Astronomers say they have identified a distant star with the same chemical makeup as our sun, showing it must have been created in the same stellar nursery and, at the same time, making it a solar sibling.
Although a little larger and a little hotter, the star's matching chemical fingerprint shows it was born in the same gas cloud that formed our sun 4.5 billion years ago, they say.
"Stars that were born in different clusters have different compositions," says University of Texas at Austin astronomer Ivan Ramirez. "If a star has the exact same chemical composition as our sun, that establishes that they were born in the same place."
The star named HD 162826, 110 light-years from Earth in the constellation Hercules, is invisible to the naked eye but it can be spotted with a low-power pair of binoculars, the researchers said.
In addition to matching chemical makeups, the orbits of our sun and HD 162826 -- their comings and goings along their paths around the Milky Way galaxy's center -- are strong evidence for their being solar siblings.
"The [cluster] member stars have broken off into their own orbits around the galactic center, taking them to different parts of the Milky Way today," Ramirez says. "A few, like HD 162826, are still nearby."
In a group of 30 stars that other studies had tagged as possible sibling candidates, only HD 162826 satisfied the "dynamical and chemical criteria for being a true sibling of the Sun," the international team led by Ramirez says in a study to be published June 1 in The Astrophysical Journal.
With further astronomical surveys expected to find and identify more solar siblings, astronomers expect the; will get ever closer to knowing exactly where and how our sun formed.
"We want to know where we were born," Ramirez says. "If we can figure out in what part of the galaxy the sun formed, we can constrain conditions on the early solar system. That could help us understand why we are here."
There's also a slim chance that HD 162826 or other sibling stars may have developed their own solar systems of orbiting planets, Ramirez says, that could possibly harbor life.
"So it could be argued that solar siblings are key candidates in the search for extraterrestrial life," he says.
