Discovery and spectroscopy of the young Jovian planet 51 Eri b with the Gemini Planet Imager

TL;DR

This paper reports the discovery and spectral analysis of a young Jovian planet, 51 Eri b, using the Gemini Planet Imager, revealing its atmospheric composition, luminosity, and implications for its formation mechanism.

Contribution

First direct detection and spectral characterization of 51 Eri b, providing insights into its atmospheric properties and formation history.

Findings

Spectral evidence of methane and water vapor in 51 Eri b

Luminosity and temperature estimates consistent with both hot-start and cold-start formation models

Mass estimated to be twice that of Jupiter

Abstract

Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric composition and luminosity, which is influenced by their formation mechanism. Using the Gemini Planet Imager, we discovered a planet orbiting the \$sim$20 Myr-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water vapor absorption. Modeling of the spectra and photometry yields a luminosity of L/LS=1.6-4.0 x 10-6 and an effective temperature of 600-750 K. For this age and luminosity, "hot-start" formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the "cold- start" core accretion process that may have formed Jupiter.