Hitchhiking PAHs Caught Catching a Ride on Galactic Winds

JWST's view of the spiral galaxy IC 5332. JWST's infrared instruments are sensitive to emission from molecules called polycyclic aromatic hydrocarbons.Credit: NASA, ESA, CSA, STScI, PHANGS Team, Janice Lee (STScI), Thomas Williams (Oxford), Rupali Chandar (UToledo)

Title: JWST Discovery of Warm Dust in the Circumgalactic Medium of the Makani Galaxy
Authors: Sylvain Veilleux et al.
First Author’s Institution: University of Maryland
Status: Published in ApJ

The Windy Galaxy

Billions of light-years away lies Makani, a record-breaking galaxy discovered in 2019 by researchers at the Keck Observatory atop Maunakea, Hawaiʻi. The galaxy shows evidence of a large merger event, where two galaxies collided to form a larger galaxy. This event triggered starburst activity, or several waves of intense star formation, that changed the makeup of not just Makani, but the region around it.

There are several processes that can create galactic winds. An active supermassive black hole at the center of the galaxy can slingshot particles out of the galaxy at close to the speed of light, or supernovae leftover from previous starburst activity can help to expel material from the galaxy. Makani, whose name in Hawaiian just so happens to mean “wind,” has both factors contributing to its galactic winds: massive amounts of star formation and a very active black hole in its center.

This contributes to some of the strongest galactic winds discovered to date, stretching approximately 100 kiloparsecs (330,000 light-years) beyond the galaxy, roughly ten times the extent of a typical galactic wind. These galactic winds remove gas from the galaxy and help to enrich the circumgalactic medium around the galaxy. There is still much to discover about how galactic winds change the makeup of such galaxies, and what exactly they take with them on their way out.

Figure 1: Makani’s spectrum overlaid on top of the JWST filters. The peaks in the spectrum are PAH features that neatly overlap with JWST’s observing bands. Credit: Veilleux et al. 2025

PAHs Gone Extragalactic

Using JWST, the authors scrutinized Makani for any signs of PAHs. They found that not only did PAHs exist within the galaxy, these molecules were found up to 30 kpc (~100,000 light-years) outside the galaxy. Makani’s strong galactic winds were ejecting the dust grains from the galaxy over an estimated timescale of a billion years.

Previously, astronomers had not expected to find high quantities of dust grains outside the protection of a galaxy. The journey across a galaxy is long and hot, with temperatures in the millions of degrees. A dust grain would likely not survive the trip, as it would be destroyed by high-energy photons. This suggests that the PAHs were somehow shielded from the hotter parts of the interstellar medium and circumgalactic medium in large enough volumes to make it beyond the edge of Makani.

This answered questions about how galaxies enrich the circumgalactic medium, but it also added several more. Since today’s authors were limited by the sensitivity and range of their instruments, they were unable to confirm if there were PAHs along Makani’s entire wind structure, or just the first 35 kpc (114,000 light-years) of it. They also would like to turn their sights towards the intergalactic medium to see if PAHs could make it even farther beyond the reach of their host galaxy.

Earth’s Favorite Carcinogen: Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs, pronounced P-A-Hs or “paws”) are small flat dust grains scattered into every corner of the universe, from the atmosphere of Earth in the form of exhaust and wildfire smoke to the circumgalactic medium (the mostly empty space between galaxies). These PAHs contribute to regulating the temperature of the interstellar medium, but astronomers have long wondered how they migrate across galaxies.

Even though they are smaller than a human hair, PAHs are still easily observable even in very distant galaxies. These dust grains emit infrared light, and if there are enough PAHs in a region, they are bright enough to be observed with modern telescopes, such as JWST. By combining multiple observations across multiple filters, astronomers can calculate ratios that reveal information about the PAHs’ size, temperature, and charge, allowing reserachers to further discern properties about the regions in which these PAHs reside.

With redshifted galaxies like Makani, the light from PAHs is stretched beyond its usual wavelength, but fortunately for today’s authors, the light was stretched just enough to land known PAH features well within JWST filters, as seen in Figure 1. The authors were then able to use this information to track the distribution of these PAHs across Makani.

Original astrobite edited by Chloe Klare.

Source: American Astronomical Society/AAS-Nova

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About the author, Natalie Price:

As a first-year master’s student at Wesleyan University, I study how stellar winds interact with the local interstellar medium. Outside of the observatory, you can find me dancing, with my nose in a book, or running at non-relativistic speeds.

