During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.
One of these is the spiral galaxy located in the constellation Canes Venatici known as the Whirlpool Galaxy (aka. Messier 51). Located between 19 and 27 million light-years from the Milky Way, this deep sky object was the very first to be classified as a spiral galaxy. It is also one of the best known galaxies among amateur astronomers, and is easily observable using binoculars and small telescopes.
Description:
Located some 37 million light years away, M51 is the largest member of a small group of galaxies, which also houses M63 and a number of fainter galaxies. To this time, the exact distance of this group isn’t properly known… Even when a 2005 supernova event should have helped astronomers to correctly calculate! As K. Takats stated in a study:
“The distance to the Whirlpool galaxy (M51, NGC 5194) is estimated using published photometry and spectroscopy of the Type II-P supernova SN 2005cs. Both the expanding photosphere method (EPM) and the standard candle method (SCM), suitable for SNe II-P, were applied. The average distance (7.1 +/- 1.2 Mpc) is in good agreement with earlier surface brightness fluctuation and planetary nebulae luminosity function based distances, but slightly longer than the distance obtained by Baron et al. for SN 1994I via the spectral fitting expanding atmosphere method. Since SN 2005cs exhibited low expansion velocity during the plateau phase, similarly to SN 1999br, the constants of SCM were recalibrated including the data of SN 2005cs as well. The new relation is better constrained in the low-velocity regime, that may result in better distance estimates for such SNe.”
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