# What will “the Earth being consumed by the Sun” look like?

Sometime soon (astronomically speaking) the Sun will, as a main sequence star, expand into a red giant and, potentially, "consume the Earth".

If we take it as read that the surface of Sol will expand past the aphelion of Earth's orbit, what will Earth inside Sol entail, physically speaking, considering Earth as a rock, not an ecosystem, both as the surface of Sol expands past the orbit of Earth, and as the stellar envelope is ejected, leaving Sol as a white dwarf?

• It will cease to exist as it evaporates completely as it spirals towards Sun due to increased drag with the Solar wind and extended solar atmosphere.. – planetmaker Aug 19 '20 at 17:26
• There's some relevant info at en.wikipedia.org/wiki/Sun#After_core_hydrogen_exhaustion The Sun is about 4.6 Gyr (billion years) old and it won't start being a red giant for another 5 Gyr or so, but in about 1 Gyr it will be too hot for life to exist on Earth. – PM 2Ring Aug 19 '20 at 18:35
• Are you asking what it would look like from the POV of the Earth's surface, or from the POV of an observer at a safe distance from the Sun? Bear in mind that the outer layer of a star is rather tenuous, although a red giant's atmosphere is more opaque (and they tend to spew out a lot of dust). – PM 2Ring Aug 19 '20 at 18:40
• @PM2Ring I'm asking about what specifically would happen to the Earth, considered solely as a piece of stone floating in the abyss, the effects on various ecosystems and so on being beyond obvious (we all dead). – Williham Totland Aug 19 '20 at 19:11
• Oh, ok. But as I said, the ecosystems get trashed long before then. Wikipedia has a rough timeline. The oceans will be gone before the Sun enters the RGB (Red Giant Branch). Earth probably won't get swallowed until the Sun is near the tip of the RGB. As planetmaker said, the inner planets will get vapourised, and some of their matter will get spewed out as dust. – PM 2Ring Aug 19 '20 at 19:43

The first is that as the sun expands, its surface gravity $$GM_\odot/R_\odot$$ will decrease and gas can more easily escape as solar wind. This will reduce the mass of the sun, making Earth's orbit spiral outwards. But how much expansion depends on details of the far future solar wind we do not know yet, and this makes it slightly uncertain whether Earth can get into an orbit beyond the maximal solar radius. (The gas will also produce some drag, but it is likely negligible in this case)
Once the planet is inside the envelope it will rapidly get dragged in. To get a timescale, consider the time to push aside an Earth mass of gas: $$\tau = M_\oplus / \pi R_\oplus^2 \rho v$$. For $$\rho=$$ 0.1kg/m$$^3$$ I get $$\tau=0.4972$$ years. Maybe a bit longer if the orbit got wider and slower. Since the density of Earth is much higher than the gas, the planet will not be tidally disrupted but instead leave a hot plasma wake (that paper has more detailed calculations of infall timescales etc.).