Featured Research

from universities, journals, and other organizations

Cosmic Ray History Encoded In Abundances Of Light Elements

Date:
June 1, 1999
Source:
University Of Illinois Urbana-Champaign
Summary:
By taking a closer look at two of the lightest elements in the universe, a University of Illinois scientist is helping to solve a mystery that lies at the intersection of cosmology, cosmic rays and chemical evolution.

CHAMPAIGN, Ill. -- By taking a closer look at two of the lightest elements in the universe, a University of Illinois scientist is helping to solve a mystery that lies at the intersection of cosmology, cosmic rays and chemical evolution.

"The origin and history of cosmic rays are encoded in the cosmic abundances of beryllium and boron," said Brian Fields, a visiting professor of astronomy at the U. of I. "These elements, 'orphans' of nucleosynthesis, are made neither in stars nor in the big bang. Instead, they are created by cosmic rays, high-energy particles that fly through space and smash into atoms in interstellar gas, fragmenting them into lighter elements."

While astronomers generally agree that cosmic rays originate in supernova explosions, they differ over the mechanism responsible. "The traditional view is that cosmic rays are particles of the interstellar medium that were ionized and accelerated by a supernova shock wave," Fields said. "An alternate view, however, suggests that cosmic rays are pieces of the star blown off in the explosion."

The cosmic abundances of three elements -- hydrogen, helium and lithium -- were initially set in the big bang. But these amounts -- as well as those of all the other elements -- are continually changing because of the life cycle of stars. In a grand recycling theme, supernova remnants enrich the interstellar medium with heavy elements that eventually condense into new stars.

Because stars are net producers of certain elements -- iron and oxygen, for example -- the amounts of those elements will slowly increase in the interstellar medium. "This provides a kind of 'yardstick' for measuring the cosmic abundances of beryllium and boron over time and space," Fields said. "These two elements should scale with iron in definite, predictable ratios."

When measured, however, these ratios were found to be off significantly, leading many astronomers to conclude that the standard cosmic ray scenario was either incomplete or incorrect. Additional sources and mechanisms for light-element production were then proposed.

Fields and colleague Keith Olive, a professor of physics at the University of Minnesota, decided to re-examine the data. "Instead of comparing how the abundances of beryllium and boron change with iron, we chose to compare them with oxygen," Fields said. "After all, oxygen nuclei are what are being broken up by cosmic rays to make the lighter elements."

By carefully analyzing the abundances of beryllium, boron, iron and oxygen in stars of different ages, Fields and Olive derived new scaling factors that strongly support the traditional view of cosmic ray and light-element production, without requiring additional sources or mechanisms.

"The standard picture of cosmic ray origin may be correct after all," Fields said. "That is, cosmic ray particles originate in interstellar gas, not directly from supernovae. The data, as we read them, support this."

Fields and Olive discussed their findings in the May issue of the Astrophysical Journal.


Story Source:

The above story is based on materials provided by University Of Illinois Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois Urbana-Champaign. "Cosmic Ray History Encoded In Abundances Of Light Elements." ScienceDaily. ScienceDaily, 1 June 1999. <www.sciencedaily.com/releases/1999/06/990601081817.htm>.
University Of Illinois Urbana-Champaign. (1999, June 1). Cosmic Ray History Encoded In Abundances Of Light Elements. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/1999/06/990601081817.htm
University Of Illinois Urbana-Champaign. "Cosmic Ray History Encoded In Abundances Of Light Elements." ScienceDaily. www.sciencedaily.com/releases/1999/06/990601081817.htm (accessed October 22, 2014).

Share This



More Space & Time News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

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
Latin America Launches Communications Satellite

Latin America Launches Communications Satellite

AFP (Oct. 17, 2014) — Argentina launches a home-built satellite, a first for Latin America. It will ride a French-made Ariane 5 rocket into orbit, and will provide cell phone, digital TV, Internet and data services to the lower half of South America. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
This Week @ NASA, October 17, 2014

This Week @ NASA, October 17, 2014

NASA (Oct. 17, 2014) — Power spacewalk, MAVEN’s “First Light”, Hubble finds extremely distant galaxy and more... Video provided by NASA
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