What change characterizes a star transforming into a Red Giant?
Answer
Its radius swells hundreds of times its original size, and its surface temperature drops
The increased energy from shell burning forces the external layers to expand dramatically, causing the radius to swell hundreds of times its original size while the surface temperature drops, resulting in a reddish hue.

Related Questions
What two opposing forces define a star's hydrostatic equilibrium?What event signals the definitive end of a star's main-sequence life?What happens immediately after the core hydrogen fuel is spent?How does hydrogen shell burning generally affect a star's energy output?What change characterizes a star transforming into a Red Giant?What mechanism supports the remnant core of a Sun-like star after it forms a white dwarf?What is the final fusion product achieved in the core of a very massive star before terminal instability?Why does the formation of an iron core lead to instantaneous energy loss?What is the result if the remnant core mass after collapse exceeds the neutron star limit?In variable stars like Cepheids, what triggers the violent expansion phase?