  We have compiled the first all-sky mid-infrared variable-star catalog based
on Wide-field Infrared Survey Explorer (WISE) five-year survey data. Requiring
more than 100 detections for a given object, 50,282 carefully and robustly
selected periodic variables are discovered, of which 34,769 (69%) are new. Most
are located in the Galactic plane and near the equatorial poles. A method to
classify variables based on their mid-infrared light curves is established
using known variable types in the General Catalog of Variable Stars. Careful
classification of the new variables results in a tally of 21,427 new EW-type
eclipsing binaries, 5654 EA-type eclipsing binaries, 1312 Cepheids, and 1231 RR
Lyraes. By comparison with known variables available in the literature, we
estimate that the misclassification rate is 5% and 10% for short- and
long-period variables, respectively. A detailed comparison of the types,
periods, and amplitudes with variables in the Catalina catalog shows that the
independently obtained classifications parameters are in excellent agreement.
This enlarged sample of variable stars will not only be helpful to study
Galactic structure and extinction properties, they can also be used to
constrain stellar evolution theory and as potential candidates for the James
Webb Space Telescope.
