SOFIA Uncovers Clues to the Evolution of Universe and Search for Life

Magnetic fields in the Orion Nebula, shown as stream lines over an infrared image taken by the Very Large Telescope in Chile, are regulating the formation of new stars. SOFIA’s HAWC+ instrument is sensitive to the alignment of dust grains, which line up along magnetic fields, letting researchers infer the direction and strength. Credits: NASA/SOFIA/D. Chuss et al. and European Southern Observatory/M.McCaughrean et al.

A compilation of scientific results from The Stratospheric Observatory for Infrared Astronomy, SOFIA, reveal new clues to how stars form and galaxies evolve, and closer to understanding the environment of Europa and its subsurface ocean. The airborne observatory carries a suite of instruments, each sensitive to different properties of infrared light, that gives astronomers insights into the flow of matter in galaxies.

“Much of the light in the universe is emitted as infrared light that does not reach Earth’s surface,” said Bill Reach, chief science advisor at the University Space Research Association’s SOFIA Science Center. “Infrared observations from SOFIA, which flies above most of the atmosphere, let us study what’s happening deep inside cosmic clouds, analyze celestial magnetic fields and investigate the chemical universe in ways that are not possible with visible light.”

Unlike space-based telescopes, SOFIA’s instruments can be exchanged, serviced or upgraded to harness new technologies. Its newest instrument, called the High-resolution Airborne Wideband Camera-Plus, or HAWC+, enables studies of celestial magnetic fields with ground-breaking precision.

“How magnetic fields affect the process of star formation has not been well understood, though it has long been suspected that they play an important role,” said David Chuss, professor of physics at Villanova University in Pennsylvania. “With SOFIA’s HAWC+ instrument, we can now begin to understand how these fields influence the dynamics of regions where gas and dust are collapsing to produce new stars."

Some observations highlighted in the Astrophysical Journal “Focus on Results from SOFIA” include:

• The magnetic fields in the Orion Nebula are preventing star-forming clouds from collapsing under gravity, thereby regulating the formation of new stars. This can help better explain the number of stars in our galaxy and those that may form in the future. If magnetic fields inhibit the gravitational collapse of celestial clouds in other regions of the galaxy, the number of new stars may be lower than current models predict.

• Magnetic fields are trapping material, keeping it close enough to be fed into the black hole in the Cygnus A Galaxy. These findings may mean that magnetic fields regulate black hole activity and explain why some are actively gobbling up material from their surroundings, while others, like the one in our own Milky Way Galaxy, are not.

• A map of the entire grand-design spiral galaxy M51 (also known as the Whirlpool Galaxy), including its small companion galaxy, reveals that the companion is not forming new stars at the same rate as the its larger neighbor. Understanding how stars are born in different celestial environments is key to learning how star birth evolved from the early universe to the present day.

• The region called Sagittarius B1 — near the black hole at the center of our Milky Way Galaxy — must be part of a large, young star-formation complex, but the stars were formed elsewhere and are remnants of a previous generation of star formation, which includes the Arches cluster. Observations like these are helping researchers develop a template to understand distant galaxies, which are often too far away for even the most powerful telescopes to see clearly, and ultimately learn how the universe works.

• Water plumes that may be erupting from Jupiter’s moon Europa, suggested by data from NASA’s Galileo and Hubble spacecraft, contain, at most, the amount of water in an Olympic-sized swimming pool. SOFIA’s observations in 2017 did not directly detect the plume, but established an upper limit on how much water could be in the plumes. This upper limit is crucial to ongoing studies that will analyze the contents of the plumes and investigate their origins, which will help reveal if Europa has the ingredients to support life.

SOFIA is a Boeing 747SP jetliner modified to carry a 106-inch diameter telescope. It is a joint project of NASA and the German Aerospace Center, DLR. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science and mission operations in cooperation with the Universities Space Research Association headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart. The aircraft is maintained and operated from NASA’s Armstrong Flight Research Center Hangar 703, in Palmdale, California.

Editor: Kassandra Bell

Source: NASA/Galaxies

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Magnetic Waves Create Chaos in Star-Forming Clouds

Offner’s research will shed light on the processes inside star-forming regions such as 30 Doradus, seen in this view from Hubble Space Telescope. Credit: NASA/ESA/F. Paresce/R. O’Connell/WFC3 (Click image to access download options from hubblesite.org). Hi-res images

Cloud Models 

Models of two turbulent clouds without stars (left) and with stars launching winds (right). The colors show gas speed: grey (6-10 km/s), blue (12-25 km/s), and red (180-250 km/s). Credit: Stella Offner/UT Austin

Magnetic Waves from a Young Star

Gas density and velocity (top) and magnetic field strength and magnetic field lines (bottom) showing magnetic waves propagating ahead of the wind shell. The left and right panels show different models. The waves stand out when the surrounding gas is not turbulent. Credit: Stella Offner/UT Austin

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New research by Stella Offner, assistant professor of astronomy at The University of Texas at Austin, finds that magnetic waves are an important factor driving the process of star formation within the enormous clouds that birth stars. Her research sheds light on the processes that are responsible for setting the properties of stars, which in turn affects the formation of planets orbiting them, and, ultimately, life on those planets. The research is published in the current issue of the journal Nature Astronomy.

Offner used a supercomputer to make models of the multitude of processes happening inside a cloud where stars are forming, in an effort to sort out which processes lead to which effects.

“These clouds are violent places,” Offner said. “It’s an extreme environment with all kinds of different physics happening at once,” including gravity and turbulence as well as radiation and winds from forming stars (called stellar feedback). The fundamental question, Offner said, is: “Why are the motions in these clouds so violent?”

