SOFIA: Stratospheric Observatory for Infrared Astronomy

by Anashe Bandari

Most stars in spiral galaxies form within the galaxy’s arms. Building the “skeletons” of these galaxies are galactic bones, long filaments that outline the densest parts of the arms.

At the largest scales, the magnetic fields of a galaxy follow its spiral arms. Fields in the bones were accordingly believed to be aligned with respect to the bone, but research from the Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint project of NASA and the German Space Agency at DLR, hints that this is generally not the case. The magnetic fields do not follow the spiral shape of the galaxy’s arms, nor are they in general perpendicular to the bones.

“Before SOFIA, it was difficult to image magnetic fields at high resolution over the entirety of the bones,” said Ian Stephens, an astrophysicist at Worcester State University. “We are now able to get so many independent measurements of the magnetic field direction across these bones, allowing us to really delve into the importance of the magnetic field in these massive filamentary clouds.”

Stephens is part of the Filaments Extremely Long and Dark: a MAgnetic Polarization Survey (FIELDMAPS) project, the first attempt to map the magnetic field of any galactic bone in its entirety. Of the ten bones the group plans to map, the first project completed by FIELDMAPS is that of G47, a giant filamentary bone within the Milky Way that is 200 light-years in length and 5 light-years in width.

“Magnetic fields…can potentially set the rate at which stars form in a cloud. They can also guide the flow of gas, shape the bones, and affect the quantity and size of the densest pockets of gas that will eventually collapse to form stars,” Stephens said. “By mapping the orientation of the fields, we can estimate the relative importance of the magnetic field to that of gravity to quantify how much magnetic fields affect the star formation process.”

The researchers did just that and were able to determine that the magnetic fields are strong enough to prevent gas in many areas from succumbing to gravitational collapse to form stars. They found the magnetic fields in the G47 bone were complex, changing directions frequently – though in the densest areas, they trended perpendicular to the bone. This means the parallel fields from the less dense regions are feeding material into the denser regions, where fields play a key role in the star formation rate by impeding the birth of new stars.

FIELDMAPS used the HAWC+ polarimeter aboard SOFIA, which determines the alignment of dust, allowing astrophysicists to sense the direction of the magnetic field so it can be observed from afar. This enabled the largest and most detailed maps ever made of magnetic fields across galactic bones.

The group has more galactic bones to analyze, which they plan to compare with computer simulations of spiral galaxies. Together, these results will help develop a more thorough description of the role of magnetic fields in spiral galaxies’ arms.

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. 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 at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.

versión en español

By Maggie McAdam

NASA’s Stratospheric Observatory for Infrared Astronomy, or SOFIA, landed at the Santiago International Airport on March 18, 2022. Like other deployments to the Southern Hemisphere, SOFIA is temporarily changing its base of operations from Palmdale, California, to Santiago, Chile, to observe celestial objects that can only be seen from Southern Hemisphere latitudes. NASA and its partner of the SOFIA mission, the German Space Agency at DLR, are excited to deploy to Chile for the first time.

This is SOFIA’s first visit to South America, and its first short-term deployment that will last two weeks. The team will operate from the Santiago International Airport to accomplish eight science flights. SOFIA will primarily observe the Large and Small Magellanic Clouds during the deployment, which are two galaxies that are our Milky Way’s closest galactic neighbors. Both are gravitationally bound with the Milky Way and will eventually merge with our galaxy in several billion years.

“Scientific collaboration, particularly in astronomy, has been a cornerstone of the U.S.-Chile relationship dating back to the establishment of the Observatorio de Cerro Santa Lucia in Santiago more than 170 years ago,” said Richard Glenn, the U.S. Embassy Chile Chargé d’Affaires. “NASA’s SOFIA deployment to Chile is the next exciting milestone in that relationship, bringing us closer to the stars than ever before.”

This is called a short deployment because of the shorter time in country compared to SOFIA’s long deployments, where more than 25 flights are typically planned using multiple instruments. The SOFIA team is taking a single instrument, the Far Infrared Field Imaging Line Spectrometer, or FIFI-LS, and will observe several critical Southern Hemisphere celestial targets.

