Kia ora SOFIA – Airborne observatory welcomed in New Zealand

Long winter nights, crystal-clear insights

SOFIA took off from its home base in Palmdale, California, on 21 June 2017, landing in Christchurch after a refuelling stop in Hawaii. The airborne observatory takes advantage of the long winter nights in New Zealand, as the concentration of water vapour in the atmosphere at this time of year is far lower than in the northern hemisphere, which is currently experiencing summer. “This provides ideal conditions for crystal-clear observations. After all, even the tiniest quantities of water vapour in the air can absorb cosmic infrared radiation, making it undetectable by our spectrometer," explains Heinz Hammes, German Project Manager for SOFIA.

Flying above New Zealand at an altitude of 13 kilometres, where the amount of infrared-absorbing water vapour is substantially lower than on the ground, SOFIA will observe and analyse prominent star forming regions in the Small and Large Magellanic Clouds: "These regions have already been thoroughly scanned with optical instruments in the visible range, but more research in the infrared range is needed. This campaign is a follow-up from the last observation campaign in June 2016 to learn more about these regions," says Hammes. The SOFIA telescope will also be directed at the centre of the Milky Way – which is better visible from the southern hemisphere and for longer periods of time – to observe the motion of matter.

Three instruments for different observations

Various instruments can be fitted to the 2.7-metre diameter reflector telescope, allowing SOFIA to conduct its wide range of observations. "This year's New Zealand campaign, like in previous years, will feature three instruments. These will allow scientists to investigate star forming regions across the various stages of their development," explains Hammes. This campaign will include the German-built far-infrared spectrometers GREAT (German REceiver for Astronomy at Terahertz Frequencies) and FIFI-LS (Field-Imaging Far-Infrared Line Spectrometer), as well as the US-American instrument FORCAST (Faint Object InfraRedCAmera for the SOFIA Telescope). With these spectrometers it is possible to closely examine the overall dynamics of star formation and take spectral 'fingerprints' of atoms and molecules to determine gas densities and temperatures, as well as the velocity of the clouds.

Exploring uncharted territory in spectroscopy with GREAT

The GREAT spectrometer was originally equipped with one detector to, among other things, find out more about the chemical composition of star forming regions. This campaign will use two significantly improved versions of the instrument: upGREAT is equipped with 21 detectors spread over two arrays (14 +7), which for the first time will permit simultaneous, parallel observations at two different frequencies. 4GREAT extends the spectroscopic range as far down as 490 GHz (which is particularly interesting for the spectral lines of water and ammonia), and has four individual detectors that enable simultaneous observations in four different frequency ranges.

"These upgrades increase the performance and observation efficiency of our instrument by more than a factor of 10, opening up new, unexplored frequency ranges," explains Rolf Güsten, Principal Investigator for GREAT, 4GREAT and upGREAT at the Max Planck Institute for Radio Astronomy in Bonn. "This year's investigations will range from mapping atomic oxygen in the Magellanic Clouds and in the galactic centre, to studies of the chemistry of protoplanetary disks and planetary nebulae, and even the search for hitherto undetected molecules in space," adds Güsten.

FIFI-LS acquires data on star formation

It is the second time that FIFI-LS will be used to investigate the sky from the southern hemisphere. This instrument, equipped with two detector arrays, can measure substantially more wavelengths than GREAT and is able to produce large-scale maps of expansive molecular clouds faster. In particular, FIFI-LS will again observe the elements oxygen, nitrogen and carbon in the star forming regions and in the interstellar medium. This time it will turn its attention to the Milky Way, as well as the Large Magellanic Cloud region and other distant galaxies. "For the first time, we will be able to produce a precise and detailed inventory of the matter around the galactic centre," explains Alfred Krabbe, Principal Investigator for the FIFI-LS instrument and Director of the German SOFIA Institute (German SOFIA Institute (DSI)) at the University of Stuttgart. "In addition, we want to understand the motion of matter in the vicinity of the black hole at the centre of the Milky Way – and this is only possible by deploying SOFIA from New Zealand."

Campaign concludes with the FORCAST instrument

Earmarked for six flights during the deployment, FORCAST will conduct measurements at shorter wavelengths than FIFI-LS and GREAT, mainly to observe debris discs around newly formed stars, but also the dust spewed into space by old stars and supernovae. SOFIA is scheduled to fly back to Palmdale on 13 August for maintenance on the aircraft and telescope. Another 32 scientific flights will then be carried out from California from early September to mid-November 2017.