Supernova Explosion Tied to Origin of Heavy Metals

Observations of an exploding star in a satellite galaxy near the Milky Way have produced important new evidence that iron and other heavy elements that make up the Earth and other bodies in the solar system are formed in such supernova explosions.

The evidence, reported Wednesday by the National Aeronautics and Space Administration, came in the form of gamma radiation detected by an American satellite in August and by instruments carried aloft by balloons launched from Australia in October and November.

Japanese and Soviet scientists previously had reported X-rays from the supernova, labeled 1987A, but detection of higher energy gamma radiation added evidence that heavy elements are created from lighter ones in the intense energy of exploding stars.

The discovery of 1987A, the closest supernova event to Earth in the last 400 years, was made by Ian Shelton, a Canadian scientist working in Peru.

The close proximity of the event provided astronomers a historic opportunity to study the climactic event in the evolution of a star, when gravitational forces lead to its rapid collapse and death in a tremendous explosion.

Gamma rays were first detected in August by instruments aboard the United States’ Solar Max satellite, which was launched in 1980.

Subsequent observations by two balloons launched by NASA from Alice Springs, Australia, not only confirmed the emission of gamma rays but determined that the supernova, and not a nearby star, was indeed the source.

The observations amount to the most solid confirmation of theories widely held for more than 30 years, that supernovas produce unstable forms of nickel, cobalt and titanium, which decay into other products, including iron, emitting high-energy gamma radiation in the process.

Edward L. Chupp of the University of New Hampshire was the principal investigator on the satellite observations, which used a spectrometer jointly designed and built by the United States and West Germany. Instruments carried by the balloons were developed by the Lockheed Palo Alto Research Laboratory and NASA’s Marshall Space Flight Center. Caltech Prof. Thomas Prince was the principal investigator using the balloon-borne gamma ray telescope.