The brightest long-period pulsating variable
star, located in the constellation Cetus.
Mira was the first star discovered to vary in
brightness over a regular period. In 1596
Dutch astronomer David Fabricus noticed Mira
as a third-magnitude object. Because it did
not appear on any of the star charts
available at the time, he mistook it for a
nova. The German astronomer Johann Bayer
included it on his star atlas 1603 and
designated it Omicron Ceti. The star vanished
from view again, only to reappear within a
year. Continued observation revealed a
periodic variation between third or fourth
magnitude and ninth magnitude over an average
period of 331 days. Mira can sometimes reach
second magnitude and once, in 1779, it almost
attained first magnitude.