How to Shape a Spiral Galaxy

Magnetic fields in NGC 1086, or M77, are shown as streamlines over a visible light and X-ray composite image of the galaxy from the Hubble Space Telescope, the Nuclear Spectroscopic Array, and the Sloan Digital Sky Survey. The magnetic fields align along the entire length of the massive spiral arms — 24,000 light years across (0.8 kiloparsecs) — implying that the gravitational forces that created the galaxy’s shape are also compressing the its magnetic field. This supports the leading theory of how the spiral arms are forced into their iconic shape known as “density wave theory.” SOFIA studied the galaxy using far-infrared light (89 microns) to reveal facets of its magnetic fields that previous observations using visible and radio telescopes could not detect. Credits: NASA/SOFIA; NASA/JPL-Caltech/Roma Tre Univ. Hi-res image

Our Milky Way galaxy has an elegant spiral shape with long arms filled with stars, but exactly how it took this form has long puzzled scientists. New observations of another galaxy are shedding light on how spiral-shaped galaxies like our own get their iconic shape.

Magnetic fields play a strong role in shaping these galaxies, according to research from the Stratospheric Observatory for Infrared Astronomy, or SOFIA. Scientists measured magnetic fields along the spiral arms of the galaxy called NGC 1068, or M77. The fields are shown as streamlines that closely follow the circling arms.

“Magnetic fields are invisible, but they may influence the evolution of a galaxy,” said Enrique Lopez-Rodriguez, a Universities Space Research Association scientist at the SOFIA Science Center at NASA’s Ames Research Center in California’s Silicon Valley. “We have a pretty good understanding of how gravity affects galactic structures, but we’re just starting to learn the role magnetic fields play.”

The M77 galaxy is located 47 million light years away in the constellation Cetus. It has a supermassive active black hole at its center that is twice as massive as the black hole at the heart of our Milky Way galaxy. The swirling arms are filled with dust, gas and areas of intense star formation called starbursts.

SOFIA’s infrared observations reveal what human eyes cannot: magnetic fields that closely follow the newborn-star-filled spiral arms. This supports the leading theory of how these arms are forced into their iconic shape known as “density wave theory.” It states that dust, gas and stars in the arms are not fixed in place like blades on a fan. Instead, the material moves along the arms as gravity compresses it, like items on a conveyor belt.

The magnetic field alignment stretches across the entire length of the massive, arms — approximately 24,000 light years across. This implies that the gravitational forces that created the galaxy’s spiral shape are also compressing its magnetic field, supporting the density wave theory. The results are published in the Astrophysical Journal. 

“This is the first time we’ve seen magnetic fields aligned at such large scales with current star birth in the spiral arms,” said Lopez-Rodriquez. “It’s always exciting to have observational evidence that supports theories.”

Celestial magnetic fields are notoriously difficult to observe. SOFIA’s newest instrument, the High-resolution Airborne Wideband Camera-Plus, or HAWC+, uses far-infrared light to observe celestial dust grains, which align perpendicular to magnetic field lines. From these results, astronomers can infer the shape and direction of the otherwise invisible magnetic field. Far-infrared light provides key information about magnetic fields because the signal is not contaminated by emission from other mechanisms, such as scattered visible light and radiation from high-energy particles. SOFIA’s ability to study the galaxy with far infrared light, specifically at the wavelength of 89 microns, revealed previously unknown facets of its magnetic fields.

Further observations are necessary to understand how magnetic fields influence the formation and evolution of other types of galaxies, such as those with irregular shapes.

SOFIA, the Stratospheric Observatory for Infrared Astronomy, 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 Building 703, in Palmdale, California. The HAWC+ instrument was developed and delivered to NASA by a multi-institution team led by the Jet Propulsion Laboratory in Pasadena, California.

Media Contact


Felicia Chou
NASA Headquarters, Washington
202-358-0257
felicia.chou@nasa.gov

Editor: Kassandra Bell

Source: NASA/SOFIA

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Black Hole or Newborn Stars? SOFIA Finds Galactic Puzzle

Artist’s concept of a jet from an active black hole that is perpendicular to the host galaxy (left) compared to a jet that is launching directly into the galaxy (right) illustrated over an image of a spiral galaxy from the Hubble Space Telescope. SOFIA found a strange black hole with jets that are irradiating the host galaxy, called HE 1353-1917. The galaxy has 10 times more ionized carbon than its stars could produce. The gas, illustrated in blue in the right image, is concentrated near the galaxy’s center, which indicates that the intense radiation from the black hole’s jet is the source of the excess gas. This contradicts the long-held assumption that ionized carbon primarily indicates the presence of newborn stars, and forces scientists to reevaluate the effect black holes have on galaxies. Credits: ESA/Hubble&NASA and NASA/SOFIA/L. Proudfit

Even celestial objects can seem like they're playing tricks. In a new study, scientists are puzzled by a black hole that seems to be changing its galactic surroundings in a way that is usually associated with newborn stars.

Black holes are inherently strange, with gravitational forces so strong that nothing, not even light, can escape. As active black holes consume gas and dust, some of that material is instead launched outward as jets of high-energy particles and radiation. Usually these jets are perpendicular to the host galaxy, but NASA's Stratospheric Observatory for Infrared Astronomy, or SOFIA, found one that is shooting directly into its galaxy.

That jet is heating up gas around the galaxy's center in a way that's characteristic of stars being born. This is prompting scientists to reevaluate their ideas about a key gas associated with baby stars, and about how black holes affect their host galaxies generally.

