300 Pulsars and Counting …

Pulsars are a kind of neutron star, a city-sized remnant of a supernova. Neutron stars contain more mass than our Sun in a ball less than 25 km across.; they’re the densest matter we can see directly. They possess strong magnetic fields, produce streams of energetic particles, and spin quickly.

This visualization shows 294 gamma-ray pulsars, first plotted on an image of the sky as seen from Earth and then transitioning to a view from above the galaxy. The symbols identify different types of pulsars. Young pulsars appear to blink in real time—except for the Crab because its rate is only slightly lower than the video frame rate. Millisecond pulsars appear steady because their pulse rate too quickly to see.

The Fermi Gamma-ray Space Telescope is credited with the discovery of 294 of these pulsars. The Crab, Vela, and Geminga were among the 11 gamma-ray pulsars known before Fermi launched. Other notable objects are also highlighted. Distances are shown in light-years.

Video Credit: NASA

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

The Constellation Godzilla

Godzilla isn’t one of the official 88 constellations. It’s a new, unofficial x-ray constellation. The NASA team responsible for the Fermi Gamma-ray Space Telescope has devised a set of constellations constructed from sources in the gamma-ray sky. The new constellations include a few characters from modern myths. Among them are the Little Prince; the TARDIS from “Doctor Who;” Godzilla and his heat ray; the antimatter-powered U.S.S. Enterprise from “Star Trek: The Original Series;” and the Hulk, the product of a gamma-ray experiment gone awry.

To explore Fermi’s Gamma-ray Constellations, visit the interactive x-ray sky chart at https://fermi.gsfc.nasa.gov/science/constellations/.

Image Credit: NASA

Gamma Ray Burst

When a massive star collapses to form a black hole, a burst of gamma rays results as particles are blasted outward at nearly the speed of light. This animation shows the most common type of gamma-ray burst. An end-on view of a jet greatly boosts its apparent brightness. One especially bright burst (GRB 130427A) was detected in 2013 by the Fermi and Swift satellites. A Fermi image of that burst ends the animation sequence.

Video Credit: NASA