronomy [IoA], Cambridge, UK), Richard G. McMahon (IoA), Chris Simpson (Liverpool John Moores University, UK), Tom Theuns (Institute for Computational Cosmology, Durham, UK and University of Antwerp, Belgium), Eduardo A. Gonzáles-Solares (IoA), Andy Adamson (Joint Astronomy Centre, Hilo, USA), Simon Dye (Centre for Astronomy and Particle Theory, Nottingham, UK), Nigel C. Hambly (Institute for Astronomy, Edinburgh, UK), Paul Hirst (Gemini Observatory, Hilo, USA), Mike J. Irwin (IoA), Ernst Kuiper (Leiden Observatory, The Netherlands), Andy Lawrence (Institute for Astronomy, Edinburgh, UK), Huub J. A. Röttgering (Leiden Observatory, The Netherlands).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. 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 a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

    Research paper: Nature paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1122/eso1122.pdf

    Photos of the VLT: http://www.eso.org/public/images/archive/category/paranal/

Images, Text, Credits: ESO / M. Kornmesser / UKIDSS / SDSS / Digitized Sky Survey 2. Acknowledgment: Davide De Martin / videos:  ESO/A. Fujii/Digitized Sky Survey 2. Music: John Dyson (from the album Moonwind) / M. Kornmesser.

Greetings, Orbiter.ch

Driving a robot from Space Station





ESA / ESTEC logo.

29 June 2011

The Justin mobile robotic system, developed at the German Aerospace Center, DLR

Meet Justin, an android who will soon be controlled remotely by the astronauts in ESA’s Columbus laboratory on the International Space Station. With this and other intriguing experiments like the Eurobot rover, ESA is paving the way for exploring the Moon and planets with tele-operated robots.

In two to three years, the experimental robot on Earth will faithfully mimic the movements of an astronaut on the Space Station.

By wearing an exoskeleton – a combination of arm and glove with electronic aids to reproduce the sensations a human hand would feel – a distant operator can work as though he were there.

Distant robots can be controlled...

To help turn robotics and telepresence into a standard tool for space missions, ESA is linking the Space Station and Earth for remotely controlling terrestrial robotic experiments from the orbital outpost.

This Meteron (Multi-purpose End-To-End Robotic Operations Network) initiative is a testbed for future missions to the Moon, Mars and other celestial bodies.

“The Space Station is the perfect orbital platform to simulate very realistic scenarios for human exploration,” says Kim Nergaard, ESA’s Meteron coordinator.

...from the Space Station

“First we have to set up a robust communication architecture, establish an operations system and define a protocol to allow astronauts, robots and our ESA control centre to work efficiently together. This is not as easy a task as it seems.”

Many ideas around

ESA called earlier this year for new ideas for the Space Station to be used as a testbed for exploration missions. Many proposals called for operating ground-based robots from a workstation on the Station.

“The multitude of submissions shows the strength of the idea,” comments Philippe Schoonejans, ESA’s Head of Robotics in the Human Spaceflight and Operations directorate.

Working on Meteron

“The multitude of submissions shows the strength of the idea,” comments Philippe Schoonejans, ESA’s Head of Robotics in the Human Spaceflight and Operations directorate.

"This allows ESA to take into account all suggested experiments and give opportunities to the countries, companies and institutes who have shown their interest by submitting the idea."

Communications test robot

"Meteron is suitable for early realisation because it can exploit the existing infrastructure and technologies without requiring huge investments," explains François Bosquillon de Frescheville, responsible for ESA future human exploration mission operations concepts studies, whose idea triggered the programme.

First a rover, then an android

In the first Meteron tests, the Station astronauts will operate ESA’s Eurobot prototype from a computer equipped with special screens and a joystick.

This prototype is a four-wheel rover with two arms, an advanced navigation system, cameras and sensors that has been under testing since 2008 at the Agency’s ESTEC space research and technology centre in the Netherlands.

Eurobot prototype

In the first Meteron tests, the Station astronauts will operate ESA’s Eurobot prototype from a computer equipped with special screens and a joystick.

