74 ASTRONOMY • SEPTEMBER 2019
BREAKTHROUGH
A GALAXY PAIR CRASH AND BURN
Irregular galaxy NGC 4485 in Canes Venatici has only a single neighbor, but it has proved to be less than welcoming.
The Cocoon Galaxy (NGC 4490), which lies off the lower right edge of this Hubble image, sideswiped its partner millions
of years ago. The collision left NGC 4485’s spiral nature in tatters, though hints of it survive on the galaxy’s left side. On
the opposite flank, however, gravitational interactions have created a stream of material extending 25,000 light-years to
NGC 4490. The crash triggered a firestorm of star birth visible as bright blue star clusters and the reddish emission nebulae
that are building new ones. Both galaxies lie about 25 million light-years from Earth. NASA/ESA