Monday, September 30, 2013

NASA's Cassini Spacecraft Finds Ingredient of Household Plastic in Space

NASA's Cassini spacecraft looks toward the night side of Saturn's largest moon and sees sunlight scattering through the periphery of Titan's atmosphere and forming a ring of color. Image credit: NASA/JPL-Caltech/Space Science Institute.  › Full image and caption

PASADENA, Calif. - NASA's Cassini spacecraft has detected propylene, a chemical used to make food-storage containers, car bumpers and other consumer products, on Saturn's moon Titan.

This is the first definitive detection of the plastic ingredient on any moon or planet, other than Earth.

A small amount of propylene was identified in Titan's lower atmosphere by Cassini's composite infrared spectrometer (CIRS). This instrument measures the infrared light, or heat radiation, emitted from Saturn and its moons in much the same way our hands feel the warmth of a fire.

Propylene is the first molecule to be discovered on Titan using CIRS. By isolating the same signal at various altitudes within the lower atmosphere, researchers identified the chemical with a high degree of confidence. Details are presented in a paper in the Sept. 30 edition of the Astrophysical Journal Letters.

"This chemical is all around us in everyday life, strung together in long chains to form a plastic called polypropylene," said Conor Nixon, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., and lead author of the paper. "That plastic container at the grocery store with the recycling code 5 on the bottom -- that's polypropylene."

CIRS can identify a particular gas glowing in the lower layers of the atmosphere from its unique thermal fingerprint. The challenge is to isolate this one signature from the signals of all other gases around it.

The detection of the chemical fills in a mysterious gap in Titan observations that dates back to NASA's Voyager 1 spacecraft and the first-ever close flyby of this moon in 1980.

Voyager identified many of the gases in Titan's hazy brownish atmosphere as hydrocarbons, the chemicals that primarily make up petroleum and other fossil fuels on Earth.

On Titan, hydrocarbons form after sunlight breaks apart methane, the second-most plentiful gas in that atmosphere. The newly freed fragments can link up to form chains with two, three or more carbons. The family of chemicals with two carbons includes the flammable gas ethane. Propane, a common fuel for portable stoves, belongs to the three-carbon family.

Previously, Voyager found propane, the heaviest member of the three-carbon family, and propyne, one of the lightest members. But the middle chemicals, one of which is propylene, were missing.

As researchers continued to discover more and more chemicals in Titan's atmosphere using ground- and space-based instruments, propylene was one that remained elusive. It was finally found as a result of more detailed analysis of the CIRS data.

"This measurement was very difficult to make because propylene's weak signature is crowded by related chemicals with much stronger signals," said Michael Flasar, Goddard scientist and principal investigator for CIRS. "This success boosts our confidence that we will find still more chemicals long hidden in Titan's atmosphere."

Cassini's mass spectrometer, a device that looks at the composition of Titan's atmosphere, had hinted earlier that propylene might be present in the upper atmosphere. However, a positive identification had not been made.

"I am always excited when scientists discover a molecule that has never been observed before in an atmosphere," said Scott Edgington, Cassini's deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This new piece of the puzzle will provide an additional test of how well we understand the chemical zoo that makes up Titan's atmosphere."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The CIRS team is based at Goddard.

For more information about the Cassini mission, visit: and .

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown 202-358-1726
NASA Headquarters, Washington

Nancy Neal-Jones/Elizabeth Zubritsky
Goddard Space Flight Center, Greenbelt, Md.
301-286-0039/301-614-5438 /

Observations reveal critical interplay of interstellar dust, hydrogen

Intense molecular hydrogen formation shown in near infrared image of the reflection nebula IC 63 in the constellation Cassiopeia. The white bars represent polarization seen toward stars in the background of the nebula. The largest polarization shows the most intense emission, demonstrating that hydrogen formation influences alignment of the dust grain with a magnetic field.  Image: B-G Andersson, USRA

For astrophysicists, the interplay of hydrogen — the most common molecule in the universe — and the vast clouds of dust that fill the voids of interstellar space has been an intractable puzzle of stellar evolution.

The dust, astronomers believe, is a key phase in the life cycle of stars, which are formed in dusty nurseries throughout the cosmos. But how the dust interacts with hydrogen and is oriented by the magnetic fields in deep space has proved a six-decade-long theoretical challenge.

Now, an international team of astronomers reports key observations that confirm a theory devised by University of Wisconsin-Madison astrophysicist Alexandre Lazarian and Wisconsin graduate student Thiem Hoang. The theory describes how dust grains in interstellar space, like soldiers in lock-drill formation, spin and organize themselves in the presence of magnetic fields to precisely align in key astrophysical environments.

 Alexandre Lazarian

The effort promises to untangle a theoretical logjam about key elements of the interstellar medium and underpin novel observational tactics to probe magnetic fields in space.

The new observations, conducted by a team led by B-G Andersson of the Universities Space Research Association (USRA), and their theoretical implications are to be reported in the Oct. 1, 2013 edition of the Astrophysical Journal. The observations were conducted using a variety of techniques — optical and near infrared polarimetry, high-accuracy optical spectroscopy and photometry, and sensitive imaging in the near infrared — at observatories in Spain, Hawaii, Arizona and New Mexico.

"We need to understand grain alignment if we want to make use of polarimetry as a means of investigating interstellar magnetic fields," says Lazarian, who was encouraged to attack the problem by the renowned astrophysicist Lyman Spitzer. "Spitzer himself worked on the problem extensively."

Scientists have long known that starlight becomes polarized as it shines through clouds of neatly aligned, rapidly spinning grains of interstellar dust. And the parsing of polarized light is a key observational technique. But how the grains of dust interact with hydrogen, become aligned so that starlight shining through becomes polarized, and are set spinning has been a mystery.

"While interstellar polarization has been known since 1949, the physical mechanisms behind grain alignment have been poorly understood until recently," explains Andersson. "These observations form part of a coordinated effort to — after more than 60 years — place interstellar grain alignment on a solid theoretical and observational footing."

The observations made by Andersson and his colleagues support an analytical theory posed by Lazarian and Hoang known as Radiative Alignment Torque, which describes how irregular grains can be aligned by their interaction with magnetic fields and stellar radiation. Under the theory, grains are spun, propeller-like, by photons. Their alignment is modified by magnetic fields, which orients them with respect to the field, telling an observer its direction. Impurities and defects on the dust grains produce catalytic sites for the formation of hydrogen molecules, which are subsequently ejected, creating miniature "rocket engines," also called "Purcell thrusters" after Nobel laureate Edwin Purcell, who studied grain alignment.

The theory devised by Lazarian and Hoang predicts how the molecular hydrogen thrust changes grain alignment, and was put to the test by Andersson's team of observers.

Confirming the theory, Lazarian notes, not only helps explain how interstellar dust grains align, but promises a new ability for astronomers to use polarized visible and near infrared light to reliably probe the strength and structure of magnetic fields in interstellar space, a notoriously difficult phenomenon to measure quantitatively.
Interstellar magnetic fields are ubiquitous in spiral galaxies like our Milky Way and are believed to be essential regulators of star formation and the evolution of proto-planetary disks. They also control the regulation and propagation of cosmic rays.

The murky piece of the astrophysical puzzle, says Lazarian, was how the irregular grains of interstellar dust were set in spinning motion. The observations conducted by Andersson demonstrate that intense molecular hydrogen formation on the surface of the interstellar dust grains is an important contributor to the dust grains spinning.

Hydrogen does not exist in the element's gas phase in space since the two atoms of the molecule cannot rid themselves of the formation reaction energy without a third body. The two hydrogen atoms therefore use the surfaces of dust grains as a substrate, and the force of the reaction energy is enough to set the dust grains in motion.

The new work, which was supported by the National Science Foundation, is especially timely, Lazarian says, as two new observatories — the ground-based ALMA, the Atacama Large Millimeter Array, and the space-based Planck Telescope — are poised to build on the new results.

Saturday, September 28, 2013

SUNRISE Offers New Insight on Sun's Atmosphere

The right image shows an image captured by the Sunrise balloon-borne telescope of a region of the chromosphere in close proximity to two sunspots. It serves as a close up of the left images, which were captured by NASA's Solar Dynamics Observatory. The images were taken on July 16, 2013.
Image Credit: NASA/SDO/MPS
Three months after the flight of the solar observatory Sunrise – carried aloft by a NASA scientific balloon in early June 2013 -- scientists from the Max Planck Institute for Solar System Research in Germany have presented unique insights into a layer on the sun called the chromosphere. Sunrise provided the highest-resolution images to date in ultraviolet light of this thin corrugated layer, which lies between the sun's visible surface and the sun's outer atmosphere, the corona.

With its one-meter mirror, Sunrise is the largest solar telescope to fly above the atmosphere. The telescope weighed in at almost 7,000 pounds and flew some 20 miles up in the air. Sunrise was launched from Kiruna in the north of Sweden and, after five days drifting over the Atlantic, it landed on the remote Boothia Peninsula in northern Canada, gathering information about the chromosphere throughout its journey.

The temperature in the chromosphere rises from 6,000 K/10,340 F/5,272 C at the surface of the sun to about 20,000 K/ 35,540 F/19,730 C. It's an area that's constantly in motion, with different temperatures of hot material mixed over a range of heights, stretching from the sun's surface to many thousands of miles up. The temperatures continue to rise further into the corona and no one knows exactly what powers any of that heating.

"In order to solve this riddle it is necessary to take as close a look as possible at the chromosphere – in all accessible wavelengths," said Sami Solanki, the principal investigator for Sunrise from the Max Planck Institute. Sunrise used an instrument that was able to filter particular ultraviolet wavelengths of light that are only emitted from the chromosphere.
Two images of the chromosphere as captured by the Sunrise solar observatory that flew on a NASA balloon in July 2013. On the left a typical pattern can be seen: dark areas surrounded by bright rims. On the right, the images show bright, stretched structures on the edges of the darker sunspots.Image Credit: MPS
Sunrise's extremely high-resolution images in this wavelength painted a complex picture of the chromosphere. Where the sun is quiet and inactive, dark regions with a diameter of around 600 miles can be discerned surrounded by bright rims. This pattern is created by the enormous flows of solar material rising up from within the sun, cooling off and sinking down again. Especially eye-catching are bright points that flash up occasionally—much richer in contrast in these ultraviolet images than have been seen before. Scientists believe these bright points to be signs of what's called magnetic flux tubes, which are the building blocks of the sun's magnetic field. The magnetic field is of particular interest to scientists since it is ultimately responsible for all of the dynamic activity we see on our closest star.

"These first analyses are extremely promising," said Solanki. "They show that the ultraviolet radiation from the chromosphere is highly suitable for visualizing detailed structures and processes."

The researchers now hope that the next months will provide more new insights – and are looking forward to a close collaboration with colleagues from NASA’s Interface Region Imaging Spectrograph, or IRIS mission. IRIS launched on June 27, only weeks after the end of the Sunrise mission, and also studies the ultraviolet radiation from chromosphere and corona. Michael Knoelker at the High Altitude Observatory in Boulder, Colo. Is the NASA principal investigator for Sunrise.

Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, Md. 


Friday, September 27, 2013

A scattering of spiral and elliptical galaxies

Credit: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt

This image shows the massive galaxy cluster MACS J0152.5-2852, captured in detail by the NASA/ESA Hubble Space Telescope's Wide Field Camera 3. Almost every object seen here is a galaxy, each containing billions of stars. Galaxies are not usually randomly distributed in space, but instead appear in concentrations of hundreds, held together by their mutual gravity. Elliptical galaxies, like the yellow fuzzy objects seen in the image, are most often found close to the centres of galaxy clusters, while spirals, such as the bluish patches, are usually found to be further out and more isolated.

A version of this image obtained tenth prize in the Hubble's Hidden Treasures image processing competition, entered by contestant Judy Schmidt.

How Engineers Revamped Spitzer to Probe Exoplanets

Credit: NASA/JPL-Caltech 

Now approaching its 10th anniversary, NASA's Spitzer Space Telescope has evolved into a premier observatory for an endeavor not envisioned in its original design: the study of worlds around other stars, called exoplanets. While the engineers and scientists who built Spitzer did not have this goal in mind, their visionary work made this unexpected capability possible. Thanks to the extraordinary stability of its design and a series of subsequent engineering reworks, the space telescope now has observational powers far beyond its original limits and expectations. 

"When Spitzer launched back in 2003, the idea that we would use it to study exoplanets was so crazy that no one considered it," said Sean Carey of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena. "But now the exoplanet science work has become a cornerstone of what we do with the telescope." 

Spitzer views the universe in the infrared light that is a bit less energetic than the light our eyes can see. Infrared light can easily pass through stray cosmic gas and dust, allowing researchers to peer into dusty stellar nurseries, the centers of galaxies, and newly forming planetary systems. 

This infrared vision of Spitzer's also translates into exoplanet snooping. When an exoplanet crosses or "transits" in front of its star, it blocks out a tiny fraction of the starlight. These mini-eclipses as glimpsed by Spitzer reveal the size of an alien world. 

Exoplanets emit infrared light as well, which Spitzer can capture to learn about their atmospheric compositions. As an exoplanet orbits its sun, showing different regions of its surface to Spitzer's cameras, changes in overall infrared brightness can speak to the planet's climate. A decrease in brightness as the exoplanet then goes behind its star can also provide a measurement of the world's temperature. 

While the study of the formation of stars and the dusty environments from which planets form had always been a cornerstone of Spitzer's science program, its exoplanet work only became possible by reaching an unprecedented level of sensitivity, beyond its original design specifications.

Researchers had actually finalized the telescope's design in 1996 before any transiting exoplanets had even been discovered. The high degree of precision in measuring brightness changes needed for observing transiting exoplanets was not considered feasible in infrared because no previous infrared instrument had offered anything close to what was needed. 

Nevertheless, Spitzer was built to have excellent control over unwanted temperature variations and a better star-targeting pointing system than thought necessary to perform its duties. Both of these foresighted design elements have since paid dividends in obtaining the extreme precision required for studying transiting exoplanets. 

The fact that Spitzer can still do any science work at all still can be credited to some early-in-the-game, innovative thinking. Spitzer was initially loaded with enough coolant to keep its three temperature-sensitive science instruments running for at least two-and-a-half years. This "cryo" mission ended up lasting more than five-and-a-half-years before exhausting the coolant.

But Spitzer's engineers had a built-in backup plan. A passive cooling system has kept one set of infrared cameras humming along at a super-low operational temperature of minus 407 degrees Fahrenheit (minus 244 Celsius, or 29 degrees above absolute zero). The infrared cameras have continued operating at full sensitivity, letting Spitzer persevere in a "warm" extended mission, so to speak, though still extremely cold by Earthly standards.

To stay so cool, Spitzer is painted black on the side that faces away from the sun, which enables the telescope to radiate away a maximum amount of heat into space. On the sun-facing side, Spitzer has a shiny coating that reflects as much of the heat from the sun and solar panels as possible. It is the first infrared telescope to use this innovative design and has set the standard for subsequent missions. 

Fully transitioning Spitzer into an exoplanet spy required some clever modifications in-flight as well, long after it flew beyond the reach of human hands into an Earth-trailing orbit. Despite the telescope's excellent stability, a small "wobbling" remained as it pointed at target stars. The cameras also exhibited small brightness fluctuations when a star moved slightly across an individual pixel of the camera. The wobble, coupled with the small variation in the cameras, produced a periodic brightening and dimming of light from a star, making the delicate task of measuring exoplanet transits that much more difficult.

To tackle these issues, engineers first began looking into a source for the wobble. They noticed that the telescope's trembling followed an hourly cycle. This cycle, it turned out, coincided with that of a heater, which kicks on periodically to keep a battery aboard Spitzer at a certain temperature. The heater caused a strut between the star trackers and telescope to flex a bit, making the position of the telescope wobble compared to the stars being tracked. 

Ultimately, in October 2010, the engineers figured out that the heater did not need to be cycled through its full hour and temperature range -- 30 minutes and about 50 percent of the heat would do. This tweak served to cut the telescope's wobble in half. 

Spitzer's engineers and scientists were still not satisfied, however. In September 2011, they succeeded in repurposing Spitzer's Pointing Control Reference Sensor "Peak-Up" camera. This camera was used during the original cryo mission to put gathered infrared light precisely into a spectrometer and to perform routine calibrations of the telescope's star-trackers, which help point the observatory. The telescope naturally wobbles back and forth a bit as it stares at a particular target star or object. Given this unavoidable jitter, being able to control where light goes within the infrared camera is critical for obtaining precise measurements. The engineers applied the Peak-Up to the infrared camera observations, thus allowing astronomers to place stars precisely on the center of a camera pixel.  

Since repurposing the Peak-Up Camera, astronomers have taken this process even further, by carefully "mapping" the quirks of a single pixel within the camera. They have essentially found a "sweet spot" that returns the most stable observations. About 90 percent of Spitzer's exoplanet observations are finely targeted to a sub-pixel level, down to a particular quarter of a pixel. "We can use the Peak-Up camera to position ourselves very precisely on the camera and put light right on the best part of a pixel," said Carey. "So you put the light on the sweet spot and just let Spitzer stare."

These three accomplishments -- the modified heater cycling, repurposed Peak-Up camera and the in-depth characterization of individual pixels in the camera -- have more than doubled Spitzer's stability and targeting, giving the telescope exquisite sensitivity when it comes to taking exoplanet measurements. 

"Because of these engineering modifications, Spitzer has been transformed into an exoplanet-studying telescope," said Carey. "We expect plenty of great exoplanetary science to come from Spitzer in the future."
For more information on exoplanets, visit

NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

Thursday, September 26, 2013

IGR J18245-2452: Neutron Star Undergoes Wild Behavior Changes

Credit: X-ray: NASA/CXC/ICE/A.Papitto et al

These two images from NASA's Chandra X-ray Observatory show a large change in X-ray brightness of a rapidly rotating neutron star, or pulsar, between 2006 and 2013. The neutron star - the extremely dense remnant left behind by a supernova - is in a tight orbit around a low mass star. This binary star system, IGR J18245-2452 (mouse over the image for its location) is a member of the globular cluster M28.

As described in a press release from the European Space Agency, IGR J18245-2452 provides important information about the evolution of pulsars in binary systems. Pulses of radio waves have been observed from the neutron star as it makes a complete rotation every 3.93 milliseconds (an astonishing rate of 254 times every second), identifying it as a "millisecond pulsar."

Credit: X-ray: NASA/CXC/ICE/A.Papitto et al 

The widely accepted model for the evolution of these objects is that matter is pulled from the companion star onto the surface of the neutron star via a disk surrounding it. During this so-called accretion phase, the system is described as a low-mass X-ray binary because bright X-ray emission from the disk is observed. Spinning material in the disk falls onto the neutron star, increasing its rotation rate. The transfer of matter eventually slows down and the remaining material is swept away by the whirling magnetic field of the neutron star as a millisecond radio pulsar forms.

The complete evolution of a low-mass X-ray binary into a millisecond pulsar should happen over several billion years, but in the course of this evolution, the system might switch rapidly between these two states. The source IGR J18245-2452 provides the first direct evidence for such drastic changes in behavior. In observations from July 2002 to May 2013 there are periods when it acts like an X-ray binary and the radio pulses disappear, and there are times when it switches off as an X-ray binary and the radio pulses turn on.

The latest observations with both X-ray and radio telescopes show that the transitions between an X-ray binary and a radio pulsar can take place in both directions and on a time scale that is shorter than expected, maybe only a few days. They also provide powerful evidence for an evolutionary link between X-ray binaries and radio millisecond pulsars.

The X-ray observations contained data from Chandra, ESA's XMM-Newton, the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) and NASA's Swift/XRT and the radio observations used the Australia Telescope Compact Array, the Green Bank Telescope, Parkes radio telescope and the Westerbok Synthesis Radio Telescope.

The observations of IGR J18245-2452 and their implications are described in a paper published in the September 26th, 2013 issue of Nature. The first author is Alessandro Papitto from the Institute of Space Sciences in Barcelona, Spain. The co-authors are C. Ferrigno and E. Bozzo from Université de Genève, Versoix, Switzerland; N. Rea from the Institute of Space Sciences in Barcelona, Spain; L. Pavan from Université de Genève, Versoix, Switzerland; L. Burderi from Universit´a di Cagliari, Monserrato, Italy; M. Burgay from INAF-Osservatorio Astronomico di Cagliari, Capoterra, Italy; S. Campana from INAF-Osservatorio Astronomico di Brera, Lecco, Italy; T. Di Salvo from Universit´a di Palermo, Palermo, Italy; M. Falanga from International Space Science Institute, Bern, Switzerland; M. Filipovi´c from University of Western Sydney, Penrith, Australia; P. Freire from Max-Planck-Institut f´ur Radioastronomie, Bonn, Germany; J. Hessels from Netherlands Institute for Radio Astronomy, Dwingeloo, The Netherlands; A. Possenti from INAF-Osservatorio Astronomico di Cagliari, Capoterra, Italy; S. Ransom from National Radio Astronomy Observatory, Charlottesville, VA; A. Riggio from Universit´a di Cagliari, Monserrato, Italy; P. Romano from INAF-Istituto di Astrosica Spaziale e Fisica Cosmica, Palermo, Italy; J. Sarkissian from CSIRO Astronomy and Space Science, Epping, Australia; I. Stairs from University of British Columbia, Vancouver, Canada; L. Stella from INAF-Osservatorio Astronomico di Roma, Roma, Italy; D. Torres from the Institute of Space Sciences in Barcelona, Spain; M. Wieringa from CSIRO Astronomy and Space Science, Narrabri, Australia and G. Wong from University of Western Sydney, Penrith, Australia.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra Program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Fast Facts for IGR J18245-2452: 

Scale: Each panel is 1.2 arcmin across (About 6 light years) 
Category: Neutron Stars/X-ray Binaries
Coordinates (J2000): RA 18h 24m 32.00s | Dec -24° 52' 10.70" 
Constellation: Sagittarius
Observation Date: 30 May 2006 and 29 Apr 2013 
Observation Time: 26 (1 day, 2 hours). 
Obs. ID: 6769, 15645 I
Instrument: ACIS
References: Papitto, A. et al, 2013, Nature (accepted); arXiv:1305.3884 
Color Code: X-ray: Blue  
Distance Estimate: 18,000 light years

Missing link found between X-ray and Radio Pulsars

Pulsar caught in evolutionary change
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Astronomers using ESA’s Integral and XMM-Newton space observatories have caught a fast-spinning ‘millisecond pulsar’ in a crucial evolutionary phase for the first time, as it swings between emitting pulses of X-rays and radio waves. 

Pulsars are spinning, magnetised neutron stars, the dead cores of massive stars that exploded as a dramatic supernova after having burned up their fuel. As they spin, they sweep out pulses of electromagnetic radiation hundreds of times per second, like beams from a lighthouse. This tells us that the spin period of the neutron stars can be as short as a few milliseconds. 

Pulsars are classified according to how their emission is generated. For example, radio pulsars are powered by the rotation of their magnetic field, while X-ray pulsars are fuelled by the accretion of material siphoned off from a companion star. 

Theory holds that initially slowly rotating neutron stars with a low-mass companion are spun up as matter accretes onto them from a surrounding disc fed by the companion. X-rays are emitted as the accreting material heats up as it falls onto the neutron star. 

After a billion years or so, the rate of accretion drops and the pulsars are thought to switch on again as a radio-emitting millisecond pulsar. 

There is thought to be an intermediate phase during which they swing back and forth between the two states several times, but until now, there has been no direct and conclusive evidence for this transitional phase.
Thanks to the combined forces of ESA’s Integral and XMM-Newton space observatories, along with follow-up observations by NASA’s Swift and Chandra satellites and by ground-based radio telescopes, scientists have finally caught a pulsar in the act of changing between the two evolutionary steps. 

“The search is finally over: with our discovery of a millisecond pulsar that, within only a few weeks, switched from being accretion-powered and X-ray-bright to rotation-powered and bright in radio waves, we finally have the missing link in pulsar evolution,” says Alessandro Papitto from the Institute of Space Sciences in Barcelona, Spain, who led the research published this week in  Nature

The object, identified as IGR J18245-2452, was first detected in X-rays on 28 March 2013 by Integral in the globular cluster M28, which lies in the constellation Sagittarius. 

Observations by XMM-Newton determined the pulsar’s spin period to be 3.9 milliseconds, meaning that it rotates on its axis more than 250 times every second, clearly identifying it as an X-ray-bright millisecond pulsar. 

But comparing its spin period and other key characteristics with those of other known pulsars in M28 showed it matched perfectly those of another pulsar that had been observed in 2006 – but only at radio wavelengths.

“At that time, it appeared to be just another millisecond radio pulsar, but now here it was shining in X-rays – this is clearly no ordinary pulsar,” adds Dr Papitto. 

The astronomers kept monitoring the object with X-ray telescopes, but also started a series of radio observations, on the lookout for hints that it might change personalities again. 

What the astronomers didn’t expect was that the change in behaviour would happen within just a few weeks.
“We used to think the change would occur only once over the billion-year evolution of these systems, yet within a month, the neutron star swung back and forth between an X-ray and a radio pulsar state, showing the switch can be made even on extremely short timescales,” says co-author Enrico Bozzo of the University of Geneva, Switzerland. 

Despite occurring on a far quicker timescale than previously imagined, the characteristics of the transformation, which is thought to lie in the interplay between the pulsar’s magnetic field and the pressure of material falling onto it from its low-mass companion star, still fits current theory. 

When the inflow of material from the neighbouring star is more intense, the high density of matter shuts off the radio emission, and the pulsar is only visible through the X-rays emitted by the accreting matter as it heats up while falling onto the pulsar. 

Conversely, when the accretion rate decreases, the magnetic field of the pulsar expands and pushes any remaining matter away from the pulsar, allowing the radio emission to switch back on. 

Looking back through archival data for this particular pulsar, the astronomers have shown that these cycles may repeat on timescales of just a few years. 

“The discovery of this transitional pulsar completes a decades-long quest for such an object and will help us to understand better the evolution of pulsars,” says Erik Kuulkers, Integral Project Scientist at ESA.
“Although it took a long time to make this first detection, we believe that pulsars in such binary systems are fairly common, so we’re looking forward to finding more,” adds Norbert Schartel, XMM-Newton Project Scientist at ESA. 

Read an in-depth version of this story on ESA SciTech: Swinging between X-rays and radio waves: the missing-link pulsar
Swings between rotation and accretion power in a millisecond binary pulsar by A. Papitto et al. is published in Nature 26 September 2013. 

The study is based on data from a number of space-based high-energy observatories and ground-based radio telescopes: ESA’s Integral and XMM-Newton and NASA’s Swift and Chandra space telescopes, and CSIRO's Australia Telescope Compact Array and Parkes radio telescope, NRAO's Robert C. Byrd Green Bank Telescope, and ASTRON's Westerbork Synthesis Radio Telescope. 

For further information, please contact:
Markus Bauer
ESA Science and Robotic Exploration Communication Officer

Tel: +31 71 565 6799

Mob: +31 61 594 3 954


Alessandro Papitto Institut de Ciències de l’Espai (ICE), CSIC-IEEC (Spanish National Research Council - Institute for Space Studies of Catalonia)
Barcelona, Spain
Tel: +34 935 868355

Enrico Bozzo
ISDC Data Centre for Astrophysics
University of Geneva, Switzerland
Tel: +41 79 3129209

Erik Kuulkers
ESA Integral Project Scientist
Tel: +34 918131358

Norbert Schartel
ESA XMM-Newton Project Scientist
Tel: +34 91 8131 184

Source: ESA

Wednesday, September 25, 2013

The Cool Glow of Star Formation

The star-forming Cat’s Paw Nebula through ArTeMiS’s eyes

The ArTeMiS cryostat in position at APEX

Harsh conditions at the APEX control building

The stellar nursery NGC 6334 in the constellation of Scorpius 



Zooming in on ArTeMiS’s view of the Cat’s Paw Nebula NGC 6334
Zooming in on ArTeMiS’s view of the Cat’s Paw Nebula NGC 6334

Cross-fading between infrared VISTA and submillimetre ArTeMiS views of NGC 6334
Cross-fading between infrared VISTA and submillimetre ArTeMiS views of NGC 6334

First Light of Powerful New Camera on APEX

A new instrument called ArTeMiS has been successfully installed on APEX — the Atacama Pathfinder Experiment. APEX is a 12-metre diameter telescope located high in the Atacama Desert, which operates at millimetre and submillimetre wavelengths — between infrared light and radio waves in the electromagnetic spectrum — providing a valuable tool for astronomers to peer further into the Universe. The new camera has already delivered a spectacularly detailed view of the Cat’s Paw Nebula.

ArTeMiS [1] is a new wide-field submillimetre-wavelength camera that will be a major addition to APEX’s suite of instruments and further increase the depth and detail that can be observed. The new generation detector array of ArTeMIS acts more like a CCD camera than the previous generation of detectors. This will let wide-field maps of the sky be made faster and with many more pixels.

The commissioning team [2] that installed ArTeMIS had to battle against extreme weather conditions to complete the task. Very heavy snow on the Chajnantor Plateau had almost buried the APEX control building. With help from staff at the ALMA Operations Support Facility and APEX, the team transported the ArTeMiS boxes to the telescope via a makeshift road, avoiding the snowdrifts, and were able to install the instrument, manoeuvre the cryostat into position, and attach it in its final location.

To test the instrument, the team then had to wait for very dry weather as the submillimetre wavelengths of light that ArTeMiS observes are very strongly absorbed by water vapour in the Earth's atmosphere. But, when the time came, successful test observations were made. Following the tests and commissioning observations, ArTéMiS has already been used for several scientific projects. One of these targets was the star formation region NGC 6334, (the Cat’s Paw Nebula), in the southern constellation of Scorpius (The Scorpion). This new ArTeMiS image is significantly better than earlier APEX images of the same region.

The testing of ArTeMiS has been completed and the camera will now return to Saclay in France in order to install additional detectors in the instrument. The whole team is already very excited by the results from these initial observations, which are a wonderful reward for many years of hard work and could not have been achieved without the help and support of the APEX staff.


[1] ArTeMiS stands for: Architectures de bolomètres pour des Télescopes à grand champ de vue dans le domaine sub-Millimétrique au Sol (Bolometer arrays for wide-field submillimetre ground-based telescopes).

[2] The commissioning team from CEA consists of Philippe André, Laurent Clerc, Cyrille Delisle, Eric Doumayrou, Didier Dubreuil, Pascal Gallais, Yannick Le Pennec, Michel Lortholary, Jérôme Martignac, Vincent Revéret, Louis Rodriquez, Michel Talvard and François Visticot.

More information

APEX is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. Operation of APEX at Chajnantor is entrusted to ESO.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.




Michel Talvard
Project Manager for ArTeMiS / CEA
Saclay, France
Tel: +33 1 6908 8352

Carlos De Breuck
ESO APEX Project Manager
Garching, Germany
Tel: +49 89 3200 6613

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591

By the Pale Saturn-light

This view of Saturn’s moon Enceladus and its prominent plumes was taken by the Cassini
Credit: NASA/JPL-Caltech/Space Science Institute 

Enceladus's unusual plume is only easily visible when the Cassini spacecraft and the Sun are on opposite sides of Enceladus. So what's lighting up the moon then? It's light reflected off Saturn. This lighting trick allows the Cassini spacecraft to capture both the back-lit plume and the surface of Enceladus in one shot. 

This view looks toward the Saturn-facing hemisphere of Enceladus. North on Enceladus is up. The image was taken in blue light with the Cassini spacecraft narrow-angle camera on April 2, 2013. 

The view was acquired at a distance of approximately 517,000 miles (832,000 kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 175 degrees. Image scale is 3 miles (5 kilometers) per pixel. 

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo. 

For more information about the Cassini-Huygens mission visit or . The Cassini imaging team homepage is at

Tuesday, September 24, 2013

M60-UCD1: NASA's Hubble and Chandra Find Evidence for Densest Nearby Galaxy

M60-(NGC 4649) - M60-UCD1  (inset)
Credit:  X-ray: NASA/CXC/MSU/J.Strader et al, Optical: NASA/STScI

The densest galaxy in the nearby Universe may have been found, as described in our latest press release. The galaxy, known as M60-UCD1, is located near a massive elliptical galaxy NGC 4649, also called M60, about 54 million light years from Earth.

This composite image shows M60 and the region around it, where data from NASA's Chandra X-ray Observatory are pink and data from NASA's Hubble Space Telescope (HST) are red, green and blue. The Chandra image shows hot gas and double stars containing black holes and neutron stars and the HST image reveals stars in M60 and neighboring galaxies including M60-UCD1. The inset is a close-up view of M60-UCD1 in an HST image.

Packed with an extraordinary number of stars, M60-UCD1 is an "ultra-compact dwarf galaxy". It was discovered with NASA's Hubble Space Telescope and follow-up observations were done with NASA's Chandra X-ray Observatory and ground-based optical telescopes.

It is the most luminous known galaxy of its type and one of the most massive, weighing 200 million times more than our Sun, based on observations with the Keck 10-meter telescope in Hawaii. Remarkably, about half of this mass is found within a radius of only about 80 light years. This would make the density of stars about 15,000 times greater than found in Earth's neighborhood in the Milky Way, meaning that the stars are about 25 times closer.

The 6.5-meter Multiple Mirror Telescope in Arizona was used to study the amount of elements heavier than hydrogen and helium in stars in M60-UCD1. The values were found to be similar to our Sun.

Another intriguing aspect of M60-UCD1 is that the Chandra data reveal the presence of a bright X-ray source in its center. One explanation for this source is a giant black hole weighing in at some 10 million times the mass of the Sun.

Astronomers are trying to determine if M60-UCD1 and other ultra-compact dwarf galaxies are either born as jam-packed star clusters or if they are galaxies that get smaller because they have stars ripped away from them. Large black holes are not found in star clusters, so if the X-ray source is in fact due to a massive black hole, it was likely produced by collisions between the galaxy and one or more nearby galaxies. The mass of the galaxy and the Sun-like abundances of elements also favor the idea that the galaxy is the remnant of a much larger galaxy.

If this stripping did occur, then the galaxy was originally 50 to 200 times more massive than it is now, which would make the mass of its black hole relative to the original mass of the galaxy more like the Milky Way and many other galaxies. It is possible that this stripping took place long ago and that M60-UCD1 has been stalled at its current size for several billion years. The researchers estimate that M60-UCD1 is more than about 10 billion years old.

These results appear online and have been published in the September 20th issue of The Astrophysical Journal Letters. The first author is Jay Strader, of Michigan State University in East Lansing, MI. The co-authors are Anil Seth from University of Utah, Salt Lake City, UT; Duncan Forbes from Swinburne University, Hawthorn, Australia; Giuseppina Fabbiano from Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, MA; Aaron Romanowsky from San Jos'e State University, San Jose, CA; Jean Brodie from University of California Observatories/Lick Observatory, Santa Cruz, CA; Charlie Conroy from University of California, Santa Cruz, CA; Nelson Caldwell from CfA; Vincenzo Pota and Christopher Usher from Swinburne University, Hawthorn, Australia, and Jacob Arnold from University of California Observatories/Lick Observatory, Santa Cruz, CA.