“The black hole’s jet orientation is so peculiar,” said Irina Smirnova-Pinchukova, scientist at the Max Planck Institute for Astronomy in Heidelberg, Germany. “It transforms the surroundings in the same way newborn stars would, but stars alone could not cause what we observed.”

Stars are born deep inside celestial clouds of dust and gas, a process hidden from our view in visible light. But infrared light, which our eyes cannot see, can penetrate these clouds. SOFIA, for example, uses infrared light to study how stars are born. But even with powerful telescopes, astronomers cannot see details like newborn stars in extremely distant galaxies. Instead, they hunt for signatures of gas that is heated by newborn stars, called ionized carbon. Because ionized carbon is so often found in connection with newborn stars, scientists often assume star formation is occurring when they find the gas in distant galaxies.

But when scientists on SOFIA studied five nearby galaxies with active black holes, they discovered that the one with the lowest rate of star birth contained the most ionized carbon. In fact, there was 10 times more than in other galaxies of similar size and composition. But the star birth rate is so low that it can only produce 25% of the gas they detected. In other words, newborn stars alone could not explain the abundance of ionized carbon. There must be some other explanation for this important chemical signature.

The team used SOFIA’s instrument called the Field Imaging Far-Infrared Line Spectrometer, or FIFI-LS, to closely examine the galaxy, HE 1353-1917. They found that the black hole’s jet is shooting radiation directly into the galaxy, rather than into the space surrounding it. Most of the ionized carbon is concentrated near the galaxy’s active black hole, indicating that the mysterious source of the gas is the intense radiation the black hole’s jet generates.

This contradicts the long-held assumption that ionized carbon is primarily a signature of newborn stars. The results are published in the journal Astronomy and Astrophysics.

“Without numerous observations of nearby galaxies, we might not find such exceptional cases where a black hole is a source of ionized carbon,” said Smirnova-Pinchukova. “This gas is one of the most important tools we have for studying extremely distant galaxies that cannot be seen in great detail.”

Information from nearby galaxies, such as how black holes can create ionized carbon and affect a galaxy’s subsequent evolution, are crucial for understanding the data from other observatories including the Atacama Large Millimeter/submillimeter Array, or ALMA observatory, in Chile. Radio telescopes like ALMA study some of the most distant and faint galaxies, which are often so far away that even powerful telescopes can only detect them as a point of light. That light is full of information, but details about nearby galaxies gathered by SOFIA are required to interpret data from the most distant regions of the universe. Now scientists know that high levels of ionized carbon in a distant galaxy may indicate not only that a lot of stars are being born, but also that a black hole's jet may be responsible for the same kinds of chemical signatures.

SOFIA, the Stratospheric Observatory for Infrared Astronomy, 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 Building 703, in Palmdale, California.

Media Contact

Felicia Chou
NASA Headquarters, Washington
202-358-0257
felicia.chou@nasa.gov

Editor: Kassandra Bell

Source: NASA/Black Holes

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Magnetic Field May Be Keeping Milky Way’s Black Hole Quiet

Streamlines showing magnetic fields layered over a color image of the dusty ring around the Milky Way’s massive black hole. The Y-shaped structure is warm material falling toward the black hole, which is located near where the two arms of the Y-shape intersect. The streamlines reveal that the magnetic field closely follows the shape of the dusty structure. Each of the blue arms has its own field that is totally distinct from the rest of the ring, shown in pink. Credits: Dust and magnetic fields: NASA/SOFIA; Star field image: NASA/Hubble Space Telescope

Supermassive black holes exist at the center of most galaxies, and our Milky Way is no exception. But many other galaxies have highly active black holes, meaning a lot of material is falling into them, emitting high-energy radiation in this “feeding” process. The Milky Way’s central black hole, on the other hand, is relatively quiet. New observations from NASA’s Stratospheric Observatory for Infrared Astronomy, SOFIA, are helping scientists understand the differences between active and quiet black holes.

These results give unprecedented information about the strong magnetic field at the center of the Milky Way galaxy. Scientists used SOFIA’s newest instrument, the High-resolution Airborne Wideband Camera-Plus, HAWC+, to make these measurements.

Magnetic fields are invisible forces that influence the paths of charged particles, and have significant effects on the motions and evolution of matter throughout the universe. But magnetic fields cannot be imaged directly, so their role is not well understood. The HAWC+ instrument detects polarized far-infrared light, which is invisible to human eyes, emitted by celestial dust grains. These grains align perpendicular to magnetic fields. From the SOFIA results, astronomers can map the shape and infer the strength of the otherwise invisible magnetic field, helping to visualize this fundamental force of nature.

“This is one of the first instances where we can really see how magnetic fields and interstellar matter interact with each other,” noted Joan Schmelz, Universities Space Research Center astrophysicist at NASA Ames Research Center in California’s Silicon Valley, and a co-author on a paper describing the observations.  “HAWC+ is a game-changer.”

Previous observations from SOFIA show the tilted ring of gas and dust orbiting the Milky Way’s black hole, which is called Sagittarius A* (pronounced “Sagittarius A-star”). But the new HAWC+ data provide a unique view of the magnetic field in this area, which appears to trace the region’s history over the past 100,000 years.

Details of these SOFIA magnetic field observations were presented at the June 2019 meeting of the American Astronomical Society and will be submitted to the Astrophysical Journal.

