Featured Research

from universities, journals, and other organizations

One promising puzzle piece for confirming dark matter now seems unlikely fit

Date:
November 28, 2011
Source:
The Kavli Foundation
Summary:
In 2008, the Italian satellite PAMELA detected a curious excess of antimatter positrons -- a startling discovery that could have been a sign of the existence of dark matter. With assistance from the Earth's magnetic field, the Fermi Gamma-ray Telescope confirms a cosmic excess of antimatter positrons, but not the spike expected if evidence of dark matter.

By finding a clever way to use the Earth itself as a scientific instrument, researchers turned the Fermi Gamma-ray Space Telescope into a positron detector – and confirmed a startling discovery from 2009 that found an excess of these antimatter particles in cosmic rays, a possible sign of dark matter.
Credit: Image courtesy of The Kavli Foundation

Like jazz musicians who make up a melody as they go along, scientists often improvise even after an experiment is underway. One recent example of this comes from the Fermi Gamma-ray Space Telescope. Launched by NASA in June 2008, the $690 million telescope has since been working as advertised, providing scientists with the most complete look yet at gamma rays, the highest energy forms of light. But just two months after the launch, a tantalizing finding from a European experiment hinting at evidence of dark matter had Stefan Funk and Justin Vandenbroucke wondering if the telescope could be used to look at something for which it wasn't intended -- specifically, electrons and their antimatter twins, positrons, that are streaming across the universe in cosmic rays.

Related Articles


Using Earth as a Scientific Instrument

By finding a clever way to use Earth itself as a scientific instrument, researchers turned the Fermi Gamma-ray Space Telescope into a positron detector -- and confirmed a startling discovery from 2009 that found an excess of these antimatter particles in cosmic rays, a possible sign of dark matter.

Their problem was that the telescope, designed to detect neutral gamma rays, doesn't have a magnet for separating negatively charged electrons and positively charged positrons. So Funk, Vandenbroucke, and Stanford graduate student Warit Mitthumsiri, all at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, started looking beyond the experimental hardware. They found a magnet a few hundred miles away from the telescope that might do the trick. It happened to be Earth itself, which, thanks to its magnetic field, bends the paths of charged particles raining more or less continuously from space. (The spectacular aurora visible at high latitudes is the result of charged particles being bent and funneled toward the poles and impacting Earth's atmosphere.)

After studying up on geophysics maps and calculating precisely how Earth was filtering out charged particles seen by the telescope, the researchers went ahead with their analysis, and wound up with somewhat dramatic results.

Their paper, submitted to Physical Review Letters and originally published on the internet physics archive on Sept. 2, confirmed the curious excess of antimatter positrons formally reported in the 2009 study in the journal Nature that had the physics world agog. However, Funk and Vandenbroucke's analysis is most noteworthy for what it didn't see -- a sudden drop-off of this excess in those cosmic rays beyond a certain energy level, as many theories predicted would happen if dark matter was involved. Their result casts doubt on the dark matter explanation, which is one reason why the paper started making news just four days after it was published online. The first scholarly paper on the implications of Funk and Vandenbroucke's work appeared on the physics archive soon thereafter. That paper declared that "the standard positron production scenario must be incomplete." In other words: Who knows where these excess positrons are coming from?


Story Source:

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


Journal Reference:

  1. The Fermi LAT Collaboration: M. Ackermann, M. Ajello, A. Allafort, L. Baldini, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, A. Bouvier, J. Bregeon, M. Brigida, P. Bruel, R. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, C. Cecchi, E. Charles, A. Chekhtman, C. C. Cheung, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, S. Cutini, A. de Angelis, F. de Palma, C. D. Dermer, S. W. Digel, E. do Couto e Silva, P. S. Drell, A. Drlica-Wagner, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, P. Fortin, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, S. Germani, N. Giglietto, P. Giommi, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, I. A. Grenier, J. E. Grove, et al. Measurement of separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Physical Review Letters, 2011 [link]

Cite This Page:

The Kavli Foundation. "One promising puzzle piece for confirming dark matter now seems unlikely fit." ScienceDaily. ScienceDaily, 28 November 2011. <www.sciencedaily.com/releases/2011/11/111128115955.htm>.
The Kavli Foundation. (2011, November 28). One promising puzzle piece for confirming dark matter now seems unlikely fit. ScienceDaily. Retrieved January 31, 2015 from www.sciencedaily.com/releases/2011/11/111128115955.htm
The Kavli Foundation. "One promising puzzle piece for confirming dark matter now seems unlikely fit." ScienceDaily. www.sciencedaily.com/releases/2011/11/111128115955.htm (accessed January 31, 2015).

Share This


More From ScienceDaily



More Space & Time News

Saturday, January 31, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Video Shows Stars If They Were as Close to Earth as Sun

Video Shows Stars If They Were as Close to Earth as Sun

Buzz60 (Jan. 30, 2015) Russia&apos;s space agency created a video that shows what our sky would look like with different star if they were as close as our sun. Patrick Jones (@Patrick_E_Jones) walks us through the cool video. Video provided by Buzz60
Powered by NewsLook.com
Dog-Loving Astronaut Wins Best Photo of 2015

Dog-Loving Astronaut Wins Best Photo of 2015

Buzz60 (Jan. 30, 2015) Retired astronaut and television host, Leland Melvin, snuck his dogs into the NASA studio so they could be in his official photo. As Mara Montalbano (@maramontalbano) shows us, the secret is out. Video provided by Buzz60
Powered by NewsLook.com
NASA Holds Memorial to Remember Astronauts

NASA Holds Memorial to Remember Astronauts

AP (Jan. 29, 2015) NASA is remembering 17 astronauts who were killed in the line of duty and dozens more who have died since the agency&apos;s beginning. A remembrance ceremony was held Thursday at NASA&apos;s Marshall Space Flight Center in Alabama. (Jan. 29) Video provided by AP
Powered by NewsLook.com
Asteroid's Moon Spotted During Earth Flyby

Asteroid's Moon Spotted During Earth Flyby

Rumble (Jan. 27, 2015) Scientists working with NASA&apos;s Deep Space Network antenna at Goldstone, California discovered an unexpected moon while observing asteroid 2004 BL86 during its recent flyby past Earth. Credit to &apos;NASA JPL&apos;. Video provided by Rumble
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