Astrophys. J. 705, 255–260 (2009)

A survey of distant galaxies shows that more loosely packed ones tend to form more stars.

The survey looked at 225 galaxies at distances of between about 2.8 and 3.4 parsecs from Earth. It found that compact galaxies tend to have fewer new stars than do their larger counterparts of comparative mass.

Sune Toft of the University of Copenhagen and his colleagues conclude that compact galaxies formed many stars quickly in one intense burst, early in the history of the Universe. Conversely, larger, more diffuse galaxies form stars gradually over a longer period of time. The results may explain why very distant galaxies are often more compact than the younger ones nearby.