Alfa 177 was an uninhabited planet. This was the homeworld for a species of canines: the Alfa-177 Canine. It's the second planet in the Alpha Honorus star system located inside Federation space, located in the Beta Quadrant.
This planet had a nighttime temperature that reached 120° below zero. The planet was capable of supporting life despite this, and it was also rich in a soft yellow magnetic ore with highly unusual properties.
In 2266, the USS Enterprise was on a specimen-gathering mission to this planet. While there, they brought aboard one of the dogs native to the planet. Also, Crewman Fisher, a member of the landing party, became covered with the yellow magnetic ore, which damaged the transporters and caused the device to divide transporter signals. (TOS: "The Enemy Within")
In 2293, the location of Alfa 177 in the Milky Way Galaxy was labeled in the star chart The Explored Galaxy, which was on display in James T. Kirk's quarters aboard the USS Enterprise-A. (Star Trek VI: The Undiscovered Country, okudagram)