U Andromedae is avariable star in the constellation ofAndromeda, at a distance of approximately2,200 ly. It is a star of spectral type M6e and it is classified as aMira variable.
U Andromedae is thevariable star designation of this star. Its brightness varies by several magnitudes with a mean period of347.7 d, although the exact length of each cycle is somewhat variable. Similarly, the magnitude of each maximum and minimum varies. The meanapparent magnitude is 11.6, with a mean maximum magnitude of 9.9.[6] The brightest recorded maxima are at magnitude 9.0, and the faintest minima at magnitude 15.0.[3] The rise to maximum brightness is faster than the fall to minimum, taking on average 40% of the period.[7]
The large amplitude, long period, and shape of the light curve mean that U Andromedae is classified as aMira variable, a type of pulsatingasymptotic giant branch (AGB) star.[3] It was first observed to be variable by Thomas D. Anderson during 1894 and 1895.[8][9] AGB stars have exhausted both hydrogen and helium in their cores and are not massive enough to fuse carbon and oxygen, so they erratically fuse helium and hydrogen shells outside the core.[10]
^abcdeU And, database entry, Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.), N. N. Samus, O. V. Durlevich, et al.,CDS IDII/250.
^Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities".Carnegie Institute Washington D.C. Publication.Bibcode:1953GCRV..C......0W.
