... Credit Copyright: A. Dyer (Ground based image); NASA , ESA , and H. Weaver ( JHU APL ) (Hubble image) Explanation: Why did Comet Holmes brighten? The unexpectedly bright Comet 17P/Holmes continues to grace northern skies as a naked-eye addition to the constellation Perseus. ... Clues to the nearly million-fold brightness increase are therefore being sought in dramatic images of the enigmatic comet's central regions taken earlier this month by the Hubble Space Telescope . ... Forest and Sky . ...