Ask Ethan: Will The Earth Eventually Be Swallowed By The Sun?
“When the Sun eventually goes Red Giant, will the Earth simply be orbiting within the outer envelope of the sun, or will something more interesting happen?”
In 2008, a now-famous astronomy paper was published that purported to determine the fate of the Earth as the Sun swelled to become a red giant. In particular, it claimed that not only would Mercury and Venus definitely be engulfed, but that the Earth would be, too. Sure, the Sun loses mass, which causes the planets to spiral outward, but it also grows in size, which leads to both drag forces on the orbiting planets as well as tidal forces that can sap a planet’s orbital angular momentum. The authors concluded that Earth’s orbit would need to presently be about 15% larger in order for it to have a chance of surviving. But there are other important factors at play, and they legitimately could change the outcome.