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Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at  astrobites.org.

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Astronomy’s dirty window to space

Visualization of the wavelength-dependence of extinction (the “extinction curve”) caused by dust, for the plane of our galaxy’s disk, out to a distance of 8,000 light-years from the Sun. Red indicates regions where extinction falls off more rapidly at long wavelengths (the red end of the spectrum), while blue indicates that extinction is less dependent on wavelength. Regions with insufficient data are shown in white. The gray contours enclose regions of high dust density. © X. Zhang/G. Green, MPIA

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Astronomers from the Max Planck Institute for Astronomy have constructed the first detailed 3D map of the properties of cosmic dust in our home galaxy. For their map, the astronomers used 130 million spectra from ESA’s Gaia mission, results from the LAMOST spectral survey, and machine learning. Dust makes distant astronomical objects appear more reddish and dimmer than they really are, so the new map will be an important tool for astronomers to make sense of their observations. The study has also revealed unusual properties of cosmic dust that will lead to further research.

When we observe distant celestial objects, there is a possible catch: Is that star I am observing really as reddish as it appears? Or does the star merely look reddish, since its light has had to travel through a cloud of cosmic dust to reach our telescope? For accurate observations, astronomers need to know the amount of dust between them and their distant targets. Not only does dust make objects appear reddish (“reddening”), it also makes them appear fainter than they really are (“extinction”). It’s like we are looking out into space through a dirty window. Now, two astronomers have published a 3D map that documents the properties of dust all around us in unprecedented detail, helping us make sense of what we observe.

Behind this is the fact that, fortunately, when looking at stars, there is a way of reconstructing the effect of dust. Cosmic dust particles do not absorb and scatter light evenly across all wavelengths. Instead, they absorb light more strongly at shorter wavelengths (towards the blue end of the spectrum), and less strongly at longer wavelengths (towards the red end). The wavelength-dependence can be plotted as an “extinction curve,” and its shape provides information not only about the composition of the dust, but also about its local environment, such as the amount and properties of radiation in the various regions of interstellar space.

Retrieving dust information from 130 million spectra

This is the kind of information used by Xiangyu Zhang, a PhD student at the Max Planck Institute for Astronomy (MPIA), and Gregory Green, an independent research group leader (Sofia Kovalevskaja Group) at MPIA and Zhang’s PhD advisor, to construct the most detailed 3D map yet of the properties of dust in the Milky Way galaxy. Zhang and Green turned to data from ESA’s Gaia mission, which was a 10.5-year-effort to obtain extremely accurate measurements of positions, motions and additional properties for more than a billion stars in our Milky Way and in our nearest galactic neighbours, the Magellanic Clouds. The third data release (DR3) of the Gaia mission, published in June 2022, provides 220 million spectra, and a quality check told Zhang and Green that about 130 million of those would be suitable for their search for dust.

The Gaia spectra are low-resolution, that is, the way that they separate light into different wavelength regions is comparatively coarse. The two astronomers found a way around that limitation: For 1% of their chosen stars, there is high-resolution spectroscopy from the LAMOST survey operated by the National Astronomical Observatories of China. This provides reliable information about the basic properties of the stars in question, such as their surface temperatures, which determines what astronomers call a star’s “spectral type.” Reconstructing a 3D map

Zhang and Green trained a neural network to generate model spectra based on a star’s properties and the properties of the intervening dust. They compared the results to 130 million suitable spectra from Gaia, and used statistical (“Bayesian”) techniques to deduce the properties of the dust between us and those 130 million stars.

The results allowed the astronomers to reconstruct the first detailed, three-dimensional map of the extinction curve of dust in the Milky Way. This map was made possible by Zhang and Green’s measurement of the extinction curve towards an unprecedented number of stars – 130 million, compared to previous works, which contained approximately 1 million measurements.

But dust is not just a nuisance for astronomers. It is important for star formation, which occurs in giant gas clouds shielded by their dust from the surrounding radiation. When stars form, they are surrounded by disks of gas and dust, which are the birthplaces of planets. The dust grains themselves are the building blocks for what will eventually become the solid bodies of planets like our Earth. In fact, within the interstellar medium of our galaxy, most of the elements heavier than hydrogen and helium are locked up in interstellar dust grains.