“We are thrilled to deploy to Chile so we can provide more access to the Southern Hemisphere skies for our scientific community,” said Naseem Rangwala, SOFIA’s project scientist. “We are increasing our deployment tempo with a focus on efficiency and prioritized targets, and we are grateful for the opportunity to do that from Santiago.”

Since the Large Magellanic Cloud, or LMC, is so close to our galaxy, SOFIA can observe it in great detail, on relatively small astronomical scales, to help scientists better understand how stars formed in the early universe. Having the context of the physical areas in which stars form is why these LMC observations are so powerful. Scientists cannot see detailed physical structures in distant, ancient galaxies, so, instead, galaxies like the LMC are observed as local stand-ins. The planned observations are to create the first map of ionized carbon in the LMC. These observations pair well with NASA’s upcoming Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory, or GUSTO mission, and they extend the legacy of the Herschel Space Observatory.

In addition to the observations of the Large Magellanic Cloud, SOFIA will observe supernova remnants to investigate how certain types of supernovas might have contributed to the abundance of dust in the early universe. SOFIA will also attempt its first observation to measure the primordial abundance of lithium by looking into the halo of our galaxy where clouds of neutral hydrogen can be found. These clouds have been relatively undisturbed and thus directly probe the properties of pristine gas that existed in the early universe. A successful observation of lithium could have implications for our understanding of fundamental physics and the early universe because there is a significant discrepancy in lithium abundance between the big-bang theory of the evolution of the universe and the observed abundance from astronomical measurements.

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. 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 at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.

Media inquiries regarding SOFIA’s southern deployment should be sent to the NASA Ames newsroom.

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Ciencia en el hemisferio sur: SOFIA se despliega en Chile

By Maggie McAdam

El Observatorio Estratosférico para Astronomía Infrarroja de la NASA, o SOFIA, aterrizó en el Aeropuerto Internacional de Santiago el 18 de marzo de 2022. Al igual que otros despliegues en el hemisferio sur, SOFIA cambia temporalmente su base de operaciones de Palmdale, California, a Santiago de Chile, para observar objetos celestes que solo pueden verse desde latitudes del hemisferio sur. La NASA y su socio en la misión SOFIA, la Agencia Espacial Alemana (DLR por sus siglas en alemán), están entusiasmados con el primer despliegue en Chile.

Esta es la primera visita de SOFIA a Sudamérica, y su primer despliegue a corto plazo que durará dos semanas. El equipo operará desde el Aeropuerto Internacional de Santiago para realizar ocho vuelos científicos. Durante el despliegue, SOFIA observará principalmente la Nube Grande y la Nube Pequeña de Magallanes, dos galaxias que son las vecinas más cercanas de nuestra Vía Láctea. Las dos están ligadas gravitacionalmente a la Vía Láctea y acabarán fusionándose con nuestra galaxia dentro de varios miles de millones de años.

“La colaboración científica, especialmente en el campo de la astronomía, ha sido un pilar de la relación entre Estados Unidos y Chile que comenzó con el establecimiento del Observatorio de Cerro Santa Lucía en Santiago hace más de 170 años”, dijo Richard Glenn, Encargado de Negocios de la Embajada de Estados Unidos en Chile. “El despliegue de SOFIA de la NASA en Chile es el siguiente hito emocionante en esa relación, acercándonos a las estrellas como nunca antes”.

Este despliegue se considera corto debido al menor tiempo de permanencia en el país en comparación con los despliegues largos de SOFIA, en los que normalmente se planifican más de 25 vuelos con múltiples instrumentos. El equipo de SOFIA llevará un solo instrumento, el Espectrómetro de Línea de Imagen del Campo Infrarrojo Lejano, o FIFI-LS, y observará varios objetivos celestes críticos del hemisferio sur.

“Estamos encantados de desplegarnos en Chile para poder ofrecer a nuestra comunidad científica un mayor acceso a los cielos del hemisferio sur”, declaró Naseem Rangwala, científico del proyecto SOFIA. “Estamos aumentando nuestro ritmo de despliegue con un enfoque en la eficiencia y en los objetivos prioritarios, y estamos agradecidos por la oportunidad de hacerlo desde Santiago”.

