A space agency satellite and two balloon experiments, lofted to study the supernova sighted last February in the skies of the southern hemisphere, have provided the first direct proof that iron and other heavy metals, which form planets, moons and ultimately life, are forged in exploding stars.
In a development long awaited by astrophysicists, the instruments made the first direct detection of gamma-ray emissions from such an explosion, the National Aeronautics and Space Administration's space science office announced yesterday.
This is the first supernova close enough to Earth since the invention of modern instruments to make possible the observation of gamma rays. The balloon-borne instruments, lofted in October and November from Alice Springs, Australia, are the most sensitive gamma-ray detectors ever flown.
"In a sense, we're finding out our own origin," said Edward Chupp of the University of New Hampshire, principal investigator of the gamma ray instrument on NASA's Solar Max satellite, which first spotted the emissions from the region of the supernova in August.
Gamma rays, which are radiation of extremely short wavelength and high energy, are released with the decay of radioactive elements formed by nuclear reactions at the core of the exploding star. They do not penetrate the Earth's atmosphere and must be studied from above it. Scientists can "read" them and tell the amount and type of elements that are decaying.
These observations were crucial in order for scientists to confirm the theory of "explosive nucleosynthesis," which has been widely held since the late 1950s and says that the cataclysmic death of a star -- a supernova -- creates heavier elements, including metals, from lighter ones.
The emissions from Supernova 1987A, located in the neighboring galaxy known as the Large Magellanic Cloud, confirmed that the energy in the explosion causes nuclear reactions that create, among other things, radioactive nickel, which rapidly decays into cobalt, which decays into stable iron.