U Andromedae is a

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

in the constellation of Andromeda, at a distance of approximately . It is a star of spectral type M6e and it is classified as a

Mira variable Mira variables (named for the prototype star Mira) are a class of pulsating stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wave ...

. U Andromedae is the

variable star designation In astronomy, a variable-star designation is a unique identifier given to variable stars. It extends the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in whic ...

of this star. Its brightness varies by several magnitudes with a mean period of , although the exact length of each cycle is somewhat variable. Similarly, the magnitude of each maximum and minimum varies. The mean

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

is 11.6, with a mean maximum magnitude of 9.9. The brightest recorded maxima are at magnitude 9.0, and the faintest minima at magnitude 15.0. The rise to maximum brightness is faster than the fall to minimum, taking on average 40% of the period. The large amplitude, long period, and shape of the light curve mean that U Andromedae is classified as a

, a type of pulsating

asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

(AGB) star. It was first observed to be variable by Thomas D. Anderson during 1894 and 1895. 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.

References

{{DEFAULTSORT:U Andromedae Mira variables Andromeda (constellation) 007482 M-type giants Andromedae, U Durchmusterung objects Emission-line stars J01152971+4043082 IRAS catalogue objects