The
X-type asteroid is classified as a Xc-subtype on the
SMASS taxonomic scheme, while the
NEOWISE mission of NASA's space-based
Wide-field Infrared Survey Explorer groups it into the
P-type spectral class.
Rotation period In December 2014, a rotational
lightcurve of
Alvema was obtained from photometric observations by French amateur astronomer
Laurent Bernasconi. It gave a
rotation period of with a brightness variation of 0.33
magnitude (). The asteroid's first lightcurve was reported by astronomer Darryl Sergison at the Gothers Observatory () in the United Kingdom, from observations made in November 2009, showing a period of hours with an amplitude of 0.17 magnitude ().
Diameter and albedo According to the survey carried out by NEOWISE,
Alvema measures 13.8 and 14.5 kilometers in diameter and its surface has a low
albedo of 0.031 and 0.047, respectively, while the
Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a diameter of 14.0 kilometers. == Naming ==