As both astronomers noted, it hints that these stars lie in a thin sheet or ring that's tilted slightly with respect to the plane of the Milky Way--a structure now known as Gould's Belt.
The star chart above shows the approximate centerline of Gould's Belt as an orange line stretching from Perseus to Crux; you can see it across the entire Milky Way on the star chart in the center of the July 2013 issue.
Gould's Belt is tilted about 17[degrees] with respect to the galactic equator, crossing it in Crux and Cassiopeia.
The true space center of Gould's Belt is in the vicinity of the Alpha Persei Cluster.
At present the most vigorous star formation in Gould's Belt is occurring in the Orion Nebula, the IC 348 nebula in the Zeta Persei Association, and the Rho Ophiuchi complex near the Scorpius-Ophiuchus border.
Thus when we look toward the winter Milky Way proper, along the galactic equator from Auriga to Puppis, we are in fact looking "over" Gould's Belt, which is a foreground structure within our Orion-Cygnus Arm.
It is 4,500 light-years away, about twice the distance of Delta Canis Majoris, which is the brightest member of the Canis Major Association, a Gould's Belt object.
The Perseus Arm, which is so conspicuous in the Cassiopeia Window of the autumn Milky Way, is lost to view east of the Perseus Double Cluster, hidden behind the Gould's Belt dust clouds of southern Perseus and northern Taurus.
Tracing the itinerant cloud's motion back in time and space, White and Bally conclude that the cloud may have been launched toward the Pleiades 15 million years ago by an energetic supernova explosion associated with Gould's belt
, about 750 light-years distant in the constellation of Vulpecula.