New research from the Stratospheric Observatory for Infrared Astronomy (SOFIA) has shown that the magnetic fields in 30 Doradus — a region of ionized hydrogen at the heart of the Large Magellanic Cloud — could be the key to its surprising behavior.
Most of the energy in 30 Doradus, also called the Tarantula Nebula, comes from the massive star cluster near its center, R136, which is responsible for multiple, giant, expanding shells of matter. But in this region near the nebula’s core, within about 25 parsecs of R136, things are a bit weird. The gas pressure here is lower than it should be near R136’s intense stellar radiation, and the area’s mass is smaller than expected for the system to remain stable.
Using SOFIA’s High-resolution Airborne Wideband Camera Plus (HAWC+), astronomers studied the interplay between magnetic fields and gravity in 30 Doradus. Magnetic fields, it turns out, are the region’s secret ingredient.
The recent study, published in The Astrophysical Journal, found the magnetic fields in this region are simultaneously complex and organized, with vast variations in geometry related to the large-scale expanding structures at play.
But how do these complex-but-organized fields help 30 Doradus survive?
In most of the area, the magnetic fields are incredibly strong. They’re strong enough to resist turbulence, so they can continue to regulate gas motion and hold the cloud’s structure intact. They’re also strong enough to prevent gravity from taking over and collapsing the cloud into stars.
However, the field is weaker in some spots, enabling gas to escape and inflate the giant shells. As the mass in these shells grows, stars can continue to form despite the strong magnetic fields.
Observing the region with other instruments can help astronomers better understand the role of magnetic fields in the evolution of 30 Doradus and other similar nebulae.
SOFIA was a joint project of NASA and the German Space Agency at DLR. DLR provided the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed 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 was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational capability in 2014 and concluded its final science flight on Sept. 29, 2022.
Once a star evolves beyond the main sequence – the longest stage of stellar evolution, during which the radiation generated by nuclear fusion in a star’s core is balanced by gravitation – the fate of any planetary system it may have had is an enigma. Astronomers generally don’t know what happens to planets beyond this point, or whether they can even survive.
In a paper published recently in The Astronomical Journal, researchers used new data from the Stratospheric Observatory for Infrared Astronomy (SOFIA) and the Atacama Large Millimeter/submillimeter Array (ALMA), as well as archival data from the Spitzer Space Telescope and the Herschel Space Observatory, to study the Helix Nebula. These observations provide one potential explanation for the fate of these planetary remains.
A Process of Elimination, and a Disruptive Origin
The Helix Nebula is an old planetary nebula – expanding, glowing gas ejected from its host star after its main-sequence life ended. The nebula has a very young white dwarf at its center, but this central white dwarf is peculiar. It emits more infrared radiation than expected. To answer the question of where this excess emission comes from, the astronomers first determined where it could not have come from.
Collisions between planetesimals – small, solid objects formed out of cosmic dust left over from the creation of a planetary system around a star – can produce this type of excess emission, but SOFIA and ALMA failed to see the large dust grains required for such objects to exist, ruling out one option. The astronomers also didn’t find any of the carbon monoxide or silicon monoxide molecules characteristic of the gas disks that can surround evolving post-main-sequence stellar systems that precede objects like the Helix Nebula, excluding another potential explanation.
Different strands of evidence place strict constraints on the size, structure, and orbit of the source of the emission, and eventually come together to identify the same culprit: dust – from full-fledged planets destroyed during the nebula’s formation – returning toward its inner regions.
“In piecing together the size and shape of the excess emission, and what those properties infer regarding the dust grains in the white dwarf environment, we conclude that a disrupted planetary system is the best solution to the question of how the Helix Nebula’s infrared excess was created and maintained,” said Jonathan Marshall, the lead author on the paper and a researcher at Academia Sinica in Taiwan.
Once they realized the remnants of a former planetary system are at the origin of the infrared emission, they calculated how many grains need to be returning to the Helix Nebula’s center to account for the emission: about 500 million over the 100,000-year lifetime of the planetary nebula, conservatively.
