At a Glance

According to astrophysicist Ethan Siegel, the sun is ever-so-gradually getting lighter and expanding into a red gas giant.Eventually it will burn so hot that it will boil Earth's seas away.That won't happen for at least a billion years, however.

Before the sun dies in about 10 billion years, its decreasing mass will make the star hotter and hotter, eventually boiling Earth's seas away, a scientist said.

Astrophysicist Ethan Siegel wrote in an article for Forbes this week that the sun and expanding into a red gas giant. As it does, it will become hotter and ultimately make the Earth uninhabitable.

But not to worry. It won't occur fora billion years or so.

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The sun makes up approximately 99.8 percent of the solar system's mass, said Siegel. The sun, which burns at 10,000 degrees Fahrenheit at its surface,fuses hydrogen into helium, a lighter element.

"As this occurs, the mass of the sun slowly drops; the energy gets transported to the surface, and the 'waste product' of helium sinks further down into the central region of the core," wrote Siegel.

During its lifetime, the sun has shed the massequivalent of 95 Earths, Seigel also noted.

The sun also loses mass by releasing material as solar wind.Siegel wrote that mass roughly equivalent to that of the Earth is released by the sun as solar wind every 150 million years.

Siegel's article cameafter the May release of a study detailing when and how the sun will die.

According to research publishedin the journal Nature Astronomy, a team of international astronomers concludedin about5 billion years after it burns up all the hydrogen at its core. By that time, it will have extended in size and swallowed up Venus and Mars,and Earth will be long gone.

The researchers noted in the study thatEarth will be gone in about a billion years because as the sun ages, it becomes 10 percent brighter every billion years or so. The increased brightnesswill be enough to evaporate our oceans, making lifeon our planet impossible.