parsecs distant, the cloud is known to contain many protostars such as Serpens FIRS 1 and Serpens SVS 20. The Serpens South protocluster was uncovered by NASA's Spitzer Space Telescope in the southern portion of the cloud, and it appears that star formation is still continuing in the region. Another site of star formation is the Westerhout 40 complex, consisting of a prominent HII region adjacent to a molecular cloud. Located around 500 parsecs distant, 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. The embedded cluster likely contains over 600 stars above 0.1 solar masses, with several massive stars, including at least one O-type star, being responsible for lighting the HII region and the production of a bubble. Despite the presence of the Milky Way, several active galaxies are visible in Serpens Cauda as well, such as PDS 456, found near Xi Serpentis. The most intrinsically luminous nearby active galaxy, this AGN has been found to be extremely variable in the X-ray spectrum. This has allowed light to be shed on the nature of the supermassive black hole at the center, likely a Kerr black hole. It is possible that the quasar is undergoing a transition from an ultraluminous infrared galaxy to a classical radio-quiet quasar, but there are problems with this theory, and the object appears to be an exceptional object that does not completely lie within current classification systems. Nearby is NRAO 530, a blazar that has been known to flare in the X-rays occasionally. One of these flares was for less than 2000 seconds, making it the shortest flare ever observed in a blazar as of 2004. The blazar also appears to show periodic variability in its radio wave output over two different periods of six and ten years. Meteor showers There are two daytime meteor showers that radiate from Serpens, the Omega Serpentids and the Sigma Serpentids. Both showers peak between December 18 and December 25. References External links The Deep Photographic Guide to the Constellations: Serpens (Caput) The clickable Serpens (Caput) Warburg Institute Iconographic Database (medieval and early modern images of Serpens), more can be found under Serpentarius Constellations Equatorial constellations Constellations listed by Ptolemy Legendary serpents