Looking to Jupiter, a Jovial Surprise

by Anashe Bandari

During flights in August 2018 and July 2019, planetary scientists used the Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint project of NASA and the German Space Agency at DLR, to study the atmospheric circulation on Jupiter – for the first time during the planet’s northern winter.

Two images of Jupiter side by side. On the left is Jupiter with its red spot and swirling brown, beige, and white cloud bands. On the right is Jupiter in the same position but with only a few bands showing yellow and dark orange against an orange background, with no red spot visible.
Left: Optical image of Jupiter taken by the Hubble Space Telescope. Right: SOFIA image of Jupiter demonstrating the variation in its brightness temperature with latitude. The two images show Jupiter in approximately the same orientation. Image credit: Left: NASA/ESA; Right: NASA/SOFIA/de Pater et al., 2021

To do so, they looked at hydrogen.

Hydrogen molecules – H2 – can be arranged in two different ways, known as parahydrogen and orthohydrogen. The two orientations have distinct energies, so determining the ratio of parahydrogen to orthohydrogen can tell astronomers about the overall temperature.

The researchers looked at the concentration of parahydrogen and orthohydrogen at altitudes just above Jupiter’s main cloud deck. They discovered that, around the equator, warm gas is rising into the atmosphere. At the north and south poles, however, the opposite is occurring: Cold gas from the higher, cooler levels of the atmosphere is traveling downward.

“This gives a sense of the general circulation: rising at the equator, sinking near the poles,” said Imke de Pater, lead author on a recent paper in the Planetary Science Journal describing the observations.

Jupiter’s atmosphere had been looked at through the lens of hydrogen before – by SOFIA in 2014, and by NASA’s Voyager 1 and 2 in 1979 – but only during the northern Jovian summer. The current observations were the first ever taken during Jupiter’s northern winter, about half a Jovian year after the 2014 SOFIA studies. This comparison illustrated how Jupiter’s poles change with the seasons, showing that its far north remains cooler than its far south, regardless of time of year.

Jupiter’s northern and southern hemispheres are known to have an asymmetric aerosol distribution, so this temperature imbalance between its two poles is likely an effect of its asymmetry.

In studying Jupiter, de Pater and her colleagues also saw four other objects that had entered SOFIA’s field of view and the data collected: Jupiter’s four largest moons, known collectively as its Galilean satellites – Io, Europa, Ganymede, and Callisto.

“We were surprised that we actually captured all four satellites, and could determine their brightness temperature,” de Pater said.

Thanks to this pleasant surprise, the group could clearly see how the moons’ temperatures decrease with depth in their subsurface layers. These temperature changes can eventually be used to determine the composition, density, and other properties inside the satellites.

The satellites all have unique characteristics – ranging from water ice on Europa, to heavy craters on the ancient Callisto, to extreme volcanic activity on Io – making their material makeup particularly interesting to investigate.

Jupiter and its moons are too bright to be observed by the long wavelength channels on the James Webb Space Telescope as they can saturate the instrument, and they cannot be measured from the ground due to Earth’s atmosphere blocking a large amount of mid-infrared radiation. SOFIA’s unique access to the mid-infrared, therefore, enables these measurements and provides critical information about Jupiter and its moons.

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.

Make No Bones About It: SOFIA Maps the First Magnetic Fields of a Galactic Bone in Their Entirety

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.

A long horizontal narrow orange cloud on a background of soupy brown and gray clouds. Magnetic field streamlines are laid over the orange cloud like stripes on a tiger's back.
A map shows the direction of magnetic fields in the G47 bone overlain atop an image of the G47 filament as seen by the Herschel Space Observatory. The red and yellow areas are high-density regions of dust and gas. Credit: G47: ESA/Herschel/PACS/SPIRE/Ke Wang et al. 2015; Polarization map: Stephens et al., 2022

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.

Science in the Southern Hemisphere: SOFIA Deploys to Chile

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.

SOFIA on the runway at Santiago International Airport
SOFIA arrives at the Santiago International Airport. Credit: NASA/Raphael Ko

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.

Large Magellanic Cloud
The Large Magellanic Cloud, one of the objects SOFIA will observe during deployment. Credit: ESA/NASA/Hubble

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.


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.

SOFIA on the runway at Santiago International Airport
SOFIA llega al Aeropuerto Internacional de Santiago. Crédito: NASA/Raphael Ko

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.