This prototype is a four-wheel rover with two arms, an advanced navigation system, cameras and sensors that has been under testing since 2008 at the Agency’s ESTEC space research and technology centre in the Netherlands.

Christer Fuglesang works with Exoskeleton

In the next phase, the engineers will allow astronauts to control a robot with the sense of force and ‘touch’. It can be connected to robots like Justin, developed by the DLR German Aerospace Center.

“With these senses, the astronauts will have a real feeling of the forces that the arms of the robots are experiencing in their environment,” explains André Schiele, in charge of ESA’s Telerobotics & Haptics Laboratory.

Justin with wheels

“For example, when they push against a rock or do more complex tasks such as setting up hardware.”

Whatever route the future exploration of Moon and Mars might follow, it will require sophisticated communications and advanced tools. Boosted by new human–machine interface technology, astronauts in orbit will almost certainly link up with robots to explore planetary surfaces.

Related links:

Justin at DLR: http://www.dlr.de/rm/en/desktopdefault.aspx/tabid-5471/

ESA Human Spaceflight: http://www.esa.int/spaceflight

Automation & Robotics: http://www.esa.int/TEC/Robotics/

Images, Text, Credits: ESA / J. v. Haarlem / DLR.

Best regards, Orbiter.ch

mardi 28 juin 2011

Neutron star bites off more than it can chew












ESA - XMM Newton Mission patch.

28 June 2011

ESA’s XMM-Newton space observatory has watched a faint star flare up at X-ray wavelengths to almost 10 000 times its normal brightness. Astronomers believe the outburst was caused by the star trying to eat a giant clump of matter.

The flare took place on a neutron star, the collapsed heart of a once much larger star. Now about 10 km in diameter, the neutron star is so dense that it generates a strong gravitational field.

Artist's impression of a neutron star partially devouring a massive clump of matter

The clump of matter was much larger than the neutron star and came from its enormous blue supergiant companion star.

“This was a huge bullet of gas that the star shot out, and it hit the neutron star allowing us to see it,” says Enrico Bozzo, ISDC Data Centre for Astrophysics, University of Geneva, Switzerland, and team leader of this research.

The flare lasted four hours and the X-rays came from the gas in the clump as it was heated to millions of degrees while being pulled into the neutron star’s intense gravity field. In fact, the clump was so big that not much of it hit the neutron star. Yet, if the neutron star had not been in its path, this clump would probably have disappeared into space without trace.

XMM-Newton caught the flare during a scheduled 12.5-hour observation of the system, which is known only by its catalogue number IGR J18410-0535, but the astronomers were unaware of their catch immediately.

The telescope works through a sequence of observations carefully planned to make the best use of the space observatory’s time, then sends the data to Earth.

XMM-Newton

It was about ten days after the observation that Dr Bozzo and his colleagues received the data and quickly realised they had something special. Not only were they pointing in the right direction to see the flare, but the observation had lasted long enough for them to see it from beginning to end.

“I don’t know if there is any way to measure luck, but we were extremely lucky,” says Dr Bozzo. He estimates that an X-ray flare of this magnitude can be expected a few times a year at the most for this particular star system.

The duration of the flare allowed them to estimate the size of the clump. It was much larger than the star, probably 16 million km across, or about 100 billion times the volume of the Moon. Yet, according to the estimate made from the flare’s brightness, the clump contained only one-thousandth of our natural satellite’s mass.

These figures will help astronomers understand the behaviour of the blue supergiant and the way it emits matter into space. All stars expel atoms into space, creating a stellar wind. The X-ray flare shows that this particular blue supergiant does it in a clumpy fashion, and the estimated size and mass of the cloud allow constraints to be placed on the process.

“This remarkable result highlights XMM-Newton's unique capabilities,” comments Norbert Schartel, XMM-Newton Project Scientist. “Its observations indicate that these flares can be linked to the neutron star attempting to ingest a giant clump of matter.”

Related links:

XMM-Newton operations: http://www.esa.int/SPECIALS/Operations/SEMI2HZTIVE_0.html

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

Images, Animation, Text, Credits: ESA / AOES Medialab / C. Carreau.

Greetings, Orbiter.ch