Short answers, pulled from the story.
Kerberos was first detected on the 28th of June 2011 by the Pluto Companion Search Team using the Hubble Space Telescope's Wide Field Camera 3. Its existence was formally verified and announced on the 20th of July 2011.
Kerberos measures approximately 19 km along its longest dimension and about 9 km across its shortest. It is the second-smallest of Pluto's five moons, after Styx.
Kerberos is a contact binary, meaning it is believed to be two smaller objects that merged after a gentle collision. The larger lobe is approximately 8 km across and the smaller lobe is approximately 5 km across.
Kerberos completes one orbit around the Pluto-Charon barycenter every 32.167 days at a distance of 57,783 km. Its orbital period is close to a 1:5 resonance with Charon, with a discrepancy of about 0.7%.
New Horizons imaged Kerberos during its flyby of the Pluto system on the 14th of July 2015. The first image was released to the public on the 22nd of October 2015, making Kerberos the last of Pluto's moons to have its photograph published.
The moon was named Kerberos by the International Astronomical Union on the 2nd of July 2013. The name is the Greek form of Cerberus, the dog that guards Pluto's underworld in classical mythology. A public poll conducted in 2013 by Mark Showalter and the SETI Institute had originally favored Vulcan, but the IAU rejected that name because it is not an underworld deity and had prior astronomical use.