Unexpected properties of cosmic dust

The new results not only produce an accurate 3D map. They have also turned up a surprising property of interstellar dust clouds. Previously, it had been expected that the extinction curve should become flatter (less dependent on wavelength) for regions with a higher dust density. “Higher density,” of course, is in this case still very little: approximately ten billionth billionth grams of dust per cubic meter, equivalent to just 10 kg of dust in a sphere with Earth’s radius. In such regions, dust grains tend to grow in size, which changes the overall absorption properties.

Instead, the astronomers found that in areas of intermediate density, the extinction curve actually becomes steeper, with smaller wavelengths absorbed much more effectively than longer ones. Zhang and Green surmise that the steepening might be caused by the growth not of dust, but of a class of molecules called polycyclic aromatic hydrocarbons (PAHs), the most abundant hydrocarbons in the interstellar medium, which may even have played a role in the origin of life. They have already set out to test their hypothesis with future observations.

Background information

The results reported here have been published as Xiangyu Zhang and Gregory M. Green, “Three-dimensional maps of the interstellar dust extinction curve within the Milky Way galaxy,” in the journal Science. Both authors work at the Max Planck Institute for Astronomy.

Source: Max Planck for Radio Astronomy/News

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Contacts: 

Dr. Markus Pössel
tel: +49 6221 528-261
pr@mpia.de
MPIA press department
Max Planck Institute for Astronomy, Heidelberg

Dr. Gregory Green
Sofia Kovalevskaja Group Leader
tel: +49 6221 528-460
green@mpia.de
Gregory Green / MPIA
Max-Planck-Institut für Astronomie, Heidelberg, Deutschland

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Original publication

Xiangyu Zhang, Gregory M. Green
Three-dimensional maps of the interstellar dust extinction curve within the Milky Way galaxy
Science (2025). DOI: 10.1126/science.ado9787
Preprint available at: https://www.eurekalert.org/press/scipak/

Download

• mpia-pm_green_figure_notext 175.53 kB
• mpia-pm_green_figure_withtext 469.75 kB

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Astronomers Discover New Building Blocks of Complex Organic Matter

Credit: NSF/NSF NRAO/AUI/S. Dagnello

CfA scientists help detect a new molecule in interstellar space as list of identified complex molecules grows

The element carbon is a building block for life, both on Earth and potentially elsewhere in the vast reaches of space. There should be a lot of carbon in space, but surprisingly, it's not always easy to find.

While it can be observed in many places, it doesn’t add up to the volume astronomers would expect to see. The discovery of a new, complex molecule (1-cyanopyrene), challenges expectations about where the building blocks for carbon are found and how they evolve.

Astronomers have long understood that certain carbon-rich stars are soot factories that release copious quantities of small molecular sheets of carbon into the interstellar medium. Scientists thought, however, that these types of carbon-rich molecules could neither survive the harsh conditions of interstellar space nor be re-formed there by combustion-like chemistry because the temperature is far too low.

Researchers from the Center for Astrophysics | Harvard & Smithsonian (CfA) helped lead this research. A paper describing these results was published today in the journal Science.

“Our detection of 1-cyanopyrene gives us important new information about the chemical origin and fate of carbon -- the single most important element to complex chemistry both on Earth and in space,” said Bryan Changala of the CfA, a co-author of the Science paper.

The 1-cyanopyrene molecule is made up of multiple fused benzene rings. It belongs to a class of compounds known as Polycyclic Aromatic Hydrocarbons (PAHs), which were previously believed to form only at high temperatures in regions with lots of energy, like the environments surrounding aging stars. On Earth, PAHs are found in burning fossil fuels, and as char marks on grilled food.

Astronomers study PAHs not just to learn about their particular lifecycle, but to learn more about how they interact with and reveal more about the interstellar medium (ISM) and celestial bodies around them. PAHs are believed to be responsible for the unidentified infrared bands observed in many astronomical objects. These bands arise from the infrared fluorescence of PAHs after they absorb ultraviolet (UV) photons from stars. The intensity of these bands reveal PAHs could account for a significant fraction of carbon in the ISM.

However, the newly observed 1-cyanopyrene molecules were found in Taurus Molecular Cloud-1 (TMC-1), a cold interstellar cloud. Located in the Taurus constellation, TMC-1 has not yet begun forming stars, and the temperature is only about 10 degrees above absolute zero.

