Free Astronomy Magazine January-February 2015

SPACE CHRONICLES acal light looks like a faint diffuse white glow seen in the night sky after the end of twilight, or before dawn. It is created by sunlight re- flected off tiny particles and ap- pears to extend up from the vicinity of the Sun. This reflected light is not just observed from Earth but can be observed from everywhere in the Solar System. The glow being observed in this new study is a much more extreme version of the same phenomenon. While this exozodiacal light — zo- diacal light around other star sys- tems — had been previously de- tected, this is the first large sys- tematic study of this phenomenon around nearby stars. In contrast to earlier obser- vations the team did not observe dust that will later form into planets, but dust created in colli- sions between small planets of a few kilometres in size — objects called planetes- imals that are sim- ilar to the aster- oids and comets of the Solar Sys- tem. Dust of this kind is also the origin of the zo- diacal light in the Solar System. “If we want to study the evolu- tion of Earth-like planets close to the habitable zone, we need to observe the zo- diacal dust in this region around other stars,” said Steve Ertel, lead author of the paper, from ESO and the Universi- ty of Grenoble in France. “Detect- ing and character- ising this kind of dust around other stars is a way to study the architecture and evolution of planetary systems.” Detecting faint dust close to the dazzling cen- tral star requires high resolution ob- servations with high contrast. Interferometry — combining light collected at the exact same time at several different telescopes — per- formed in infrared light is, so far, A glorious starry sky, with a bright column due to zo- diacal light, illuminates the desert landscape around Cerro Paranal, home to ESO’s VLT. [ESO/Y.Beletsky] the only technique that allows this kind of system to be discovered and studied. By using the power of the VLTI and pushing the instrument to its limits in terms of accuracy and ef- ficiency, the team was able to reach a performance level about ten times better than other available instru- ments in the world.