SOFIA’s Role
SOFIA’s capabilities fell right into a gap between the previous Spitzer and Herschel observations, allowing the group to understand the shape and brightness of the dust, and improving the resolution of how far it spreads out.
“This gap lay around where we expected the dust emission to peak,” Marshall said. “Pinning down the shape of the dust emission is vital to constraining the properties of the dust grains that produce that emission, so the SOFIA observation helped refine our understanding.”
Though the researchers are not planning any follow-up observations of the Helix Nebula in particular, this study is a piece in a larger effort to use observations to understand what happens to planetary systems once their star evolves past the main sequence. The group hopes to study other late-stage stars using similar techniques.
SOFIA was a joint project of NASA and the German Space Agency at DLR. DLR provided the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed 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 was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational capability in 2014 and concluded its final science flight on Sept. 29, 2022.
Molecular clouds — clumps of gas and dust in space, where molecules form — make up the densest regions of the Milky Way, but how they assemble is largely unknown: Some theories point to a slow, long process, while others suggest a fast, dynamic one.
A recent study, published in Nature Astronomy, used data from the Stratospheric Observatory for Infrared Astronomy (SOFIA)’s upGREAT instrument to observe ionized carbon emission from molecular clouds in the Cygnus X region, one of the most massive star formation regions in the Milky Way. The astronomers, led by Nicola Schneider, a researcher at the University of Cologne in Germany, found areas of diffuse gas surrounding two molecular clouds are colliding very rapidly, creating a dense region in which new stars can form.
“Before this, there was a lot of uncertainty and debate on the timescale of cloud formation, because it is extremely difficult to observe,” said Lars Bonne, a postdoctoral research associate at SOFIA and author on the recent paper. “This is direct evidence of how it’s actually going: It’s fast!”
For decades, most processes in the interstellar medium were thought to take place on timescales of around 10 million years or more, but this high-velocity flow is leading to materials assembling in only about 1.2 million years — fast, as Bonne said.
Previous studies have shown that a very similar process is also at work in low-mass clouds. Coupled with these previous findings, this first observation of cloud collision in such a massive region helps complete the picture. Together, the studies indicate a degree of universality: Both smaller and more major cloud collision events that lead to star formation are now known to be quick.
This study also provides the first evidence that ionized carbon can unveil the interactions between molecular clouds. The group used data from SOFIA’s FEEDBACK program, which created large maps of ionized carbon in the Milky Way’s clouds. Schneider, Bonne, and their collaborators plan to continue to explore the FEEDBACK data to see if they can find similar processes occurring in other giant molecular clouds.
SOFIA was a joint project of NASA and the German Space Agency at DLR. DLR provided the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed 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 was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational capability in 2014 and concluded its final science flight on Sept. 29, 2022.
The Stratospheric Observatory for Infrared Astronomy (SOFIA) made the first-ever measurement of heavy atomic oxygen in Earth’s upper atmosphere.
Heavy oxygen is so called because it has 10 neutrons, rather than the normal eight of “main” oxygen, the form we breathe. Heavy oxygen is seen as a signature of biological activity, common in the lower atmosphere. Both forms are byproducts of photosynthesis, but main oxygen is consumed by the respiration of living things more than its heavy counterpart, leaving a larger concentration of heavy oxygen behind.
Little is known, however, about how this abundance of heavy oxygen permeates from the location of its creation near the ground into higher regions of the atmosphere. With its high spectral resolution, SOFIA’s GREAT instrument measured the ratio of main to heavy oxygen in the mesosphere and lower thermosphere, making the first spectroscopic detection of heavy oxygen outside a laboratory.
“It’s tracing biological activity — that’s well-proven,” said Helmut Wiesemeyer, a scientist at the Max Planck Institute for Radio Astronomy. “So far, the altitude to which this signature extends was thought to be 60 kilometers [around 37 miles] — so, barely the lower part of the mesosphere — and the question was, does it reach higher altitudes? And if it does, because there are no living organisms up there, the only way to reach higher altitudes would be an efficient vertical mixing.”