“TMC-1 is a natural laboratory for studying these molecules that go on to form the building blocks of stars and planets,” said Gabi Wenzel, a postdoctoral fellow at the Massachusetts Institute of Technology who led the lab work and is the first author on the Science paper.

“These are the largest molecules we’ve found in TMC-1 to date. This discovery pushes the boundaries of our understanding of the complexity of molecules that can exist in interstellar space,” said co-author Brett McGuire, an Assistant Professor of Chemistry at MIT and an adjunct astronomer at the National Science Foundation (NSF) National Radio Astronomy Observatory (NRAO).

Astronomers used the NSF Green Bank Telescope, the largest fully steerable radio telescope in the world, to discover 1-cyanopyrene. Every molecule has a unique rotational spectrum, like a fingerprint, which allows for its identification. However, their large size and lack of a permanent dipole moment, can make some PAHs difficult – or even impossible – to detect. The observations of cyanopyrene can provide indirect evidence for the presence of even larger and more complex molecules in future observations.

“Identifying the unique rotational spectrum of 1-cyanopyrene required the work of an interdisciplinary scientific team,” explains co-author Harshal Gupta, NSF Program Director for the Green Bank Observatory and Research Associate at the CfA. “This discovery is a great illustration of synthetic chemists, spectroscopists, astronomers, and modelers working closely and harmoniously.”

This research combined the expertise of astronomy and chemistry with measurements and analysis conducted in the molecular spectroscopy laboratory of Dr. Michael McCarthy at the CfA.

“The microwave spectrometers developed at the CfA are unique, world-class instruments specifically designed to measure the precise radio fingerprints of complex molecules like 1-cyanopyrene,” said McCarthy. “Predictions from even the most advanced quantum chemical theories are still thousands of times less accurate than what is needed to identify these molecules in space with radio telescopes, so experiments in laboratories like ours are indispensable to these ground-breaking astronomical discoveries."

Source: Harvard-Smithsonian Center for Astrophysics (CfA)/News Release

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Media Contact:

Megan Watzke
Interim CfA Public Affairs Officer
Center for Astrophysics | Harvard & Smithsonian
617-496-7998
mwatzke@cfa.harvard.edu

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About the Center for Astrophysics | Harvard & Smithsonian

The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask—and ultimately answer—humanity's greatest unresolved questions about the nature of the universe. The Center for Astrophysics is headquartered in Cambridge, MA, with research facilities across the U.S. and around the world.

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NASA's Webb Probes an Extreme Starburst Galaxy

M82 (Hubble and Webb)
Credit: Image: NASA, ESA, CSA, STScI, Alberto Bolatto (UMD)

M82 (NIRCam Image)
Credit: Image: NASA, ESA, CSA, STScI, Alberto Bolatto (UMD)

M82 (NIRCam Image)
Credit: Image: NASA, ESA, CSA, STScI, Alberto Bolatto (UMD)

Images

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A team of astronomers has used NASA’s James Webb Space Telescope to survey the starburst galaxy Messier 82 (M82). Located 12 million light-years away in the constellation Ursa Major, this galaxy is relatively compact in size but hosts a frenzy of star formation activity. For comparison, M82 is sprouting new stars 10 times faster than the Milky Way galaxy.

Led by Alberto Bolatto at the University of Maryland, College Park, the team directed Webb’s NIRCam (Near-Infrared Camera) instrument toward the starburst galaxy’s center, attaining a closer look at the physical conditions that foster the formation of new stars.

“M82 has garnered a variety of observations over the years because it can be considered as the prototypical starburst galaxy,” said Bolatto, lead author of the study. “Both NASA’s Spitzer and Hubble space telescopes have observed this target. With Webb’s size and resolution, we can look at this star-forming galaxy and see all of this beautiful, new detail.”

A Vibrant Community of Stars

Star formation continues to maintain a sense of mystery because it is shrouded by curtains of dust and gas, creating an obstacle in observing this process. Fortunately, Webb’s ability to peer in the infrared is an asset in navigating these murky conditions. Additionally, these NIRCam images of the very center of the starburst were obtained using an instrument mode that prevented the very bright source from overwhelming the detector.

While dark brown tendrils of heavy dust are threaded throughout M82’s glowing white core even in this infrared view, Webb’s NIRCam has revealed a level of detail that has historically been obscured. Looking closer toward the center, small specks depicted in green denote concentrated areas of iron, most of which are supernova remnants. Small patches that appear red signify regions where molecular hydrogen is being lit up by a nearby young star’s radiation.

