Exozodiacal light
Artist's impression of the brilliant glow of exozodiacal light extending up into the sky and swamping the Milky Way. (ESO/L. Calçada)

Brightly-glowing grains of interstellar dust are hampering the search for habitable planets, experts have said.

Researchers at the European Organisation for Astronomical Research in the Southern Hemisphere (ESO) and the University of Grenoble in France were observed 92 nearby stars using the Very Large Telescope Interferometer (VLTI).

They were analysing exozodiacal light from hot dust close to the stars' habitable zones. The dust was found around nine of the planets examined.

Zodiacal light looks like a faint white glow seen in the sky just before dawn and is created by sunlight reflected off tiny particles. In this study, scientists observed a much more extreme version of the same phenomenon – exozodiacal light.

Normally, detecting this dust requires high resolution observations, combining light collected at the same time from several different telescopes. Using the VLTI, researchers were able to make observations about ten times better than any other instrument in the world.

Researchers found their observations included 14 stars where exoplanets have been discovered. The planets are located in the same region as the exozodiacal dust – which is likely to cause problems for further studies of the planets.

This is because the dust makes it much harder to detect Earth-like planets with direct imaging – the light from the dust is about 1,000 times brighter than the zodiacal light from the Sun.

They also said the number of stars containing light this bright is probably much higher than what they found in their survey.

Olivier Absil, co-author of the paper, said: "The high detection rate found at this bright level suggests that there must be a significant number of systems containing fainter dust, undetectable in our survey, but still much brighter than the Solar System's zodiacal dust. The presence of such dust in so many systems could therefore become an obstacle for future observations, which aim to make direct images of Earth-like exoplanets."

Researchers also found most of the dust was found around older stars, which raised questions about our understanding of planetary systems – dust created by collisions should diminish over time.

Steve Ertel, lead author of the study, said: "If we want to study the evolution of Earth-like planets close to the habitable zone, we need to observe the zodiacal dust in this region around other stars. Detecting and characterising this kind of dust around other stars is a way to study the architecture and evolution of planetary systems."