Size Doesn’t Matter?

A recent press release from the Herschel Space Observatory noted the fact that Herschel has the “largest mirror ever launched into space.” This is true. Herschel’s primary mirror is 3.5 meters in diameter, while Hubble’s primary mirror is only 2.4 meters across. Given that knowledge, one might expect the images from Herschel to surpass those [...]

Galaxy Cluster Abell 2218 from Herschel & Hubble. Image credit: ESA/SPIRE and HerMES Consortia (top); ESA/NASA/STScI (bottom).A recent press release from the Herschel Space Observatory noted the fact that Herschel has the “largest mirror ever launched into space.” This is true. Herschel’s primary mirror is 3.5 meters in diameter, while Hubble’s primary mirror is only 2.4 meters across. Given that knowledge, one might expect the images from Herschel to surpass those of Hubble. After all, bigger is better, right?Within the press release is the above Herschel image of the galaxy cluster Abell 2218, including a comparison to a Hubble image. It may surprise you to see that Herschel’s view is incredibly fuzzy compared to Hubble’s view. What happened? Perhaps size doesn’t matter?The important point to recognize is that the Herschel image captures infrared light, while Hubble’s view uses visible light. The resolution of a ...