In other words, the only explanation for large concentrations of heavy oxygen in these regions is the upward and downward motion of air, which can have important implications for climate change.
Measuring heavy oxygen is complex because it looks so similar to main oxygen. From up in the stratosphere, SOFIA could separate the two against a lunar backdrop: the Moon’s brightness enabled the highest sensitivity to these hard-to-distinguish features.
This allowed the researchers to measure the main-to-heavy oxygen ratios up to 200 kilometers in the atmosphere. The results — published in Physical Review Research — ranged from a 382 to 468 factor difference in the two types of oxygen, similar to the ratio on the ground.
“There are processes that are altering these ratios. For Earth, this process is oxygenic life,” Wiesemeyer said — though there are other potential chemical explanations to be considered as well.
Wiesemeyer and his collaborators were very conservative in their uncertainty estimates, so they cannot completely attribute their heavy oxygen measurements to biology. Solar wind, for example, can also deliver heavy oxygen to Earth, but it is unlikely to make such a large contribution.
This pilot study measuring the balance between the two forms of oxygen proves a technique that atmospheric scientists could use to study vertical mixing. The study’s findings can also help better define a biologically relevant boundary of Earth’s atmosphere.
More ambitiously, future instruments that may be sensitive to various oxygen signatures can potentially use similar techniques to measure oxygen ratios in exoplanets. A combination of high oxygen abundances with an understanding of the vertical mixing on these exoplanets could indicate biological activity — though the group warns such a study would require huge sensitivities that current technologies do not have.
“The idea is to first understand what happens in front of your own door before you go into deeper studies elsewhere,” Wiesemeyer said.
These observations are too low for even low-orbit satellites, but too sensitive to be done from the ground. Stratospheric balloon-based observations may be able to offer potential follow-up studies in the future.
SOFIA was a joint project of NASA and the German Space Agency at DLR. DLR provided the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed 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 was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational capability in 2014 and concluded its final science flight on Sept. 29, 2022.
Catching a massive star in the early stages of formation is a rare event in astronomy, making it an exciting moment to study. A group of researchers took advantage of the discovery of one youthful star and used the Stratospheric Observatory for Infrared Astronomy (SOFIA) to reveal the magnetic processes that allow such a massive star to form.
The stellar nursery where the action is taking place, called BYF 73, is not your typical star-forming cloud. It’s relatively small, but at its central core is a young star that holds the record for the highest known rate of protostellar mass accretion, the process by which a growing star accumulates mass from its surrounding material.
Using SOFIA and another observatory – the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile – Peter Barnes, a research scientist at the Space Science Institute in Boulder, Colorado, and his team examined the magnetic fields within this cloud amid ongoing star formation. Studying the orientation of magnetic fields can shed light on their role in massive-star formation, a long-standing question. Massive stars form through a different process from their more average counterparts, relying on an ongoing exchange of material with their environment, rather than accreting mass from a surrounding disk of matter.
Birth of a “Masquerading Monster”
Previous ALMA research had shown that within the core of BYF 73 lies a “masquerading monster:” a single protostar, MIR 2, which is about 1,300 times the Sun’s mass and responsible for about half of the region’s power output. These ALMA values place MIR 2 in the very early stages of massive star formation, with an age of around 40,000 years — on human timescales, it began forming sometime after the arrival of humans to Australia.
“It’s exciting because MIR 2 seems to be so young, and massive stars evolve very quickly by astronomical standards and are very rare, making their early stages easy to miss,” said Barnes.
Data from SOFIA and ALMA both offer high resolution and sensitivity in their respective wavelength ranges, allowing Barnes and his team to map the polarization of dust grains in BYF 73. This helped the researchers determine the relationship between the cloud’s magnetic field and gas density – and what that might mean for the formation of MIR 2.
