Yes, the Sun will almost certainly consume the Earth. The best current models predict that roughly 7.6 billion years from now, our planet will be swallowed by the Sun as it swells into a red giant star. But long before that dramatic end, Earth will already be a lifeless, ocean-free rock, baked beyond recognition by a steadily brightening Sun.
Why the Sun Will Expand
Stars like the Sun spend most of their lives fusing hydrogen into helium in their cores. This phase is stable and predictable, and the Sun is currently about halfway through it. Around 6 billion years from now, the hydrogen fuel in the core will run out. When that happens, the core contracts and heats up while the outer layers of the Sun inflate enormously, turning it into what astronomers call a red giant.
During this transformation, the Sun’s radius will grow from its current size to somewhere around 1 to 2 astronomical units (AU). One AU is the current distance between Earth and the Sun, about 93 million miles. So the Sun’s outer edge will reach, and likely exceed, the orbit where Earth sits today.
Why Earth Can’t Outrun It
There’s a hopeful twist in this story that, unfortunately, doesn’t play out. As the Sun expands, it also sheds mass. A lighter Sun means weaker gravity, and weaker gravity means the planets gradually drift outward into wider orbits. Earth’s orbit will expand as the Sun loses roughly a third of its total mass during the red giant phase. Some earlier analyses suggested this expansion might be enough to keep Earth just ahead of the Sun’s ballooning surface.
A detailed 2008 study published in the Monthly Notices of the Royal Astronomical Society by K.P. Schröder and Robert Connon Smith found otherwise. Their model accounted for two forces working against Earth’s escape: tidal interaction with the giant Sun (the same type of gravitational tug that causes ocean tides, but vastly stronger) and drag from the Sun’s thin outer atmosphere. These forces slow Earth down and pull it inward. The conclusion: Earth will not be able to escape engulfment. The study calculated that a planet would need to orbit at least 1.15 AU from the Sun today to survive the red giant phase. Earth sits at 1.0 AU.
Mercury will be consumed first and earliest. Venus follows. Earth meets its end during the tip of the red giant branch phase, roughly 7.6 billion years from now, when the Sun reaches its maximum size before shedding its outer layers entirely.
Earth Dies Long Before It’s Consumed
The engulfment itself is almost an afterthought. Earth will become uninhabitable billions of years earlier due to a much quieter process: the Sun is slowly getting brighter. Solar luminosity increases by about 7% every billion years. At the time the solar system formed 4.5 billion years ago, the Sun was only 70% as bright as it is today.
In roughly one billion years, the Sun’s output will reach a tipping point. Climate models predict this happens when the average solar energy hitting Earth’s surface climbs from today’s 341 watts per square meter to about 375 watts per square meter. At that point, surface temperatures will approach 70°C (158°F), the oceans will begin to boil, and Earth will enter a runaway greenhouse effect. Water vapor traps heat, which evaporates more water, which traps more heat, until the oceans are gone entirely. This process has nothing to do with human-caused climate change; it operates on a timescale of hundreds of millions of years.
Once the oceans evaporate, ultraviolet radiation from the Sun will break apart water molecules in the upper atmosphere, and the hydrogen will escape into space. Earth’s water will be lost permanently. By the time the Sun begins its red giant expansion billions of years later, Earth will already be a dry, scorched world with little resemblance to the planet we know.
What Happens During Engulfment
When the Sun’s outer envelope finally reaches Earth’s orbit, our planet won’t collide with a solid wall. The outer layers of a red giant are extraordinarily thin, more like a hot, diffuse gas than anything resembling the Sun’s current surface. The core of the red giant Sun will be compressed into a region only about 10 Earth radii across, while the glowing envelope stretches out to 1 or 2 AU. That means the outer layers are spread over a volume more than 2,000 times the size of the core.
Still, even this thin gas creates enough drag to slow Earth’s orbit. As Earth spirals inward through increasingly dense layers, friction heats the planet’s surface to thousands of degrees. The rocky crust would melt and eventually vaporize. Earth would be broken apart and absorbed into the Sun’s material over a relatively short period.
What Comes After
After the red giant phase, the Sun will shed its outer layers into space, forming a colorful shell of gas called a planetary nebula. What remains will be a white dwarf, a dense, Earth-sized remnant of the Sun’s core that slowly cools over trillions of years. Mars, Jupiter, Saturn, and the outer planets will likely survive, orbiting this fading ember in wider orbits than they have today. Earth, however, will be gone.