Puesto que la Gran Nube de Magallanes, o LMC por sus siglas en inglés, está tan cerca de nuestra galaxia, SOFIA puede observarla con gran detalle, en escalas astronómicas relativamente pequeñas, para ayudar a los científicos a entender mejor cómo se formaron las estrellas en el universo primitivo. Tener el contexto de las zonas físicas en las que se forman las estrellas es la razón por la que estas observaciones de la LMC son tan potentes. Los científicos no pueden ver las estructuras físicas detalladas de las galaxias antiguas y lejanas, por lo que, en su lugar, las galaxias como la LMC se observan como sustitutos locales. Las observaciones previstas tienen por objeto crear el primer mapa del carbono ionizado en la LMC. Estas observaciones se combinan con el próximo Observatorio Espectroscópico de Terahercios ULDB Galáctico/Extra galáctico de la NASA, o misión GUSTO, y amplían el legado del Observatorio Espacial Herschel.

Además de las observaciones de la Gran Nube de Magallanes, SOFIA observará restos de supernovas para investigar cómo ciertos tipos de supernovas podrían haber contribuido a la abundancia de polvo en el universo primitivo. SOFIA también intentará llevar a cabo su primera observación para medir la abundancia primordial de litio mirando en el halo de nuestra galaxia donde se encuentran las nubes de hidrógeno neutro. Estas nubes han permanecido relativamente inalteradas y, así, pueden investigar directamente las propiedades del gas prístino que existía en el universo primitivo. Una observación exitosa del litio podría tener implicaciones para nuestra comprensión de la física fundamental y del universo primitivo, ya que existe una discrepancia significativa en la abundancia de litio entre la teoría del Big Bang de la evolución del universo y la abundancia observada a partir de las mediciones astronómicas.

SOFIA es un proyecto conjunto de la NASA y la Agencia Espacial Alemana (DLR). DLR proporciona el telescopio, el mantenimiento programado para el avión y otros apoyos para la misión. El Centro de Investigación Ames de la NASA, en el Silicon Valley de California, administra el programa SOFIA, la ciencia y las operaciones de la misión en cooperación con la Asociación de Universidades de Investigación Espacial, con sede en Columbia, Maryland, y el Instituto SOFIA alemán de la Universidad de Stuttgart. El avión es mantenido y operado por el Armstrong Flight Research Center Building 703 de la NASA, en Palmdale, California.

Las preguntas de la prensa sobre el despliegue de SOFIA en el sur deben enviarse a la sala de prensa de la NASA en Ames.

This short video gives you a glimpse at our flying observatory – the Stratospheric Observatory for Infrared Astronomy, or SOFIA – and the science we do from the skies.

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. 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 at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.

by Anashe Bandari

Because the effects of observing a galaxy at an angle are complex, spiral galaxies are much easier to study if their orientation is just right – that is, if telescopes can see them face-on rather than at an angle. Now, observations of Caldwell 30, a spiral galaxy with a similar size and shape to our own, have begun to identify these effects.

Jessica Sutter and Dario Fadda looked at the various factors that affect the detection of the ionized carbon emission – an important measurement in astronomy, as it can reveal star formation, cooling, and more – from Caldwell 30, including its angle of inclination. Because ionized carbon is so ubiquitous in astronomy, identifying its source ensures its proper usage.

“Knowing where the ionized carbon emission is coming from – whether photodissociation regions, or ionized hydrogen regions, or diffuse ionized gas – is going to affect how we might use it to trace molecular gas, star formation, or photodissociation conditions,” Sutter said. “Our observing angle may have an effect.”

From our point of view on Earth, Caldwell 30 is inclined at about 72 degrees. As a result of this inclination, Sutter and Fadda found the observed fraction of ionized carbon varies depending on which side of the galaxy is being looked at.

“That was both unexpected and semi-novel,” said Sutter, adding that it should be a significant consideration for researchers going forward, especially if they aren’t sure of the inclination of the galaxy they are studying. If the viewing angle is unknown, the contribution from various ionized carbon emission sources is hard to determine, impacting how the emission can be used in analyses.

As the only observatory capable of studying ionized carbon from within the Earth’s stratosphere for nearby galaxies, SOFIA is uniquely qualified to help clarify the role of a galaxy’s angle in its ionized carbon emission.

“One of the reasons more people haven’t looked at ionized carbon emission is because…you can’t do it from the ground. You need something at least from the stratosphere, if not in space,” Sutter said. “With SOFIA, we have some more opportunities to get these full maps.”