“This image shows the power of Webb,” said Rebecca Levy, second author of the study at the University of Arizona in Tucson. “Every single white dot in this image is either a star or a star cluster. We can start to distinguish all of these tiny point sources, which enables us to acquire an accurate count of all the star clusters in this galaxy.”

Finding Structure in Lively Conditions

Looking at M82 in slightly longer infrared wavelengths, clumpy tendrils represented in red can be seen extending above and below the galaxy’s plane. These gaseous streamers are a galactic wind rushing out from the core of the starburst.

One area of focus for this research team was understanding how this galactic wind, which is caused by the rapid rate of star formation and subsequent supernovae, is being launched and influencing its surrounding environment. By resolving a central section of M82, scientists could examine where the wind originates, and gain insight on how hot and cold components interact within the wind.

Webb’s NIRCam instrument was well-suited to trace the structure of the galactic wind via emission from sooty chemical molecules known as polycyclic aromatic hydrocarbons (PAHs). PAHs can be considered as very small dust grains that survive in cooler temperatures but are destroyed in hot conditions.

Much to the team’s surprise, Webb’s view of the PAH emission highlights the galactic wind’s fine structure – an aspect previously unknown. Depicted as red filaments, the emission extends away from the central region where the heart of star formation is located. Another unanticipated find was the similar structure between the PAH emission and that of hot, ionized gas.

“It was unexpected to see the PAH emission resemble ionized gas,” said Bolatto. “PAHs are not supposed to live very long when exposed to such a strong radiation field, so perhaps they are being replenished all the time. It challenges our theories and shows us that further investigation is required.”

Lighting a Path Forward

Webb’s observations of M82 in near-infrared light spur further questions about star formation, some of which the team hopes to answer with additional data gathered with Webb, including that of another starburst galaxy. Two other papers from this team characterizing the stellar clusters and correlations among wind components of M82 are almost finalized.

In the near future, the team will have spectroscopic observations of M82 from Webb ready for their analysis, as well as complementary large-scale images of the galaxy and wind. Spectral data will help astronomers determine accurate ages for the star clusters and provide a sense of timing for how long each phase of star formation lasts in a starburst galaxy environment. On a broader scale, inspecting the activity in galaxies like M82 can deepen astronomers’ understanding of the early universe.

“Webb’s observation of M82, a target closer to us, is a reminder that the telescope excels at studying galaxies at all distances,” said Bolatto. “In addition to looking at young, high-redshift galaxies, we can look at targets closer to home to gather insight into the processes that are happening here – events that also occurred in the early universe.”

These findings have been accepted for publication in The Astrophysical Journal.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Source: NASA's James Webb Space Telescope/News

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About This Release

Credits:

Media Contact:

Abigail Major
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Science: Alberto Bolatto (UMD)

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team

Related Links and Documents

• The science paper by A. Bolatto et al.
• The Max Planck Institute for Astronomy Press Release

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“Kitchen Smoke” Molecules in Nebula Offer Clues to the Building Blocks of Life

Combination of three color images of NGC 7023 from SOFIA (red & green) and Spitzer (blue) show different populations of PAH molecules. Credits: NASA/DLR/SOFIA/B. Croiset, Leiden Observatory, and O. Berné, CNRS; NASA/JPL-Caltech/Spitzer.

Using data collected by NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) and other observatories, an international team of researchers has studied how a particular type of organic molecules, the raw materials for life – could develop in space. This information could help scientists better understand how life could have developed on Earth.

Bavo Croiset of Leiden University in the Netherlands and his collaborators focused on a type of molecule called polycyclic aromatic hydrocarbons (PAHs), which are flat molecules consisting of carbon atoms arranged in a honeycomb pattern, surrounded by hydrogen. PAHs make up about 10 percent of the carbon in the universe, and are found on the Earth where they are released upon the burning of organic material such as meat, sugarcane, wood etc.  Croiset’s team determined that when PAHs in the nebula NGC 7023, also known as the Iris Nebula, are hit by ultraviolet radiation from the nebula’s central star, they evolve into larger, more complex molecules. Scientists hypothesize that the growth of complex organic molecules like PAHs is one of the steps leading to the emergence of life.

Some existing models predicted that the radiation from a newborn, nearby massive star would tend to break down large organic molecules into smaller ones, rather than build them up. To test these models, researchers wanted to estimate the size of the molecules at various locations relative to the central star.