When Gravity Takes Over
The researchers found that both the strength of the magnetic field and density of the gas are on the higher end of the range typical for star-forming clouds, but the relationship between the two scales is as expected. This means what’s happening in BYF 73 isn’t necessarily something unique — it just happens to be massive, and its monstrous density compared to its small size may help astronomers uncover a threshold necessary for gravity to take over and allow stars to form.
Gravity is the sole force responsible for forming stars, but the unusually strong magnetic field in BYF 73 could be acting in opposition, preventing lower-mass stars from forming until gravity becomes strong enough to form a monster.
“The original discovery of the massive inflow of material [onto MIR 2] was very exciting, since so few examples were known for higher-mass protostars. From that point on, BYF has been the gift that keeps on giving,” Barnes said.
MIR 2 is still in the very early stages of forming a massive star, and the synergies between SOFIA and ALMA’s magnetic field studies have helped clarify the factors at play in the process.
“Without their discoveries, BYF 73, and MIR 2 within it, would still be real head-scratchers,” said Barnes.
SOFIA was a joint project of NASA and the German Space Agency at DLR. DLR provided the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed 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 was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational capability in 2014 and concluded its final science flight on Sept. 29, 2022.
SOFIA is on its way to a new “forever home” at the Pima Air & Space Museum in Tucson. Today, SOFIA took off for the last time from NASA’s Armstrong Flight Research Center in Palmdale, California. The pilots performed one last flyby of the area with a wing tilt to acknowledge everyone in the community who has supported and worked on SOFIA. The aircraft will land in Tucson, at the Davis-Monthan Air Force Base, where it will undergo final preparations before it is towed to the museum to eventually be on display to the public.
“The SOFIA mission may have ended, but the future is bright,” said Dr. Naseem Rangwala, the SOFIA project scientist at NASA’s Ames Research Center in California’s Silicon Valley. “SOFIA has made numerous and significant contributions to astrophysics and will continue to do so as our scientific community finds new and creative ways to analyze SOFIA data in the archive.”
SOFIA is a modified Boeing 747SP jet that was operated out of Armstrong. The SOFIA mission’s operations ended on Sept. 29, 2022 , but the team of incredible and diligent pilots and mechanics continued to support SOFIA as it prepared to go to its new home.
SOFIA is part of NASA’s legacy of airborne astronomy. Building on the successes of the Galileo I aboard a Learjet and the Kuiper Airborne Observatory, SOFIA was developed to provide the astrophysical community unprecedented access to the mid- and far-infrared wavelengths of light. This part of the electromagnetic spectrum is difficult to observe from Earth’s surface, because water in the atmosphere blocks mid- and far-infrared light from reaching the ground. SOFIA, flying above 99.9% of water in the atmosphere, could make observations of a wide variety of phenomena, from to cosmic magnetic fields.
In fact, SOFIA revolutionized the study of cosmic magnetic fields in astrophysics. Other observatories, like ESA’s (European Space Agency’s) Planck space observatory, could also detect polarized light and learn how these invisible forces affect galaxies. SOFIA, however, allowed scientists to make observations on much smaller scales. With the HAWC+ instrument, SOFIA probed dark rivers of material, called filaments, where stars start to form. They investigated the “bones” in galactic arms and caught the aftermath of galactic mergers. SOFIA also studied our galaxy and closest galactic companions, the Magellanic clouds.
SOFIA observed cosmic bubbles and how groups of massive stars trigger star formation or quench it, in some cases. SOFIA also could study molecules, making the first-ever detection of helium hydride, the first type of molecule that ever formed in the universe. SOFIA also turned its gaze on things much closer to home, like Venus’s atmosphere, comets, Pluto, and the Moon.
As the aircraft heads off to the Pima Air & Space Museum, the SOFIA leadership team at NASA would like to share some thoughts:
“We want to express our gratitude to everyone, both our U.S. and German colleagues, who, over the years, developed, tested, and operated the observatory at Ames and Armstrong. It has been an incredible team effort to create and operate the world’s largest airborne observatory. None of this would have been possible without the community of scientists who have used and supported SOFIA over the years. We look forward to hearing everything the SOFIA scientific community learns as we go on. It is with heartfelt thanks that we at NASA say goodbye to SOFIA. We are sad to see you go but so happy to have worked with the SOFIA team.”
