Astronomers Find Sun’s ‘Long-Lost Brother,’ Pave Way for Family Reunion

May 8, 2014

AUSTIN, Texas — A team of researchers led by astronomer Ivan Ramirez of The University of Texas at Austin has identified the first “sibling” of the sun — a star almost certainly born from the same cloud of gas and dust as our star. Ramirez’s methods will help astronomers find other solar siblings, which could lead to an understanding of how and where our sun formed, and how our solar system became hospitable for life. The work appears in the June 1 issue of The Astrophysical Journal.

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. A high-resolution version of this chart is available at http://mcdonaldobservatory.org/news/releases/2014/05/08 . (Credit: Ivan Ramirez/Tim Jones/McDonald Observatory)

“We want to know where we were born,” Ramirez said. “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.”

Additionally, there is a chance, “small, but not zero,” Ramirez said, that these solar sibling stars could host planets that harbor life. In their earliest days within their birth cluster, he explains, collisions could have knocked chunks off of planets, and these fragments could have traveled between solar systems, and perhaps even may have been responsible for bringing primitive life to Earth. “So it could be argued that solar siblings are key candidates in the search for extraterrestrial life,” Ramirez said.

The solar sibling his team identified is called HD 162826, a star 15 percent more massive than the sun, located 110 light-years away in the constellation Hercules. The star is not visible to the unaided eye but easily can be seen with low-power binoculars, not far from the bright star Vega.

The team identified HD 162826 as our sun’s sibling by following up on 30 possible candidates found by several groups around the world looking for solar siblings. Ramirez’s team studied 23 of these stars in depth with the Harlan J. Smith Telescope at McDonald Observatory, and the remaining stars (visible only from the southern hemisphere) with the Clay Magellan Telescope at Las Campanas Observatory in Chile. All of these observations used high-resolution spectroscopy to get a deep understanding of the stars’ chemical make-up.

But several factors are needed to really pin down a solar sibling, Ramirez said. In addition to chemical analysis, his team also included information about the stars’ orbits — where they had been and where they are going in their paths around the center of the Milky Way galaxy. 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. But by “lucky coincidence,” Ramirez said, the McDonald Observatory Planet Search team has been observing HD 162826 for more than 15 years. Studies by The University of Texas’ Michael Endl and William Cochran, together with calculations by Rob Wittenmyer of the University of New South Wales, have ruled out any massive planets orbiting close to the star (so-called hot Jupiters), and indicate that it’s unlikely that a Jupiter analog orbits the star. The studies do not rule out the presence of smaller terrestrial planets.

The finding of a single solar sibling is intriguing, but Ramirez points out 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 Gaia, the European Space Agency mission to create the largest and most precise 3-D map of the Milky Way.

The data coming soon from Gaia is “not going to be limited to the solar neighborhood,” Ramirez said, noting that Gaia will provide accurate distances and proper motions for a billion stars, allowing astronomers to search for solar siblings all the way to the center of our galaxy. “The number of stars that we can study will increase by a factor of 10,000,” Ramirez said.

He says his team’s road map will speed up the process of winnowing down the field of potential solar siblings.

“Don’t invest a lot of time in analyzing every detail in every star,” he said. “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. Ramirez’s team has identified the elements barium and yttrium as particularly useful.

Once many more solar siblings have been identified, astronomers will be one step closer to knowing where and how the sun formed. 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.

Note to editors: A high-resolution version of this chart is available at http://mcdonaldobservatory.org/news/releases/2014/05/08

For more information, contact: Rebecca Johnson, McDonald Observatory, College of Natural Sciences, 512 475 6763; Dr. Ivan Ramirez: The University of Texas at Austin, 512-471-7216; ivan@astro.as.utexas.edu.

13 Comments to "Astronomers Find Sun’s ‘Long-Lost Brother,’ Pave Way for Family Reunion"

1.  Xerxes Aga said on May 8, 2014

Good to know that our Sun has a sibling. Any idea where the parents are?

2.  den syahputra said on May 9, 2014

good....

3.  Setnom said on May 9, 2014

The parents died in gigantic supernova explosions.

4.  carlos santos said on May 9, 2014

So by measuring the distance from our Sun to HD 162826 that could give the idea of how big the supernova was thus estimating the primordial star size. The primordial star's size probably five to six times the Sun's size. Anything above that, then we are entertaining neutron star level, which is not conductive to second generation star formation.

5.  Sarah said on May 9, 2014

Good to know that our Sun has a sibling. Any idea where the parents are?

It's quite sad, but actually all stars are orphans. Their parents explode and give rise to dense clouds of gas and heavy elements, and new star are born inside those clouds... Stars are more like phoenixes in a way.

6.  Thomas Sevcik said on May 9, 2014

This should make for a good public star party "must-see!" for those of us members in a astronomy club. With Comet C/2012 K1 (PanSTARRS) and the Camelopardalis meteor shower also visible this month, these present great opportunities for our outreach programs.

7.  Davidh said on May 10, 2014

Brother...sister? You have got to be kidding. While it may all have come from the Big B. To call anything brother and sister begs some serious scientific thought

8.  John Maguire said on May 10, 2014

The mind boggles! With so much theorising and, may I say, perhaps the fitting of data to all these notions, I am on the brink of becoming a hard-nosed agnostic as far as macro and micro astronomy science is concerned. Maybe "sceptic" is a better word. I will still keep my telescope to simply enjoy the beauty of the heavens.

9.  gaman said on May 10, 2014

but why don't its light reaches to earth if it is 110ly away

10.  david (england) said on May 11, 2014

really interesting to know where to point to in the sky to show my 9 year old daughter where one of our suns sisters is. she will enjoy that. and for us (humans) to eventually be able to pinpoint where in the galaxy our sun formed would be a really cool thing.

11.  Roland said on May 12, 2014

@Xerxes Aga

Parents are dead as the sun was formed in a gascloud that partially was made up from heavier elements than hydrogen and helium. Anything heavier than H and He is made in stars that release those heavier elements at the end of their lives by going supernova meaning that the star selfdestructs by exploding. The gas expelled from the now dead star becomes available to form new stars.

Take the salmon as an analogy. It lays eggs and then dies. The new generation comes into existence without ever knowing their parents.

12.  Aki Airomaa said on May 12, 2014

Xerxes Aga:

Parent(s) said "boom" more than 5 billion years ago my friend :)

13.  Ossi Hallikainen said on May 15, 2014

It is a pity that the Kepler does not see until HD 162826.