May 17, 2005
The sky area of the globule ("dark cloud") Barnard 68 , imaged in six different wavebands, clockwise from the blue to the near-infrared spectral region. Three of these frames ("blue" B-band at wavelength 440 nm = 0.44 Âµm; "green-yellow" V-band at 0.55 Âµm; near-infrared I-band at 0.90 Âµm) were obtained with the FORS1 instrument at the VLT ANTU telescope and three with SOFI at the NTT through near-infrared filters (J-band at 1.25 Âµm; H-band at 1.65 Âµm; Ks-band at 2.16 Âµm). It is evident that the obscuration caused by the cloud diminishes dramatically with increasing wavelength. Since the outer regions of the cloud are less dense than the inner ones, the apparent size of the cloud also decreases, as more background stars shine through the outer parts. Each frame covers an area of 4.9 x 4.9 arcmin2. North is up and East is left.
Topics: Entertainment Culture, Optical filters, Infrared, Electromagnetic spectrum, Barnard 68, Filter, Cloud, Very Large Telescope