Heater and heater system

A heater comprising:

• an insulating base comprising a first main surface and a second main surface on a back of the first main surface,
• a resistance heating element extending in the base along the first main surface and the second main surface,
• a hollow member, wherein
• the hollow member comprises
• a first plate-shaped part overlapping the second main surface,
• a second plate-shaped part facing the first plate-shaped part through a space,
• a side surface part surrounding the space from an outside in a planar direction of the first plate-shaped part and the second plate-shaped part,
• a plurality of solid connecting parts located between the first plate-shaped part and the second plate-shaped part, connected to the first plate-shaped part and the second plate-shaped part, and distributed in the space in a perspective plan view of the first main surface, and
• an inlet and a plurality of outlets that communicate an inside of the space and an outside of the space,
• wherein the plurality of solid connecting parts are radially outwardly located with respect to the inlet in the perspective plan view of the first main surface and the plurality of outlets are located radially outward with respect to the plurality of solid connecting parts in the perspective plan view of the first main surface, and
• a pipe that passes through the hollow member in a direction orthogonal to the second main surface and is joined to the second main surface, the pipe including a circumferential direction, and the inlet arranged in the circumferential direction of the pipe.