The Helping Hand in Cassiopeia

Distance of the dark clouds measured for two cold cores of the same complex, from the reddening of stars (Guo et al. 2021, 969 and 980 parsecs), in agreement with the almost 3,000 light-years of the APOD of 8 November 2024. Older studies associated the clouds with the stars of SU Cas (Turner & Evans 1984, about 850 light-years), so the distance of the clouds remains uncertain. SU Cas and the blue nebula around it are at ≈ 1,400 light-years (Turner et al. 2012). Distances of the stars from Gaia parallax (SIMBAD); that of the galaxy was calculated from redshift (NED), with H0 = 70 km/s/Mpc. No real width: the field mixes objects at very different distances. Positions from SIMBAD and NED; those of the Lynds nebulae are approximate.