In 5 billion years, the Sun will expand to engulf Mercury, Venus, and possibly Earth
Our Sun is a middle-aged star approximately 4.6 billion years old. In about 5 billion years, it will exhaust its hydrogen fuel and expand into a red giant, growing to roughly 200 times its current diameter — large enough to swallow Mercury and Venus completely. Whether Earth will be engulfed or merely scorched depends on how much mass the Sun loses during expansion. Either way, the Sun's increased luminosity will render Earth uninhabitable in about 1 billion years — long before the final expansion.
The warmth keeping you alive right now will kill you — not in a metaphorical sense but literally. In geological terms, the Sun has about 20% of its habitable lifespan remaining.
“The Sun will expand in 5 billion years to engulf Earth. But it will make Earth uninhabitable in just 1 billion — much sooner.”