As I promised a few days ago, the “first light” images from the Herschel instrumment SPIRE have now been released (along with news of the other instruments on Herschel) and I have to say they’re pretty spectacular! I’m told that these pictures are much better than anyone expected at this stage because Herschel as a whole still hasn’t finished its calibration and other preparations it needs to do before commencing as an observatory proper.
Here, for example, is an image of the spiral galaxy M74 (also known as NGC 628) as shown by SPIRE and by the American Spitzer satellite, which was launched a few years ago. This image is taken at 250 microns, which is further into the infrared than the Spitzer image (160 microns), but has higher resolution owing to Herschel’s bigger mirror (3.5m). The SPIRE instrument is also much more sensitive than Spitzer so by a combination of these effects the detail this image reveals is really stunning.
What you’re actually seeing in this image is long-wavelength radiation emitted by dust which has been heated up by stars in the galaxy. The dust obscures the optical light from the stars but they leave clues to their existence in the infrared light the dust gives off. You can see dark lanes in the optical image here where the dust is absorbing the starlight.
Here is M74 again, but shown with two additional infrared “colours” (at 350 and 500 microns). By making observations like this at different wavelengths SPIRE can reveal information about the spectrum and hence temperature of the dust emission.
Congratulations to the Cardiff SPIRE team for a stunning success. If these images are any guide to the quality of data Herschel is going to be producing over the next few years then we’re all in for a treat!