New infrared spectrometer from Germany on SOFIA, the airborne observatory
During its first scientific flight, the new infrared spectrometer FIFI-LS (Field-Imaging Far-Infrared Line Spectrometer) investigated the birth of young stars in the Orion Nebula and nine other celestial regions. The instrument, carried on board the airborne observatory SOFIA (Stratospheric Observatory for Infrared Astronomy) operated by the US space agency NASA and the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), gathered important data on the formation of stars while simultaneously proving its suitability for this type of mission. This means that a second German instrument has successfully entered its operational phase on board SOFIA, in addition to the far-infrared spectrometer GREAT.
For stars to form, molecular clouds must cool
The Orion Nebula is located in the Milky Way at a distance of roughly 1300 light years from Earth. This celestial region is particularly interesting to science because it is one of the galaxy's most active star forming regions. The scientists used FIFI-LS specifically to analyse the Becklin Neugebauer Object – a stellar nursery containing both young stars and dense gas in which new stars are being created. For this to happen, the hot gas in the region must cool from an initial temperature of around 100 Kelvin (-173 degrees Celsius) to roughly 10 Kelvin (-263 degrees Celsius) – only then does the pressure within the cloud drop sufficiently to allow condensation to occur and stars to form.
Elements such as oxygen and carbon promote this cooling by radiating heat from inside the cloud to the exterior. Leslie Looney, the project's senior scientist from the University of Illinois, wants to find out, in detail, how this process works: "At very specific far-infrared wavelengths, oxygen and carbon radiate a substantial portion of the thermal energy found in the cloud, and FIFI-LS is perfectly equipped to detect this." SOFIA is currently the only observatory that enables investigations at these far-infrared wavelengths.
In addition, FIFI-LS observed nine other infrared objects, including the centre of the Milky Way, during the three scientific flights held on 21, 23 and 25 April 2014. "With FIFI-LS, one of the most modern far-infrared spectrometers is now fitted on board SOFIA," says Alois Himmes, SOFIA Project Manager at DLR. "Together with GREAT and four other NASA spectrometers and cameras, the scientists currently have six instruments with which they can study the infrared skies."
FIFI-LS was delivered to Palmdale, California, the home base of the SOFIA airborne observatory, back in November 2013, where it was prepared for its first mission. Two successful test flights were held at the beginning of March and mid-April 2014, during which scientists, engineers and technicians put the spectrometer's functionality and performance through an extensive series of tests.
FIFI-LS was initially developed and built at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, near Munich, and from 2012 the Institute of Space Systems at the University of Stuttgart under the direction of Alfred Krabbe. The Deutsches SOFIA Institut (DSI), based at the University of Stuttgart, coordinates the airborne observatory's German operations.
SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a joint project of the German Aerospace Center (DLR) and the US National Aeronautics and Space Administration (NASA). The German component of the SOFIA programme is being carried out under the auspices of DLR with funds from the Federal Ministry of Economic Affairs and Energy, the State of Baden-Württemberg and the University of Stuttgart. The development of the German instruments is funded by the Max Planck Society (MPG), the German Research Foundation (DFG) and DLR. Scientific operations are coordinated on the German side by the German SOFIA Institute (DSI) at the University of Stuttgart, and on the American side by the Universities Space Research Association (USRA).