Looking ahead, the pair hopes to expand their analysis, which was recently published in The Astrophysical Journal, by mapping the ionized carbon emission from an additional set of galaxies using SOFIA.

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. 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 at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.

by Anashe Bandari

A black hole at the center of a galaxy plays a role in the galaxy’s death, eating up their surrounding dust and gas and not leaving enough matter behind for new stars to form. Gravity alone, however, is not strong enough to account for all this material transfer on its own.

Theories have proposed that magnetic fields could be helping gravity in feeding black holes, spooning matter in their direction. With the help of observations from the Stratospheric Observatory for Infrared Astronomy, or SOFIA, these theories have now been confirmed. By mapping out the shape of the magnetic fields in the central region of NGC 1097, a spiral galaxy, researchers discovered the magnetic fields assist in directing dust and gas toward the supermassive black hole at the galaxy’s center.

“We can, for the first time, analyze the effect of the magnetic field in the gas flows toward [the central] star-forming regions using SOFIA and the galaxy’s center using radio polarimetric observations,” said Enrique Lopez-Rodriguez, lead author on the recent paper describing NGC 1097’s magnetic fields.

NGC 1097 has a region of intense star formation toward its center, known as a starburst ring. Because looking at magnetic fields in very dense areas is one of SOFIA’s strengths, Lopez-Rodriguez and his team used SOFIA to probe the dense regions merging into the starburst ring. This was complemented by radio polarimetric observations within the starburst ring, a different type of astronomical observation better suited for studying sparse regions.

The researchers found a striking difference in the morphology of the magnetic fields between the two regions. The SOFIA observations show the magnetic field feeding matter into the starburst ring, while the radio polarimetric observations show the magnetic field spiraling into the galaxy’s center, feeding the supermassive black hole.

But despite this striking difference, the two are not fully disconnected: The study proves that the magnetic fields in the galaxy help deliver gas and dust to the black hole at its center. Altogether, the large-scale fields follow the shape of NGC 1097’s spiral arms, channeling matter from the arms to the starburst ring in its innermost regions, and from the starburst ring deeper toward the black hole, where it can eat the material up.

This confirms that it is not just gravity that helps a black hole feed on the material in its host galaxy, but magnetic fields also play a role.

“Our observations also provide evidence that the magnetic fields located in the proximity of the black holes at the center of active galaxies may be coming from the large-scale magnetic field in the host galaxy,” Lopez-Rodriguez said.

This first observation of magnetic fields nourishing black holes helps answer critical questions about how galaxies evolve, and ultimately die.

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. 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 at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.

Written by Maggie McAdam on behalf of the SOFIA Project

SOFIA recently completed a new set of observations of Venus to study the chemical composition of the planet’s atmosphere. Observing Venus was particularly challenging.  Venus was in a tricky part of the sky to observe, and the Sun was about to set. For safety reasons, SOFIA can only open the door to the telescope while the Sun is above the horizon under very specific circumstances. Great care must be taken to avoid the telescope accidentally observing the Sun and causing damage to the telescope or aircraft. Due to these specific requirements, the flight planning and coordination for these observations took extra care, discussion, and special preparations.

The planning and preparations for observing Venus began more than two months before the flights. The flight crew were specifically trained by the telescope engineers on the exact directions that would be safe to fly with the door open before the Sun went down. They carefully planned contingencies and turns to ensure the telescope’s and aircraft’s safety.

Another challenge for these pre-sunset observations is timing each event in the flight plan. The exact time the Sun sets is different depending on your altitude.

Furthermore, weather and barometric pressure can change the density of the atmosphere, which in turn affects the atmosphere’s refractive properties. Refraction is the bending of light by a medium. A famous example of refraction is a pencil in a glass of water. We know the pencil is straight, but the water refracts the light, making it appear to dramatically bend. The variability of the atmosphere’s pressure and therefore its ability to refract the Sun’s light is a potential safety concern for the observatory. The flight planners for SOFIA designed and timed the delicate dance of the Venus observations to ensure that there was no risk of SOFIA accidently observing the Sun. Still, everyone on the flight carefully monitored the sky to see the green flash, a phenomenon that indicates the Sun has set over the horizon. Once the Sun was down, the pilots turned the aircraft so SOFIA could observe Venus.

