Evidence of Rocky Planetesimals Orbiting Two Hyades Stars

TL;DR

This study presents evidence of rocky planetesimals orbiting two stars in the Hyades cluster, indicating planetary formation around A-type stars through ultraviolet spectroscopy and metal pollution analysis.

Contribution

First detection of rocky planetesimals orbiting Hyades stars via ultraviolet metal pollution, linking stellar pollution to planetary formation evidence.

Findings

Metal pollution indicates ongoing accretion of rocky material.

Polluting material is more carbon-deficient than meteorites.

Results suggest formation of rocky planetesimals around A-type stars.

Abstract

The Hyades is the nearest open cluster, relatively young and containing numerous A-type stars; its known age, distance, and metallicity make it an ideal site to study planetary systems around 2-3 Msun stars at an epoch similar to the late heavy bombardment. Hubble Space Telescope far-ultraviolet spectroscopy strongly suggests ongoing, external metal pollution in two remnant Hyads. For ongoing accretion in both stars, the polluting material has log[n(Si)/n(C)] > 0.2, is more carbon deficient than chondritic meteorites, and is thus rocky. These data are consistent with a picture where rocky planetesimals and small planets have formed in the Hyades around two main-sequence A-type stars, whose white dwarf descendants bear the scars. These detections via metal pollution are shown to be equivalent to infrared excesses of Lir/L* ~ 1e-6 in the terrestrial zone of the stars.