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Scientists identify Sun’s “long-lost brother,” hope life might turn up

May 12, 2014
Courtesy of the Uni­vers­ity of Tex­as at Aus­tin
and World Science staff

As­tro­no­mers say they’ve found the Sun’s first known “si­b­ling”—a star al­most cer­tainly born from the same cloud of gas and dust as our star.

The meth­ods used to find it will help sci­en­tists find oth­er “so­lar sib­lings” and un­der­stand con­di­tions in the early so­lar sys­tem—in­clud­ing, per­haps, why it was suit­a­ble for life, said as­tron­o­mer Ivan Ramirez, who led the work.

Diagram showing location of HD 162826 (Courtesy of U. Texas at Austin)


It seems “the Sun was born in a clus­ter with a thou­sand or a hun­dred thou­sand stars,” Ramirez ex­plained. “This clus­ter, which formed more than 4.5 bil­lion years ago, has since bro­ken up,” he added. “A lot of things can hap­pen” in that time, and only a few of those stars are still rel­a­tively close by.

“If we can fig­ure out in what part of the gal­axy the Sun formed,” we can nar­row down what the ear­ly so­lar sys­tem was like, add­ed Ram­ir­ez, of the Uni­vers­ity of Tex­as at Aus­tin. “That could help us un­der­stand why we are here.” 

The­re’s al­so a small but real chance these so­lar sib­lings could host plan­ets with life, he said. Frag­ments of such plan­ets might even have trav­eled to Earth and brought life he­re, or vice-versa, “so it could be ar­gued that so­lar sib­lings are key can­di­dates” in the search for al­ien life.

The star in ques­tion is called HD 162826. It’s an esti­mated 15 per­cent heav­i­er than the Sun and lies 110 light-years away in the di­rec­tion of the con­stella­t­ion Her­cu­les. (A light-year is the dis­tance light trav­els in a year.) The star can’t be seen with the un­aided eye, but easily can be with light bin­oc­u­lars, not far from the bright star Ve­ga.

The team iden­ti­fied the star as a so­lar sib­ling by fol­low­ing up on 30 pos­si­ble can­di­dates found by sev­er­al groups around the world look­ing for such sib­lings. The meth­ods in­volved us­ing high-resolution spec­tros­co­py, a break­down of the col­ors re­leased from each star, to un­der­stand its chem­i­cal make-up. It al­so in­volved an­a­lyz­ing the paths of these stars as they or­bit the cen­ter of out Milky Way gal­axy, to find where they’ve been and where they’re go­ing.

The work is to be pub­lished in the June 1 is­sue of The As­t­ro­phys­i­cal Jour­nal.

By “lucky co­in­ci­dence,” Ramirez said, this star has been stud­ied by the Mc­Don­ald Ob­serv­a­to­ry Plan­et Search team at his uni­vers­ity. “They have been ob­serv­ing it for more than 15 years,” he said. Those stud­ies have ruled out gi­ant plan­ets close to the star, but not smaller, Earth-like plan­ets.


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Astronomers say they’ve found the Sun’s first known “sibling”—a star almost certainly born from the same cloud of gas and dust as our star. The methods used to find it will help scientists find other “solar siblings” and understand conditions in the early solar system—including, perhaps, why it was suitable for life, said astronomer Ivan Ramirez, who led the work. It seems “the Sun was born in a cluster with a thousand or a hundred thousand stars,” Ramirez explained. “This cluster, which formed more than 4.5 billion years ago, has since broken up,” he added. “A lot of things can happen” in that time, and only a few of those stars are still relatively close by. “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,” added Ramirez, of the University of Texas at Austin. There’s also a small but real chance these solar siblings could host planets with life, he added. Fragments of such planets might even have traveled to Earth and brought life here, or vice-versa, “so it could be argued that solar siblings are key candidates” in the search for alien life. The star in question is called HD 162826. It’s 15 percent heavier than the Sun and lies 110 light-years away in the direction of the constellation Hercules. (A light-year is the distance light travels in a year.) The star can’t be seen with the unaided eye, but easily can be with low-power binoculars, not far from the bright star Vega. The team identified the star as a solar sibling by following up on 30 possible candidates found by several groups around the world looking for such siblings. The methods involved using high-resolution spectroscopy, a breakdown of the colors released from each star, to understand its chemical make-up. It also involved analyzing the paths of these stars as they orbit the center of out Milky Way galaxy, to find where they’ve been and where they’re going. The work is to be published in the June 1 issue of The Astrophysical Journal. By “lucky coincidence,” Ramirez said, this star has been studied by the McDonald Observatory Planet Search team at his university. “They have been observing it for more than 15 years,” he said. Those studies have ruled out giant planets close to the star, but not smaller, Earth-like planets.