How big will our sun gets when it becomes a red giant?
Answers
The future of the sun
In approximately 5 billion years, the sun will begin the helium-burning process, turning into a red giant star. When it expands, its outer layers will consume Mercury and Venus, and reach Earth. Scientists are still debating whether or not our planet will be engulfed, or whether it will orbit dangerously close to the dimmer star. Either way, life as we know it on Earth will cease to exist.
"A similar fate may await the inner planets in our solar system, when the sun becomes a red giant and expands all the way out to Earth's orbit some five billion years from now," astronomer Alex Wolszczan, an astronomer at Pennsylvania State University, said in a statement.
"The future of the Earth is to die with the sun boiling up the oceans, but the hot rock will survive," astrophysicist Don Kurtz, of the University of Lancashire, told Reuters.
The changing sun may provide hope to other planets, however. When stars morph into red giants, they change the habitable zones of their system. The habitable zone is the region where liquid water can exist, considered by most scientists to be the area ripe for life to evolve. Because a star remains a red giant for approximately a billion years, it may be possible for life to arise on bodies in the outer solar system, which will be closer to the sun.
"When a star ages and brightens, the habitable zone moves outward and you're basically giving a second wind to a planetary system," exoplanet scientist Ramses M. Ramirez, a researcher at Cornell's Carl Sagan Institute, said in a statement. "Currently objects in these outer regions are frozen in our own solar system, like Europa and Enceladus — moons orbiting Jupiter and Saturn."
The window of opportunity will only be open briefly, however. When the sun and other smaller stars shrinks back down to a white dwarf, the life-giving light will dissipate. And supernovae from larger stars could present other habitability issues.