Croiset’s team used SOFIA to observe Nebula NGC 7023 with two instruments, the FLITECAM near-infrared camera and the FORCAST mid-infrared camera. SOFIA’s instruments are sensitive to two wavelengths that are produced by these particular molecules, which can be used to estimate their size. The team analyzed the SOFIA images in combination with data previously obtained by the Spitzer infrared space observatory, the Hubble Space Telescope and the Canada-France-Hawaii Telescope on the Big Island of Hawaii.

The analysis indicates that the size of the PAH molecules in this nebula vary by location in a clear pattern. The average size of the molecules in the nebula’s central cavity, surrounding the illuminating star, is larger than on the surface of the cloud at the outer edge of the cavity.

In a paper published in Astronomy and Astrophysics, The team concluded that this molecular size variation is due both to some of the smallest molecules being destroyed by the harsh ultraviolet radiation field of the star, and to medium-sized molecules being irradiated so they combine into larger molecules. Researchers were surprised to find that the radiation resulted in net growth, rather than destruction.

“The success of these observations depended on both SOFIA’s ability to observe wavelengths inaccessible from the ground, and the large size of its telescope, which provided a more detailed map than would have been possible with smaller telescopes,” said Olivier Berné at CNRS, the National Center for Scientific Research in Toulouse, France, one of the published paper’s co-authors.

For more information on SOFIA, go to: www.nasa.gov/sofia

For more information SOFIA Science, go to: https://www.sofia.usra.edu/

Dr. Dana Backman
SOFIA Science Center, NASA Ames Research Center, Moffett Field, California

Kassandra Bell
SOFIA Science Center, NASA Ames Research Center, Moffett Field, California

Editor: Kassandra Bell

Source: NASA/SOFIA

Citizen Scientists Discover Yellow "Space Balls"

 A new ScienceCast video examines "yellow balls" and their role in star formation.

Play it

Citizen scientists scanning images from NASA’s Spitzer Space Telescope, an orbiting infra-red observatory, recently stumbled upon a new class of curiosities that had gone largely unrecognized before: yellow balls. 

"The volunteers started chatting about the yellow balls they kept seeing in the images of our galaxy, and this brought the features to our attention," said Grace Wolf-Chase of the Adler Planetarium in Chicago. 

The rounded features captured by the telescope, of course, are not actually yellow, red, or green—they just appear that way in the infrared, color-assigned images that the telescope sends to Earth. The false colors provide a way to humans to talk about infrared wavelengths of light their eyes cannot actually see. 

"With prompting by the volunteers, we analyzed the yellow balls and figured out that they are a new way to detect the early stages of massive star formation," said Charles Kerton of Iowa State University, Ames. "The simple question of 'Hmm, what's that?' led us to this discovery." 

A thorough analysis by the team led to the conclusion that the yellow balls precede the green bubbles, representing a phase of star formation that takes place before the bubbles form. 

"Basically, if you wind the clock backwards from the bubbles, you get the yellow balls," said Kerton. 

An artist's concept shows how "yellow balls" fit into the process of star formation

Researchers think the green bubble rims are made largely of organic molecules called polycyclic aromatic hydrocarbons (PAHs). PAHs are abundant in the dense molecular clouds where stars coalesce. Blasts of radiation and winds from newborn stars push these PAHs into a spherical shells that look like green bubbles in Spitzer's images. The red cores of the green bubbles are made of warm dust that has not yet been pushed away from the windy stars. 

How do the yellow balls fit in? 

"The yellow balls are a missing link," says Wolf-Chase. They represent a transition "between very young embryonic stars buried in dense, dusty clouds and slightly older, newborn stars blowing the bubbles." 

Essentially, the yellow balls mark places where the PAHs (green) and the dust (red) have not yet separated. The superposition of green and red makes yellow. 

So far, the volunteers have identified more than 900 of these compact, yellow features.  The multitude gives researchers plenty of chances to test their hypotheses and learn more about the way stars form. 

Meanwhile, citizen scientists continue to scan Spitzer's images for new finds. Green bubbles.  Red cores.  Yellow balls.  What's next?  You could be the one who makes the next big discovery.  To get involved, go to zooniverse.org and click on "The Milky Way Project." 

