Flip through them yourself and you’ll see why NASA calls these “galaxies gone wild.” Far from the static, staid islands of stars depicted in textbooks, galaxies are dynamic, antsy and even promiscuous, having what astronomers call “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.” Although only one in a million galaxies in the nearby universe is colliding, many more in the distant environs are: farther away equals longer ago, and longer ago galaxies were closer together because the expanding universe was smaller.
Among the standouts in the 59 images is Arp 148, the detritus of an encounter between two galaxies that produced a shockwave that first drew matter inward and then pushed it outward, creating a ring-shaped galaxy and a long-tailed hanger-on perpendicular to the ring. (Arp 148 is located in Ursa Major, the Great Bear, about 500 million light-years from Earth.)
Then there is Arp 256, two spiral galaxies in flagrante delicto: the merger has triggered blue knots of star formation that look like a 4th of July display. (Arp 256 is in the constellation of Cetus, the Whale, 350 million light-years away.)
Arp 220 is what happens when two spiral galaxies collide. This one is 250 million light-years away in the constellation of Serpens, the Serpent. The collision, 700 million years ago, ignited a fury of star formation, producing 200 huge star clusters in a packed, dusty region 5,000 light-years across (about 5 percent of the Milky Way’s diameter, it holds as much gas as the entire Milky Way).
ESO 148-2 looks like a flying owl, and is a pair of disk galaxies in the act of colliding. The centers of the two contain myriads of stars, while two enormous “wings” curving out from the center are actually the tidal tails of stars and gas that have been pulled from the disks.
I could go on, but it’s much more fun to see the photos yourself.
