Red Giants: Sun Will 'Bubble' to Death—and Destroy Earth in the Process

By Katherine Hignett On 12/22/17 at 7:51 AM EST

12_22_π1 Gruis — Scientists have directly observed bubbles on the surface of the aging π1 Gruis red giant outside of our solar system. Their unique telescopic images shed light on how our own sun will eventually die, taking Earth with it. ESO

Tech & Science Solar Astronomy Sun Earth

Scientists have observed giant bubbles on an aging red giant outside of our solar system. Their unique telescopic images shed light on how our own sun will eventually die, taking Earth with it.

The π1 Gruis star sits 500 light years away in the Grus constellation—also known as the Crane. Images captured using the European Space Observatory's Very Large Telescope show the huge, hot bubbles on the surface of the red giant.

Previous research had predicted the bubbles, but this is the first time they have been directly observed.

The lifecycle of a star

Stars expand enormously as they age into red giants. When they eventually burn through their vast stores of hydrogen, stars shrink and become extremely hot. Scorched by the burning core, the outer layers of the star then balloon.

This behemoth expansion leaves the star hundreds of times its original size, but thinly spread. This particular red giant is 350 times larger than the sun, but it has only 1.5 times the mass.

Giant, bubbling surface

The aging process drastically alters the surface of stars, which are covered in something called "convection cells" or granules. These are spots of liquid kept in place by the movement of heat. As hot fluid moves up toward the center of each spot, cool fluid moves down from the edges. This suspends the fluid in "bubbles" on the surface of stars.

8804537584_56e8fa819d_o — The red giant will eventually shed its outer layers into a planetary nebula, like this one pictured by the Hubble Space Telescope. Hubble Heritage Team/NASA

"About two million convective cells with typical sizes of around 2,000 kilometers (1,250 miles) across are present on the surface of the sun," the authors write in Nature. In comparison, they observed just a few on the surface of π1 Gruis.

Each of these cells measures about 75 billion miles in diameter. That's roughly the distance from the sun to Venus.

This red giant will gradually shed its outer layers over a few tens of thousands of years, creating a planetary nebula.

As our sun expands into a red giant, it will boil the Earth's seas and clog the atmosphere with nitrogen and carbon dioxide. This will render the planet uninhabitable far before the eventual solar explosion rips through the solar system.

But there is no need to evacuate just yet. Scientists predict we have about five billion years before the Sun swells into a red giant.

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