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Evidence for spiral structure in distant galaxies was first noticed by William Parsons, the Third Earl of Rosse, in April 1845 within a few
 

Summary: Evidence for spiral structure in distant galaxies was first noticed by
William Parsons, the Third Earl of Rosse, in April 1845 within a few
months of the first trial of his great six-foot reflector the "Leviathan
of Parsonstown" on 11 February 1845. Despite the significance of
this discovery there are puzzling inconsistencies in the story, and
the discovery date sometime in April is curiously vague. Here
we review the chronology of observations of the two principal
players in the story: Messier 51 and Messier 99. The former was
identified by Lord Rosse as having a spiral arrangement in the
spring of 1845, and the latter "the following spring". The Revd
Thomas Romney Robinson, the third Director of the Armagh
Observatory, was observing with Lord Rosse during February and
March 1845, and again in 1848, but he apparently only confirmed
Rosse's detection of spirality in both galaxies around 11 March
1848. No-one doubted Lord Rosse's discovery of spirality in M51
(and the following year also in M99), but it was almost three years
before the observation was confirmed by another astronomer.
1:M51,theWhirlpoolgalaxy,indetailinthisHubbleSpaceTelescope
image,whichshowsthespiralarmsanddustclouds,whicharethebirth
sitesofmassiveandluminousstars,pickedoutinred.(NASAandthe

  

Source: Armagh Observatory

 

Collections: Physics