Some astronomers attribute the observed motions to gravitational collapse, while others attribute it to turbulence and stellar feedback. Offner wanted to test these theories and study how stars shape their birth environment, but it’s virtually impossible to use telescope observations of these clouds to separate the influence of the various processes, she said.

“That’s why we need computer models,” Offner explained.

After comparing models of clouds with gravity, magnetic fields, and stars, Offner noticed extra motions.

 Her models showed that stellar winds interacting with the cloud magnetic field generated energy and influenced gas at far greater distances across the cloud than previously thought: These local magnetic fields caused action at a distance.

“Think of the magnetic fields like rubber bands that stretch across the cloud,” Offner said. “The winds push the field — it’s like rubber bands being plucked. The waves outrun the wind and cause distant motions.”

This research has implications for the tug-of-war between feedback — that is, the effect that the newly formed star has on its environment — and gravity on the scale of solar systems up to entire galaxies, Offner said.

As for the next step, Offner says she plans to study this process on larger scales, both in time and space. Her current study focused on one area within star-forming clouds; she said future studies will study the effects of magnetic fields and feedback on scales larger than a single cloud.

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Media Contact:

Rebecca Johnson, Communications Mgr.
McDonald Observatory
The University of Texas at Austin
512-475-6763

Science Contact:

Dr. Stella Offner, Asst. Professor
Department of Astronomy
The University of Texas at Austin
512-471-3853

Source: McDonald Observatory/News

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Herschel's hunt for filaments in the Milky Way

Left: The Aquila Rift. Credit: ESA/Herschel/SPIRE/PACS/Ph. André for the 'Gould Belt survey' Key Programme Consortium. Right: The star-forming cloud IC 5146. Credit: ESA/Herschel/SPIRE/PACS/D. Arzoumanian for the "Gould Belt survey" Key Programme Consortium 

The Orion A Molecular Cloud.  

Credit: ESA/Herschel/Ph. André, D. Polychroni, A. Roy, V. Könyves, N. Schneider for the Gould Belt survey Key Programme

 

The Polaris Flare

Credit: ESA/Herschel/SPIRE/Ph. André for the "Gould Belt survey" Key Programme Consortium and A. Abergel for the "Evolution of Interstellar Dust" Key Programme Consortium

 

Observations with ESA's Herschel space observatory have revealed that our Galaxy is threaded with filamentary structures on every length scale. From nearby clouds hosting tangles of filaments a few light-years long to gigantic structures stretching hundreds of light-years across the Milky Way's spiral arms, they appear to be truly ubiquitous. The Herschel data have rekindled the interest of astronomers in studying filaments, emphasising the crucial role of these structures in the process of star formation. 

Stars are born in the densest pockets of the interstellar medium, a diffuse mixture of gas and dust that pervades galaxies, including our Milky Way. One of the most intriguing questions in astrophysics concerns understanding how this material, which is typically characterised by very low density, can come together, creating denser concentrations that later evolve into compact cores and, finally, give birth to stars.

In the search for answers, astronomers observe giant molecular clouds, the cosmic incubators where gas and dust are transformed into stars. While these studies are performed using a variety of techniques, one crucial approach is the observation of infrared light, since the interstellar material shines brightly at these long wavelengths.

In this context, ESA's Herschel space observatory has been a true game changer. Probing the portion of the electromagnetic spectrum that ranges from the far-infrared to sub-millimetre wavelengths, it has collected unprecedented data during its three and a half years of observing. One of the key aspects that emerged from these observations is the presence of a filamentary network nearly everywhere in our Galaxy's interstellar medium. The picture that is emerging is that these structures are closely linked to the formation of stars.

Prior to Herschel, astronomers had already identified several filaments in interstellar clouds and recognised their potential importance for star formation. However, only with the increased sensitivity and spatial resolution granted by this observatory, combined with its large-scale surveys, could they reveal the full extent of filamentary patterns in the Milky Way.

One of the surveys performed with Herschel – the Gould Belt Survey – focussed on a giant ring of star-forming regions, all located no more than 1500 light-years away from the Sun. The vicinity of these clouds allowed astronomers to obtain exceptionally detailed images using Herschel, unearthing intricate webs of filaments in each region that they examined.

“The greatest surprise was the ubiquity of filaments in these nearby clouds and their intimate connection with star formation,” explains Philippe André from CEA/IRFU, France, Principal Investigator for the Herschel Gould Belt Survey.

“But there is more: these observations revealed that filaments, which may extend to several light-years in length, appear to have a universal width of about one third of a light year. This suggests that something fundamental is lurking underneath.”

The astronomers are still trying to understand the details of the star formation processes taking place in these clouds, aided by the abundance and variety of data collected with Herschel.

While most filaments are dotted with compact cores, suggesting that stars are readily taking shape in these dense 'fibres' of the interstellar medium, there are also regions that exhibit complex tangles of filaments but no signs of on-going star formation. A study of the most spectacular example of this phenomenon, the Polaris Flare, indicates that filaments must somehow precede the onset of star formation.

The scenario that has emerged from the new Herschel data suggests that star formation proceeds in two steps: first, turbulent motions of the interstellar gas and dust create an intricate web of filamentary structures; then, gravity takes over, causing only the densest filaments to contract and fragment, eventually leading to the formation of stars.

Indeed, the universal width of filaments seems to correspond, at least in the nearby clouds of the Gould Belt Survey, to the scale at which interstellar material undergoes the transition from supersonic to subsonic state.

In addition, the material along filaments is not at all static: astronomers have detected what appear to be accretion flows, with the most prominent filaments drawing matter from their surroundings through a network of smaller filaments. A striking example of such processes is seen in the Taurus Molecular Cloud, where the B211/B213 filament exhibits a series of so-called 'striations' perpendicular to the main filament.

