Astronomers have discovered exozodiacal light, which is caused by the reflection of starlight from dusts that are produced by the collision of asteroids and evaporations of comets, near the habitable zones around nine nearby stars.

Steve Ertel, an astronomer from the University of Grenoble in France, and colleagues used European Southern Observatory's (ESO) Very Large Telescope Interferometer (VLTI) in Chile to observe 92 nearby stars, which led to the discovery of bright exozodiacal light around nine of these target stars.

Exozodiacal light had already been observed in the past prior to this new study, which was reported in the journal Astronomy & Astrophysics on Nov. 3. The survey involved scanning dozens of stars.

Unlike earlier observations, the exozodiacal light that the astronomers detected was not caused by dusts that later form into planets. The newly observed exozodiacal light was produced by grains of dust that were created as a result of the collision of objects known as planetesimals. These are small planets that span a few kilometers and are similar to the comets and asteroids that are found in the solar system.

An analysis of the properties of the stars that were enveloped by exozodiacal dust also revealed that the dust were mostly around older stars, which contradicts the idea that the production of dust should be reduced over time.

"The detection rate decreases from early type to late type stars and increases with the age of the host star," the researchers wrote. "Our spectrally dispersed data suggest that either the dust is extremely hot or the emission is dominated by the scattered light in most cases."

Ertel said that the observation of zodiacal dust is crucial in studying how Earth-like planets that are close to the habitable zone evolved. It could also shed light on the evolution and architecture of the planetary systems.

There is concern, though, that the presence of large amounts of dust around some stars could have a negative impact on the ability of scientists to observe and conduct direct imaging of Earth-like exoplanets in the future.

"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," said study co-author Olivier Absil from the University of Liège. "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."

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