SOFIA was a joint project of NASA and the German Space Agency at DLR. DLR provided the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed 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 was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational capability in 2014 and concluded its final science flight on Sept. 29, 2022.
Phosphine is a gas found in Earth’s atmosphere, but the announcement of phosphine discovered above Venus’s clouds made headlines in 2020. The reason was its potential as a biomarker. In other words, phosphine could be an indicator of life. Though common in the atmospheres of gas planets like Jupiter and Saturn, phosphine on Earth is associated with biology. Here, it’s formed by decaying organic matter in bogs, swamps, and marshes.
“Phosphine is a relatively simple chemical compound — it’s just a phosphorus atom with three hydrogens — so you would think that would be fairly easy to produce. But on Venus, it’s not obvious how it could be made,” said Martin Cordiner, a researcher in astrochemistry and planetary science at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
There may be other potential ways to form phosphine on a rocky planet, like through lightning or volcanic activity, but none of these apply if there simply isn’t any phosphine on Venus. And according to SOFIA, there isn’t.
Following the 2020 study, a number of different telescopes conducted follow-up observations to confirm or refute the finding. Cordiner and his team followed suit, using SOFIA in their search.
The recently retired SOFIA was a telescope on an airplane and, over the course of three flights in November 2021, it looked for hints of phosphine in Venus’s sky. Thanks to its operation from Earth’s sky, SOFIA could perform observations not accessible from ground-based observatories. Its high spectral resolution also enabled it to be sensitive to phosphine at high altitudes in Venus’s atmosphere, about 45 to 70 miles (about 75 to 110 kilometers) above the ground — the same region as the original finding — with spatial coverage across Venus’s entire disk.
The researchers didn’t see any sign of phosphine. According to their results, if there is any phosphine present in Venus’s atmosphere at all, it’s a maximum of about 0.8 parts phosphine per billion parts everything else, much smaller than the initial estimate.
Pointing SOFIA’s telescope at Venus was a challenge in and of itself. The window during which Venus could be observed was short, about half an hour after sunset, and the aircraft needed to be in the right place at the right time. Venus also goes through phases similar to the Moon, making it difficult to center the telescope on the planet. Add in its proximity to the Sun in the sky — which the telescope must avoid — and the situation quickly became tense.
“You don’t want sunlight accidentally coming in and shining on your sensitive telescope instruments,” Cordiner said. “The Sun is the last thing you want in the sky when you’re doing these kinds of sensitive observations.”
Despite the fact the group did not find phosphine after the stressful observations, the study was a success. Along with complementary data from other observatories that vary in the depths they probe within Venus’s atmosphere, the SOFIA results help build the body of evidence against phosphine anywhere in Venus’s atmosphere, from its equator to its poles.
SOFIA was a joint project of NASA and the German Space Agency at DLR. DLR provided the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed 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 was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational capability in 2014 and concluded its final science flight on Sept. 29, 2022.
Black holes potentially have an even larger influence on the galaxies around them than we thought. And the Stratospheric Observatory for Infrared Astronomy (SOFIA) provided a new way to look at their impact.
Active galactic nuclei (AGN) — the central region of a galaxy, which houses its supermassive black hole — are classified by how strong of a jet they produce, shooting matter away at near light speed. Since the jets are mostly visible at radio wavelengths, they are described as either radio loud or radio quiet.
“We see that some AGN have very powerful radio jets and some don’t, even though all AGN are intrinsically the same — they all have a supermassive black hole in the center and accrete mass,” said Enrique Lopez-Rodriguez, a research scientist at Stanford University’s Kavli Institute for Particle Astrophysics and Cosmology and lead author on the new SOFIA finding. “We don’t understand why some of them are so powerful, and some of them are not.”
Now, using SOFIA, Lopez-Rodriguez and his team have found that the polarization of infrared light from AGN also increases with their radio loudness, providing a new way to study black hole characteristics.
