SOFIA views a star-forming region

The name W40 designates this object's number in a catalog of HII regions, clouds of ionized hydrogen often associated with star formation and massive stars. W40 is in the constellation Aquila the Eagle, visible in the Northern hemisphere's autumn sky. W40 itself is a difficult target for optical astronomers because it lies less than 3 degrees from the central plane of the Milky Way, at a distance of about 1600 light years behind obscuring clouds of interstellar dust and gas.

This three image comparison shows W40 in visible, near-infrared and mid-infrared wavelengths. The visible-light image on the left is from the Digitized Sky Survey. The W40 region is not especially prominent at visual wavelengths due to intervening interstellar dust. The near-infrared image in the middle is a composite produced by SOFIA Basic Science Principal Investigators Shuping and Vacca using archived Spitzer infrared space telescope data. The interstellar dust in the foreground and within the W40 region is mostly transparent at these wavelengths, so W40 stands out prominently and one can view into the interior of the nebula to see embedded protostars. Some of these objects were labeled with IRS ("InfraRed Source") numbers by earlier investigators. The mid-infrared image on the right is a composite of 5.4 micron (blue), 24.2 micron (green) and 34.8 micron (red) images taken with SOFIA's FORCAST camera in May 2011.

The field of view is approximate 3 arcminutes on a side. The bright sources in this image are protostars and thermal emission from dust and gas. Emission at 24 and 35 microns is primarily from warm dust. Some of the protostars can be seen in the Spitzer near-infrared image, but the SOFIA data allow easier determination of their dust temperatures. The hottest object, appearing blue and located at lower left, has very little dust surrounding it and is likely nearest to completing its evolution into a fully-fledged star. The other protostars represented by white in this color balance are cooler and thus have a large amount of circumstellar dust, some of it probably in a disk surrounding the central star.

See www.sofia.usra.edu