Credits:

Author: Rachel Molina

 Production editor: Dr. Tony Phillips 

Credit: Science@NASA

Source: NASA/Science News

Citizen Scientists Lead Astronomers to Mystery Objects in Space

Volunteers using the web-based Milky Way Project brought star-forming features nicknamed "yellowballs" to the attention of researchers, who later showed that they are a phase of massive star formation. Image credit: NASA/JPL-Caltech.   › Full image and caption

This series of images show three evolutionary phases of massive star formation, as pictured in infrared images from NASA's Spitzer Space Telescope. Image credit: NASA/JPL-Caltech.  › Full image and caption

Sometimes it takes a village to find new and unusual objects in space. Volunteers scanning tens of thousands of starry images from NASA's Spitzer Space Telescope, using the Web-based Milky Way Project, recently stumbled upon a new class of curiosities that had gone largely unrecognized before: yellow balls. The rounded features are not actually yellow -- they just appear that way in the infrared, color-assigned Spitzer images. 

"The volunteers started chatting about the yellow balls they kept seeing in the images of our galaxy, and this brought the features to our attention," said Grace Wolf-Chase of the Adler Planetarium in Chicago. A colorful, 122-foot (37-meter) Spitzer mosaic of the Milky Way hangs at the planetarium, showcasing our galaxy's bubbling brew of stars. The yellow balls in this mosaic appear small but are actually several hundred to thousands of times the size of our solar system.

"With prompting by the volunteers, we analyzed the yellow balls and figured out that they are a new way to detect the early stages of massive star formation," said Charles Kerton of Iowa State University, Ames. "The simple question of 'Hmm, what's that?' led us to this discovery." Kerton is lead author, and Wolf-Chase a co-author, of a new study on the findings in the Astrophysical Journal.

The Milky Way Project is one of many so-called citizen scientist projects making up the Zooniverse website, which relies on crowdsourcing to help process scientific data. So far, more than 70 scientific papers have resulted from volunteers using Zooniverse, four of which are tied to the Milky Way Project. In 2009, volunteers using a Zooniverse project called Galaxy Zoo began chatting about unusual objects they dubbed "green peas." Their efforts led to the discovery of a class of compact galaxies that churned out extreme numbers of stars.

In the Milky Way Project, volunteers scan through images that Spitzer took of the thick plane of our galaxy, where newborn stars are igniting in swaths of dust. The infrared wavelengths detected by Spitzer have been assigned visible colors we can see with our eyes. In addition to the yellow balls, there are many green bubbles with red centers, populating a landscape of swirling gas and dust. These bubbles are the result of massive newborn stars blowing out cavities in their surroundings. The green bubble rims are made largely of organic molecules called polycyclic aromatic hydrocarbons (PAHs), cleared away by blasts of radiation and winds from the central star. Dust warmed by the star appears red in the center of the bubbles.

Volunteers have classified more than 5,000 of these green bubbles using the project's Web-based tools. When they started reporting that they were finding more reoccurring features in the shape of yellow balls, the Spitzer researchers took note and even named the features accordingly. In astronomy and other digital imaging, yellow represents areas where green and red overlap. So what are these yellow balls? 

A thorough analysis by the team led to the conclusion that the yellow balls precede the green bubble features, representing a phase of star formation that takes place before the bubbles form.

"The yellow balls are a missing link," said Wolf-Chase, "between the very young embryonic stars buried in dark filaments and newborn stars blowing the bubbles."

"If you wind the clock backwards from the bubbles, you get the yellow ball features," said Kerton. 

The researchers explained why the yellow balls appear yellow: The PAHs, which appear green in the Spitzer images, haven't been cleared away by the winds from massive stars yet, so the green overlaps with the warm dust, colored red, to make yellow. The yellow balls are compact because the harsh effects of the massive star have yet to fully expand into their surroundings.

So far, the volunteers have identified more than 900 of these compact yellow features. The next step for the researchers is to look at their distribution. Many appear to be lining the rims of the bubbles, a clue that perhaps the massive stars are triggering the birth of new stars as they blow the bubbles, a phenomenon known as triggered star formation. If the effect is real, the researchers should find that the yellow balls statistically appear more often with bubble walls.

"These results attest to the importance of citizen scientist programs," said Wolf-Chase. Kerton added, "There is always the potential for serendipitous discovery that makes citizen science both exciting for the participants and useful to the professional astronomer."