The gravity of the black hole dominates the dynamics of the center of the Milky Way, but the role of the magnetic field has been a mystery. The new observations with HAWC+ reveal that the magnetic field is strong enough to constrain the turbulent motions of gas. If the magnetic field channels the gas so it flows into the black hole itself, the black hole is active, because it is eating a lot of gas. 

However, if the magnetic field channels the gas so it flows into an orbit around the black hole, then the black hole is quiet because it’s not ingesting any gas that would otherwise eventually form new stars.

Researchers combined mid- and far-infrared images from SOFIA’s cameras with new streamlines that visualize the direction of the magnetic field. The blue y-shaped structure (see figure) is warm material falling toward the black hole, which is located near where the two arms of the y-shape intersect. Layering the structure of the magnetic field over the image reveals that the magnetic field follows the shape of the dusty structure. Each of the blue arms has its own field component that is totally distinct from the rest of the ring, shown in pink. But there are also places where the field veers away from the main dust structures, such as the top and bottom endpoints of the ring.

“The spiral shape of the magnetic field channels the gas into an orbit around the black hole,” said Darren Dowell, a scientist at NASA’s Jet Propulsion Laboratory, principal investigator for the HAWC+ instrument, and lead author of the study. “This could explain why our black hole is quiet while others are active.”

The new SOFIA and HAWC+ observations help determine how material in the extreme environment of a supermassive black hole interacts with it, including addressing a longstanding question of why the central black hole in the Milky Way is relatively faint while those in other galaxies are so bright. 

SOFIA, the Stratospheric Observatory for Infrared Astronomy, 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 Building 703, in Palmdale, California. The HAWC+ instrument was developed and delivered to NASA by a multi-institution team led by the Jet Propulsion Laboratory in Pasadena, California.


Written by Kassandra Bell and Joan Schmelz

 

Editor: Kassandra Bell

Source: NASA/Black Holes

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Media Contacts


Nicholas Veronico
SOFIA Science Center
Ames Research Center, Silicon Valley, California
650-604-4589 / 650-224-8726
nicholas.a.veronico@nasa.gov

Elizabeth Landau
NASA Headquarters, Washington
818-359-3241
elandau@jpl.nasa.gov

Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov

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Galactic Wind Provides Clues to Evolution of Galaxies

The magnetic field lines of the the Cigar Galaxy (also called M82) appear in this composite image. The lines follow the bipolar outflows (red) generated by exceptionally high rates of star formation. Credit: NASA/SOFIA/E. Lopez-Rodiguez; NASA/Spitzer/J. Moustakas et al.  › Full image and caption

The Cigar Galaxy (also known as M82) is famous for its extraordinary speed in making new stars, with stars being born 10 times faster than in the Milky Way. Now, data from the Stratospheric Observatory for Infrared Astronomy, or SOFIA, have been used to study this galaxy in greater detail, revealing how material that affects the evolution of galaxies may get into intergalactic space.

Researchers found, for the first time, that the galactic wind flowing from the center of the Cigar Galaxy (M82) is aligned along a magnetic field and transports a very large mass of gas and dust - the equivalent mass of 50 million to 60 million Suns. 

"The space between galaxies is not empty," said Enrique Lopez-Rodriguez, a Universities Space Research Association (USRA) scientist working on the SOFIA team. "It contains gas and dust - which are the seed materials for stars and galaxies. Now, we have a better understanding of how this matter escaped from inside galaxies over time." 

Besides being a classic example of a starburst galaxy, which means it is forming an extraordinary number of new stars compared with most other galaxies, M82 also has strong winds blowing gas and dust into intergalactic space. Astronomers have long theorized that these winds would also drag the galaxy's magnetic field in the same direction, but despite numerous studies, there has been no observational proof of the concept.

Researchers using the airborne observatory SOFIA found definitively that the wind from the Cigar Galaxy not only transports a huge amount of gas and dust into the intergalactic medium, but also drags the magnetic field so it is perpendicular to the galactic disc. In fact, the wind drags the magnetic field more than 2,000 light-years across - close to the width of the wind itself.

"One of the main objectives of this research was to evaluate how efficiently the galactic wind can drag along the magnetic field," said Lopez-Rodriguez. "We did not expect to find the magnetic field to be aligned with the wind over such a large area." 

These observations indicate that the powerful winds associated with the starburst phenomenon could be one of the mechanisms responsible for seeding material and injecting a magnetic field into the nearby intergalactic medium. If similar processes took place in the early universe, they would have affected the fundamental evolution of the first galaxies.

The results were published in January 2019 in the Astrophysical Journal Letters.

SOFIA's newest instrument, the High-resolution Airborne Wideband Camera-Plus, or HAWC+, uses far-infrared light to observe celestial dust grains, which align along magnetic field lines. From these results, astronomers can infer the shape and direction of the otherwise invisible magnetic field. Far-infrared light provides key information about magnetic fields because the signal is clean and not contaminated by emission from other physical mechanisms, such as scattered visible light.

"Studying intergalactic magnetic fields - and learning how they evolve - is key to understanding how galaxies evolved over the history of the universe," said Terry Jones, professor emeritus at the University of Minnesota, in Minneapolis, and lead researcher for this study. "With SOFIA's HAWC+ instrument, we now have a new perspective on these magnetic fields."

The HAWC+ instrument was developed and delivered to NASA by a multi-institution team led by the Jet Propulsion Laboratory. JPL scientist and HAWC+ Principal Investigator Darren Dowell, along with JPL scientist Paul Goldsmith, were part of the research team using HAWC+ to study the Cigar Galaxy.