SOFIA started off the night before sunset by opening the upper rigid door – which recently went through a special maintenance period – so SOFIA could observe Jupiter to prepare the instrument and telescope for Venus. Jupiter is 90 degrees away from the setting Sun in the sky, so SOFIA was able to observe it safely while the Sun was above the horizon. During this short look at Jupiter, the telescope operators and instrument scientists got set up and did calibrations as the Sun continued to set. Right on schedule, the aircraft turned and began to collect photos of Venus using the German REceiver for Astronomy at Terahertz Frequencies, or GREAT, instrument.

One of the goals of the observations was to address recent reports of phosphine on Venus. Due to their higher sensitivities, SOFIA and the GREAT instrument will be able to set a strict upper limit on Venus’ phosphine abundance. Applying GREAT’s ability to make multiple simultaneous observations, the Venus observations also studied hydrogen chloride and conducted the first search for atomic oxygen in Venus’ atmosphere. Now that GREAT has observed Venus, the teams of scientists who proposed these observations will begin the creative process of reducing and analyzing the data. We look forward to learning the results of their work.

by Anashe Bandari

Everything we see in the universe is a snapshot of the past: As light takes its time to reach our telescopes, the system we’re observing continues to evolve, and what we end up seeing is a moment in its history. By revisiting an object over the course of decades, we can look not only into its past, but can watch its history unfold.

Eleven years after it was last observed and 17 years after a stellar merger occurred, SOFIA looked at V838 Monocerotis, or V838 Mon, a binary star system about 19 thousand light-years away from Earth, capturing a snapshot in time of its makeup. This confirmed that the dust chemistry of the system has changed significantly over the course of nearly two decades following the merger, particularly over the past decade. This provided a history we otherwise cannot look at and offered an archaeological view of its evolution.

Because V838 Mon is quite bright and can saturate other telescopes, SOFIA is the only observatory capable of observing it at infrared wavelengths required to monitor this dust process. The researchers used SOFIA’s FORCAST camera, which allows for low-resolution spectroscopy and deep imaging of bright objects.

“It’s very rare to see this progression of dust transformation in objects that is predicted to happen,” said Charles Woodward, astrophysicist at the University of Minnesota and lead author on the paper describing the observation. “To catch one is pretty cool.”

Material expelled as a result of a merger may provide hints about how our own early solar system evolved. Understanding how dust condensation occurs from material originally in a hot gas phase is related to how rocky planets, like Earth, form out of the gas and debris that surround young stars.

“It’s these small, micron-sized pieces of material that eventually build into planets like the one we sit on,” Woodward said.

In environments like this that are conducive to forming dust, the way that the different materials are incorporated and condense affects the geology of the final product. This is especially true when aluminum – which is very chemically active and can quickly deplete its surrounding oxygen – is involved. In V838 Mon, the chemical composition of the dust has changed from primarily comprising of alumina components in 2008 to being dominated by silicates, as the alumina bond with their oxygen neighbors. Notably, this progression can be seen in real time.

“If we look at theoretical condensation sequences for how this is supposed to work, this is an example of us being able to test those hypotheses,” Woodward said.

While most astronomical events occur on a timescale of millions of years, this is one example of human-timescale astronomy, reminding us that immense changes can occur in a very short period of time.

“Often when people think about astronomy, things are in stasis and they take millions and billions of years to occur. This was in the blink of an eye that the source went through evolution,” Woodward said. “Certain astrophysical phenomena are really dynamic.”

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. 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 at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.

by Anashe Bandari

NGC 7479 – also known as Caldwell 44 – is a barred spiral galaxy, with a bar-shaped center filled with stars, as is characteristic of the majority of spiral galaxies, and S-shaped arms. But looking at features of NGC 7479 that are hidden to the naked eye reveals another pair of S-shaped arms, bending in the opposite direction to the visible galaxy.

Radio wavelength emissions from these small, so-called “counter-arms” have been observed before, but with the help of SOFIA – along with observations by ALMA and archival data from a number of other observatories – their presence has now been confirmed by X-ray, ionized carbon, and carbon monoxide emissions as well. SOFIA’s new observations of the counter-arms can help reveal their origin.

