Space

July 19, 2013

NASA’s Hubble shows link between stars’ ages and their orbits

nasa-hubble
Astronomers using NASA’s Hubble Space Telescope have determined the orbital motion of two distinct populations of stars in an ancient globular star cluster, offering proof they formed at different times and providing a rare look back into the Milky Way galaxy’s early days.

Researchers led by Harvey Richer of the University of British Columbia in Vancouver combined recent Hubble observations with eight years’ worth of data from the telescope’s archive to determine the motions of the stars in the globular cluster 47 Tucanae, which is located about 16,700 light-years away in the southern constellation Tucana.

The analysis enabled researchers, for the first time, to link the movement of stars in the clusters with the stars’ ages. The two populations in 47 Tucanae differ in age by less than 100 million years.

“When analyzing the motions of stars, the longer the time baseline for observations, the more accurately we can measure their motion,” said Richer. “These data are so good, we can actually see the individual motions of the stars in the cluster. The data offer detailed evidence to help us understand how various stellar populations formed in such clusters.”

The Milky Way’s globular clusters are the surviving relics from our galaxy’s formation. They offer insights into the early history of our galaxy. 47 Tucanae is 10.5 billion years old and one of the brightest of our galaxy’s more than 150 globular clusters. The cluster measures about 120 light-years wide.

Previous spectroscopic studies revealed many globular clusters contain stars of varying chemical compositions, suggesting multiple episodes of star birth. This Hubble analysis supports those studies, but adds the stars’ orbital motion to the analysis.

Richer and his team used Hubble’s Advanced Camera for Surveys to observe the cluster in 2010. They combined those observations with 754 archival images to measure the change in position of more than 30,000 stars. Using these data, they could discern how fast the stars move. The team also measured the stars’ brightness and temperatures.

This stellar archaeology identified the two distinct populations of stars. The first population consists of redder stars, which are older, less chemically enriched, and orbiting in random circles. The second population consists of bluer stars, which are younger, more chemically enhanced, and moving in more elliptical orbits.

The lack of heavier elements in the redder stars reflects the initial composition of the gas that formed the cluster. After the most massive of these stars completed their stellar evolution, they expelled gas enriched with heavier elements back into the cluster. This gas collided with other gas and formed a second, more chemically enriched generation of stars that was concentrated toward the cluster center. Over time these stars moved slowly outward into more elliptical orbits.

This is not the first time Hubble has revealed multiple generations of stars in globular clusters. In 2007, Hubble researchers found three generations of stars in the massive globular cluster NGC 2808. But Richer’s team is the first to link stellar dynamics to separate populations.

The team’s results appeared July 1 in The Astrophysical Journal Letters.

The Hubble Space Telescope is a cooperative project between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy Inc. in Washington.




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


 
 

 

Headlines April 23, 2014

News: U.S. conducts spy flights over Russia - After a tit-for-tat series of delays, the United States conducted an Open Skies Treaty intelligence flight over Russian territory April 21, a State Department official said.  Army paratroopers heading to Poland after Russian annexation of Crimea - U.S. Army paratroopers are arriving in Poland to begin a series of...
 
 

News Briefs April 23, 2014

U.S. military deaths in Afghanistan at 2,177 As of April 22, 2014, at least 2,177 members of the U.S. military had died in Afghanistan as a result of the U.S.-led invasion of Afghanistan in late 2001, according to an Associated Press count. The AP count is one less than the Defense Department’s tally. At least...
 
 

Northrop Grumman sets new greenhouse gas emission reduction goal of 30 percent by 2020

Northrop Grumman announced April 22 its commitment to reduce greenhouse gas emissions by 30 percent from 2010 levels by 2020, as part of its commemoration of Earth Day.   “Northrop Grumman is dedicated to top performance in environmental sustainability,” said Wes Bush, chairman, chief executive officer and president. “This new goal sets the bar significantly...
 

 

Lockheed Martin demonstrates enhanced ground control system, software for small UAV

Lockheed Martin’s Group 1 family of unmanned aircraft systems is migrating to enhanced automation capabilities using its Kestrelô “Fly Light” flight control systems and industry-leading mobile Ground Control Station software. The increased automation allows operators to focus on executing the mission, rather than flying various aircraft. Earlier this year, Lockheed MartinR...
 
 

U.S. Navy awards General Dynamics $33 million to operate, maintain military sealift ships

The U.S. Navy has awarded General Dynamics American Overseas Marine LLC a $32.7 million contract modification to operate and maintain seven large, medium-speed, roll-on / roll-off ships for the Military Sealift Command. AMSEA is a wholly owned subsidiary of General Dynamics. Under the terms of the modification, AMSEA will provide services including crewing, engineering, maintenance,...
 
 

US Navy deploys Standard Missile-3 Block IB for first time

In partnership with the Missile Defense Agency, the U.S. Navy deployed the second-generation Standard Missile-3 Block IB made by Raytheon for the first time, initiating the second phase of the Phased Adaptive Approach. “The SM-3 Block IB’s completion of initial operational testing last year set the stage for a rapid deployment to theater,” said Dr....
 




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>