SOFIA, the Stratospheric Observatory for Infrared Astronomy, 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.

News Media Contact

Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov

Written by Kassandra Bell and Arielle Moullet, USRA SOFIA Science Center

Source: JP-Caltech/News

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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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SOFIA finds dust survives obliteration of Supernova 1987A

Artist's concept illustrating Supernova 1987A as the powerful blast wave passes through its outer ring and destroys most of its dust, before the dust re-forms or grows rapidly. SOFIA observations reveal that this dust — a building block of stars and planets — can re-form or grow immediately after the catastrophic damage caused by the supernova’s blast wave. Image credits: NASA/SOFIA/Symbolic Pictures/ The Casadonte Group.

Columbia, MD--Febriuary 11,2019. : Researchers using NASA’s SOFIA airborne telescope have found that cosmic dust, a building block of planets, forms in the wake of a supernova blast wave.

Cosmic dust, a building block of stars and planets, can form in the wake of a violent stellar explosion called a supernova, according to a new study using the Stratospheric Observatory for Infrared Astronomy, SOFIA. These surprising findings provide clues to an astronomical mystery surrounding cosmic dust.

Dust particles form as dying red giant stars throw off material and become part of interstellar clouds of various sizes, densities and temperatures. This cosmic dust is then destroyed by supernova blast waves, which propagate through space at more than 6,000 miles per second (10,000 km/sec)!

Supernova explosions are among the most powerful events in the universe, with a peak brightness equivalent to the light from billions of individual stars. The explosion also produces a blast wave that destroys almost everything in its path, including dust in the surrounding interstellar medium, the space between the stars. Current theories predict when a supernova blast sweeps through a region of space, much of the dust would be destroyed, so there should be little dust left.

Observations with SOFIA, however, tell a different, mysterious story — revealing more than 10 times the dust expected. This suggests that dust is much more abundant in the wake of a blast wave than theories estimate.

The new study is based on observations of a nearby supernova explosion, called Supernova 1987A. When it was discovered in 1987, it was one of the brightest supernovae seen in 400 years! Due to its close proximity, astronomers have been able to monitor its impact on the surrounding environment continuously for the past 30 years.

SOFIA’s observations of the iconic supernova suggest dust may actually be forming in the wake of the powerful blast wave. These results are helping astronomers solve the mystery surrounding the abundance of dust in our galaxy.

“We already knew about the slow-moving dust in the heart of 1987A,” said Mikako Matsuura, a senior lecturer at Cardiff University, in the United Kingdom, and the lead author on the paper. “It formed from the heavy elements created in the core of the dead star. But the SOFIA observations tell us something new about a completely unexpected dust population.”

The observations were published in a recent issue of Monthly Notices of the Royal Astronomical Society.

Supernova 1987A has a distinctive set of rings that are part of a cavity created in an earlier, pre-explosion phase of the star’s evolution. The fast-expanding blast wave has passed through these ring structures. Astronomers thought that any dust particles in these rings would have been destroyed, but recent observations from SOFIA show emission consistent with a growing population of dust in the rings. The results indicate that dust particles can re-form or grow rapidly, even after the catastrophic damage caused during the passage of the blast wave, suggesting that although this might be the end of a chapter in the life cycle of dust, it does not appear to be the end of the story.

The dust detected by SOFIA could result from either significant growth of the existing dust particles or the formation of a new dust population. These new observations compel astronomers to consider the possibility that the post-blast environment might be ready to form or re-form dust immediately after the blast wave passes — a new clue that may be pivotal in resolving the discrepancy between dust destruction models and observations.

From ground-based telescopes on Earth, observing cosmic dust particles in the infrared is difficult — or impossible — due to strong absorption, primarily from water and carbon dioxide in the Earth’s atmosphere. By flying above most of the obscuring molecules, the airborne observatory SOFIA provides access to portions of the infrared spectrum not available from the ground. In particular, SOFIA’s Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST) is a powerful instrument for understanding warm dust in particular.

“FORCAST is the only instrument that can observe at these critical wavelengths and detect this newly-forming population of warm dust,” said James De Buizer, the USRA manager for science operations at the SOFIA Science Center and co-author on the study. “We plan to continue monitoring with FORCAST to gain more insight into dust creation and evolution in supernova remnants.”

In the future, NASA’s James Webb Space Telescope will examine this dust in further detail, looking for clues about its origins and composition.

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, or USRA, 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.

Contact:

Suraiya Farukhi
Director, External Communications
sfarukhi@usra.edu
410-740-6224

Source: Universities Space Research Association (USRA)

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Cosmic Collisions: SOFIA Unravels the Mysterious Formation of Star Clusters

Illustration of a star cluster forming from the collision of turbulent molecular clouds, which appear as dark shadows in front of the background galactic star field.Credits: NASA/SOFIA/Lynette Cook. Hi-res image

Illustration of the molecular clouds surrounded by atomic envelopes, in green, which have been detected by SOFIA via emission from ionized carbon. The spatial offset and motions of these envelopes confirm predictions of simulations of cloud collisions.Credits: NASA/SOFIA/Lynette Cook. Hi-res image

The sun, like all stars, was born in a giant cold cloud of molecular gas and dust. It may have had dozens or even hundreds of stellar siblings – a star cluster – but these early companions are now scattered throughout our Milky Way galaxy. Although the remnants of this particular creation event have long since dispersed, the process of star birth continues today within our galaxy and beyond. Star clusters are conceived in the hearts of optically dark clouds where the early phases of formation have historically been hidden from view. But these cold, dusty clouds shine brightly in the infrared, so telescopes like the Stratospheric Observatory for Infrared Astronomy, SOFIA, can begin to reveal these long-held secrets. 

