CTB 102 (KR 1) is an enormous filamentary HII region approximately 200 parsecs in size, lying at a distance of about 4500 parsecs. Although visually obscured by dust in the local Cyg OB7 molecular clouds, KR 1 has been detected in great detail at radio frequencies by the Canadian Galactic Plane Survey.
Title: The enormous outer Galaxy HII region CTB 102 Authors: K. Arvidsson, C. R. Kerton, T. Foster
We present new radio recombination line observations of the previously unstudied HII region CTB 102. Line parameters are extracted and physical parameters describing the gas are calculated. We estimate the distance to CTB 102 to be 4.3 kpc. Through comparisons with HI and 1.42 GHz radio continuum data, we estimate the size of CTB 102 to be 100-130 pc, making it one of the largest HII regions known, comparable to the W4 complex. A stellar wind blown bubble model is presented as the best explanation for the observed morphology, size and velocities.