Optical spectrum of brown dwarf TWA-5B

This optical spectrum (600 - 900 nm wavelength range) of TWA-5 B was obtained with the FORS-2 instrument at the 8.2-m VLT/KUEYEN telescope on 23 February 2000. A 30-min exposure was made through a 0.7 arcsec wide slit, positioned on the object in east-west direction, i.e., perpendicular to the direction to the much brighter TWA-5 A, only 2 arcsec to the south, see ESO Press Photo eso0023. Thanks to this, the obtained spectrum was very "clean". Also shown is the optical spectrum of a typical M9-type star. The spectra are very similar, with broad molecular absorption bands from TiO and VO. TWA-5 B also shows strong hydrogen emission (H-alpha) and weak sodium (Na) absorption, both indicative of its comparatively young age.