So, um, maybe the Sun *will* eventually swallow the Earth. Bummer. - SYFY WIRE

If it helps, you can postpone your panic for about 7 billion years.

The Sun is currently a very stable star, with hydrogen in the core merrily undergoing nuclear fusion, transmogrifying itself into helium and energy.

It's been doing this for over four billion years, and that's where we are now.

But, over time, helium builds up in the core.

In roughly 6 billion years the Sun will run out of hydrogen in the core, but the core will shrink and heat up so much that hydrogen will fuse in a thin shell just outside the core.

The process above repeats, except this time helium fuses into carbon and oxygen, which build up in the core, generating vast amounts of energy*.

The size of the Sun now (1.4 million km) compared to when it becomes a red giant in about 7 billion years.

They will literally exist for some time inside the Sun, orbits decaying as they plow through the hot plasma, falling farther in and eventually vaporizing entirely.

If a dying star engulfs a big planet (like Jupiter), then it will lose a lot of mass as the planet orbiting inside it spins it up like a fork whipping up a bowl of eggs.

But if the star lacks such a close-in planet, it won't lose nearly as much mass.

Mercury and Venus won't do much inside the Sun but fizzle and die, so the Sun's wind won't be very strong, so it'll keep more mass, which means its gravity won't drop as much as previously thought.

The Sun’s size over time (starting about 7.5 billion years from now; Gyr = gigayears) in terms of its size now (top panel; the Sun’s current radius is 700,000 km), and in terms of the size of Earth’s orbit (bottom).

In the bottom panel, if the Sun’s size gets over 1, the Earth will be inside the Sun.

It will be so hot that the solid rock of our planet will boil, so being inside or outside the Sun is kindof a technicality at that point.