Abstract details

The discovery of an excess of light in the far-ultraviolet (UV) in 1969 in elliptical galaxies was a major surprise. While it is now clear that this UV excess is probably caused by an old population of helium-burning stars. Here we show that the population is most likely resulted from binary interactions. This has major implications for understanding the evolution of the UV excess and elliptical galaxies in general; contrary to previous postulates, it implies that the UV excess in not a sign of age, but could be a potentially powerful indicator for a recent minor burst of star-forming activity.