The Obelisk

An obelisk is a tall, tapering monument topped with a pyramid first created in ancient Egypt. Symbolizing the sun god, Ra, the obelisk may have been inspired by the sun pillar, a natural atmospheric phenomenon that produces an apparent column of light near sunrise and sunset. The Washington Monument in the U.S. capitol is both the tallest obelisk in the world as well as the tallest stone structure, composed of more than 36,000 blocks.

The Obelisk constellation represents Washington, D.C., and its vicinity, where several institutions tied to Fermi are located. The U.S. Naval Research Laboratory in Washington designed, built, and tested the Large Area Telescope's (LAT) calorimeter system, which measures the energy of incoming subatomic particles. NASA's Goddard Space Flight Center in Greenbelt, Maryland, developed the LAT's anticoincidence detector, which tells Fermi when a particle enters the instrument instead of a gamma ray. Goddard also hosts the Fermi Science Support Center, which provides analysis tools for the scientific community, archives Fermi data, and runs the Fermi guest investigator program.

The Obelisk's origin in sun worship also connects to Fermi science. Our daytime star is a faint, steady source for Fermi thanks to gamma rays released when high-speed particles called cosmic rays impact the Sun. During eruptions known as solar flares, however, the Sun becomes a bright gamma-ray source for both Fermi instruments. A large flare in 2012 produced record-breaking emission 1,000 times greater than the Sun's steady gamma-ray output.

Flares and other eruptive solar events produce gamma rays by accelerating charged particles, which then collide with matter in the Sun's atmosphere and visible surface. Fermi solar observations will give scientists the ability to reconstruct the energies and types of particles interacting with the Sun during flares, which will open up new avenues for understanding the behavior of our local star.

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