The sun has a distant twin, but it's 2 billion years older. And if the star at the center of our solar system evolves like its relative out in the Unicorn constellation, all the water on Earth will boil away.
The newly discovered star is the farthest of the so-called solar twins in the Milky Way galaxy. Twins get their name because they have nearly identical mass and chemical composition, not because of any shared birthday. In fact, the differences in age are one reason solar twins are so important to astronomers – one star may be a snapshot of the other's future.
The awkwardly dubbed CoRoT Sol 1 does match our sun in mass and chemical composition (although half of its lithium has been depleted), according to the team of Brazilian observers who found it. But SoRoT Sol 1 is 6.7 billion years old, the team reported.
The solar twin's radiation is also much more intense than that of our sun, which could foretell a future on Earth that is hotter than Hades.
"In 3 billion years' time ... the sun's radiation may increase and make the Earth's surface so hot that liquid water can no longer exist there in its natural state," said team leader Jose Dias do Nascimento of the Universidad do Rio Grande do Norte.
The team examined three twins before focusing in on the extremely dim CoRoT Sol 1. They used light spectra from the High Dispersion Spectrograph on the Subaru Telescope to figure out the star's age, while data from the CoRoT (convection, rotation and planetary transits) satellite pegged the rotation period - 29 days, give or take a workweek, about a day less than the sun's average.