Space Science / High Energy Astrophysics
Faculty
- Cherry - (Hard x-ray/gamma-ray astronomy, terrestrial gamma flashes, cosmic rays, CALET, TETRA)
- Guzik - (Cosmic rays, ATIC, CALET, LaACES, Highland Road Observatory, Louisiana Space Consortium)
- Matthews - (Very high energy cosmic ray air showers, Auger)
- Stacy - (Hard x-ray/gamma-ray astronomy)
- Wefel - (Cosmic rays, high-energy interactions, CALET, ATIC, Louisiana Space Consortium)
Space Science and High Energy Astrophysics is the study of the highest energy radiation coming from the Universe - x-rays, gamma-rays, and cosmic rays and their sources. The targets include black holes in binaries and active galaxies, cosmic rays from the "knee" near 1015 eV to the highest energies above 1019 eV, gamma-ray bursts, supernova explosions, and terrestrial gamma flashes. Questions attacked include "What is the origin of the highest energy cosmic rays?", and "Where are the black holes in our Universe?". The group uses spacecraft experiments (CALET, Fermi-GBM), balloon-borne experiments (ATIC), and ground-based experiments (Auger, TETRA) Detector development includes applications to medical imaging and national security.
The Space Science/Particle Astrophysics group is primarily involved in three experiments currently:
The CALorimetric Electron Telescope (CALET) has been collecting science data on the JEM-EF external platform of the International
Space Station since mid-October 2015. As of mid-2017, more than 300 million triggers
generated by high-energy charged particles and photons from space have been recorded.
The main CALET detector consists of a deep (30 radiation lengths) calorimeter designed
to measure the cosmic ray electron spectrum up to 20 TeV (2 × 1013 eV), where features in the spectrum may indicate the presence of nearby sources or
dark matter. In addition to its primary goal to explore the high energy electron spectrum,
CALET can study the cosmic ray hadronic sector by contributing high precision measurements
of the energy spectra, relative abundances, and secondary-to-primary ratios of elements
from hydrogen to iron. Deviations from a simple power law, as reported by CREAM, PAMELA,
and AMS-02 in the spectra of light nuclei, are under study from a few tens of GeV
to the multi-TeV region. Finally, CALET is observing gamma rays up to 10 TeV, in particular
providing a capability for high energy counterpart searches for gamma ray bursts and
gravitational wave events.
The Pierre Auger Project has been measuring the highest energy (>1019 eV) cosmic rays for the past decade. No known mechanism can fully account for the
acceleration of cosmic rays to such high energies. Their extreme energy ensures that
they suffer little deflection when passing through relatively weak Galactic or intergalactic
magnetic fields. Cosmic rays interact with the cosmic background radiation, so any
observed at earth must have originated within about 100 Mpc. The Auger observatory,
spread out over 3000 km2 in western Argentina, has provided results on the spectrum, arrival directions, and
elemental composition of the highest energy cosmic rays; placed limits on the fluxes
of neutrinos, magnetic monopoles, and counterparts to gravitational wave events; and
explored the physics of elementary particle interactions at energies far above those
accessible with ground-based accelerators.
The TGF and Energetic Thunderstorm Rooftop Array (TETRA) experiment at LSU demonstrated
the existence of ground-level Terrestrial Gamma Flashes (TGFs) associated with nearby
lightning. Satellite observations of intense millisecond flashes of gamma rays produced
at the tops of thunderstorms have shown that lightning can accelerate electrons to
very high energies, apparently well above tens of MeV. TETRA produced a catalog of
TGFs produced by lightning near the Earth’s surface, and showed that the gamma ray
intensity at the source is extremely high. A follow-up experiment, TETRA-II, is now
operating with detectors at LSU, in Huntsville, AL and at sites in Puerto Rico and
Panama, where thunderstorm activity is significantly higher than at the current TETRA
site in Louisiana and where satellite overflights will enable looking at the same
storms simultaneously from the ground and from space. With sensitivity improved over
TETRA by approximately an order of magnitude, TETRA-II will measure the energy and
intensity spectrum with improved statistics, extend the energy range, determine the
height at which TGFs are produced, and provide for the first time correlated radiation
and meteorological data.
In addition to the research program, the LaACES student balloon project is giving undergraduate students a true hands-on experience
with project management, life-cycle, experiment design, construction, testing, data
collection, analysis and interpretation. During LaACES, students design, build, test,
fly and analyze the data returned from small balloon payloads (typical dimensions
10 cm x 10 cm x 10 cm, typical weight ~500 grams) carried up to ~100,000 feet by a
helium-filled latex sounding balloon, launched from the National Scientific Balloon
Facility in Palestine, Texas. A balloon-borne camera system will provide pictures
of the 2017 total solar eclipse from 100,000 ft.