It was a type II-P core-collapse supernova, discovered June 28, 2005 by Wolfgang Kloehr, a German amateur astronomer.

[5] The event was positioned at an offset of 15″ west and 78″ south of the galactic nucleus of M51.

[6] It was considered under-luminous for a supernova of its type, releasing an estimated 3×1050 erg in energy.

[4] The progenitor star was identified from a Hubble Space Telescope image taken January 20–21, 2005.

A higher mass star enshrouded in a cocoon of dust has been ruled out.