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Flying observatory: SOFIA/GREAT observations offer new insights into star formation

The flying observatory SOFIA (Stratospheric Observatory For Infrared Astronomy) was stationed at Cologne Bonn Airport until 16 March 2021 / A research team from the University of Cologne used it to observe regions of the sky in which stars are forming

Left: Multi-colour image of Herschel observations of RCW36 in the constellation Vela, showing cold dust (in red) and warm dust (in green and blue). The area to be mapped with SOFIA is indicated in gray, with the lower half already observed in an earlier observing campaign in the spectroscopic line of ionized carbon (CII) at 158 µm wavelength. The resulting map is displayed at the right side.

The flying observatory SOFIA (Stratospheric Observatory For Infrared Astronomy) has successfully completed its observation flights from Cologne Bonn Airport. On board, amongst others, were scientists from the University of Cologne and the Max Planck Institute for Radio Astronomy in Bonn, who gained new insights into the formation of new stars during the observations.

SOFIA is a Boeing 747SP with a 2.5-m-diameter telescope on board, built for astronomical observations from the infrared to the submillimetre wavelength range. From 4 February to 16 March 2021, the aircraft was stationed at Cologne Bonn Airport. Typically, it embarks on its observation flights from its usual location in Palmdale/California. But SOFIA underwent maintenance for three months, carried out by Lufthansa in Hamburg. Since the coronavirus pandemic is currently making it impossible for German scientists to travel to California, SOFIA was used for an observation campaign in the night sky over Europe, conducted from Cologne Bonn Airport, before the aircraft’s return to California. This campaign has now been successfully completed.

The flying observatory is a joint project of NASA and the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt – DLR). SOFIA's flight altitude is more than 13 kilometres. This allows the aircraft to fly above most of the water vapour in the Earth's atmosphere, which would block infrared light at lower altitudes, thus enabling scientists to observe a wavelength range that is not accessible from Earth. Onboard SOFIA is the high-resolution receiver for far-infrared spectroscopy GREAT (German Receiver for Astronomy at Terahertz Frequencies), developed by the Max Planck Institute for Radio Astronomy in Bonn and the Institute for Astrophysics at the University of Cologne with the participation of the DLR’s Institute for Optical Sensor Systems (Berlin).

Scientists use the GREAT instrument, a spectrally high-resolution imaging spectrometer, to create a kind of chemical fingerprint of vast regions of the sky with high spatial and spectral resolution. The GREAT team not only performs measurements for its own research projects, but also collects data for other scientists.

Central to the Cologne campaign were observations made as part of the SOFIA legacy programme FEEDBACK, led by Dr Nicola Schneider at the University of Cologne’s Institute for Astrophysics and Professor Alexander Tielens at the University of Maryland. Several scientists from the MPIfR/Bonn participate in the FEEDBACK program. The goal of the programme is to systematically observe galactic massive star-forming regions. ‘First results from FEEDBACK and other recent SOFIA projects have yielded new discoveries, including bubbles of expanding gas caused by stellar winds, which can be observed clearly in the spectral line of ionized carbon (CII). This expansion causes further star formation,’ Dr Schneider explained. Furthermore, the rate at which new stars form in the Milky Way can also be determined by observing CII, providing insights into the evolution of our galaxy.


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