This image shows the Whirlpool Galaxy, 23 million light years away in the constellation Canes Venatici. It was obtained with the Photodetector Array Camera and Spectrometer (PACS) aboard ESA’s Herschel Space Telescope.
This galaxy was first catalogued by Charles Messier in 1773, who placed it as item 51 on his list of cloud-like celestial objects. However, Messier’s telescope only saw the galaxy’s central portion as a faint smudge. It was not until 1845 that the great spiral pattern was seen.
The bright blue dot at the top of the image is the centre of a smaller galaxy that is passing by the larger. Its gravitational field has slightly deformed the spiral shape of the Whirlpool Galaxy. Had this smaller galaxy passed any closer to the centre of M51, it would have destroyed the delicate spiral shape of the larger galaxy altogether.
This image was taken on 14 June 2009, when Herschel opened its infrared ‘eyes’ to the Universe for the very first time. Even before the instruments were finely tuned, it revealed that Herschel was working extremely well, and gave a hint of the extraordinary images to come.
The Herschel images are a visual treat and can be found here.
Credits: ESA and the PACS consortium