A late addition to the northern sky, this group of stars
was originally intended to represent a fox carrying a goose in its jaws. Perhaps its most notable
feature is the Dumbbell Nebula, M27.
Vulpecula in the Sky
Historically, this narrow strip of sky had formed the southern boundaries of Cygnus the Swan, but Hevelius defined it as a small separate constellation, naming it Vulpecula cum Ansere, the 'Little Fox with the Goose'. Some astronomers went on to subdivide this already small constellation even further, making the eastern part the Fox and the western part the Goose. The entire group is now known simply as Vulpecula (strictly 'the Little Fox' but usually translated simply as the 'Fox'). A vestige of the constellation's history is retained in the name of its brightest star, still known as Anser, meaning 'Goose'.
Though lacking in bright stars, Vulpecula is surrounded on three sides by much more prominent constellations. It is directly southward of Cygnus, the constellation to which it once belonged, and directly westward of the Square of Pegasus, while the quadrangle that forms the body of Hercules lies to the northwest of the Fox. To the south, Vulpecula is bordered by two other small constellations, Delphinus the Dolphin and Sagitta the Arrow.
Anser is marginally the brightest of Vulpecula's stars, but with an apparent magnitude of just +4.44 it is far from distinctive. It is a distant red giant, nearly 300 light years from the Solar System, and forms an optical double with 8 Vulpeculae, an even more distant orange giant that appears just seven arcminutes away from Anser in the skies of Earth. Due to its history as part of Cygnus, Anser is the only star in Vulpecula to have a Bayer designation, specifically Alpha Vulpeculae.
Vulpecula has no stars exceeding Anser's magnitude +4.44, but several approach the meagre brightness of that star. In particular, 23, 31 and 13 Vulpeculae are all brighter than +4.6 (these stars are all giants, classified orange, yellow and blue respectively).
Below the threshold of naked-eye visibility, Vulpecula holds a number of other stars with interesting properties. In the southern parts of the constellation lies HD 195034, notable as having physical parameters very close to those of the Sun. Several stars within Vulpecula have been established as possessing planetary systems, notably V452 Vulpeculae or HD 189733, a binary system with a massive gas giant in close orbit around its primary. Water vapour has been detected in this planet's atmosphere, with significant implications for the possibility of exoplanetary life.
Vulpecula is also significant as the location of the first pulsar to be discovered. Designated PSR B1919+21, this is a neutron star - the remnant of a supernova - that rotates at immense speed, sending out oscillating radio signals that pulse regularly, in this case just over once every 1.3 seconds.
Deep Sky Objects
The best known deep sky object in Vulpecula is the Dumbbell Nebula, a planetary nebula nearly 1,400 light years from the Solar System, whose structure contains two distinct lobes giving rise to the 'dumbbell' shape from which it takes its name. The strip of sky delineated by Vulpecula crosses much of the band of the Milky Way, and thus the constellation is home to several galactic clusters, especially in its western half.