Traditional models claim that the force of gravity may be solely responsible for the formation of stars and star clusters. More recent observations suggest that magnetic fields, turbulence, or both are also involved and may even dominate the creation process. But just what triggers the events that lead to the formation of star clusters?

Astronomers using SOFIA’s instrument, the German Receiver for Astronomy at Terahertz Frequencies, known as GREAT, have found new evidence that star clusters form through collisions between giant molecular clouds.

The results were published in the Monthly Notices of the Royal Astronomical Society.

"Stars are powered by nuclear reactions that create new chemical elements," said Thomas Bisbas, a postdoctoral researcher at the University of Virginia, Charlottesville, Virginia, and the lead author on the paper describing these new results. "The very existence of life on earth is the product of a star that exploded billions of years ago, but we still don't know how these stars — including our own sun — form."

Researchers studied the distribution and motion of ionized carbon around a molecular cloud where stars can form. There appear to be two distinct components of molecular gas colliding with each other at speeds of more than 20,000 miles per hour. The distribution and velocity of the molecular and ionized gases are consistent with simulations of cloud collisions, which indicate that star clusters form as the gas is compressed in the shock wave created as the clouds collide.

“These star formation models are difficult to assess observationally,” said Jonathan Tan, a professor at Chalmers University of Technology in Gothenburg, Sweden, and the University of Virginia, and a lead researcher on the paper. “We’re at a fascinating point in the project, where the data we are getting with SOFIA can really test the simulations.”

While there is not yet scientific consensus on the mechanism responsible for driving the creation of star clusters, these SOFIA observations have helped scientists take an important step toward unraveling the mystery. This field of research remains an active one, and these data provide crucial evidence in favor of the collision model. The authors expect future observations will test this scenario to determine if the process of cloud collisions is unique to this region, more widespread, or even a universal mechanism for the formation of star clusters.

“Our next step is to use SOFIA to observe a larger number of molecular clouds that are forming star clusters,” added Tan. “Only then can we understand how common cloud collisions are for triggering star birth in our galaxy.”

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.

Media Point of Contact

Nicholas A. Veronico
Nicholas.A.Veronico@nasa.gov • SOFIA Science Center
NASA Ames Research Center, Moffett Field, California

Editor: Kassandra Bell

Source:  NASA/Stars

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What’s Happening in Orion’s Horsehead Nebula?

The Horsehead Nebula is shown in red and green against the surrounding cold molecular cloud (blue). The red areas are carbon monoxide molecules sheltered in the dense nebula and the green areas are carbon atoms and ions that have been affected by the radiation from nearby stars. Credits: NASA/SOFIA/J. Bally et. al

Two research teams used a map from NASA’s Stratospheric Observatory for Infrared Astronomy, SOFIA, to uncover new findings about stars forming in Orion’s iconic Horsehead Nebula. The map reveals vital details for getting a complete understanding of the dust and gas involved in star formation.

The Horsehead Nebula is embedded in the much larger Orion B giant molecular cloud and is extremely dense, with enough mass to make about 30 Sun-like stars. It marks the boundary between the surrounding cold molecular cloud -- filled with the raw materials needed to make stars and planetary systems -- and the area to the west where massive stars have already formed. But the radiation from the stars erodes those raw materials. While the cold molecules, like carbon monoxide, deep within the dense nebula are sheltered from this radiation, molecules on the surface are exposed to it. This triggers reactions that can affect star formation, including the transformation of carbon monoxide molecules into carbon atoms and ions, called ionization.

A team, led by John Bally at the Center for Astrophysics and Space Astronomy, at the University of Colorado in Boulder, wanted to learn if the intense radiation from nearby stars is strong enough to compress the gas within the nebula and trigger new star formation. They combined data from SOFIA and two other observatories to get a multifaceted view of the structure and motion of the molecules there.

Bally’s team found that the radiation from the nearby stars creates hot plasma that compresses the cold gas inside the Horsehead, but the compression is insufficient to trigger the birth of additional stars. Nevertheless, they learned key details about the nebula’s structure.  

The radiation caused a destructive ionization wave to crash over the cloud. That wave was stopped by the dense Horsehead portion of the cloud, causing the wave to wrap around it. The Horsehead developed its iconic shape because it was dense enough to block the destructive forces of the ionization wave.

“The shape of the iconic Horsehead Nebula speaks to the movement and velocity of this process,” said Bally. “It really illustrates what happens when a molecular cloud is destroyed by ionized radiation.” 

Researchers are trying to understand how stars formed in the Horsehead Nebula --  and why additional stars did not -- because its proximity to Earth allows astronomers to study it in great detail. This provides clues to how stars may form in distant galaxies that are too far away for fine details to be observed clearly by even the most powerful telescopes.  

“In studies such as this, we are learning that star formation is a self-limiting process,” said Bally.  “The first stars to form in a cloud can prevent the birth of additional stars nearby by destroying adjacent parts of the cloud.”  

In another study based on SOFIA’s map, a team of researchers lead by Cornelia Pabst, of Leiden University, Netherlands, analyzed the structure and brightness of the gas within cold dark regions in and around the Horsehead Nebula. This region has very little star formation compared to the Orion B Cloud or the Great Nebula in Orion, southwest of the Horsehead Nebula. Pabst and her team wanted to understand the physical conditions in the dark region that may be affecting the star formation rate.

