Swirling W

Credit: NASA and the Hub­ble Her­itage Team (STScI)

Loop­ing arcs of stars and dust cre­ate a cos­mic let­ter “W” caught in the mid­dle of this galac­tic encounter.

Explore the NASA Hub­ble Space Tele­scope image of spi­ral galax­ies NGC 2207, on the left, and IC 2163, on the right. The strong grav­i­ta­tional tug of NGC 2207 has already dis­torted the shape of the smaller galaxy. The larger galaxy looks like a huge saw blade whirling into the smaller galaxy. Or is it the other way around? Grav­ity flings stars and gas out of IC 2163 in long stream­ers a 100,000 light-years long. Look for the dark lane of dust from the larger NGC 2207 as it cuts above the smaller galaxy. Look­ing through this dust makes the light from IC 2163 red­der in color. Fol­low the outer arms of NGC 2207 and explore the huge star clouds. These areas glow blue with new star birth. Sev­eral pock­ets of new stars can be seen in the outer spi­ral arms of these galaxies.

From this embrace nei­ther galaxy will escape. The galax­ies will swirl around each other, com­ing closer and closer, before merg­ing into a sin­gle large galaxy in a bil­lion years. Many of the galax­ies we see in the night sky, includ­ing our own Milky Way, have gone through cos­mic col­li­sions to become larger galaxies.

This pair of spi­ral galax­ies is found about 114 mil­lion light-years from Earth toward the con­stel­la­tion of Canis Major, the Large Dog.