  GLIMPSE imaging using the Infrared Array Camera (IRAC) on the Spitzer Space
Telescope indicates that star formation is ongoing in the RCW 49 giant H II
region. A photometric comparison of the sources in RCW 49 to a similar area to
its north finds that at least 300 stars brighter than 13th magnitude in band
[3.6] have infrared excesses inconsistent with reddening due to foreground
extinction. These are likely young stellar objects (YSOs) more massive than 2.5
M_sun suggesting that thousands more low-mass stars are forming in this cloud.
Some of the YSOs are massive (B stars) and therefore very young, suggesting
that a new generation of star formation is occurring, possibly triggered by
stellar winds and shocks generated by the older (2-3 Myr) central massive
cluster. The Spitzer IRAC camera has proven to be ideally suited for
distinguishing young stars from field stars, and the GLIMPSE survey of the
Galactic Plane will likely find thousands of new star formation regions.