They found that the shape, structure and brightness of the gas in the nebula do not fit existing models.  

Further observations are necessary to explore why the models do not match with what was observed.

“We’re just beginning to understand that, even though we only looked at a very small portion of this molecular cloud, everything is more complicated than what the models initially indicated,” said Pabst. “This map is beautiful, valuable data that we can combine with future observations to help us understand how stars form locally, in our galaxy, so we can then relate that to extragalactic research.”

The studies were published in The Astronomical Journal and Astronomy and Astrophysics. 

The Horsehead Nebula map used by both teams was created using SOFIA’s upgraded GREAT instrument. It was upgraded to use 14 detectors simultaneously, so the map was created significantly faster than it could have been on previous observatories, which used only a single detector.

“We could not have done this research without SOFIA and its upgraded instrument, upGREAT.” said Bally. “Because it lands after each flight, its instruments can be adjusted, upgraded and improved in ways not possible on space-based observatories. SOFIA is fundamental to developing ever more powerful and reliable instruments for future use in space.”

SOFIA is a Boeing 747SP jetliner modified to carry a 100-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 based at NASA’s Armstrong Flight Research Center's Hangar 703, in Palmdale, California.  NASA/SOFIA

Media Point of Contact

Nicholas A. Veronico
650.224.8726 cell
Nicholas.A.Veronico@nasa.gov

Written by Kassandra Bell
SOFIA Science Center
 
Editor: Kassandra Bell

Source:  NASA/SOFIA

What Stars Will Hatch From The Tarantula Nebula? NASA’s Flying Observatory Seeks to Find Out

The Tarantula Nebula as seen on SOFIA’s visible light guide camera during observations from Christchurch, New Zealand.

Credits: NASA/SOFIA/Nicholas A. Veronico

To have a full picture of the lives of massive stars, researchers need to study them in all stages – from when they’re a mass of unformed gas and dust, to their often dynamic end-of-life explosions.

NASA's flying telescope, the Stratospheric Observatory for Infrared Astronomy, or SOFIA, is particularly well-suited for studying the pre-natal stage of stellar development in star-forming regions, such as the Tarantula Nebula, a giant mass of gas and dust located within the Large Magellanic Cloud, or LMC.  

Researchers from the Minnesota Institute for Astrophysics, led by Michael Gordon, went aboard SOFIA to identify and characterize the brightness, ages and dust content of three young star-forming regions within the LMC.

“The Large Magellanic Cloud has always been an interesting and excellent laboratory for massive star formation,” said Gordon. “The chemical properties of star-forming regions in the LMC are significantly different than in the Milky Way, which means the stars forming there potentially mirror the conditions of star formation in dwarf galaxies at earlier times in the universe.”

In our galactic neighborhood, which includes the LMC, massive stars – generally classified as stars more than eight times the mass of Earth’s Sun – are believed to form exclusively in very dense molecular clouds. The dark dust and gas absorb background light, which prevents traditional optical telescopes from imaging these areas.

“The mid-infrared capabilities of SOFIA are ideal for piercing through infrared dark clouds to capture images of potential massive star-forming regions,” Gordon said.

The observations were completed with the Faint Object infrared Camera for the SOFIA Telescope, known as FORCAST. This infrared camera also performs spectroscopy, which identifies the elements present.

Astronomers study stars evolving in both the optical and the infrared to learn more about the photosphere, and the population of stars in the photosphere. The mid- and far-infrared data from SOFIA reaffirm dust temperature and mass accretion rates that are consistent with prior research of the LMC.

"We want to combine as many observations as we can from the optical, as seen through images from the Hubble Space Telescope, all the way out to the far infrared, imaged using the Spitzer Space Telescope and the Herschel Space Observatory, to get as broad a picture as possible," Gordon continued. "No previous researchers have used FORCAST’s wavelength range to effectively study massive star formations. We needed SOFIA to fill in the 20- to 40-micron gap to give us the whole picture of what’s taking place."

In summer 2017, further research of the Tarantula Nebula was accomplished aboard SOFIA during the observatory’s six-week science campaign operating from Christchurch, New Zealand, to study the sky in the Southern Hemisphere. Gordon and his team are hopeful that when analyzed, data obtained from the Christchurch flights will reveal previously undiscovered young massive stars forming in the region, which have never been observed outside of the Milky Way.

SOFIA is a Boeing 747SP jetliner modified to carry a 100-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 based at NASA’s Armstrong Flight Research Center's Hangar 703, in Palmdale, California.

Source: NASA/SOFIA

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Media Point of Contact

Nicholas A. Veronico
NVeronico@sofia.usra.edu • SOFIA Science Center
NASA Ames Research Center, Moffett Field, California

Editor: Kassandra Bell

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Understanding Star Formation in the Nucleus of Galaxy IC 342

A BIMA-SONG radio map of the IC 342 central molecular zone; dots indicate locations of SOFIA/GREAT observations.

Credits: Röllig et al.

An international team of researchers used NASA’s Stratospheric Observatory for Infrared Astronomy, SOFIA, to make maps of the ring of molecular clouds that encircles the nucleus of galaxy IC 342. 

The maps determined the proportion of hot gas surrounding young stars as well as cooler gas available for future star formation. The SOFIA maps indicate that most of the gas in the central zone of IC 342, like the gas in a similar region of our Milky Way Galaxy, is heated by already-formed stars, and relatively little is in dormant clouds of raw material.

