Direct Imaging and Spectroscopy of a Planetary Mass Candidate Companion to a Young Solar Analog

TL;DR

This study reports the direct imaging and spectroscopy of a planetary-mass companion to a young star, revealing a very low-mass object at a large separation, challenging existing formation theories.

Contribution

First direct imaging and spectroscopic characterization of a planetary-mass companion at a large separation around a young solar analog.

Findings

Companion has a mass of approximately 8 Jupiter masses.

Object exhibits low surface gravity indicating youth.

Located at a large separation of 330 AU from the host star.

Abstract

We present Gemini near-infrared adaptive optics imaging and spectroscopy of a planetary mass candidate companion to 1RXS J160929.1-210524, a roughly solar-mass member of the 5 Myr-old Upper Scorpius association. The object, separated by 2.22" or 330 AU at ~150 pc, has infrared colors and spectra suggesting a temperature of 1800(-100/+200) K, and spectral type of L4(-2/+1). The H- and K-band spectra provide clear evidence of low surface gravity, and thus youth. Based on the widely used DUSTY models, we infer a mass of 8(-2/+4)Mjupiter. If gravitationally bound, this would be the lowest mass companion imaged around a normal star thus far, and its existence at such a large separation would pose a serious challenge to theories of star and planet formation.