Fast Facts for M60-UCD1:

Scale:  Image is 3.2 arcmin across (about 50,000 light years
Category:  Normal Galaxies & Starburst Galaxies
Coordinates (J2000):  RA 12h 43m 40.30s | Dec +11° 32' 58.00"
Constellation:  Virgo
Observation Date:  6 pointings between April 2000 and August 2011
Observation Time:  85 hours 32 min (3 days 13 hours 32 min)
Obs. ID:  784, 8182, 8507, 12975, 12976, 14328 
Instrument:  ACIS
References: Strader, J. et al, 2013, ApJ 775, 6; arXiv:1307.7707
Color Code:  X-ray (Pink); Optical (Red, Green, Blue)
Distance Estimate:  About 54 million light years

Monday, September 23, 2013

New Cool Starlet in Our Backyard

Credit: ESO, and D. Minniti and J. C. Beamín (Pontificia Universidad Católica de Chile)

 This new image, from ESO’s VISTA telescope, shows a newly-discovered brown dwarf nicknamed VVV BD001, which is located at the very centre of this zoomable image. It is the first new brown dwarf spotted in our cosmic neighbourhood as part of the VVV Survey. VVV BD001 is located about 55 light-years away from us, towards the very crowded centre of our galaxy.

Brown dwarfs are stars that never quite managed to grow up into a star like our Sun. They are often referred to as “failed stars”; they are larger in size than planets like Jupiter, but smaller than stars.

This dwarf is peculiar in two ways; firstly, it is the first one found towards the centre of our Milky Way, one of the most crowded regions of the sky. Secondly, it belongs to an unusual class of stars known as “unusually blue brown dwarfs” — it is still unclear why these stars are bluer than expected.

Brown dwarfs are born in the same way as stars, but do not have enough mass to trigger the burning of hydrogen to become normal stars. Because of this they are much cooler and produce far less light, making them harder to find. Astronomers generally look for these objects using near and mid-infrared cameras and special telescopes that are sensitive to these very cool objects, but usually avoid looking in very crowded regions of space — such as the central region of our galaxy, for example.

VISTA (the Visible and Infrared Survey Telescope for Astronomy) is the world’s largest survey telescope and is located at ESO’s Paranal Observatory in Chile. It is performing six separate surveys of the sky, and the VVV (VISTA Variables in the Via Lactea) survey is designed to catalogue a billion objects in the centre of our own Milky Way galaxy. VVV BD001 was discovered by chance during this survey.

Scientists have used the VVV catalogue to create a 3 dimensional map of the central bulge of the Milky Way (eso1339). The data have also been used to create a monumental 108 200 by 81 500 pixel colour image containing nearly nine billion pixels (eso1242), one of the biggest astronomical images ever produced.


Source: ESO

Friday, September 20, 2013

A giant, smouldering star

Credit: ESA/Hubble & NASA
Acknowledgement: Jean-Christophe Lambry

This new image, snapped by NASA/ESA Hubble Space Telescope, shows the star HD 184738, also known as Campbell’s hydrogen star. It is a Wolf-Rayet star — an evolutionary stage for stars with a mass of over 20 times that of our Sun, when they are rapidly blowing away material and losing mass. This type of star is named after two French astronomers, Charles Wolf and Georges Rayet, who first identified them in the mid-nineteenth century.

Stars like HD 184738 are short-lived, very massive, and extremely hot, with surface temperatures of up to 40 times higher than that of our Sun. They are also very luminous, though as they predominantly emit in the ultraviolet and X-ray parts of the spectrum, they may not appear to be exceptionally bright. The star’s distinctive fiery red colour is caused by its nitrogen content.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Jean-Christophe Lambry.

Thursday, September 19, 2013

Coma Cluster: Clues to the Growth of the Colossus in Coma

 Coma Cluster
Credit: X-ray: NASA/CXC/MPE/J.Sanders et al, Optical: SDSS

A team of astronomers has discovered enormous arms of hot gas in the Coma cluster of galaxies by using NASA's Chandra X-ray Observatory and ESA's XMM-Newton. These features, which span at least half a million light years, provide insight into how the Coma cluster has grown through mergers of smaller groups and clusters of galaxies to become one of the largest structures in the Universe held together by gravity.

A new composite image, with Chandra data in pink and optical data from the Sloan Digital Sky Survey appearing in white and blue, features these spectacular arms (mouse over the image for their location). In this image, the Chandra data have been processed so extra detail can be seen. 

The X-ray emission is from multimillion-degree gas and the optical data shows galaxies in the Coma Cluster, which contain only about 1/6 the mass in hot gas. Only the brightest X-ray emission is shown here, to emphasize the arms, but the hot gas is present over the entire field of view.

Researchers think that these arms were most likely formed when smaller galaxy clusters had their gas stripped away by the head wind created by the motion of the cluster through the hot gas, in much the same way that the headwind created by a roller coaster blows the hats off riders.

Coma is an unusual galaxy cluster because it contains not one, but two giant elliptical galaxies near its center. These two giant elliptical galaxies are probably the vestiges from each of the two largest clusters that merged with Coma in the past. The researchers also uncovered other signs of past collisions and mergers in the data.
From their length, and the speed of sound in the hot gas (~4 million km/hr), the newly discovered X-ray arms are estimated to be about 300 million years old, and they appear to have a rather smooth shape. This gives researchers some clues about the conditions of the hot gas in Coma. Most theoretical models expect that mergers between clusters like those in Coma will produce strong turbulence, like ocean water that has been churned by many passing ships. Instead, the smooth shape of these lengthy arms points to a rather calm setting for the hot gas in the Coma cluster, even after many mergers.