Large Magellanic Cloud
La Gran Nube de Magallanes, uno de los objetos que SOFIA observará durante su despliegue. Crédito: ESA/NASA/Hubble

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.

SOFIA: Science Above the Clouds

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.

Tilted Galaxy Turns Studies Topsy-Turvy

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.

NGC 7331 galaxy with circles showing the different sections of the galaxy.
Because NGC 7331 is viewed at an incline, there is a marked difference in the ionized carbon emission observed in different parts of the galaxy, depending on our observing perspective. Emission from within the delineated donut shape varies between the side of the galaxy that is closer to us (lower sector) and its far side (upper sector). This shows that viewing perspective has an effect on the origin of the ionized carbon emission observed. Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona/Sutter et al., 2022

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.

How Magnetic Fields Help Feed a Supermassive Black Hole

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.

Image showing NGC 1097 with inset of the starburst ring in the center with magnetic streamlines
Gas streams outside and within the starburst ring (colorscale) of the spiral galaxy NGC 1097 follow the magnetic field, feeding the supermassive black hole with matter from the galaxy. Credit: NGC 1097: ESO/Prieto et al. (colorscale)

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.

Animation showing streamlines over NGC 1097
This figure shows the magnetic field orientation (streamlines) and direction (animated streamlines) in the central 1 kpc starburst ring of the spiral galaxy NGC 1097 using data from the radio polarimetric observations. Credit: Lopez-Rodriguez et al.

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.

Orientations of the magnetic field within the starburst ring of NGC 1097
Orientations of the magnetic field within the starburst ring of NGC 1097. The blue lines indicate far-infrared data obtained from SOFIA, while the red and orange lines are radio polarimetric observations. The magnetic field has different configurations at far infrared wavelengths compared to radio wavelengths. Credit: Lopez-Rodriguez et al.

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.

SOFIA Observes Venus: A Delicate Dance to Understand Our Hot and Cloudy Twin’s Atmosphere

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.

Image through one of SOFIA’s windows, overlooking over one wing with two of the engines in view. The colorful sunset sky and the crescent moon are visible as the team prepares to observe Venus.
The sunset and crescent moon are visible as the SOFIA team prepares to observe Venus. Credit: NASA/AFRC, Carla Thomas

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.

A Stellar Merger’s Snapshot in Time

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.

SOFIA FORCAST measurements (orange) of the V838 Mon spectrum, and the best-fit composite model of SOFIA data with a silicate-to-alumina ratio of 50:50 (yellow), overlaid atop an image of V838 Mon
SOFIA FORCAST measurements (orange) of the V838 Mon spectrum, and the best-fit composite model of SOFIA data with a silicate-to-alumina ratio of 50:50 (yellow), overlaid atop an image of V838 Mon obtained by the Hubble Space Telescope, which shows the light echo illuminating circumstellar material. Credit: V838 Mon: ESA/Hubble & NASA; Spectra: Woodward et al.

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.

A Spiral Galaxy’s Invisible, Opposing Arms

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.

Hubble Space Telescope image of NGC 7479 with 20 cm radio continuum contours in yellow. The boxes highlight the ends of the lower and upper counter-arms; expanded versions of these regions are shown in the left and right panels where the circles depict the aperture of SOFIA’s FIFI-LS instrument.
Middle panel: Hubble Space Telescope image of NGC 7479 created from observations at visible and near-infrared wavelengths with 20 cm radio continuum contours in yellow. The boxes highlight the ends of the lower and upper counter-arms; expanded versions of these regions are shown in the left and right panels where the circles depict the aperture of SOFIA’s FIFI-LS instrument. Credit: ESA/Hubble & NASA

“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.

SOFIA Observes Star Formation Near the Galactic Center

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.

FORCAST image of the galactic center next to  the same area showingi onized carbon intensity contours of the Sagittarius B region
Left: An image of the Sagittarius B region in the galactic center taken by SOFIA’s FORCAST instrument, combined with images from NASA’s Spitzer Space Telescope and the Herschel Space Observatory of the European Space Agency. Right: Ionized carbon intensity contours of the Sagittarius B region. The striped pattern is a scanning artifact due to the motion of the telescope. In both panels, crosses indicate the locations of the three star-forming cores of Sagittarius B2. Credit: Left: NASA/SOFIA/JPL-Caltech/ESA/Herschel; Right: Harris et al., 2021

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.