This pattern is very similar to that predicted from numerical simulations that model the process of star formation in molecular clouds. According to these simulations, interstellar material flows towards dense filaments along routes that are parallel to the direction of the local magnetic field, as was observed, so the new data indicate the importance of interstellar magnetic fields in shaping these structures.

The B211/B213 filament in the Taurus Molecular Cloud.  

Credit: ESA/Herschel/PACS, SPIRE/Gould Belt survey Key Programme/Palmeirim et al. 2013

However, star formation does not appear to take place only in filaments. While these structures seem to be the preferred sites for stellar birth, the extraordinary data from Herschel confirmed that a small fraction of stars may also form far away from dense filaments.

In particular, a detailed study of the L1641 molecular clouds in the Orion A complex suggests that star formation along filaments is the preferential channel to produce typical solar-type stars, while stars that are born away from these dense, elongated structures tend to have lower masses. This dichotomy could be a result of the greater availability of raw material to protostars that are forming on a filament compared to those that take shape in less dense environments.

Another of Herschel's key findings is that the presence and abundance of filaments are not limited to our immediate neighbourhood. In fact, these structures appear everywhere also in the Herschel infrared Galactic Plane Survey (Hi-GAL), which scanned the distribution of the interstellar medium in the huge disc – about 100 000 light-years across – where most of the Milky Way's stars form and reside.

The filamentary structure of the Galactic Plane.  

Credit: ESA/PACS & SPIRE Consortium, S. Molinari, Hi-GAL Project

“We detected a wealth of huge filaments, with lengths ranging from a few to a hundred light-years, revealing what seems to be the 'skeleton' of our Galaxy,” explains Sergio Molinari from IAPS/INAF, Italy, Principal Investigator for the Hi-GAL Project.

“While it is possible that these structures arose from different physical processes than those giving rise to the small-scale filaments observed in the Sun's vicinity, the omnipresent aspect of filamentary structures in the Milky Way is beyond doubt.”

In the post-Herschel era, one thing is certain: filaments play a leading role in the build-up of galactic material, creating favourable hubs for the formation of stars. This is likely a hierarchical process, starting on very large scales and propagating onwards, to smaller and smaller scales, funnelling interstellar gas and dust into increasingly denser concentrations and thus fostering stellar birth across the Galaxy.

Filaments in outer regions of the Galactic Plane

Credit: ESA/Herschel/PACS, SPIRE/Hi-GAL Project/Schisano et al. 2014

Large-scale filaments fragmenting into compact cores that later evolve into stars have been detected all across the Galactic Plane, even in its outermost, peripheral regions. As filaments grow more massive, the material within them contracts and forms smaller structures, preserving the filamentary pattern on all length scales.

Further investigation of the Hi-GAL survey has revealed new and even more prominent filaments, extending over hundreds of light-years and weaving their way through the spiral arms of the Milky Way. The study revealed nine filaments in some very dense, inner regions of the Galactic Plane, detecting these for the first time through the direct emission of dust within them, allowing an accurate determination of their mass, size and physical characteristics. Astronomers believe that almost a hundred similar, gigantic structures are still hiding in the data.

Some of the most prominent filaments detected in the Milky Way: G49 (top), G47 (bottom left) and G64 (bottom right). 

Credit: ESA/Herschel/PACS/SPIRE/Ke Wang et al. 2015

“The intricate distribution of filaments in the interstellar medium revealed by Herschel has definitely revolutionised our view of how stars form in the Milky Way and, presumably, also in other similar galaxies,” comments Göran Pilbratt, ESA Herschel Project Scientist.

“An increasingly coherent picture is now emerging from combining the analysis of these data with predictions from theory and numerical simulations, as astronomers continue to study the physical processes underlying the fascinating origin of stars and planets.”

More information

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

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

Related publications  

Ph. André et al. 2010, Astronomy & Astrophysics, 518, L102
S. Molinari et al. 2010, Astronomy & Astrophysics, 518, L100
D. Arzoumanian et al. 2011, Astronomy & Astrophysics, 529, L6
D. Polychroni et al. 2013, Astrophysical Journal Letters, 777, L33
P. Palmeirim et al. 2013, Astronomy & Astrophysics, 550, A38
D. Arzoumanian et al. 2013, Astronomy & Astrophysics, 553, A119
Ph. André et al. 2014, in Protostars and Planets VI, p. 27
D. Elia et al. 2013, Astrophysical Journal, 772, 45
E. Schisano et al. 2014, Astrophysical Journal, 791, 27
K. Wang et al. 2015, Monthly Notices of the Royal Astronomical Society, 450, 4043


Contacts  

Philippe André
CEA/DSM/IRFU Service d'Astrophysique
Centre d'Etudes de Saclay
Gif-sur-Yvette Cedex, France
E-mail: pandre@cea.fr
Phone: +33-1-6908-9265

Sergio Molinari
IAPS/INAF
Roma, Italy
Email: Sergio.molinari@iaps.inaf.it
Phone: +39-06-4993-4396

Göran Pilbratt
Herschel Project Scientist
Scientific Support Office
Science and Robotic Exploration Directorate
ESA, The Netherlands
Email: gpilbratt@cosmos.esa.int
Phone: +31-71-565-3621

 Source: ESA/Herschel

A Bubbly Cosmic Celebration

PR Image eso1521a

The star forming cloud RCW 34

 

PR Image eso1521b

The star-forming cloud RCW 34 in the constellation of Vela

PR Image eso1521c

Around the star-formation region Gum 19 (RCW 34)

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Videos

 

PR Video eso1521a

Zooming in on the star forming cloud RCW 34

PR Video eso1521b

Close-up pan across the star forming cloud RCW 34

In the brightest region of this glowing nebula called RCW 34, gas is heated dramatically by young stars and expands through the surrounding cooler gas. Once the heated hydrogen reaches the borders of the gas cloud, it bursts outwards into the vacuum like the contents of an uncorked champagne bottle — this process is referred to as champagne flow. But the young star-forming region RCW 34 has more to offer than a few bubbles; there seem to have been multiple episodes of star formation within the same cloud.

