  We investigate the electromagnetic signals accompanied with planetary
collisions and their event rate, and explore the possibility of directly
detecting such events. A typical Earth--Jupiter collision would give rise to a
prompt EUV-soft-X-ray flash lasting for hours and a bright IR afterglow lasting
for thousands of years. With the current and forthcoming observational
technology and facilities, some of these collisional flashes or the
post-collision remnants could be discovered.
