Exozodiacal clouds: hot and warm dust around main sequence stars

Abstract

A warm/hot dust component (at temperature >300 K) has been detected around ∼20% of A, F, G, K stars. This component is called 'exozodiacal dust' as it presents similarities with the zodiacal dust detected in our solar system, even though its physical properties and spatial distribution can be significantly different. Understanding the origin and evolution of this dust is of crucial importance, not only because its presence could hamper future detections of Earthlike planets in their habitable zones, but also because it can provide invaluable information about the inner regions of planetary systems. In this review, we present a detailed overview of the observational techniques used in the detection and characterisation of exozodiacal dust clouds ('exozodis') and the results they have yielded so far, in particular regarding the incidence rate of exozodis as a function of crucial parameters such as stellar type and age, or the presence of an outer cold debris disc. We also present the important constraints that have been obtained, on dust size distribution and spatial location, using state-of-the-art radiation transfer models on some of these systems. Finally, we investigate the crucial issue of how to explain the presence of exozodiacal dust around so many stars (regardless of their ages) despite the fact that such dust so close to its host star should disappear rapidly due to the coupled effect of collisions and stellar radiation forces. Several potential mechanisms have been proposed to solve this paradox and are reviewed in detail in this paper. The review finishes by presenting the future of this growing field.

Is the infrared background excess explained by the isotropic zodiacal light from the outer solar system?

“…This result is consistent with the result in Dwek et al (1998) of 10 −3 < M shell /M Earth < 10 2 at > 700 AU for β = 2 case. On the other hand, however, the total IPD mass is dominated by large particles (∼100 µm) from the dust size distribution around the Earth (Kral et al 2017). Although this dust size distribution is valid around the Earth, it is difficult to believe that the small IPD particles (a < 1 µm) is dominated in the outer Solar system.…”

Ubiquitous instabilities of dust moving in magnetized gas

“…Mukai et al 1974;. More recently similar coronae have been inferred around a large number of nearby stars (Kral et al 2017).…”

Review and scientific prospects of high-contrast optical stellar interferometry

“…exozodis) are the extrasolar counterpart of the zodiacal dust found in the solar system. They are both a key to understanding the evolution of planetary systems 21 and a source of noise for the direct detection of Earth-like exoplanets. [22][23][24] Exozodiacal dust emits primarily in the near-infrared to mid-infrared where it is outshone by the host star.…”