Origin of galactic cosmic rays focus of NASA grant

WUSTL astrophysicists have received a five-year, $3,225,740 grant from the National Aeronautics and Space Administration (NASA) to design and build Super-TIGER — a Trans-Iron Galactic Element Recorder — and then fly it aboard a high-altitude balloon over Antarctica to collect rare atomic particles called galactic cosmic rays.

Super-TIGER’s first flight in search of the origin of cosmic rays is planned for December 2012.

W. Robert Binns, Ph.D., research professor of physics in Arts & Sciences, and the high-energy astrophysics group in the Department of Physics and the McDonnell Center for the Space Sciences, received the grant, titled “Super-TIGER: A Very-Large-Area, High-Resolution Trans-Iron Cosmic Ray Investigation.”

The Super-TIGER is designed to measure the abundances of the ultra-heavy galactic cosmic ray nuclei — nuclei of atoms heavier than nickel.

When constructed, it will be four times larger — about the size of a pool table — than the previous TIGER experiment that was successfully flown twice for a total of 50 days over Antarctica — once during a flight launched in December 2001 and another launched in December 2003.

Like Super-TIGER, TIGER also was supported by NASA and built in Washington University’s cosmic ray astrophysics laboratory.

Those flights, also in search of the origin of cosmic rays — atomic particles that travel through the galaxy at near light speeds — produced a strong indication that the cosmic rays originate and are accelerated in associations of massive stars called OB associations.

However, Binns said, higher statistics measurements are needed to confirm this conclusion and to better understand the mechanism by which elements found in interstellar dust grains are accelerated more efficiently than those found in interstellar gas.

“The Super-TIGER experi-ment will be able to collect about 10 times as many particles as the TIGER experiment, enabling us to make precise abundance measurements of these very rare, heavy nuclei,” said Binns, who is principal investigator.

“These measurements will enable us to test the emerging model of cosmic ray origin in associations of massive stars,” Binns said.

Martin H. Israel, Ph.D., professor of physics and a co-investigator with Binns on both Super-TIGER and the previous TIGER instruments, said that the study of galactic cosmic rays will lead to a better understanding of their origin and the explosive processes in our galaxy that are responsible for giving the nuclei such enormous energy.

A consortium of scientists, engineers, technicians and graduate students have been working together on TIGER — most recently on data analysis — and the same research groups will be developing Super-TIGER.

The researchers are from WUSTL, which is the principal investigator institution; NASA’s Goddard Space Flight Center in Greenbelt, Md.; the California Institute of Technology, Pasadena; the Jet Propulsion Laboratory, Pasadena; and the University of Minnesota.

In addition to Binns and Israel, the other WUSTL investigators are James H. Buckley, Ph.D., professor of physics, and Henric S. Krawczynski, Ph.D., associate professor of physics.

Helping design and develop the instrument will be the physics department’s Richard G. Bose, computer/electrical engineer; Dana L. Braun, mechanical technician; Paul F. Dowkontt, electrical engineer; Martin A. Olevitch, computer programmer/analyst; and Garry E. Simburger, electrical technician.