Interstellar Dust Close to the Sun

TL;DR

This paper investigates the properties and composition of interstellar dust near the Sun, using observations and models to understand grain characteristics, destruction processes, and their interaction with the heliosphere.

Contribution

It provides new insights into the composition, size distribution, and destruction mechanisms of interstellar dust grains close to the Sun, combining observational data with theoretical models.

Findings

Interstellar dust grains are dominated by olivines and possibly iron oxides.

High interstellar oxygen depletion onto dust grains is indicated by Ne/O ratios.

Large grains (>1 micron) suggest a nearby dense interstellar medium reservoir.

Abstract

The low density interstellar medium (ISM) close to the Sun and inside of the heliosphere provides a unique laboratory for studying interstellar dust grains. Grain characteristics in the nearby ISM are obtained from observations of interstellar gas and dust inside of the heliosphere and the interstellar gas towards nearby stars. Comparison between the gas composition and solar abundances suggests that grains are dominated by olivines and possibly some form of iron oxide. Measurements of the interstellar Ne/O ratio by the Interstellar Boundary Explorer spacecraft indicate that a high fraction of interstellar oxygen in the ISM must be depleted onto dust grains. Local interstellar abundances are consistent with grain destruction in ~150 km/s interstellar shocks, provided that the carbonaceous component is hydrogenated amorphous carbon and carbon abundances are correct. Variations in relative abundances of refractories in gas suggest variations in the history of grain destruction in nearby ISM. The large observed grains, > 1 micron, may indicate a nearby reservoir of denser ISM. Theoretical three-dimensional models of the interaction between interstellar dust grains and the solar wind predict that plumes of about 0.18 micron dust grains form around the heliosphere.