Brussels (Belgium) – The European Space Agency (ESA) has released a fascinating set of pictures taken by the Hubble space telescope showing colliding galaxies and galaxy mergers.

The album consist of 59 pictures , the biggest individual Hubble gallery released to date, which were extracted from “several terabytes” of archived raw images taken by the telescope.  The images, which celebrate Hubble’s 18th birthday, document interacting galaxies that sometimes produce dramatic collisions triggering the formations of new stars or even new galaxies.

According to ESA, the “the first tentative sign of an interaction will be a bridge of matter as the first gentle tugs of gravity tease out dust and gas from the approaching galaxies.” As galaxies begin to touch each other long streamers of gas and dust, known as tidal tails, stretch out and sweep back to wrap around the cores. These long, often spectacular, tidal tails are the signature of an interaction and can persist long after the main action is over, ESA said.

As the galaxy cores approach each other their gas and dust clouds are buffeted and accelerated dramatically by the conflicting pull of matter from all directions. These forces can result in shockwaves rippling through the interstellar clouds. Gas and dust are siphoned into the active central regions, fuelling bursts of star formation that appear as characteristic blue knots of young stars. As the clouds of dust build they are heated so that they radiate strongly, becoming some of the brightest (luminous and ultraluminous) infrared objects in the sky.

ESA explained that these objects can produce “up to several thousand billion times the luminosity of our Sun” and turn into the most rapidly star-forming galaxies in today’s Universe and are linked to the occurrence of quasars. Most of the 59 new Hubble images are part of a large investigation of luminous and ultraluminous infrared galaxies called the GOALS project (Great Observatories All-sky LIRG Survey). This survey combines observations from Hubble, the NASA Spitzer Space Observatory, the NASA Chandra X-Ray Observatory and NASA Galaxy Explorer.

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