This new image from ESO’s Very Large Telescope (VLT) in Chile shows a spectacular red cloud of glowing hydrogen gas behind a collection of blue foreground stars. Within RCW 34 — located in the southern constellation of Vela — a group of massive young stars hide in the brightest region of the cloud [1]. These stars have a dramatic effect on the nebula. Gas exposed to strong ultraviolet radiation — as occurs in the heart of this nebula — becomes ionised, meaning that the electrons have escaped the hydrogen atoms.

Hydrogen is treasured by cosmic photographers because it glows brightly in the characteristic red colour that distinguishes many nebulae and allows them to create beautiful images with bizarre shapes. It is also the raw material of dramatic phenomena such as champagne flow. But ionised hydrogen also has an important astronomical role: it is an indicator of star-forming regions. Stars are born from collapsing gas clouds and therefore abundant in regions with copious amounts of gas, like RCW 34. This makes the nebula particularly interesting to astronomers studying stellar birth and evolution.

Vast amounts of dust within the nebula block the view of the inner workings of the stellar nursery deeply embedded in these clouds. RCW 34 is characterised by extremely high extinction, meaning that almost all of the visible light from this region is absorbed before it reaches Earth. Despite hiding away from direct view, astronomers can use infrared telescopes, to peer through the dust and study the nest of embedded stars.

Looking behind the red colour reveals that there are a lot of young stars in this region with masses only a fraction of that of the Sun. These seem to clump around older, more massive stars at the centre, while only a few are distributed in the outskirts. This distribution has led astronomers to believe that there have been different episodes of star formation within the cloud. Three gigantic stars formed in the first event that then triggered the formation of the less massive stars in their vicinity [2].

This image uses data from the FOcal Reducer and low dispersion Spectrograph (FORS) instrument attached to the VLT, which were acquired as part of the ESO Cosmic Gems programme [3].

Notes

[1] RCW 34 is also known as Gum 19 and is centred on the brilliant young star called V391 Velorum.

[2] The most massive very bright stars have short lives — measured in millions of years — but the less massive ones have lives longer than the current age of the Universe.

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

More Information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

• ESO Cosmic Gems programme
• Photos of the Very Large Telescope
• Photos from the Very Large Telescope

Contacts

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Source: ESO

The 'Serpent' Star-forming Cloud Hatches New Stars

Within the swaddling dust of the Serpens Cloud Core, astronomers are studying one of the youngest collections of stars ever seen in our galaxy. Image credit: NASA/JPL-Caltech/2MASS. Full image and caption

Stars that are just beginning to coalesce out of cool swaths of dust and gas are showcased in this image from NASA's Spitzer Space Telescope and the Two Micron All Sky Survey (2MASS). Infrared light has been assigned colors we see with our eyes, revealing young stars in orange and yellow, and a central parcel of gas in blue. This area is hidden in visible-light views, but infrared light can travel through the dust, offering a peek inside the stellar hatchery.

The dark patch to the left of center is swaddled in so much dust, even the infrared light is blocked. It is within these dark wombs that stars are just beginning to take shape.

Called the Serpens Cloud Core, this star-forming region is located about 750 light-years away in Serpens, or the "Serpent," a constellation named after its resemblance to a snake in visible light. The region is noteworthy as it only contains stars of relatively low to moderate mass, and lacks any of the massive and incredibly bright stars found in larger star-forming regions like the Orion nebula. Our sun is a star of moderate mass. Whether it formed in a low-mass stellar region like Serpens, or a high-mass stellar region like Orion, is an ongoing mystery.

The inner Serpens Cloud Core is remarkably detailed in this image. It was assembled from 82 snapshots representing a whopping 16.2 hours of Spitzer observing time. The observations were made during Spitzer's "warm mission," a phase that began in 2009 after the observatory ran out of liquid coolant, as planned.

Most of the small dots in this image are stars located behind, or in front of, the Serpens nebula.

The 2MASS mission was a joint effort between the California Institute of Technology, Pasadena; the University of Massachusetts, Amherst; and NASA's Jet Propulsion Laboratory, also in Pasadena.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit:

http://spitzer.caltech.edu and http://www.nasa.gov/spitzer

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

UA-Led Research Maps Where Stars Are Born

Artist's conception of the Milky Way galaxy

Image: Nick Risinger

An artist's rendition of the Milky Way, overlaid with results from the survey of early star-forming clouds. Each dot represents a dark cloud of dense gas and dust in the process of collapsing to give rise to a future cluster of stars. Most of these regions map onto the galaxy's spiral arms. (Artist's rendering: R. Hurt: NASA/JPL-Caltech/SSC)

In this artist's conception, observers peer through the dark dust of a star-forming cloud to witness the birth of a star. The survey by Yancy Shirley and his group catalogued and mapped such regions in their earliest phases, when the gas and dust in the star-forming clouds are just beginning to coalesce. (Image: NASA)

A UA-led group of astronomers has completed the largest-ever survey of dense gas clouds in the Milky Way – pockets shrouded in gas and dust where new stars are being born. 

