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May 11, 2014

Discovery Of Solar Sibling Could Shed New Light On Our Own Sun’s Formation

redOrbit Staff & Wire Reports - Your Universe Online

A team of astronomers have identified what is believed to be the sibling of our sun – a star thought to have been born from the same cloud of gas as the one that provides our solar system with light and warmth.

According to Deborah Netburn of the Los Angeles Times, the sun’s so-called long-lost brother is slightly bigger and has a somewhat hotter surface temperature than the star around which the Earth orbits. However, an international team of investigators reports that both stars have the same chemical makeup and likely share a similar origin.

The newly identified star is known as HD 162826 and it was found during a follow-up study of 30 possible candidates discovered by several groups on the lookout for solar siblings. It is located 110 light years away in the constellation known as Hercules, and while it is not visible to the naked eye, it can easily be seen with low-powered binoculars.

“We want to know where we were born,” lead investigator Ivan Ramirez, an astronomer with the University of Texas at Austin said in a statement. “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.”

Ramirez and his colleagues performed an in-depth analysis of 23 of the 30 possible candidates using the Harlan J. Smith Telescope at McDonald Observatory, and the other seven stars (which are visible only from the southern hemisphere) using the Clay Magellan Telescope at Las Campanas Observatory in Chile. High-resolution spectroscopy was used during all of the observations in order to probe the chemical make-up of each star.

In addition to chemical analysis, the research team looked at other factors, including the orbits of the stars and how they were traveling around the center of the Milky Way. Using both chemical and orbital factors, only HD 162826 met the criteria. Fortunately, the McDonald Observatory Planet Search team has been studying it for 15 years – though as of yet, they have not found any evidence that the star is being orbited by any planets.

“Stars that were born in different clusters have different compositions. If a star has the exact same chemical composition as our sun, that establishes that they were born in the same place,” Ramirez told Netburn, adding that he did not expect to discover a solar sibling this close to our own sun. “If there is another star like this one this close to us, we would have found it already, so the next siblings we find are going to be further away.”

He told the Los Angeles Times reporter that the original purpose of the research, which is currently available online and is also scheduled to appear in the June 1 edition of The Astrophysical Journal, was to come up with more efficient ways of locating additional solar siblings in the future, once space-based telescopes begin providing astronomers with data from their surveys.

“There are number of surveys that are happening right now that will allow us to learn more about stars beyond the solar neighborhood," he said. "Right now there are about 100,000 stars we can look at in this way. In five or 10 years it could be as many as a billion."

To this end, the study authors have essentially come up with a road map which will make it easier to find additional stars related to our sun by allowing astronomers to search for specific chemical elements that typically vary greatly. The chemical content of some elements, such as barium and yttrium, are largely dependent upon where in the galaxy the star originally formed, and stars with similar levels as the sun are more likely to be siblings.

“Once many more solar siblings have been identified, astronomers will be one step closer to knowing where and how the sun formed,” the university concluded. “To reach that goal, the dynamics specialists will make models that run the orbits of all known solar siblings backward in time to find where they intersect: their birthplace.”

Image 2 (below): Solar sibling HD 162826 is not visible to the unaided eye, but can be seen with low-power binoculars near the bright star Vega in the night sky. Credit: Ivan Ramirez/Tim Jones/McDonald Observatory [ Larger Image ]