At a distance of about 13 million light years, galaxy IC 342 is considered relatively nearby. It is about the same size and type as our Milky Way Galaxy, and oriented face-on so we can see its entire disk in an undistorted perspective. Like our galaxy, IC 342 has a ring of dense molecular gas clouds surrounding its nucleus in which star formation is occurring. However, IC 342 is located behind dense interstellar dust clouds in the plane of the Milky Way, making it difficult to study by optical telescopes.

The team of researchers from Germany and the Netherlands, led by Markus Röllig of the University of Cologne, Germany, used the German Receiver for Astronomy at Terahertz frequencies, GREAT, onboard SOFIA to scan the center of IC 342 at far-infrared wavelengths to penetrate the intervening dust clouds. Röllig’s group mapped the strengths of two far-infrared spectral lines – one line, at a wavelength of 158 microns, is emitted by ionized carbon, and the other, at 205 microns, is emitted by ionized nitrogen.

The 158-micron line is produced both by cold interstellar gas that is the raw material for new stars, and also by hot gas illuminated by stars that have already finished forming. The 205-micron spectral line is only emitted by the hot gas around already-formed young stars. Comparison of the strengths of the two  spectral lines allows researchers to determine of the amount of warm gas versus cool gas in the clouds.

Röllig’s team found that most of the ionized gas in IC 342’s central molecular zone (CMZ) is in clouds heated by fully formed stars rather than in cooler gas found farther out in the zone, like the situation in the Milky Way’s CMZ. The team’s research was published in Astronomy and Astrophysics, volume 591.

“SOFIA and its powerful GREAT instrument allowed us to map star formation in the center of IC 342 in unprecedented detail,” said Markus Röllig of the University of Cologne, Germany, “These measurements are not possible from ground-based telescopes or existing space telescopes.”

Researchers previously used SOFIA’s GREAT spectrometer for a corresponding study of the Milky Way’s CMZ. That research, published in 2015 by principal investigator W.D. Langer, et. al, appeared in the journal Astronomy & Astrophysics 576, A1; an overview of that study can be found here. 

SOFIA is a Boeing 747SP jetliner modified to carry a 100-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 based at NASA’s Armstrong Flight Research Center's Hangar 703, in Palmdale, California.

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For More Information

For more information about SOFIA, visit: http://www.nasa.gov/sofia • http://www.dlr.de/en/sofia

For information about SOFIA's science mission and scientific instruments, visit:  http://www.sofia.usra.edu • http://www.dsi.uni-stuttgart.de/index.en.html

Media Point of Contact

Nicholas A. Veronico
NVeronico@sofia.usra.edu • SOFIA Science Center
NASA Ames Research Center, Moffett Field, California

Editor: Kassandra Bell

Source: NASA/Galaxies

SOFIA Detects Collapsing Clouds Becoming Young Suns

An infrared image of the W43 star-forming region located 20,000 light years away in the direction of the constellation Aquila, one of the places where Wyrowski et al. detected cloud clumps collapsing to become massive stars. Credits: NASA/JPL-Caltech/2MASS. Hi-res image

Researchers on board NASA’s Stratospheric Observatory for Infrared Astronomy, SOFIA, observed the collapse of portions of six interstellar clouds on their way to becoming new stars that will be much larger than our sun.

When a gas cloud collapses on itself, the cloud’s own gravity causes it to contract and the contraction produces heat friction. Heat from the contraction eventually causes the core to ignite hydrogen fusion reactions creating a star.

Astronomers are excited about this SOFIA research because there have been very few previous direct observations of collapse motion. These SOFIA observations have enabled scientists to confirm theoretical models about how interstellar clouds collapse to become stars and the pace at which they collapse. Actually observing this collapse, called “infall,” is extremely challenging because it happens relatively quickly in astronomical terms.

“Detecting infall in protostars is very difficult to observe, but is critical to confirm our overall understanding of star formation,” said Universities Space Research Association’s Erick Young, SOFIA Science Mission Operations director.

Using the observatory’s GREAT instrument, the German Receiver for Astronomy at Terahertz Frequencies, scientists searched for this developmental stage in nine embryonic stars, called protostars, by measuring the motions of the material within them. They found that six of the nine protostars were actively collapsing, adding substantially to the previous list of less than a dozen protostars directly determined to be in this infall stage.

For several weeks each year, the SOFIA team operates from Christchurch, New Zealand, to study objects best observed from southern latitudes, including the complete center of the Milky Way where many star-forming regions are located. Heading south during the Southern Hemisphere’s winter months, when the nights are long and infrared-blocking water vapor is especially low, also creates prime observing conditions.

“With the Southern Hemisphere deployments of SOFIA, the full inner Milky Way comes into reach for star formation studies. This is crucial for observations of the earliest phases of high-mass star formation, since this is a relatively rapid and rare event,” said Friedrich Wyrowski, astronomer at the Max-Planck Institute for Radio Astronomy in Bonn, Germany.

The results were from observations made in the Southern Hemisphere in 2015, and were published in Astronomy and Astrophysics earlier this year. SOFIA spent seven weeks during 2016 observing from Christchurch. The scientific teams involved in the Southern Hemisphere observations are analyzing the acquired data now.

SOFIA is a Boeing 747SP jetliner modified to carry a 100-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 based at NASA’s Armstrong Flight Research Center's Hangar 703, in Palmdale, California.