A team of astronomers led by Yancy Shirley at the University of Arizona's Steward Observatory has completed the largest-ever survey of dense gas clouds in the Milky Way – pockets shrouded in gas and dust where new stars are being born. Cataloging and mapping more than 6,000 gas clouds, the survey allows astronomers to better understand the earliest phases of star formation.

"When you look at the Milky Way on a clear summer night, you'll notice it's not a continuous stream of stars," said Shirley. "Instead, you'll notice all those little dark patches where there seem to be no stars. But those regions are not devoid of stars – they're dark clouds containing dust and gas, the raw material from which stars and planets are forming in our Milky Way today."

According to Shirley, the survey is a major step forward in astronomy because it allows astronomers to study the earliest phases of star formation when the gas and dust in the star-forming clouds are just beginning to coalesce, before giving rise to clusters of stars. He explained that much of the research over the last 30 to 40 years has been very targeted towards regions where prospective stars, called proto-stars, have already begun to take shape.

"All the famous, major regions of star formation in our galaxy have been studied in great detail," Shirley said. "But we know very little about what happens in those star-less clumps before proto-stars form, and where."

The survey provides the first unbiased map of the galaxy that shows where all those regions are throughout the galaxy, in different galactic environments and at different evolutionary stages. This helps astronomers better understand how the properties of these regions change as star formation progresses.

"Starless clumps have only been detected in small numbers to date," Shirley said. "Now, for the first time, we have seen this earliest phase of star formation, before a cluster actually forms, in large numbers in an unbiased way."

According to the UA astronomer, the star formation rate in the Milky Way was higher in the past, and currently stars form on the order of about one solar mass per year.

How long does it take to become a full-blown star? 

"That is something we hope to be able to calculate by comparing the number of sources that are in that early phase to the number of sources that are in a later phase," Shirley explained. "The ratio between the two tells you how long each phase lasts. In our survey there seem to be fewer regions that have not yet begun forming stars than those that have, which tells us the earlier phase must be shorter. If that phase lasted much longer, there should be many more of those."

Because the dense accumulations of dust are impervious to light in the visible spectrum, astronomers can't observe them with telescopes detecting light in the visible spectrum such as the Hubble Space Telescope.

"For those of us who want to study how stars form, that's a real problem because if we want to observe a young star or a cluster of stars forming in one of those dark clouds, all that dust gets in the way," said Shirley. 

However, it turns out the same dust that blocks visible light actually glows at long wavelengths, specifically radio wavelengths, which are about a million times longer than visible light. 

"Heat emanating from the young clusters of stars forming inside the clouds, combined with ambient radiation and even starlight from the surrounding galaxy, all that heats up those dust grains just a little bit above absolute zero," Shirley said. "As a result they glow, allowing us to peer inside the clouds with a radio telescope at very long wavelengths."

For their survey, which covers all parts of the galactic plane visible from the northern hemisphere, the group used the Sub-Millimeter Telescope at the Arizona Radio Observatory, equipped with a sensitive new receiver. Shirley said the proximity and accessibility of the UA-operated telescope made this project possible in the first place. 

The survey, published in The Astrophysical Journal, resulted from a group effort including Wayne Schlingman, who completed his PhD at the UA last year and is now postdoctoral researcher at the University of Colorado Boulder; Brian Svoboda, a current doctoral student in the UA's Department of Astronomy, and Tim Ellsworth-Bowers, a current doctoral student at the University of Colorado Boulder and former UA graduate.    

"Almost everybody on the team that put this all together has a connection to the UA," said Shirley, who himself graduated from the UA's department of astronomy before returning to join the faculty. Source: University of Arizona

Contacts  

Source contact:
Yancy Shirley
520-626-3666
yancyshirley@gmail.com

UANews contact:
Daniel Stolte
520-626-4402
stolte@email.arizona.edu

Source: University of Arizona

Embracing Orion

Herschel’s view of Orion A

The Orion A star-formation cloud seen by ESA’s Herschel space observatory. The Orion Nebula is located within the central bright region of this scene, where massive star formation is most intense. Cooler gas and dust is seen in red and yellow, with point-like sources the seeds of new stars.

The image is a composite of the wavelengths of 70 microns (blue), 160 microns (green) and 250 microns (red) and spans about 1.3 x 2.4 degrees. North is up and east is to the left. 

Copyright: ESA/Herschel/ Ph. André, V. Könyves, N. Schneider (CEA Saclay, France) for the Gould Belt survey Key Programme

This new view of the Orion A star-formation cloud from ESA’s Herschel space observatory shows the turbulent region of space that hugs the famous Orion Nebula. 

The nebula lies about 1500 light years from Earth within the ‘sword of Orion’ – below the three main stars that form the belt of the Orion constellation. 

In this view, the nebula corresponds to the brightest region in the centre of the image, where it is lit up by the Trapezium group of stars at its heart. 

The scene is awash with turbulent star formation, the fierce ultraviolet radiation of massive new born stars blasting away their surrounding cloudy cocoons, carving ethereal shapes into the gas and dust. 

Wispy tendrils rise like flames away from some of the most intense regions of star formation, while pillars of denser material withstand the searing blaze for longer. 

Great arms of gas and dust extend from the Orion Nebula to form a ring, while a spine of cooler material weaves up through the scene to a halo of cloudy star-formation material above.

Embedded within the red and yellow filaments are a handful of point-like sources: these are protostars, the seeds of new stars that will soon ignite and begin to flood their surrounds with intense radiation. 

The black regions to the top of the image and to the bottom right may seem like voids, but actually contain hints of much fainter emission that has not been emphasised in this image. 