Motivated by the 2018 SOFIA discovery that the infrared light from the strongest known radio-loud AGN, Cygnus A, was highly polarized, the researchers developed a follow-up observation program with SOFIA to determine whether there’s a relationship between infrared polarization and radio loudness, and if so, why. They looked at the magnetic fields of a total of nine AGN, four of them radio loud and five radio quiet.
From SOFIA observations of light polarization, astronomers can deduce the structure of the magnetic field in the region. In the AGN sample Lopez-Rodriquez and his team studied, these polarizations show that in radio-loud AGN — AGN with strong jets — there’s a donut-shaped magnetic field perpendicular to the jets, along the equator of the AGN. That only radio-loud AGN have such a strong toroidal magnetic field indicates that the field is helping to transfer energy inward, feeding the black hole with matter coming from the host galaxy. The stronger the jets, the stronger the magnetic field, and the more energy there is in the system.
The group was surprised by the strength of the result.
“We were hoping for it, but we weren’t expecting such a nice correlation,” Lopez-Rodriguez said. “There’s so much physics behind it that we don’t understand, and future hydromagnetic models are required.”
Though a lot of science behind these objects remains unexplained, the result implies that black holes are potentially affecting galaxy evolution and jet production quite a bit more than astronomers previously realized. While astronomers typically consider gravity as the only force influencing supermassive black holes, this work shows that magnetic fields can aid in bridging the interface between black holes and matter in their host galaxy. With the help of these magnetic fields, black holes can impact not only the matter immediately around them, but can also work at even larger distances within the galaxy.
SOFIA was a joint project of NASA and the German Space Agency at DLR. DLR provided the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed 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 was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational capability in 2014 and concluded its final science flight on Sept. 29, 2022.
Astronomers using SOFIA, the Stratospheric Observatory for Infrared Astronomy, discovered something unique: a new type of stellar outburst that had never been seen before in the type of system under study. Through some scientific detective work, they were able to identify the characteristics that made this outburst different, placing it in its own brand-new category.
In what is known as a classical nova, a white dwarf – the dense remnant of a star in the final stage of its evolution – accumulates material from a nearby Sun-like companion star. The material absorbed from the companion star builds up on the surface of the white dwarf, until extreme pressures and densities cause a nuclear explosion, ejecting the material from the surface of the white dwarf. This creates a bright burst of light that lasts a few weeks to a few months, sometimes even years. Together, the pair of stars is called a cataclysmic variable.
In contrast, a dwarf nova happens in the same kind of system as a classical nova, but for a different reason. This type of nova occurs when the disc around the white dwarf becomes unstable causing an outburst that is much less powerful and bright than a classical nova. These outbursts last only a few days, but happen more frequently.
The cataclysmic variable SOFIA observed – V1047 Cen, a white dwarf and its Sun-like companion – erupted as a classical nova in 2005 (Nova Centauri 2005). But 14 years later, in April 2019, the system slowly started to re-brighten.
On days 88 and 89 after V1047 Cen began to brighten again, a team of researchers led by Dr. Elias Aydi, an astronomer at Michigan State University, used the FORCAST camera aboard SOFIA to analyze the system. They initially thought the re-brightening was indicative of a dwarf nova, but, unlike dwarf novae, this one kept going for quite a while.
“The thing about dwarf novae is they usually happen relatively quickly. The majority of them tend to rise to peak quickly and then decline quickly, they don’t spend a lot of time at the peak,” Aydi said. As far as we know, the longest dwarf nova cases have been around 100 days. V1047 Cen went on for 400. “If this was a dwarf nova, it would be a record-breaking one.”
Understanding the temperature of the gas around the system is typically an important clue as to what is going on. In this case, the researchers used the SOFIA spectra to reveal the temperature, which showed heating as a result of the outburst, helping to prove it was more than a typical dwarf nova.
With features inconsistent with both classical novae and dwarf novae, the astronomers tried to come up with an alternate explanation for this unusual event.