Large-scale magnetic fields are likely responsible for the small amount of turbulence that is present in Coma. Estimating the amount of turbulence in a galaxy cluster has been a challenging problem for astrophysicists. Researchers have found a range of answers, some of them conflicting, and so observations of other clusters are needed.

Two of the arms appear to be connected to a group of galaxies located about two million light years from the center of Coma. One or both of these arms connects to a larger structure seen in the XMM-Newton data, and spans a distance or at least 1.5 million light years. A very thin tail also appears behind one of the galaxies in Coma. This is probably evidence of gas being stripped from a single galaxy, in addition to the groups or clusters that have merged there.

These new results on the Coma cluster, which incorporate over six days worth of Chandra observing time, will appear in the September 20, 2013, issue of the journal Science. The first author of the paper is Jeremy Sanders from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. The co-authors are Andy Fabian from Cambridge University in the UK; Eugene Churazov from the Max Planck Institute for Astrophysics in Garching, Germany; Alexander Schekochihin from University of Oxford in the UK; Aurora Simionescu from the Institute of Space and Astronautical Science in Sagamihara, Japan; Stephen Walker from Cambridge University in the UK and Norbert Werner from Stanford University in Stanford, CA.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra Program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass. 

Fast Facts for Coma Cluster

Scale: Image is 23 arcmin on a side (about 2 million light years)
Category:  Groups & Clusters of Galaxies
Coordinates (J2000: RA 12h 59m 48s | Dec +27° 58' 00
Constellation: Coma Berenices
Observation Date: 13 pointings between November, 1999 and April, 2012
Observation Time: 151 hours 35 min (6 days, 7 hours, 35 min)
Obs. ID: 555, 1112-1114, 9714, 13993-13996, 14406, 14410, 14411, 14415
Instrument: ACIS
References: Sanders, J.S., et al, 2013, Science (in press)
Color Code: X-ray (Pink); Optical (Red, Green, Blue)
Distance Estimate: About 318 million light years (z = 0.0231)  

Wednesday, September 18, 2013

Young Stars Cooking in the Prawn Nebula

Detailed view of the Prawn Nebula from ESO's VST

The Prawn Nebula from ESO's VST (wide crop)

Excerpts from a view of the Prawn Nebula from ESO's VST 

The Prawn Nebula IC 4628 in the constellation of Scorpius



Zooming in on the Prawn Nebula
Zooming in on the Prawn Nebula

A close-up look at the Prawn Nebula from ESO’s VST
A close-up look at the Prawn Nebula from ESO’s VST

The glowing jumble of gas clouds visible in this new image make up a huge stellar nursery nicknamed the Prawn Nebula. Taken using the VLT Survey Telescope at ESO’s Paranal Observatory in Chile, this may well be the sharpest picture ever taken of this object. It shows clumps of hot new-born stars nestled in among the clouds that make up the nebula.

Located around 6000 light-years from Earth in the constellation of Scorpius (The Scorpion), the nebula formally known as IC 4628 is a huge region filled with gas and clumps of dark dust. These gas clouds are star-forming regions, producing brilliant hot young stars. In visible light, these stars appear as a blue-white colour, but they also emit intense radiation in other parts of the spectrum — most notably in the ultraviolet [1].

It is this ultraviolet light from the stars that causes the gas clouds to glow. This radiation strips electrons from hydrogen atoms, which then later recombine and release energy in the form of light. Each chemical element emits light at characteristic colours when this process occurs, and for hydrogen the predominant colour is red. IC 4628 is an example of an HII region [2].

The Prawn Nebula is around 250 light-years across, covering an area of sky equivalent to four times that of the full Moon. Despite this huge size it has been often overlooked by observers due to its faintness and because most of its light is emitted at wavelengths where the human eye is not sensitive. The nebula is also known as Gum 56, after the Australian astronomer Colin Gum, who published a catalogue of HII regions in 1955.

Over the last few million years this region of sky has formed many stars, both individually and in clusters. There is a large scattered star cluster named Collinder 316 which extends over most of this image. This cluster is a part of a much larger gathering of very hot and luminous stars. Also visible are many dark structures or cavities, where interstellar matter has been blown away by the powerful winds generated by the nearby hot stars.

This image was taken by the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile. The VST is the largest telescope in the world designed for surveying the sky in visible light. It is a state-of-the-art 2.6-metre telescope built around the OmegaCAM camera that contains 32 CCD detectors that together create 268-megapixel images. This new 24 000-pixel-broad image is a mosaic of two such images and is one of the largest single images released by ESO so far.

The picture forms part of a detailed public survey of a large part of the Milky Way called VPHAS+ that is using the power of the VST to search for new objects such as young stars and planetary nebulae. The survey will also provide the best images yet taken of many huge glowing star formation regions, such as the one pictured here.

The very sharp VST images were further enhanced to bring out the colour by including additional high quality imaging through other filters taken by Martin Pugh, a very skilled amateur astronomer observing from Australia using 32-centimetre and 13-centimetre telescopes [3].

This press release represents a milestone — it is the 1000th press release issued by ESO. The first one appeared in late 1985 and featured a picture of Halley's Comet. They are all available online.


[1] This is the same kind of radiation that causes unprotected human skin to burn when exposed to too much direct sunlight. But the Earth’s atmosphere shields life on the surface from most ultraviolet radiation and only longer wavelengths (between about 300 and 400 nanometres) reach the ground and cause tanning and burning of human skin. Some of the ultraviolet radiation emitted by very hot stars in HII regions is at the much shorter wavelengths (shorter than 91.2 nanometres) that can ionise hydrogen.

[2] Astronomers use the term “HII” (pronounced “aitch-two”) to refer to ionised hydrogen, and “HI” (aitch-one) for atomic hydrogen. A hydrogen atom consists of an electron bound to a proton; in an ionised gas, atoms are split into freely-moving electrons and positive ions — in this case the positive ions are just single protons.

[3] More details of his observations can be found at Martin Pugh’s information page on this object.

More information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.



Richard Hook
ESO, La Silla, Paranal, E-ELT and Survey Telescopes Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591