The researchers of Purple Mountain Observatory (PMO) have identified a new segment of a spiral arm (Figure 1). The new arm, which lies beyond the Outer Arm in the second Galactic quadrant, has the 45,000-60,000 light years of the Galactocentric distance. The new gas arm with the thickness of about 1,000-2,000 light years can be interpreted as the far-extension of the distant arm recently discovered by Dame & Thaddeus (2011). The new gas arm can be traced by the molecular cloud (>100 solar mass), which is labeled with blue circles in Figure 1. The manuscript, which is accepted by ApJL, is available at http://arxiv.org/abs/1412.2425. 

 By with Su Yang

Figure 1: An artist’s conception of the Milky Way (R. Hurt: NASA/JPL-Caltech/SSC). The blue filled stars and circles mark clouds covering Galactic longitudes from l=13d to 55d detected by Dame & Thaddeus (2011), and l=100d to 150d detected by us, respectively. The white squares indicate the locations o high mass star forming regions associated with the Outer arm. The white solid line is a log spiral which traced the fitting results to all available data including clouds detected by Dame & Thaddeus (2011).