“We were like, ‘There’s something really interesting here, and we need to try to explain it,’” Aydi said.
Supplementing the SOFIA data, the group also conducted observations using nearly a dozen other instruments, covering much of V1047 Cen’s 400-day event. Taken together, the data started to make more sense, and they realized they had come across something unique – a new type of stellar outburst that had never been seen before in this type of system. The discovery uncovers new scenarios that can take place in these types of cataclysmic variables.
“It’s definitely not a classical nova, but definitely something more than a dwarf nova. It’s something in between, and likely a combination of different processes or outbursts,” Aydi said.
Such combinations of outburst are often referred to as combination novae and have been observed to take place in systems that feature a white dwarf and a giant companion star, but there’s no evidence of a giant star in V1047 Cen — if there were, we would be able to see it. Instead of a giant star, the white dwarf in V1047 Cen has a Sun-like companion. In addition, the observed characteristics of the outburst are not exactly like those seen in combination novae. This makes the 2019 outburst of V1047 Cen quite an exotic one — the first of its kind ever to be seen in a cataclysmic variable system that has undergone a recent classical nova eruption.
Finding out what caused this outburst is key to understanding V1047 Cen, and potentially other similarly unusual outbursts that might be discovered in the future. One of the primary steps will be determining how quickly the white dwarf and its Sun-like companion are orbiting their center of mass, which will require additional observations.
SOFIA was a joint project of NASA and the German Space Agency at DLR. DLR provided the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley managed 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 was maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. SOFIA achieved full operational capability in 2014 and concluded its final science flight on Sept. 29, 2022.
Circumbinary planets – planets that orbit around two stars, like the fictional Star Wars planet Tatooine and its two suns – exist in the universe, and are sometimes referred to as Tatooine planets. Systems in which two stars rotate around each other, called binary star systems, are incredibly common, comprising over half the stars in the Milky Way galaxy. But how does a binary system like this happen?
Researchers using the Stratospheric Observatory for Infrared Astronomy (SOFIA) saw a twisted magnetic field around a protobinary star system, a very young binary star system that is still growing. This provides a hint about how the system came to be.
As stars begin to form, they obtain most of their material from a disk of dust and gas surrounding them. A larger envelope of matter surrounds and feeds the disk. From here, binaries can emerge in one of two ways – far apart, where they grow in the envelope, or much closer to one another, where they form in the disk.
There’s a caveat, though: binaries that form in the envelope can move closer to each other over time, so even if they look near to one another now, they were not necessarily always that way.
That’s where magnetic fields come in.
In a recent study, SOFIA observations – supported by data from the Atacama Large Millimeter Array (ALMA), the Pico dos Dias Observatory, and archival data from the Herschel Space Observatory – found the magnetic field in the star-forming cloud Lynds 483 (L483) is oriented east-to-west in its outer regions, but twists 45 degrees counter-clockwise toward its center. ALMA confirmed that L483 contains two protostars and Herschel provided information about some of the region’s physical properties, while SOFIA and Pico dos Dias traced the magnetic field’s shape.
“If we back up a little bit, we think these protostars formed far away, migrated, and twisted up their field in the process of coming toward each other,” said Erin Cox, a postdoctoral associate at Northwestern University in Evanston, Illinois, who led the study.
Because stars and their planets form around the same time, figuring out how the protobinary came together tells astronomers about the types of planets it can harbor.
“If we understand how the protobinary stars formed, we will get a better understanding of how much stuff is in the disk, which is the material that provides the planets with their masses,” Cox said. “We want to understand what our starting mass budget is for these planets.”
For example, the protobinaries’ inward migration can enhance the motion of the gas and dust around them, ejecting them out of the system. If too much material gets blown out, only Earth-like rocky planets can potentially form, rather than gas giants, like Jupiter.
Being able to see these magnetic fields helps decipher the formation of binary systems and, in turn, their associated Tatooine planets.
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 achieved full operational capability in 2014, and the mission will conclude no later than Sept. 30, 2022. SOFIA will continue its regular operations until then.