What was the name of the space shuttle built to replace Challenger?

The space shuttle built to replace Challenger was Endeavour. NASA began developing the orbiter after Challenger was destroyed in the 1986 launch disaster, and Congress authorized its construction in 1987.

Endeavour was assembled largely from structural spare parts left over from building Discovery and Atlantis, making its construction less expensive than designing an entirely new shuttle. NASA gave it the designation OV-105. Its name was chosen through a nationwide competition involving American schoolchildren and referred to the British research vessel HMS Endeavour.

Endeavour made its first flight in May 1992 on mission STS-49. Among its notable missions were repairs to the Hubble Space Telescope, construction work on the International Space Station, and the final servicing mission to Hubble in 2009.

The replacement was not called Enterprise. Enterprise was the first shuttle orbiter built, but it was a test vehicle that never flew into orbit. Challenger itself had originally been built as a structural test article before being converted into a flight-ready orbiter.