First Solar Images from Sunrise III
The observational data from the balloon-borne solar observatory make the smallest details on the solar surface visible.
The balloon-borne solar observatory Sunrise III captured images of the Sun with highest resolution in July of this year during its six-and-a-half-day stratospheric flight. The team has published the first, carefully processed images today. They show smallest structures on the Sun’s visible surface, only 50 kilometers in size. The Sunrise III data make it possible to follow processes on the solar surface and in its lower atmosphere at an unprecedented height resolution for several hours without interruption. The Sun has been particularly active during the entire year, and also during Sunrise III's research flight. Therefore, in addition to sunspots and dynamic magnetic fields, the observatory was able to witness two solar flares. The images from the on-board camera have now also been processed. They impressively document the unique research adventure at the boundary to space.
Six and a half days of uninterrupted observations of our star – this feat was achieved by the balloon-borne solar observatory Sunrise III this summer. After the successful launch on July 10, 2024 beyond the Arctic Circle in Sweden, a helium balloon lifted Sunrise III to a height of more than 35 kilometers. This observation position is optimal for solar researchers: above the Earth's air masses, no air turbulence obscures the view; in addition, Sunrise III has access to ultraviolet radiation from the Sun. And since the flight took place in the summer at the Arctic Circle, the midnight sun offered the opportunity to look at our star uninterruptedly during the journey. Stratospheric winds carried the observatory westward and the flight ended with an adventurous landing in Canada's Northwest Territories. Only a tiny part of the huge amount of data, which the recovery team rescued from the wilderness about two weeks later, has now been processed and can already be used scientifically.
The amount of data is indeed overwhelming: Sunrise III recorded around 200 terabytes of data. Sifting through these data image by image - assuming the frame rate of typical videos of 25 frames per second - would take approximately a month. To exploit the full potential of the data, the images must be processed carefully. "To make structures of only 50 kilometers in size visible on the Sun, we are pushing the optics to the limits of what is possible. The sensitive system must be kept adjusted to a hair's breadth during flight," explains Sunrise III project scientist Dr. Achim Gandorfer. "During flight, we correct deviations in the micrometer range, mainly caused by unavoidable temperature fluctuations, in real time. The data are given the final touches in the supercomputer”, he adds. "Sophisticated algorithms and months of computing time on the MPS high-performance cluster are necessary to remove all unwanted effects from the data," adds Dr. Tino Riethmüller, the scientist responsible for the Sunrise III software.
Detailed images
The first images cleaned up in this way show parts of the Sun’s visible surface and the chromosphere above it like never before. The ultraviolet spectropolarimeter SUSI, which was developed and built under the leadership of the MPS, captures the ultraviolet light from the solar surface, which is invisible to the human eye. In addition to sunspots and their finely structured edges, the instrument has imaged the typical pattern of ascending and descending plasma, known as granulation. In the narrow border lines between individual granules, tiny, bright spots light up. They measure barely more than 50 kilometers in diameter and are considered to be the smallest building blocks of the Sun's magnetic field.
"The level of detail in the images exceeds all our expectations," says MPS scientist Dr. Alex Feller, head of the SUSI team. Translated to more everyday standards, it corresponds to the ability to spot a one-euro coin from a distance of 50 kilometers. "Sunrise III manages to visualize the magnetic fields and their temporal development with this level of detail over hours," adds Dr. Feller. This is mainly possible because Sunrise III does not look at the Sun through the Earth's turbulent atmosphere. No ground-based telescope can maintain this level of detail for hours.
The image stabilization system developed at the Institute for Solar Physics (KIS) in Freiburg (Germany) and the ability of the gondola to automatically compensate for even the smallest wobbles during the flight were also crucial in achieving the high data quality. The gondola is the contribution of the Applied Physics Laboratory at Johns Hopkins University (Maryland, USA) to the Sunrise III mission. These properties lead to another uniqueness of Sunrise III: precise and simultaneous observations from the ultraviolet to the infrared range of the solar spectrum. "In less than a week, Sunrise III has probably recorded the most complete data set of the Sun to date," explains Dr. Andreas Korpi-Lagg, Sunrise III project manager.
Flares and a dynamic magnetic field
The Sun is currently approaching its maximum in activity and showed its temperamental side during Sunrise III's flight. For example, it was possible to point the telescope at two solar flares. In addition, images from the TuMag instrument show sunspots emerging and disappearing, as well as regions in which flows of hot plasma from the solar interior wash magnetic fields to the surface. TuMag was provided by a Spanish consortium led by the Instituto de Astrofísica de Andalucía (Granada, Spain). The infrared spectropolarimeter SCIP specializes in the precise determination of plasma streams and magnetic fields in the chromosphere. It was contributed to the mission by the National Astronomical Observatory of Japan. Above the chromosphere, the Sun's temperature rises sharply: from around 10,000 degrees to one million degrees. In the images published today, elongated, fibril-like structures can be seen above the sunspots.
"The new data from Sunrise provide a unique view of the visible surface of the Sun and the chromosphere above it," says MPS Director Prof. Dr. Sami K. Solanki, Sunrise III principal investigator. "They offer us the opportunity to understand the processes and phenomena in all layers of the solar atmosphere better than ever before," he adds.
Sunrise III flight as seen by IRIS-2
"Selfies" during the flight
Another impressive souvenir from Sunrise III's adventurous flight are the images taken by IRIS-2, an instrument equipped with four cameras belonging to a Spanish team of amateur astronomers. It was mounted on the gondola during the flight and documented take-off, flight, and landing from a "selfie perspective". The completely black sky seen in these images is impressive evidence of the space-like observation conditions in the stratosphere.
About the project
The balloon-borne solar observatory Sunrise III is a mission of the Max Planck Institute for Solar System Research (MPS, Germany) and the Johns Hopkins Applied Physics Laboratory (APL, USA). Sunrise III looks at the Sun from the stratosphere using a 1-meter telescope, three scientific instruments, and an image stabilization system. Significant contributors to the mission are a Spanish consortium, the National Astronomical Observatory of Japan (NAOJ, Japan), and the Leibniz Institute for Solar Physics (KIS, Germany). The Spanish consortium is led by the Instituto de Astrofísica de Andalucía (IAA, Spain) and includes the Instituto Nacional de Técnica Aeroespacial (INTA), Universitat de València (UV), Universidad Politécnica de Madrid (UPM) and the Instituto de Astrofísica de Canarias (IAC). Other partners include NASA's Wallops Flight Facility Balloon Program Office (WFF-BPO) and the Swedish Space Corporation (SSC).
Sunrise III is supported by funding from the Max Planck Foundation, NASA under Grant #80NSSC18K0934 and #80NSSC24M0024 (“Heliophysics Low Cost Access to Space” program), and the ISAS/JAXA Small Mission-of-Opportunity program and JSPS KAKENHI JP18H05234. The Spanish contributions have been funded by the Spanish MCIN/AEI under projects RTI2018-096886-B-C5, and PID2021-125325OB-C5, and from ”Center of Excellence Severo Ochoa” awards to IAA-CSIC (SEV-2017-0709, CEX2021-001131-S), all co-funded by European REDEF funds, “A way of making Europe”.
