... The tantalizing Pleiades star cluster seems to lie just beyond the trees above a dark castle tower in this dramatic view of The World at Night. ... Triggered by the collapsing core of a massive star or the nuclear demise of a white dwarf, supernovae occur in average spiral galaxies only about once every century. Thor s Emerald Helmet . ... The Cocoon Nebula from CFHT . ... What creates the colors of the Cocoon Nebula? ... Hurricane Ivan from the Space Station . ... Polaris Dust Nebula . ...