NASA's Jet Propulsion Laboratory, Pasadena, California, 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

Media Contact


Whitney Clavin
Jet Propulsion Laboratory, Pasadena, California
818-354-4673  

Email:  whitney.clavin@jpl.nasa.gov

Source: JPL-Caltech - News

  

Need to Track Organic Nano-Particles Across the Universe? NASA's Got an App for That

Image of a nebula taken by NASA’s Spitzer Space Telescope.

Image Credit: NASA/Jet Propulsion Laboratory

 

Scientists at NASA's Ames Research Center in Moffett Field, Calif., today released a significant expansion and upgrade to a public, online database that houses a unique and extensive collection of information about a family of complex, carbon-rich molecules that are both widespread and abundant throughout the universe. Scientists believe more than 20 percent of the carbon in the universe is tied up in this extensive family of compounds, collectively know as polycyclic aromatic hydrocarbons, or simply PAHs.

Using the Ames-developed PAH Infrared Spectroscopic Database, scientists will now have access to data on hundreds more compounds and several powerful new tools –including an advanced web app and a dedicated astronomical software package – to map the distribution of this life-essential element and track its role across the universe.

"Analyzing the PAH emission bands with the web app, new tools, and expanded database provides a powerful new way for astronomers to trace the evolution of cosmic carbon and, at the same time, probe conditions across the universe,” said Christiaan Boersma, a research fellow at Ames who designed and developed many parts of the web app and tools. "We have expanded the computational spectral collection to 700 spectra, including those of extremely large PAHs composed of hundreds of carbon atoms, and the experimental collection to 75 spectra."

Over the past 20 years, NASA scientists experimentally measured and computed PAH spectroscopic signatures to track and analyze the unexpected, widespread PAH emission originating from deep space. NASA made the original collection of spectra and accompanying software available online four years ago.

The approach of analyzing the infrared spectra emitted by everything from dying stars to clouds of gas and dust to entire galaxies using the one-two punch of known PAH spectra and the new, blind, algorithm-driven codes now available, provides a unique look into the evolution of cosmic PAHs.

In addition to substantially increasing the number of spectra available, the new version of the database includes powerful, astronomer-friendly tools that mimic the PAHs’ response to the local space environment and makes it possible to understand which types of PAHs are present in different regions of space. It also allows astronomers to tie these evolutionary changes to variations in local conditions such as those due to the radiation field, physical shape and history of the region.

"PAHs are so widespread and abundant in space that they don't just witness the conditions in their cosmic neighborhoods, they are active participants in many astronomical phenomena," said Louis Allamandola, an astrophysics researcher at Ames. "PAHs both are an important source of carbon for young, primordial planets, and influence how quickly they can form. For example, very bright PAH emission comes from places where new stars and exo-planets are forming."

NASA's Spitzer Space Telescope managed and operated by NASA's Jet Propulsion Laboratory in Pasadena, Calif., detected the PAH signature across the universe and showed PAHs were already forming only a couple of billion years after the Big Bang. Because their spectral signature is very sensitive to their local environment, especially radiation levels, the temperatures of PAHs in space can vary from nearly minus 450 degrees Fahrenheit to roughly 1,000 degrees, after which they break apart.

“Since PAHs are so sensitive to local conditions, analyzing the PAH bands as we did here represents a powerful new astronomical tool to trace the evolution of cosmic carbon and, at the same time, probe conditions in objects spanning the universe,” said Allamandola.

The upgraded database allows scientists to determine how the PAH signature changes across this vast range of temperatures. Astronomers need simply to upload the spectra of their favorite celestial object into the website and see which PAH classes are needed to reproduce their spectra.

"This capability is a major step forward because it allows astronomers to directly tie their astronomical spectra to the spectra of individual, bona-fide PAHs, not generic, model dependent, mythical, cosmic material," said Allamandola. "And they can do all this on their mobile devices like iPads and iPhones, as well as personal computers."

PAHs in space are probably made the same way soot is made in the combustion engines that power trucks and cars here on Earth. In addition to astronomical applications, the expanded PAH database and powerful new software also is a useful research tool for scientists, educators, policy makers, and consultants working in the fields of medicine, health, chemistry, fuel composition, engine design, environmental assessment, environmental monitoring and protection, and nanotechnology.

This work was supported by NASA's Astrobiology and Laboratory Astrophysics Programs and Carbon in the Galaxy Consortium under the auspices of the Astrophysics Research and Analysis Program.

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Rachel Hoover
NASA's Ames Research Center, Moffett Field, Calif.