  Short-period comet P/2010 V1 (Ikeya-Murakami, hereafter V1) was discovered
visually by two amateur astronomers. The appearance of the comet was peculiar,
consisting of an envelope, a spherical coma near the nucleus and a tail
extending in the anti-solar direction. We investigated the brightness and the
morphological development of the comet by taking optical images with
ground-based telescopes. Our observations show that V1 experienced a
large-scale explosion between UT 2010 October 31 and November 3. The color of
the comet was consistent with the Sun (g'-RC=0.61+-0.20, RC-IC=0.20+-0.20, and
B-RC=0.93+-0.25), suggesting that dust particles were responsible for the
brightening. We used a dynamical model to understand the peculiar morphology,
and found that the envelope consisted of small grains (0.3-1 micron) expanding
at a maximum speed of 500+-40 m/s, while the tail and coma were composed of a
wider range of dust particle sizes (0.4-570 micron) and expansion speeds 7-390
m/s. The total mass of ejecta is ~5x10^8 kg and kinetic energy ~5x10^12 J.
These values are much smaller than in the historic outburst of 17P/Holmes in
2007, but the energy per unit mass (1x10^4 J/kg) is comparable. The energy per
unit mass is about 10% of the energy released during the crystallization of
amorphous water ice suggesting that crystallization of buried amorphous ice can
supply the mass and energy of the outburst ejecta.
