Only two million years old[139] and 420 parsecs distant,[140] the cloud is known to contain many protostars such as Serpens FIRS 1[141] and Serpens SVS 20.[142] The Serpens South protocluster was uncovered by NASA's Spitzer Space Telescope in the southern portion of the cloud,[143] and it appears that star formation is still continuing in the region.[144] Another site of star formation is the Westerhout 40 complex, consisting of a prominent HII region adjacent to a molecular cloud.[145] Located around 500 parsecs distant,[146] it is one of the nearest massive regions of star formation, but as the molecular cloud obscures the HII region, rendering it and its embedded cluster tough to see visibly, it is not as well-studied as others.[147] The embedded cluster likely contains over 600 stars above 0.1 solar masses,[148] with several massive stars, including at least one O-type star, being responsible for lighting the HII region and the production of a bubble.[146]