Cosmic rays are electrons, positrons, and atomic nuclei that move at nearly the speed of light. Astronomers believe that the high-energy cosmic rays originate from exotic places in the galaxy, such as the debris of exploded stars.
The LAT is a wide field-of-view imaging telescope, which consists of a tracker that determines the trajectory of the gamma ray or cosmic ray being measured, and an NRL-developed cesium-iodide calorimeter that determines the energy of the incoming ray. A charged-particle anti-coincidence shield helps filter out unwanted signals, such as those produced by background particles. LAT was developed for detecting gamma rays; however, it is also proving to be a great tool for studying the high-energy electrons in cosmic rays.
Gamma rays travel in straight lines, so scientists are able to pinpoint their sources simply by measuring the direction of each gamma ray as it arrives at the LAT. In contrast, cosmic rays diffuse through our Galaxy, scattering off and spiraling through the turbulent galactic magnetic fields. Because of their movements, scientists find it challenging to determine where the cosmic rays originated. One of Fermi's main goals is determining the sources of cosmic rays.
NRL's highly sensitive LAT measured the energies of more than four million high-energy electrons between August 2008 and January 2009, far more high-energy electrons than have ever been studied before. This extremely large data set allowed scientists to make a precise census of high-energy electrons and led to a surprising excess in the rate of electrons striking the LAT, more than expected from earlier measurements and theoretical models. The LAT data appear to be key to understanding electron measurements made from the European satellite PAMELA and the ground-based High Energy Spectroscopic System located in Namibia.
The Fermi LAT's results indicate that our understanding of the sources and propagation of high-energy particles in the galaxy is incomplete, and they seem to suggest that there is a nearby object beaming cosmic rays in the direction of Earth. Some scientists suggest that a nearby pulsar – the fast-spinning leftover of an exploded star – could be the source sending the electrons and positrons toward Earth. A more exotic possibility is that the particles are evidence of the existence of dark matter. For some time, astrophysicists have suggested that some form of matter – previously undetected and invisible, hence "dark" – exists to provide the extra gravity needed to keep galaxies from whirling apart. While researchers have never directly and conclusively observed dark matter, it could be that the excess electrons LAT observes are the result of interactions or decays of the theorized dark matter particles. Looking ahead, Fermi researchers will be watching for changes in the cosmic ray activity in different parts of the sky. This activity might help them piece together the puzzle in finding the source for the cosmic rays.
NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership mission, developed in collaboration with the U.S. Department of Energy and contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.
Donna McKinney | EurekAlert!
Hubble sees Neptune's mysterious shrinking storm
16.02.2018 | NASA/Goddard Space Flight Center
Supermassive black hole model predicts characteristic light signals at cusp of collision
15.02.2018 | Rochester Institute of Technology
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).
Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
16.02.2018 | Information Technology
16.02.2018 | Health and Medicine
16.02.2018 | Physics and Astronomy