The red ‘islands’ of emission in the bottom right are also a subtle trick of image processing for they are connected to the main cloud by much fainter emission. The bright ‘eyes’ in the two most distinct clouds indicates that the tip of each pillar has already collapsed and is forming stars. 

Source: ESA

Hunting high-mass stars with Herschel

Annotated image of the W3 giant molecular cloud combining Herschel bands at 70 μm (blue), 160 μm (green) and 250 μm (red). The image spans 2 x 2 degrees. North is up and east is to the left.  Copyright: ESA/PACS & SPIRE consortia, A. Rivera-Ingraham & P.G. Martin, Univ. Toronto, HOBYS Key Programme (F. Motte).  More Images

In this new view of a vast star-forming cloud called W3, ESA’s Herschel space observatory tells the story of how massive stars are born.

W3 is a giant molecular cloud containing an enormous stellar nursery, some 6200 light-years away in the Perseus Arm, one of our Milky Way Galaxy’s main spiral arms.

Spanning almost 200 light-years, W3 is one of the largest star-formation complexes in the outer Milky Way, hosting the formation of both low- and high-mass stars. The distinction is drawn at eight times the mass of our own Sun: above this limit, stars end their lives as supernovas.

Dense, bright blue knots of hot dust marking massive star formation dominate the upper left of the image in the two youngest regions in the scene: W3 Main and W3 (OH). Intense radiation streaming away from the stellar infants heats up the surrounding dust and gas, making it shine brightly in Herschel’s infrared-sensitive eyes.

Older high-mass stars are also seen to be heating up dust in their environments, appearing as the blue regions labelled AFGL 333 in the lower left of the annotated version of the image, and the loop of KR 140, at bottom right.

Extensive networks of much colder gas and dust weave through the scene in the form of red filaments and pillar-like structures. Several of these cold cores conceal low-mass star formation, hinted at by tiny yellow knots of emission. 

By studying the two regions of massive star formation – W3 Main and W3 (OH) – scientists have made progress in solving one of the major conundrums in the birth of massive stars. That is, even during their formation, the radiation blasting away from these stars is so powerful that they should push away the very material they are feeding from. If this is the case, how can massive stars form at all? 

Observations of W3 point toward a possible solution: in these very dense regions, there appears to be a continuous process by which the raw material is moved around, compressed and confined, under the influence of clusters of young, massive protostars. 

Through their strong radiation and powerful winds, populations of young high-mass stars may well be able to build and maintain localised clumps of material from which they can continue to feed during their earliest and most chaotic years, despite their incredible energy output. 

Notes for Editors

“Herschel observations of the W3 GMC: Clues to the formation of clusters of high-mass stars,” by A. Rivera-Ingraham et al., is published in The Astrophysical Journal, 766, 85; doi:10.1088/0004-637X/766/2/85.

The study was part of the Guaranteed Time Key Programme HOBYS, the Herschel imaging survey of OB Young Stellar objects. 

The image presented here was taken in three colour bands centred on 70 μm (blue), 160 μm (green) and 250 μm (red). 

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

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




Email: markus.bauer@esa.int

Alana Rivera-Ingraham
University of Toronto
Email: rivera@cita.utoronto.ca

Göran Pilbratt


ESA Herschel Project Scientist




Tel: +31 71 565 3621




Email: gpilbratt@rssd.esa.int

The curious shape of a supernova remnant in a star-forming cloud

Data from two ESA missions combine in a new view of the peculiar supernova remnant W44. The filamentary shell-like structure, detected by the Herschel Space Observatory at far-infrared wavelengths, is filled with hot gas that shines brightly in X-rays, as seen by the XMM-Newton X-ray Observatory. This composite image highlights how the complex morphology of this remnant has been shaped by its interaction with its parent molecular cloud, the star-forming region W48.

Supernova remnant W44 (Composite)

 Copyright: ESA/PACS/SPIRE/Quang Nguyen Luong & Frederique Motte, H

OBYS Key Program consortium (far-infrared); 

ESA/XMM-Newton (X-rays)

 Image Hi-Res Versions

The most massive stars end their life cycles as supernovae – spectacular explosions that release enormous amounts of energy and matter into the surrounding interstellar space. These powerful events leave behind supernova remnants, expanding clouds of hot gas and highly-energetic particles that keep shining brightly across the electromagnetic spectrum for thousands of years after the stellar explosion. Supernova remnants display a variety of shapes and features that are often heavily influenced by the environment into which the ejected material is expanding.

The supernova remnant W44 (SNR W44) is a prime example of the interaction between the remains of a supernova and the dense interstellar material around it. The composite image from Herschel and XMM-Newton illustrates that SNR W44 consists of an asymmetric expanding shell about 100 light-years across that is filled with hot, X-ray emitting gas. Around 10 000 light-years from us, SNR W44 is located in the molecular cloud complex known as W48, a rich star-forming region where a multitude of massive stars are being born.

 Annotated composite Herschel and XMM-Newton image of SNR W44

  Image Hi-Res Versions

The Herschel view of SNR W44 shows particular features of the supernova remnant interacting with its parent molecular cloud: just above the centre of the image, the shell is impacting the arc-shaped bright feature to the right. This object, known as G34.8-0.7, is an HII region – a pocket of gas that is being energised and ionised by the action of a nearby young, massive star. Traces of dust present in the HII region's gas are also being heated up, making it shine brightly at the shortest wavelengths probed by Herschel (70 microns, shown in violet in this image).

 Most supernova remnants either possess a glowing shell created by the ejecta as they sweep up interstellar material, or the remnant has a more diffuse, nebula-like structure that is usually powered by the wind of a pulsar – a spinning neutron star which originates from the core of the exploded star. SNR W44 is one of the few supernova remnants that overlaps between these two classes. It is therefore classified as a mixed-morphology supernova remnant.

