1.   It also could be, astronomers said, that some colliding galaxies lack black holes to pull in stars and gases at high energies.

2.   Justice might have been served, since colliding galaxies fell out of favor a few years thereafter.

3.   The puzzle, he added, is that so many other colliding galaxies do not appear to have quasars, suggesting that other subtle forces may be at work.

4.   Infrared telescope glimpses colliding galaxies.

5.   Among the improvements was the installation of an upgraded camera for the telescope, which produced the image of the colliding galaxies.