The United Kingdom-led Spectral and Photometric Imaging Receiver (SPIRE) instrument on board the Herschel Space Observatory has made its first astronomical observations, with spectacular results. The European Space Agency (ESA) released the first SPIRE images, together with first-light observations from the other two Herschel instruments.
The SPIRE camera responds to light at wavelengths between 250 and 500 microns — 500 to 1,000 times longer than the wavelength of visible light. It is designed to look for emission from clouds of dust in regions where stars are forming in our own and other galaxies.
On June 24, SPIRE was able to observe the sky for the first time. The telescope was trained on two galaxies to get a first impression of what the instrument could see. The results were better than anyone expected from first observations, made before any attempt to set up the instrument or to tune the image-making software. The target galaxies showed up prominently, providing the best images seen at these wavelengths. Many more distant galaxies were also seen in the field of view.
The images show two galaxies, M66 and M74, at a wavelength of 250 microns. The images trace emission by dust in clouds where star formation is active, and the nucleus and spiral arms show up clearly. Dust is part of the interstellar material that fuels star formation, and these images effectively show the reservoirs of gas and dust that are ready to be turned into stars in the galaxies. Significantly, the frames are also filled with many other galaxies that are more distant and only show up as point sources, and there are also some extended structures, possibly due to clouds of dust in our own galaxy.
These images have given astronomers an exciting taste of the important scientific studies planned with SPIRE. The instrument will look at star formation close up in our own galaxy and in nearby galaxies, and it will search for star-forming galaxies in the distant universe. Because these galaxies are so far away, their light has taken a long time to reach us, so by detecting them we are looking into the past and learning how and when galaxies like the Milky Way were formed.
“These quick first light observations have produced dramatic results when we consider that they were made on day one,” said Matt Griffin, principal SPIRE investigator at Cardiff University in Wales. “Astronomers planning to use SPIRE are delighted because they can see that the main scientific studies planned with the instrument are going to work extremely well. In fact all three instruments on Herschel have now shown what they can do, and the results are spectacular.”
“I am thrilled by the quality of these first images from SPIRE,” said Robert Kennicutt of Cambridge University, who will use Herschel to study nearby galaxies, including the two selected for SPIRE first light. “They reveal the cold dust and star formation in these galaxies in stunning detail, and are a sneak preview of future observations that promise to revolutionize our understanding of star formation in the universe.”
“We have dreamed of seeing such images for a long time, more than 10 years,” said Laurent Vigroux of CEA/IRFU Saclay and Institut d’Astrophysique de Paris, who is the co-principal investigator of the SPIRE team. “And they are an achievement — the first real images in the far infrared, 10 years or more of work to exploit all the scientific results that SPIRE will produce.”
“We are delighted to see that the SPIRE instrument is working so effectively and returning such detailed, high quality images,” said Keith Mason, chief executive of the Science and Technology Facilities Council (STFC), which provides the United Kingdom funding for Herschel. “United Kingdom researchers have put a great deal of hard work into this complicated camera, and these amazing new images are proof of the skill and expertise we have here in the United Kingdom and why we continue to be at the forefront of new technology development for Europe’s growing space exploration activities.”