The expanding shell can be seen as the large violet bubble with filamentary texture occupying the left half of the image. As the shell blasts outwards, shock waves heat up the surrounding material, raising the temperature of dust particles present there to about 100 K. This causes them to radiate at the shortest of the wavelengths probed by Herschel.

With a temperature of several million K, the hot gas inside the bubble gives off large amounts of X-rays. These appear in the image as the dark blue and light blue clouds that fill the bubble, and correspond to lower-energy (1.2-2 keV) and higher-energy (2-8 keV) X-rays detected by XMM-Newton.

Herschel image of SNR W44.
Credit: ESA/PACS/SPIRE/Quang Nguyen Luong & Frederique Motte, 

HOBYS Key Program consortium

 Image Hi-Res Versions

  XMM-Newton image of SNR W44.
Credit: ESA/XMM-Newton

Image Hi-Res Versions

As in other mixed-morphology supernova remnants, the presence of hot gas inside a shell that is expanding and cooling down is quite puzzling. One of the possible explanations is linked to the interaction between the remnant and its clumpy environment of gas and dust clouds. Dense and cool cloudlets from the surroundings could be swept over by the expanding shell and evaporate once inside it, due to the higher temperature, contributing to replenishing the remnant's interior with gas.

Also visible in SNR W44 is the pulsar PSR 1853+01, which most likely derives from the core of the supernova's progenitor star. The pulsar, which shines brightly both in X-rays and radio waves, can be seen in the XMM-Newton image as the bright point source towards the top left of the remnant. The age of the remnant was estimated by measuring how much the pulsar’s spin slows down over time and is believed to be a relatively young 20 000 years. The pulsar drives a wind of highly energetic particles but this represents only a minor contribution to the remnant's X-ray emission.

Two HII regions stand out in violet in the image, showing the intense activity of star formation in W48. These are G035.1387-00.7622 in the upper part of the image to the right, and G35.0-0.5 just to the right of the image centre. The bright flecks scattered across the image are denser clumps in the turbulent cloud medium and are the seeds of future massive stars.

In the lower left corner of the image, the diffuse glow corresponds to emission from warm dust in the Galactic Plane, the disc-like structure that contains most of the stars and star-forming clouds in our Galaxy, the Milky Way.

Fast Facts
 

Depicted object:     W44 supernova remnant (also known as 3C 392)

Additional details:     W44 is a mixed-morphology supernova remnant, hosting the pulsar PSR 1853+01; visible in the image are also the HII regions G34.8-0.7, G35.0-0.5 and G035.1387-00.7622. The sources belong to the vast molecular complex known as W48.

Constellation:     Aquila (the Eagle)

Distance:     about 10 000 light years

Image Orientation:     North is about 45 degrees clockwise of the rightward direction; East is about 45 degrees counterclockwise of the rightward direction

Image

Satellite:     Herschel

Instruments:     PACS; SPIRE

Wavelengths:     70 μm (PACS; blue); 160 μm (PACS; green); 250 μm (SPIRE; red)

Field of view:     about 1 degree across

Observation dates:     18-19 September 2010

Release date:     14 November 2012

Credit:     ESA/PACS/SPIRE/Quang Nguyen Luong & Frederique Motte, HOBYS Key Program consortium

Satellite:     XMM-Newton

Instruments:     EPIC

Energy bands:     1.2-2 keV (shown in dark blue); 2-8 keV (shown in light blue)

Field of view:     about 0.3 degrees across
Release date:     14 November 2012
Credit:     ESA/XMM-Newton

Contacts

Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int

'Elephant Trunks' in Space

NASA's Wide-field Infrared Survey Explorer, or WISE, captured this image of a star-forming cloud of dust and gas located in the constellation of Monoceros. Image credit: NASA/JPL-Caltech/UCLA. Full image and caption | Download wallpaper

NASA's Wide-field Infrared Survey Explorer, or WISE, captured this image of a star-forming cloud of dust and gas, called Sh2-284, located in the constellation of Monoceros. Lining up along the edges of a cosmic hole are several "elephant trunks" -- or monstrous pillars of dense gas and dust.

The most famous examples of elephant trunks are the "Pillars of Creation" found in an iconic image of the Eagle nebula from NASA's Hubble Space Telescope. In this WISE image, the trunks are seen as small columns of gas stretching toward the center of the void in Sh2-284, The most notable one can be seen on the right side at about the 3 o'clock position. It appears as a closed hand with a finger pointing toward the center of the void. That elephant trunk is about 7 light-years long.

Deep inside Sh2-284 resides an open star cluster, called Dolidze 25, which is emitting vast amounts of radiation in all directions, along with stellar winds. These stellar winds and radiation are clearing out a cavern inside the surrounding gas and dust, creating the void seen in the center. The bright green wall surrounding the cavern shows how far out the gas has been eroded. However, some sections of the original gas cloud were much denser than others, and they were able to resist the erosive power of the radiation and stellar winds. These pockets of dense gas remained and protected the gas "downwind" from them, leaving behind the elephant trunks.

Sh2-284 is relatively isolated at the very end of an outer spiral arm of our Milky Way galaxy. In the night sky, it's located in the opposite direction from the center of the Milky Way.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages and operates the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu and http://jpl.nasa.gov/wise .

Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

Herschel unveils rare massive stars in the act of forming

New images from ESA's Herschel space observatory reveal high-mass protostars around two ionised regions in our Galaxy. The detection of these rare stars in an early phase of evolution is key to understanding the mysterious formation of massive stars.