“The really important thing in this galaxy are the two little counter-arms that go in the opposite direction of the optical arms that are seen in radio, but nobody had seen them in the X-ray,” said Dario Fadda, lead author on a recent paper describing the analysis. “Seeing them in X-ray is important because it shows there’s energy coming out of the nucleus, something that comes out in jets that originate in the nucleus.”

The fact that these jets originate at the galaxy’s center implies the galaxy harbors an active nucleus – a supermassive black hole.

As the jet approaches the dense molecular clouds along the bar, some of its momentum is absorbed by the clouds, causing the jet to bend in the direction opposite to the rotation of the galaxy. This process is responsible for the orientation of the counter-arms.

By comparing the X-ray emissions of the jet to the ratio of ionized carbon and carbon dioxide emissions from the same area – both of which are considered indicators of star formation – the researchers discovered an anomaly. Certain hotspots within the counter-arms have too much ionized carbon, meaning the X-ray emission cannot entirely be explained by star formation.

“We knew about these counter-arms and tried to observe with SOFIA if ionized carbon is actually produced by star formation, or if there’s some extra component that can come from the energy injected by the active galactic nucleus,” said Fadda.

This calls into question the relationship between ionized carbon and star formation, and can have implications on the study of galaxies that are more distant than NGC 7479.

“This is where SOFIA becomes uniquely useful: Studying these cases of galaxies close to us to have an idea of what to encounter when we go to higher redshift to study galaxies and the farther universe,” Fadda said.

SOFIA’s role in these observations pushes the limits of its capabilities. Primarily suited for studying objects fairly close to our home galaxy, SOFIA’s spatial and spectral resolution were just enough to distinguish ionized carbon in NGC 7479’s region of interest. Specifically, SOFIA’s Far Infrared Field-Imaging Line Spectrometer (FIFI-LS) was used to map the ionized carbon in the area.

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. 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 at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.

Looking at the ionized carbon emission from Sagittarius B provides critical information about star formation in our own galaxy and beyond.

Sagittarius, or Sgr B, a cloud of gas and dust near the center of the Milky Way is one of the brightest sources in the Central Molecular Zone – a massive, dense area of gas in the center of our galaxy, home to very high star formation rates and turbulent molecular gas clouds. At less than 27,000 light-years away, Sgr B is a relatively close neighbor, making it a useful region to study, both as a proxy for understanding other galaxies throughout the universe and also for understanding our own galactic center.

In particular, observing the concentration of ionized carbon in a molecular cloud like Sgr B is a powerful method for probing the properties of the system, including its level of star formation.

Using SOFIA’s upgraded German Receiver for Astronomy at Terahertz Frequencies, or upGREAT, a team of researchers imaged the ionized carbon characteristics of Sgr B. GREAT has ample spectral resolution to study Sgr B in detail at scales ranging from small clouds to star formation regions, allowing the scientists to understand the dynamics of gas within our galactic center. UpGREAT’s rapid imaging capabilities and detailed velocity resolution were crucial for enabling the study, which is part of a much larger scan of the area.

Among a number of findings, astronomers noted the steady carbon emission from Sgr B implies the entire region is physically connected, making it one continuous structure spanning about 34 by 15 parsecs, or about 111 by 49 light-years. It is spatially complex, comprised of arcs and ridges undergoing large-scale, turbulent motion.

By comparing the brightness of different emission lines, the group obtained an estimate of the ratio of ionized carbon emission coming from regions dominated by ionized hydrogen compared to emission from photodissociation regions, which are created by far-UV photons from massive stars.

Notably, the three star-forming cores of Sagittarius B2, within Sgr B, exhibit no ionized carbon emission, which is atypical of extreme star forming regions. They appear to be within a dark, narrow lane of dust which appears to be slightly physically distanced and in front of the rest of the region – though they remain, for the most part, dynamically related. This may answer the debate about the origin of star formation in Sgr B — dark dust lanes have been associated with cloud-cloud collisions and are a common sign of a shock-induced star formation trigger. This possibility is also consistent with the fact that multiple star formation stages coexist within Sgr B, as a recent burst of star formation within Sgr B indicates some sort of trigger has likely occurred.

