Space

December 12, 2012

NASA Astrobiology Institute shows how wide binary stars form

Using computer simulations, scientists from the NASA Astrobiology Institute team at the University of Hawaii are shedding light on a question that has challenged astronomers for years: What causes wide binary stars?

Binary stars are pairs of stars that orbit each other. Wide binary stars are separated by as much as one light-year in their orbits, farther apart than some stellar nurseries are wide. Astronomers have known about such distant pairs for a long time but have not understood how they form.

Researchers simulated the complex motions of newborn triple stars still embedded in their nascent cloud cores. They studied the motions 180,000 times and concluded the widest binary systems began as three stars, not just two. This research appears in a paper to be published in the Dec. 13 issue of the journal Nature and was released last week online.

Most stars are born in small, compact systems with two or more stars at the center of a cloud core. When more than two stars share a small space, they gravitationally pull on each other in a chaotic dance. The least massive star often is kicked to the outskirts of the cloud core while the remaining stars grow larger and closer by feeding on the dense gas at the center of the cloud core.

If the force of the kick is not forecful enough, the runt star will not escape, but instead begin a very wide orbit of the other two, creating a wide binary. However, sometimes astronomers find only two stars in a wide binary. This means either the star system formed differently or something happened to one of the original binary pair.

“What may have happened is that the stars in the close binary merged into a single larger star,” said the paper’s lead author, Bo Reipurth of the Institute for Astronomy at the University of Hawaii at Manoa. “This can happen if there is enough gas in the cloud core to provide resistance to their motion. As the two stars in the close binary move around each other surrounded by gas, they lose energy and spiral toward each other. Sometimes there is so much gas in the core that the two close stars spiral all the way in and collide with each other in a spectacular merging explosion.”

The wide binary nearest to Earth is Alpha Centauri. The star itself is a close binary. Alpha Centauri has a small companion, Proxima Centauri, which orbits at a distance of about one-quarter of a light-year, or 15,000 times the distance between Earth and the sun. All three stars were born close together several billion years ago, before a powerful dynamic kick sent Proxima out into its wide path, where it has been orbiting ever since.

NASA’s Kepler mission already has proven that more than one planet can form and persist in the stressful realm of a binary star, a testament to the diversity of planetary systems in our galaxy.

NASA supported the University of Hawaii work through a cooperative agreement with NASA’s Ames Research Center, Moffett Field, Calif., and the NASA Astrobiology Institute, which is a partnership between NASA, 15 U.S. teams, and 10 international consortia. The research on wide binary stars included the University of Turku in Finland.

 




All of this week's top headlines to your email every Friday.


 
 

 

President proclaims Memorial Day as ‘Day of Prayer’

President Barack Obama May 22 saluted the service and sacrifices of America’s military members–past and present–and proclaimed Memorial Day, May 25, 2015, “as a day of prayer for permanent peace, and I designate the hour beginning in each locality at 11 a.m. of that day as a time during which people may unite in prayer....
 
 

Air Force leaders’ Memorial Day message

Secretary of the Air Force Deborah Lee James and Air Force Chief of Staff Gen. Mark A. Welsh III send the following Memorial Day message to the Airmen of the Air Force and their families: To the Airmen of the United States Air Force and their Families: On Memorial Day, Americans pause in solemn remembrance...
 
 

Headlines May 22, 2015

News: Second Marine killed in Hawaii Osprey crash identified - Marine Corps officials have identified the second Marine to die as a result of the May 17 MV-22B Osprey crash as Lance Cpl. Matthew J. Determan of Maricopa, Ariz.   Business: Israel defense exports plunge to seven-year low - Israeli defense sales last year plunged to their...
 

 

News Briefs May 22, 2015

Ukrainian officer hit with third charge in Russia A third charge has been filed against a Ukrainian military officer who has been behind bars in Moscow for nearly a year over the deaths of two Russian journalists in Ukraine. Nadezhda Savchenko, who worked as a spotter for Ukrainian troops fighting separatist rebels in eastern Ukraine,...
 
 
Army photograph by C. Todd Lopez

Smart-mortar will help Soldiers more effectively hit targets

Army photograph by C. Todd Lopez Nick Baldwin and Evan Young, researchers with the Armament Research Development and Engineering Center at Picatinny Arsenal, Pennsylvania, discuss the 120mm Guided Enhanced Fragmentation Mortar ...
 
 

Air Force assigns new chief scientist

The Air Force announced the service’s new chief scientist to serve as a science and technology adviser to the secretary of the Air Force and the chief of staff of the Air Force, May 21. Dr. Greg Zacharias will be the 35th chief scientist and is ready to “dive in” to his new role. “I...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>