A Galaxy and Bastard Jacobite Cannon Balls

M51 (the "whirlpool galaxy") is the bright centerpiece of a relatively small cluster of galaxies, a neighbor to our Local Group, and a fellow member of the Virgo Supercluster. It's roughly 30 million light years away, and is seen face-on from our perspective. It is actually a pair of galaxies, the larger, spiral M51A (or NGC 5194) and the smaller, irregular M51B (or NGC 5195). It is a spectacular sight at almost any resolution, but astonishingly so as seen through the Hubble Space Telescope:

(A larger, higher-resolution image can be downloaded by clicking here... and a truly massive [more than 100 megs!], full-resolution file is available here -- but please come back!)

One of the first people to recognize the spiral structure of M51 was William Parsons, the Third Earl of Rosse, who built the world's largest telescope on his estate in the midlands of Ireland in the early 1840's. His ingenious 72-inch telescope, "The Leviathan of Parsonstown," was to remain the largest (and thus most powerful light-gatherer) on this planet for more than 70 years, a record of persistant dominance not likely to be equalled. Its staggering light-gathering power for the time allowed Lord Rosse to view detail in objects too faint for others' instruments.

The reconstructed Leviathan of Parsonstown in August, 2006.

Two of Lord Rosse's drawings of M51, done at the eyepiece of the Leviathan, on display in Ireland's Historic Science Centre on the grounds of the Birr Castle Demesne, home to the Third Earl of Rosse's great-great grandson, Brendan Parsons, the Seventh Earl.

M51 permeates the traditions of the Birr Castle Demesne, as Diane and I found during our stay there in August of 2006. In fact, a major, relatively new, facet of the Demesne's lovely and extensive gardens is the "Whirlpool Spiral," a modern variation on the ancient garden maze. It is a spiral of mown pathway and lime trees, laid out in porportion to imitate the appearance of M51A and M51B. I haven't been able to locate an aerial view of the spiral, but here it is in part of the Demesne's visitors' map:

(The spiral is number 13 on the map; number 2 is the reconstructed telescope.)

At the center of the spiral of young lime trees -- at the core of the verdant M51A -- is this pit at the left of the frame:

When I asked the current Lord Rosse about this odd depression, he told me that it was a "siege pit," a place where Jacobite cannon under the command of the Bastard Duke of Berwick were entrenched during the 1600s' War of the Two Kings. Balls from the cannon left marks on Birr Castle that are still visible, and some of the balls compose part of a foyer decoration:

While supermassive black holes at the centers of galaxies may be commonplace, M51 is the only one I know of with a siege pit at its core.

A short slideshow of the Birr Castle Demesne from our visit in August, 2006, can be viewed by clicking here.