Researchers have reported the first optical transmission spectrum of the atmosphere of the planet WASP-4b. This planet is a hot jupiter located roughly 880 light-years away in the Phoenix constellation. Using the Magellan/IMACS instrument as part of the Arizona-CfA-Católica-Carnegie Exoplanet Spectroscopy Survey (ACCESS), the team identified features on the photosphere of WASP-4b including small, cool and large, warm spots. The data is in agreement with previous studies using the multi-object, long-slit and IFU spectrograph and imager (GMOS) on the Gemini Observatory, and the Inamori Magellan Areal Camera and Spectrograph (IMACS) instrument at Las Campanas Observatory.

The study, “ACCESS: Ground-based Optical Transmission Spectroscopy of the Hot Jupiter WASP-4b,” was published in The Astronomical Journal. The work was supported by the Nexus for Exoplanet System Science (NExSS).  NExSS is a NASA  research coordination network supported in part by the  NASA Astrobiology Program. This program element is shared between NASA’s Planetary Science Division (PSD) and the Astrophysics Division.