After making over 35 000 observations and logging more than 25 000 hours of studying the Universe, the Herschel Space Observatory has exhausted its supply of liquid helium, which is required to cool the telescope's instruments to make highly precise measurements. Now that the school-bus sized telescope will cease its active duty, astronomers from 14 countries, including Canada, will devote their full attention to analyzing the prolific telescope's legacy of data.
"Herschel is a winning mission for Canadian science," said Gilles Leclerc, Acting President of the Canadian Space Agency (CSA). "Canadian astronomers have co-authored approximately 250 peer-reviewed science publications in just the first three years of the mission, and the most astounding discoveries are yet to come."
Since its launch on May 14, 2009, Herschel, the largest most powerful infrared telescope ever flown in space, has unveiled previously invisible celestial objects, leading to new insights into the origin and evolution of stars, planets and galaxies. Through funding from the CSA, two Canadian teams of astronomers were an integral part of the development and operations of two of the three science instruments on board the European Space Agency's telescope: the Heterodyne Instrument for the Far Infrared (HIFI) and the Spectral and Photometric Imaging Receiver (SPIRE).
Professor Michel Fich of the University of Waterloo is the Principal Investigator for HIFI in Canada, to which Canada contributed a key sub-system (known as the Local Oscillator Source Unit) built by COM DEV, in Cambridge, Ontario. Professor David Naylor of the University of Lethbridge is the Principal Investigator for Canada's contribution to SPIRE. The Canadian Herschel science team consists of scientists from: the University of British Columbia, University of Calgary, Western University, Toronto University, University of Victoria, McMaster University and the National Research Council Canada.
"The images produced by SPIRE are simply breathtaking," says Professor Naylor. "Observations over most of this wavelength range are inaccessible from the ground due to absorption by atmospheric water vapour. Free from such limitations, Herschel, with its broad spectral coverage and superb resolution, has revealed a wealth of previously unknown structures in the interstellar medium of our galaxy. These regions can only be detected because of the sensitivity of the
Canada's involvement in the development of SPIRE has allowed Canadians to take part in discoveries like observations of the glow from dust in the debris disc surrounding the young star Fomalhaut,* an analog of the primordial Solar System. Detailed studies suggest that the dust in this debris disc consists of "fluffy" aggregates of grains, which are produced by the frequent collisions taking place between comets within the disc.
A high tech spin-off company, Blue Sky Spectroscopy of Lethbridge, Alberta, was founded as one of three worldwide centres of expertise to process SPIRE's data. Privately owned and operated, Blue Sky's customers include: NASA, the CSA, the European Space Agency, Harvard University, the University of California (Berkeley), the University of Chicago, the Max Planck Institute (Germany), the National Institute of Standards and Technology (USA) and Cardiff University (Wales).
Herschel has also been a particularly useful tool for following the trail of water throughout the Universe, from star-formation clouds to stars to planet-forming discs. The space observatory detected thousands of Earth ocean's worth of water vapour in these discs, with even greater quantities of ice locked up on the surface of dust grains and in comets like Hartley-2, which was found to have almost exactly the same isotopic ratios as the water in our oceans, fueling the debate about how much of Earth's water originated from impacting comets.
"Herschel is challenging us by raising more questions than answers so far," said Professor Michel Fich. "For instance, one of our projects for the HIFI instrument began with a deceptively simple question: why do high mass stars form differently from low mass stars? What we have found is that every object in our sample is different from the others in some significant way. This is really exciting because it was completely unexpected, and it is going to take years to work out why."
Herschel will continue communicating with its ground stations for some time after the helium is exhausted, allowing a range of technical tests. Finally, in May, it will be propelled into its long-term stable parking orbit around the Sun. The science team will analyze Herschel's data for years to come. Canadian astronomers will continue to play a leading role in this analysis for both HIFI and SPIRE.