Astronomers from the United States, Russia and Australia have discovered the first true solar sibling – HD 162826.
HD 162826. Image credit: sky-map.org.
HD 162826, a star born in the same star cluster as our Sun, is located in the constellation Hercules, about 110 light-years away from Earth. It has a mass about 1.15 times that of the Sun.
The star is not visible to the unaided eye but can be seen with low-power binoculars, not far from Vega.
The astronomers led by Dr Ivan Ramirez from the University of Texas at Austin identified HD 162826 as our Sun’s sibling by following up on 30 possible candidate stars. In addition to chemical analysis, they also analyzed information about orbits of these stars.
Considering both chemistry and orbits narrowed the field of candidates down to one – HD 162826.
“No one knows whether this star hosts any life-bearing planets,” said Dr Ramirez, who reported the discovery in the Astrophysical Journal (arXiv.org version).
Dr Ramirez’s team has ruled out any massive planets orbiting close to the star.
“It’s unlikely that a Jupiter analog orbits the star,” Dr Ramirez said.
However, he and his colleagues do not rule out the presence of smaller terrestrial planets.
“The finding of a single solar sibling is intriguing, but the project has a larger purpose: to create a road map for how to identify solar siblings, in preparation for the flood of data expected soon from surveys such as ESA’s Gaia.”
Gaia will provide accurate distances and proper motions for a billion stars, allowing scientists to search for solar siblings all the way to the center of our Milky Way Galaxy.
“The number of stars that we can study will increase by a factor of 10,000,” Dr Ramirez said.
“Don’t invest a lot of time in analyzing every detail in every star. You can concentrate on certain key chemical elements that are going to be very useful. These elements are ones that vary greatly among stars, which otherwise have very similar chemical compositions. These highly variable chemical elements are largely dependent on where in the Galaxy the star formed.”
“We want to know where we were born. 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,” Dr Ramirez said.
Once many more solar siblings have been identified, astronomers will be one step closer to knowing where and how the Sun formed.
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I. Ramirez et al. 2014. Elemental Abundances of Solar Sibling Candidates. ApJ, accepted for publication; arXiv: 1405.1723
