It won’t explode as if by supernova because it’s below the Chandrasekar limit of ~1.4 times the sun’s mass needed for that to occur.

It will, however, enter its supergiant phase, and will expand its diameter to engulf the three inner planets. Many hundreds of billions or even hundreds of trillions of years later it will collapse into its stellar dwarf phase.

E: Sun, not earth. There’s a bit of difference, I guess.