This is one of the many discoveries presented this week at the Herschel First Results Symposium, ESLAB 2010, held at the European Space Research and Technology Centre, Noordwijk, The Netherlands.

Massive stars are the rare birds of astrophysics. With a mass over eight times that of the Sun, these stars are much less common than their lower-mass counterparts. In addition, they are short-lived, consuming their nuclear fuel at a rapid rate before ending their life in spectacular manner as a supernova. Their scarcity means that observations of these rare giants can prove difficult to obtain, but characterising these elusive objects is essential for understanding the chemical and dynamical evolution of galaxies.

The mechanism leading to the formation of massive stars is still largely debated. Detecting these objects in their earliest phases is a highly challenging task, since they are embedded in dusty cocoons that hide them from view. However, the dust that absorbs their light re-emits it at infrared wavelengths, making an infrared observatory such as Herschel a unique tool for locating newborn massive stars in their natal nests.

RCW 120 as seen by Herschel. Credit: ESA, PACS & SPIRE Consortia, A. Zavagno (Laboratoire d'Astrophysique de Marseille) for the Herschel HOBYS and Evolution of Interstellar Dust Key Programmes

One theory that has been put forward predicts that massive stars form at the outskirts of HII regions. An HII region is a bubble of hot hydrogen gas which has been ionised by the powerful radiation emitted by a central massive star formed in a previous generation. Temperature differences between the interior (up to 10 000 Kelvin) and the surrounding material (cooler than 100 Kelvin) cause these bubbles to expand and to reach supersonic speeds. This expanding bubble sweeps up a layer of neutral material around it, which then fragments into the dense seeds of a new generation of high-mass stars.

New data from Herschel targeting two distinct HII regions in our Galaxy, namely RCW 120 and N49, yield strong evidence in favour of this scenario. Thanks to its unprecedented resolution and sensitivity over a wide range of infrared wavelengths, ESA's new space observatory has imaged, for the first time, a handful of very young, massive stars on the border of both regions. These objects, which came to life less than a few tens of thousands of years ago, have never before been observed.

"We can finally witness the long-sought-after triggered formation of massive stars," says Annie Zavagno from Laboratoire d'Astrophysique de Marseille. "The high density of the material surrounding these bubbles and the intense motions due to stellar winds might be responsible for this particularly efficient star-forming process, leading to a new population of more massive stars around them."

The 'collect and collapse' model.

Credit: Deharveng & Zavagno

"Exploiting the unique combination of PACS and SPIRE, the two cameras on board Herschel, with a total spectral coverage that extends beyond the far-infrared into the sub-millimetre, the newly released images have refined our view on the birth of stars around expanding HII regions," says Göran Pilbratt, Herschel Project Scientist. "As a result of this new data, astronomers have been able not only to spot previously undetected young stars, but also to characterise their physical properties."

Particularly striking is the discovery, around RCW 120, of a massive protostar with a mass 8-10 times larger than the Sun's. "This object appears to be surrounded by a huge envelope of about 2000 solar masses, and it will continue to grow into an even more massive fully-fledged star," adds Zavagno.

Over the course of the next few months, PACS and SPIRE will target several other galactic HII regions that exhibit evidence of triggered star formation, in order to study this process in greater detail and to shed new light on the mechanisms producing high-mass stars in our Galaxy.

Notes to Editors

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

PACS is an imaging photometer and integral field line spectrometer covering wavelengths between 57 and 210 µm. PACS was built by a consortium of institutes and university departments from across Europe, and is led by Albrecht Poglitsch of the Max-Planck-Institute for Extraterrestrial Physics, Garching, Germany. Consortium members are: Austria: UVIE; Belgium: IMEC, KUL, CSL; France: CEA, OAMP; Germany: MPE, MPIA; Italy: IFSI, OAP/OAT, OAA/CAISMI, LENS, SISSA; Spain: IAC.

The SPIRE instrument comprises an imaging photometer (camera) and an imaging spectrometer. The camera operates in three wavelength bands centred on 250, 350 and 500 μm, and so can make images of the sky simultaneously in three submillimetre “colours”. The spectrometer covers the range 200 – 670 μm, allowing the spectral features of atoms and molecules to be measured. SPIRE has been developed by a consortium of institutes led by Cardiff Univ. (UK) and including Univ. Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, Univ. Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); and Caltech, JPL, NHSC, Univ. Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC (UK); and NASA (USA). The SPIRE consortium is led by Prof. Matt Griffin of Cardiff University, United Kingdom.

The results reported here are based on a subset of observations from the following Herschel Key Programmes: HOBYS: the Herschel imaging survey of OB Young Stellar objects, led by Principal Investigator Frédérique Motte (SAp/CEA Saclay, France); Evolution of Interstellar Dust, led by Principal Investigator Alain Abergel (Institut d'Astrophysique Spatiale, IAS, France); and Hi-GAL: the Herschel Infrared Galactic Plane Survey, led by Principal Investigator Sergio Molinari (IFSI-INAF, Italy).

Related publications

Zavagno, A., et al., "Star formation triggered by the Galactic HII region RCW 120", 2010
Zavagno, A., et al., "Star formation triggered by HII regions in our Galaxy", 2010

Both papers will appear in a special issue of the journal Astronomy & Astrophysics dedicated to Herschel's first results.

Contacts

Annie Zavagno
Laboratoire d'Astrophysique de Marseille, France
Email: annie.zavagno@oamp.fr
Phone: +33-4-95-04-41-55

Göran Pilbratt, Herschel Project Scientist
Research and Scientific Support Department
Science and Robotic Exploration Directorate, ESA, The Netherlands
Email: gpilbratt@rssd.esa.int
Phone: +31-71-565-3621