Sky area around the Orion constellation with the Gaia DR1 sources selected for this study. The number of stars shown in the figure is N = 9 926 756. The white areas correspond to the Orion A and B molecular clouds, centered at (l,b) ~ (212,−19) and (l,b) = (206,−16), respectively. Well visible are also the λ Ori ring at (l,b) ~ (196,−12) and Monoceros R2, at (l,b) ~ (214,−13). The inclined stripes reflect the Gaia scanning law and correspond to patches in the sky where Gaia DR1 is highly incomplete (see Gaia Collaboration 2016a).