If your watch has chronograph functionality, the longest hand at the center may be the chronograph second hand.
The chronograph second hand moves only while the chronograph is measuring time.
On this type of watches, the second is often indicated by a small hand at a sub dial.

Refer to the instruction manual of your watch to check whether it has the chronograph function and to see further details of the function.
Instruction manual

http://www.citizenwatch-global.com/support/guide/manual.html

Consult your nearest service center if it does not have the chronograph function.
World Wide Service Center

http://www.citizenwatch-global.com/support/network/index.html