This Hubble Space Telescope image, taken December 29, 2005 and released on October 2, 2007 shows giant star-forming nebula with massive young stellar clusters.(Xinhua/Reuters Photo) Photo Gallery>>>

    WASHINGTON, April 24 (Xinhua) -- In celebration of the Hubble Space Telescope's 18th launch anniversary on Thursday, the space agencies in U.S. and Europe released 59 new images of colliding galaxies.

    Hubble is a project of international cooperation between NASA and the European Space Agency. The new bunch of pictures constitute the largest collection of Hubble images ever released to the public, said NASA in a statement on Thursday.

    Astronomy textbooks typically present galaxies as staid, solitary, and majestic island worlds of glittering stars. However, according to Hubble's new pictures, galaxies also have a wild side. They have flirtatious close encounters that sometimes end in grand mergers and overflowing "maternity wards" of new star birth as the colliding galaxies morph into wondrous new shapes.

    Hubble's images dramatically illustrates how galaxy collisions produce a remarkable variety of intricate structures in never-before-seen detail.

    Astronomers observe only one out of a million galaxies in the nearby universe in the act of colliding. However, galaxy mergers were much more common long ago when they were closer together, because the expanding universe was smaller. Astronomers study how gravity choreographs their motions in the game of celestial bumper cars and try to observe them in action.

    For all their violence, galactic smash-ups take place at a glacial rate by human standards -- timescales on the order of several hundred million years. The images by Hubble capture snapshots of the various merging galaxies at various stages in their collision.