We present precise , \sim 1 \% , r -band relative photometry of the unusual solar system object ( 90377 ) Sedna .
Our data consist of 143 data points taken over eight nights in October 2004 and January 2005 .
The RMS variability over the longest contiguous stretch of five nights of data spanning nine days is only \sim 1.3 \% .
This subset of data alone constrain the amplitude of any long-period variations with period P to be A \lesssim 1 \% ( P / 20 ~ { } { days } ) ^ { 2 } .
Over the course of any given \sim 5 -hour segment , the data exhibits significant linear trends not seen in a comparison star of similar magnitude , and in a few cases these segments show clear evidence for curvature at the level of a few millimagnitudes per hour ^ { 2 } .
These properties imply that the rotation period of Sedna is O ( 10 ~ { } { hours } ) , can not be \lesssim 5 ~ { } { hours } , and can not be \gtrsim 10 ~ { } { days } , unless the intrinsic light curve has significant and comparable power on multiple timescales , which is unlikely .
A sinusoidal fit yields a period of P = ( 10.273 \pm 0.002 ) { hours } and semi-amplitude of A = ( 1.1 \pm 0.1 ) \% .
There are additional acceptable fits with flanking periods separated by \sim 3 ~ { } { minutes } , as well as another class of fits with P \sim 18 ~ { } { hours } , although these later fits appear less viable based on visual inspection .
Our results indicate that the period of Sedna is likely consistent with typical rotation periods of solar system objects , thus obviating the need for a massive companion to slow its rotation .