‘Wet’ Galactic Collisions and Grandiose Star Formation


An international group of astrophysicists made a rare find; they discovered a huge cluster of colliding galaxies sheltering a core bursting with new stars.

Figure A. The Antennae galaxies are a classic example of two colliding spiral galaxies where the merger of gas clouds have driven incredibly increased star formation (burgundy/red regions). Credit: NASA/ESA/HST.

In the observable universe, galaxies (the gravitational grouping of stars, dust, gas and dark matter) come in three main flavors: spirals, ellipticals and irregulars. Each flavor has its own distinguishing characteristic. Spirals, as the name suggests, have “arms” rich in stars, gas, and dust wrapping around a dense stellar core; they are still actively forming stars. Ellipticals are (semi)spherical in shape and have used up most of their gas and dust, resulting in an extremely low or no star formation at all. Irregulars are amorphous and contain great quantities of gas, dust and young stars.

Now, the latest galaxy surveys (SDSS, for example) say that 77 percent of the galaxies in the observable Universe are spirals, 20 percent are ellipticals and three percent are irregulars. Spirals, with their huge amounts of gas and dust, are believed to merge and create ellipticals. When the collision between two or more galaxies, with their respective gargantuan gas clouds, brings about new star formation the event is called a “wet merger” (and dry mergers are collisions that form no new stars).

Astronomers using the W. M. Keck telescope (University of California/Caltech) paired with observations by the Hubble, Herschel and Spitzer space telescopes, have carefully studied a cluster of merging galaxies ceremoniously known as SpARCS1049+56. The cluster is so massive that it holds the mass of 400 trillion suns and is composed of 27 individual galaxies. The Keck telescope helped astronomers determine the distance to the cluster, whose light took —> Read More