Featured Research

from universities, journals, and other organizations

Hot, Bright, Massive Stars Have Complex Mixing Processes In Their Great Depths

Date:
April 7, 2008
Source:
Royal Astronomical Society
Summary:
A surprising analysis of material churned up from the depths of massive stars shows that the mixing processes in these hot, bright stars are much more complicated than thought. The study used the FLAMES instrument on the Very Large Telescope (VLT) to decipher the spectra of light emitted by over 800 stars and estimate the chemical composition of the stars' surfaces. This is the most extensive survey of massive stars ever undertaken.

A spectacular feature of the Small Magellanic Cloud is the young cluster NGC346 with its many young hot stars.
Credit: A. Nota (ESA/STScI) et al., ESA, NASA

A surprising analysis of material churned up from the depths of massive stars shows that the mixing processes in these hot, bright stars are much more complicated than thought. The results will be presented at the RAS National Astronomy Meeting held at Queen’s University Belfast on Wednesday 2nd April.

Related Articles


The study, led by astronomers from Queen’s University, used the FLAMES instrument on the Very Large Telescope (VLT) to decipher the spectra of light emitted by over 800 stars and estimate the chemical composition of the stars’ surfaces. This is the most extensive survey of massive stars ever undertaken.

Massive stars rotate at speeds of up to a million kilometres per hour and this rotation drives huge circulatory currents. Models predict that gas from the star’s core, containing nitrogen and other elements produced in fusion reactions, should be thrust up to the surface. In the study, the team used the concentration of nitrogen measured at the surface to analyse the efficiency of mixing in the star. They found that nearly half the stars did not have the levels of nitrogen predicted, indicating rotation is not the only factor driving mixing.

Ian Hunter, who led the study, said "Current models of star rotation could be compared to a food processor – as you turn up the speed, the mixing between the layers of a star becomes more thorough and more nitrogen should be visible at the surface. However, 20% of the stars we looked at were slow rotators that were rich in nitrogen and another 20% were fast rotators without much nitrogen. The food processor model doesn’t seem to be working, or at least can’t explain the whole picture."

The FLAMES instrument can observe 140 stars at the same time and take a detailed spectrum of each simultaneously. Professor Philip Dufton, of Queen’s University, commented, "We’ve known for nearly a hundred years that very massive stars spin fast but how this affects their behaviour is still quite a controversial subject. It’s only now, with this unique European instrument, that we can study enough stars to draw some conclusions."

The team believe that magnetic fields could explain the slow rotating, well-mixed group. Previous studies imply a link between fossil magnetic fields, intrinsic magnetic fields left over from the star formation stage, and nitrogen-rich stellar surfaces. However, the physical processes involved in this magnetically driven mixing are still unknown.

The rapidly rotating, nitrogen-poor stars would fit in with model predictions if they were in binary systems. However, the surveys do not appear to show any evidence of companions for stars in this group.

Professor Norbert Langer of the University of Utrecht commented, "There is a mystery here that we need to understand. We now have to look at what is missing in our models – possibly magnetic fields – or maybe there are more stars in double systems than we thought and we don’t fully understand how they interact. After 100 years of studying spinning stars we still can’t explain all we see."

The stars analysed are located in two nearby galaxies, the Large and Small Magellanic Clouds. The study was carried out over 100 hours of VLT time by a consortium comprising 20 scientists from five European countries.


Story Source:

The above story is based on materials provided by Royal Astronomical Society. Note: Materials may be edited for content and length.


Cite This Page:

Royal Astronomical Society. "Hot, Bright, Massive Stars Have Complex Mixing Processes In Their Great Depths." ScienceDaily. ScienceDaily, 7 April 2008. <www.sciencedaily.com/releases/2008/04/080402160844.htm>.
Royal Astronomical Society. (2008, April 7). Hot, Bright, Massive Stars Have Complex Mixing Processes In Their Great Depths. ScienceDaily. Retrieved October 24, 2014 from www.sciencedaily.com/releases/2008/04/080402160844.htm
Royal Astronomical Society. "Hot, Bright, Massive Stars Have Complex Mixing Processes In Their Great Depths." ScienceDaily. www.sciencedaily.com/releases/2008/04/080402160844.htm (accessed October 24, 2014).

Share This



More Space & Time News

Friday, October 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: China Launches Moon Orbiter

Raw: China Launches Moon Orbiter

AP (Oct. 24, 2014) — China launched an experimental spacecraft Friday to fly around the moon and back to Earth in preparation for the country's first unmanned return trip to the lunar surface. (Oct. 24) Video provided by AP
Powered by NewsLook.com
China Prepares Unmanned Mission To Lunar Orbit

China Prepares Unmanned Mission To Lunar Orbit

Newsy (Oct. 23, 2014) — The mission is China's next step toward automated sample-return missions and eventual manned missions to the moon. Video provided by Newsy
Powered by NewsLook.com
Russian Cosmonauts Kick Off Final Spacewalk of 2014

Russian Cosmonauts Kick Off Final Spacewalk of 2014

Reuters - US Online Video (Oct. 22, 2014) — Russian cosmonauts Maxim Suraev and Alexander Samokutyaev step outside the International Space Station to perform work on the exterior of the station's Russian module. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
Comet Siding Spring Grazes Mars' Atmosphere

Comet Siding Spring Grazes Mars' Atmosphere

Newsy (Oct. 19, 2014) — A comet from the farthest reaches of the solar system passed extremely close to Mars this weekend, giving astronomers a rare opportunity to study it. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins