First Resolution of a Main-sequence G star’s Astrosphere Using Chandra

Abstract We report the resolution of a halo of X-ray line emission surrounding the zero-age main-sequence G8.5V star HD 61005 by Chandra/ACIS-S. Located only ∼36 pc distant, HD 61005 is young (100 ± 50 Myr) and X-ray bright (∼300 × solar), observed with a nearly edge-on geometry and surrounded by very local interstellar medium (VLISM) material denser than in the Sun’s environs. HD 61005 is known to harbor large amounts of circumstellar dust in a dense ecliptic plane full of millimeter-sized particles plus attached, extended “Wing like structures” full of micron-sized particles, which are evidence for strong VLISM–dust disk interaction. These properties aided our ability to resolve the system’s ∼220 au wide astrosphere, the first ever observed for a main-sequence G star. The observed X-ray emission morphology is roughly spherical, as expected for an astrospheric structure dominated by the host star. The Chandra spectrum of HD 61005 is a combination of a hard stellar coronal emission ( T ∼ 8 MK) at L X ∼ 6 × 10 29 erg s −1 , plus an extended halo contribution at L X ∼ 1 × 10 29 erg s −1 dominated by charge exchange (CX) lines, such as those of O VIII and Ne IX . The Chandra CX X-ray morphology does not track the planar dust morphology but does extend out roughly to ∼110 au where the base of the dust wings begins. We present a toy model of the astrosphere emission produced by stellar wind–VLISM CX interactions, similar to the state of the young Sun when it was only ∼10 8 yr old and transiting through an ∼10 3 times denser part of the interstellar medium (such as a giant molecular cloud).