# Accounting for planet-shaped planetary nebulae

## TL;DR

This paper suggests that lowering the mass loss rate in stellar evolution models leads to the formation of observable elliptical planetary nebulae from single stars, explaining bright PNe in old populations.

## Contribution

It introduces a revised low mass loss rate for single stars, accounting for binary contamination, which better explains the formation of bright elliptical planetary nebulae.

## Key findings

- Lower mass loss rate results in stars swallowing planets and forming elliptical PNe.
- Stars with reduced mass loss leave the AGB with higher luminosities.
- The proposed rate explains bright PNe in old stellar populations.

## Abstract

By following the evolution of several observed exoplanetary systems we show that by lowering the mass loss rate of single solar-like stars during their two giant branches, these stars will swallow their planets at the tip of their asymptotic giant branch (AGB) phase. This will most likely lead the stars to form elliptical planetary nebulae (PNe). Under the traditional mass loss rate these stars will hardly form observable PNe. Stars with a lower mass loss rate as we propose, about 15 per cent of the traditional mass loss rate of single stars, leave the AGB with much higher luminosities than what traditional evolution produces. Hence, the assumed lower mass loss rate might also account for the presence of bright PNe in old stellar populations. We present the evolution of four exoplanetary systems that represent stellar masses in the range of 0.9-1.3 Mo. The justification for this low mass loss rate is our assumption that the stellar samples that were used to derive the traditional average single-star mass loss rate were contaminated by stars that suffer binary interaction.