Our Sun's Long Lost Stellar 'Sister' Found

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Stars like the sun may end up alone but they are born in stellar nurseries, with a thousand — or a hundred thousand — siblings. Over time, the family disbands, victims of gravitational nudges and other tidings after 4.5 billion years of life in the cosmos.

Astronomers have been on the hunt for solar siblings as part of a quest to learn more about how and where the sun was born and perhaps why our star became host to a life-bearing planet.

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This week, a team headed by the University of Texas reports it has found a star that “almost certainly” formed from the same cloud of gas and dust that produced the sun.

The star, known as HD 162826, is about 15 percent bigger than the sun and located about 110 light-years away in the constellation Hercules.

Solar sibling HD 162826 is not visible to the naked eye, but can be seen with low-power binoculars near the bright star Vega.
Ivan Ramirez/Tim Jones/McDonald Observatory

Scientists matched the star’s chemistry — telltale concentrations of the rare elements barium and yttrium proved particularly useful — with the sun’s chemical components. They also tracked HD 162826’s past orbits around the center of the Milky Way to discover its link with the sun.

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Out of 30 potential sibling stars, “only the star HD 162826 satisfies both our dynamical and chemical criteria for being a true sibling of the sun,” lead author Ivan Ramirez writes in a paper to be published in the June 1 issue of The Astrophysical Journal.

HD 162826  has been on astronomers’ watch lists for some time. So far, they’ve pretty much ruled out the presence of an orbiting “hot Jupiter’ planet — a massive planet circling closer to its host star than Mercury orbits the sun. But HD 162826 may have smaller, terrestrial planets, the scientists said.

With new surveys, including an ongoing study by Europe’s Gaia telescope, more solar siblings should be discovered soon, Ramirez writes.

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