“The nuclear regions of galaxies are fascinating places, and our relatively nearby galactic center lets us explore its gas clouds, stars, and black hole in far more detail than we can get in any other galaxy,” said Andrew Harris, astronomer at the University of Maryland and lead author on the paper. “The SOFIA results we found in our US-German project join those made at wavelengths across the electromagnetic spectrum made from telescopes all over the world and in space, allowing us to better understand not only our galaxy but others as well.”

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. 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 at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.

The Stratospheric Observatory for Infrared Astronomy, or SOFIA, the largest airborne observatory in the world, is in its annual maintenance period at NASA’s Armstrong Flight Research Center (AFRC) in California. During the six weeks of down time when there are no science flights, SOFIA will undergo both routine aircraft maintenance and specialized procedures unique to the aircraft.

This is the first year that the annual maintenance for the observatory will be performed during one period, rather than during multiple shorter maintenance periods throughout the year. This is an example of some of the strategic changes designed to enhance efficiency and ensure there are more hours for science observations. Executing all of the care and maintenance of the observatory during one period requires meticulous planning, coordination, and teamwork.

“Our biggest challenges are coordination and balancing our priorities,” said Paul Martinez, the operations manager for the observatory and a member of the AFRC-based SOFIA team. “We have some highly important, specialized maintenance for one of SOFIA’s unique features—the upper rigid door that opens to allow the telescope to view the sky—as well as other general aircraft maintenance activities that are necessary for flight airworthiness.”

The upper rigid door is one of the key aspects of SOFIA that allows the observatory to operate. The door was designed and tested at NASA’s Ames Research Center in California using its wind tunnel facilities. One of the engineers who led the development of the upper rigid door even returned to the SOFIA team from retirement to assist in its maintenance.

“This is the largest port that has ever flown on an aircraft,” said Paul Fusco, former SOFIA team engineer. It is a really thrilling aviation innovation. This is the first time the door has been taken off the aircraft since 2008.”

In fact, this is the door’s first maintenance since it was installed, as it has had a very high-performance life to this point. During the period when the door is off the aircraft, the bearings that allow the door to roll open will be inspected, cleaned, and replaced, as necessary. The team expects another period of high performance for the door.

“The maintenance period is an incredibly team-oriented effort,” said Jonathan Brown, SOFIA’s systems engineer and integration lead. “Whether it’s the telescope, mission systems, or avionics technicians, without everyone playing their part, we would not be successful.”

All of the SOFIA mission partners have worked together for months, meticulously planning every event that will happen during this maintenance period, based both on the needs and requirements for the aircraft as well as other aspects, like the telescope, that are unique to this facility. Now that the maintenance period is here, the team is working seamlessly to do the work necessary to ensure SOFIA is flight-ready and able to do the best science possible for the rest of the year.

“Down times are a time of improvements, not just maintenance,” said Michael Huetwohl, the DSI team lead at NASA’s Armstrong Flight Research Center in Palmdale, California, and the SOFIA telescope manager.

In addition to the need for maintenance on the aircraft and observatory systems, improvements and innovations can be implemented to ensure that SOFIA can do all of the science demanded by the astronomical community.

“What attracted me to SOFIA after 25 years in the semi-conductor industry,” Huetwohl said, “is the opportunity to strive for the best solution.”

The team is working to ensure human safety and flight worthiness as well as staying on the cutting edge of technology for astronomical observation in the mid- and far-infrared wavelengths of light.

While the aircraft and telescope are undergoing their routine and specialized maintenance, USRA is using the downtime to prepare for upcoming observations as well as incorporating the newest facility instrument into the observatory, the Echelon-Cross-Echelle Spectrograph, or EXES. EXES was initially operated by a group of scientists and engineers from the University of California, Davis, and has flown on SOFIA to study Mars’ atmospheric water loss and the chemistry of the universe. Now that EXES is transitioning to a facility instrument, the SOFIA Science Center needs to gain proficiency in using the instrument and to develop maintenance manuals and software to fully incorporate the instrument into the observatory.

This time-lapse video shows the SOFIA team attaching the upper rigid door to the crane then lifting and gently lowering the door onto the stand for its inspection and servicing. This is one of the key activities during SOFIA’s downtime. Like all of SOFIA’s maintenance, this event took meticulous planning and teamwork by a large group of experts. Video Credit: NASA/Agnew.

SOFIA is a joint project of NASA and the German Space Agency at DLR. DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. 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 at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.