CWISEP J1047+5457 (CWISEP J104756.81+545741.6, CWISEP J1047+54) is a Y-dwarf discovered in 2020.
CWISEP J1047+5457 was discovered in 2020 from a preliminary CatWISE catalog. It was initially determined to have a spectral type of Y0. Follow-up observations with JWST spectroscopy (NIRSpec and MIRI) showed that it had a spectral type of Y1. The observations showed that it had unusually strong carbon monoxide and carbon dioxide absorption. This causes the Spitzer ch1-ch2 color to be extremely blue (2.47 ±0.19 mag) for its spectral type and explains the misidentification as a Y0 in the discovery paper. The strong absorption might be explained with extreme disequilibrium chemistry, low surface gravity, or a low carbon to oxygen ratio. Other molecules, such as water vapor, methane and ammonia are also detected in the spectra. Phosphine is not detected.