HAT-P-1b

HAT-P-1b is an extrasolar planet orbiting the Sunlike star HAT-P-1, also known as ADS 16402 B. HAT-P-1 is the dimmer component of the ADS 16402 binary star system. It is located 453 light years away from Earth in the constellation Lacerta. HAT-P-1b is among the least dense of any of the known extrasolar planets.

Read more about HAT-P-1b:  Discovery, Orbit and Mass, Rotation, Characteristics