A planet is a celestial body in orbit around a star or stellar remnants, that has sufficient mass for
self-gravity and is nearly spherical in shape. A planet must not share its orbital region with other bodies
of significant size (except for its own satellites), and must be below the threshold for thermonuclear
fusion of deuterium.
If a celestial body meets those requirements, it is considered a planet; at that point, the planet is further
classified by its atmosphere and surface conditions into one of twenty-two categories.