Point of Contact 

Nicholas A. Veronico
Email: NVeronico@sofia.usra.edu
SOFIA Science Center NASA Ames Research Center, Moffett Field, California

Editor: Kassandra Bell

Source: NASA/SOFIA

“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

Gluttonous Star May Hold Clues to Planet Formation

The brightness of outbursting star FU Orionis has been slowly fading since its initial flare-up in 1936. Researchers found that it has dimmed by about 13 percent in short infrared wavelengths from 2004 (left) to 2016 (right). Credits: NASA/JPL-Caltech. Full image and caption

In 1936, the young star FU Orionis began gobbling material from its surrounding disk of gas and dust with a sudden voraciousness. During a three-month binge, as matter turned into energy, the star became 100 times brighter, heating the disk around it to temperatures of up to 12,000 degrees Fahrenheit (7,000 Kelvin). FU Orionis is still devouring gas to this day, although not as quickly.

This brightening is the most extreme event of its kind that has been confirmed around a star the size of the sun, and may have implications for how stars and planets form. The intense baking of the star's surrounding disk likely changed its chemistry, permanently altering material that could one day turn into planets. 

"By studying FU Orionis, we're seeing the absolute baby years of a solar system," said Joel Green, a project scientist at the Space Telescope Science Institute, Baltimore, Maryland. "Our own sun may have gone through a similar brightening, which would have been a crucial step in the formation of Earth and other planets in our solar system."

Visible light observations of FU Orionis, which is about 1,500 light-years away from Earth in the constellation Orion, have shown astronomers that the star's extreme brightness began slowly fading after its initial 1936 burst. But Green and colleagues wanted to know more about the relationship between the star and surrounding disk. Is the star still gorging on it? Is its composition changing? When will the star's brightness return to pre-outburst levels? 

To answer these questions, scientists needed to observe the star’s brightness at infrared wavelengths, which are longer than the human eye can see and provide temperature measurements.

Green and his team compared infrared data obtained in 2016 using the Stratospheric Observatory for Infrared Astronomy, SOFIA, to observations made with NASA's Spitzer Space Telescope in 2004. 

SOFIA, the world's largest airborne observatory, is jointly operated by NASA and the German Aerospace Center and provides observations at wavelengths no longer attainable by Spitzer. The SOFIA data were taken using the FORCAST instrument (Faint Object infrared Camera for the SOFIA Telescope).

"By combining data from the two telescopes collected over a 12-year interval, we were able to gain a unique perspective on the star's behavior over time," Green said. He presented the results at the American Astronomical Society meeting in San Diego, this week.

Using these infrared observations and other historical data, researchers found that FU Orionis had continued its ravenous snacking after the initial brightening event: The star has eaten the equivalent of 18 Jupiters in the last 80 years.

The recent measurements provided by SOFIA inform researchers that the total amount of visible and infrared light energy coming out of the FU Orionis system decreased by about 13 percent over the 12 years since the Spitzer observations. Researchers determined that this decrease is caused by dimming of the star at short infrared wavelengths, but not at longer wavelengths. That means up to 13 percent of the hottest material of the disk has disappeared, while colder material has stayed intact.  

"A decrease in the hottest gas means that the star is eating the innermost part of the disk, but the rest of the disk has essentially not changed in the last 12 years," Green said. "This result is consistent with computer models, but for the first time we are able to confirm the theory with observations."

Astronomers predict, partly based on the new results, that FU Orionis will run out of hot material to nosh on within the next few hundred years. At that point, the star will return to the state it was in before the dramatic 1936 brightening event. Scientists are unsure what the star was like before or what set off the feeding frenzy.

"The material falling into the star is like water from a hose that's slowly being pinched off," Green said. 

"Eventually the water will stop."

If our sun had a brightening event like FU Orionis did in 1936, this could explain why certain elements are more abundant on Mars than on Earth. A sudden 100-fold brightening would have altered the chemical composition of material close to the star, but not as much farther from it. Because Mars formed farther from the sun, its component material would not have been heated up as much as Earth's was.

At a few hundred thousand years old, FU Orionis is a toddler in the typical lifespan of a star. The 80 years of brightening and fading since 1936 represent only a tiny fraction of the star's life so far, but these changes happened to occur at a time when astronomers could observe.

"It's amazing that an entire protoplanetary disk can change on such a short timescale, within a human lifetime," said Luisa Rebull, study co-author and research scientist at the Infrared Processing and Analysis Center (IPAC), based at Caltech, Pasadena, California. 

Green plans to gain more insight into the FU Orionis feeding phenomenon with NASA's James Webb Space Telescope, which will launch in 2018. SOFIA has mid-infrared high-resolution spectrometers and far-infrared science instrumentation that complement Webb’s planned near- and mid-infrared capabilities. 

Spitzer is expected to continue exploring the universe in infrared light, and enabling groundbreaking scientific investigations, into early 2019.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA. Science operations are conducted at the Spitzer Science Center at Caltech. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.

SOFIA is a joint project of NASA and the German Aerospace Center (DLR). The aircraft is based at NASA Armstrong Flight Research Center's facility in Palmdale, California. NASA's Ames Research Center in Moffett Field, California, manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart.

For more information about Spitzer, visit: http://www.nasa.gov/spitzer - http://spitzer.caltech.edu

For more information about SOFIA, visit: http://www.nasa.gov/sofia - http://www.dlr.de/en/sofia

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
elizabeth.landau@jpl.nasa.gov

Editor: Tony Greicius

Source: NASA/Spitzer Telescope