Dust Populations in the Iconic Vega Planetary System Resolved by ALMA

TL;DR

This study uses ALMA observations to resolve and analyze the dust belt in the Vega system, providing new insights into its structure and potential planetary configurations, including scenarios with no planets, multiple low-mass planets, or a single giant planet.

Contribution

First ALMA resolution of Vega's outer dust belt, constraining its structure and exploring three planetary system scenarios based on new observational data.

Findings

The dust belt extends to at least 150-200 au.

The belt has a steep inner edge at 60-80 au.

Constraints on potential planets include a minimum mass of 6 Earth masses and location within 71 au.

Abstract

The Vega planetary system hosts the archetype of extrasolar Kuiper belts, and is rich in dust from the sub-au region out to 100's of au, suggesting intense dynamical activity. We present ALMA mm observations that detect and resolve the outer dust belt from the star for the first time. The interferometric visibilities show that the belt can be fit by a Gaussian model or by power-law models with a steep inner edge (at 60-80 au). The belt is very broad, extending out to at least 150-200 au. We strongly detect the star and set a stringent upper limit to warm dust emission previously detected in the infrared. We discuss three scenarios that could explain the architecture of Vega's planetary system, including the new {ALMA} constraints: no outer planets, a chain of low-mass planets, and a single giant planet. The planet-less scenario is only feasible if the outer belt was born with the observed sharp inner edge. If instead the inner edge is currently being truncated by a planet, then the planet must be $\gtrsim$6 M$_{\oplus}$ and at $\lesssim71$ au to have cleared its chaotic zone within the system age. In the planet chain scenario, outward planet migration and inward scattering of planetesimals could produce the hot and warm dust observed in the inner regions of the system. In the single giant planet scenario, an asteroid belt could be responsible for the warm dust, and mean motion resonances with the planet could put asteroids on star-grazing orbits, producing the hot dust.