Gamma Ray Bursts


Just before 2000 UTC on 14 January, the Fermi and Swift satellites detected a spike of gamma rays from the constellation Fornax. The missions alerted the astronomical community to the location of the burst, dubbed GRB 190114C. Ground-based facilities detected radiation with up to a trillion times the energy of visible light from the gamma-ray burst.

The illustration above shows the set-up for the most common type of GRB. The core of a massive star (left) has collapsed and formed a black hole. This “engine” drives a jet of particles that moves through the collapsing star and out into space at nearly the speed of light. The so-called prompt emission, which typically lasts a minute or less, may arise from the jet’s interaction with gas near the newborn black hole and from collisions between shells of fast-moving internal shockwaves within the jet itself. The afterglow emission occurs as the leading edge of the jet sweeps through the surroundings creating an external shock wave, and emitting radiation across a broad spectrum. That may continue for months to years in the case of radio and visible light and for hours at the highest gamma-ray energies yet observed.

Image Credit: NASA

Note: My principal contribution to the Swift satellite was the design and testing of the power regulation system for the X-ray detectors in Burst Alert Telescope.

GRB 080916C


Gamma ray bursts are the brightest explosions we see in the Universe. The farthest known GRB occurred 12.2 billion light-years away in the constellation Carina. The explosion that created GRB 080916C contained the power of 9,000 supernovae. This very short movie shows Fermi Large Area Telescope observations of GRB 080916C. About 8 minutes of data are compressed into 6 seconds. The colored dots represent gamma rays of different energies. The blue dots represent lower-energy gamma rays; green, moderate energies; and red, the highest energies.

Video Credit: NASA / DOE / Fermi LAT Collaboration

Fermi’s Spriagraph


Fermi's Motion Produces a Study in SpirographThe Fermi Gamma-ray Space Telescope orbits the Earth every 95 minutes, it’s scans building up increasingly more complex views of the universe with every circuit. The image above was put together from eight frames from a movie showing over 4 years’ position and exposure data recorded by Fermi‘s Large Area Telescope (LAT) into a single snapshot. The pattern reflects the various motions of the spacecraft, including its orbit around Earth, the precession of its orbital plane, and the manner in which the LAT nods north and south on alternate orbits.

The LAT sweeps across the entire sky every three hours, capturing the highest-energy form of light—gamma rays—from sources across the universe. Those sources range from supermassive black holes billions of light-years away to objects in our own galaxy, such as X-ray binaries, supernova remnants, and pulsars.

Image Credit: NASA/DoE