BeppoSAX - An Italian - Dutch satellite actively involved in the quest to collect gamma-ray burst data in the X-ray range of the electromagnetic spectrum. It was named after the Italian physicist Gieuseppe "Beppo" Occhialini who was instrumental in forming what is today known as the European Space Agency.

Black hole - The final stage in the lifecycle of a supermassive star. A black hole is so dense that its gravitational field prevents even photons of light from escaping

Blazar – An object which consists of a supermassive black hole that emits an intense beam of particles and light over a broad frequency range from radio waves to gamma-rays.

Compton Gamma-Ray Observatory - A NASA satellite launched in 1991. It carries four instruments designed to observe the Universe in gamma-rays. The observatory was named in honor of Dr. Arthur Holly Compton, winner of a Nobel Prize in physics.

Density - The amount of mass per unit of volume.

Electromagnetic radiation - Another term for light. Light waves are actually fluctuations of electric and magnetic fields in space.

Electromagnetic spectrum - The orderly arrangement of electromagnetic radiation. The arrangement is based on wavelength, or energy level. The longer the wavelength the lower the energy level. Starting with the longest wavelength, the order is radio wave, microwave, infrared, visible light, ultraviolet, X-ray, and gamma-ray.

ESA – European Space Agency

Gamma-ray - The highest energy electromagnetic radiation. It has a very short wavelength.

Gamma-ray burst - A sudden burst of gamma-rays coming from a source usually in deep space. The burst may last from a fraction of a second to several minutes.

Gamma Ray Large Area Space Telescope - A proposed five year high-energy gamma-ray astronomy mission scheduled for launch in 2005

Hypernova - A phenomena new to astronomy discussions. It occurs as the result of a supermassive star undergoing an explosion more power than a supernova. Almost all of the energy generated by the explosion is in the gamma-ray range of the electromagnetic spectrum. It results in the formation of a black hole.

Massive star - A star with a mass 10-15 times that of the Sun.

Neutron star - The remnant core of a massive star after a supernova explosion. It is extremely dense. Though its diameter is only about 15 kilometers, its mass is about 1.4 times that of the Sun.

Quasar - A quasi-stellar radio source. A star-like object that is a powerful producer of radio waves.

Solar flare - A sudden, rapid and intense variation in brightness that occurs when magnetic energy built up in the solar atmosphere is suddenly released.

Supermassive star - A star with a mass at least 15 times that of the Sun.

Supernova - The explosion of a massive star. This explosion occurs in the star's death phase right after the red giant stage. At the peak of the explosion, it can outshine a galaxy.

Swift - A multiwavelength observatory for gamma-ray burst astronomy proposed for launch in 2003.