200 Trillion Trillion H-Bombs

Nature's most catastrophic events are supernovae--rare stars that burst with a brilliance 100 million times more luminous than the sun, releasing the equivalent of 200 trillion trillion 100-megaton hydrogen bombs. Swiss Astronomer Paul Wild has just added a new one to the stellar log--the first supernova seen from the earth in the unnamed galaxy N.G.C. 4189 in the constellation Virgo.

Since supernovae result from stars already shining for millions of years, the Latin term nova (new) is rather a misnomer that stems from Tycho Brahe's 1572 naked-eye study of an exploding star in the constellation Cassiopeia. Ever since the irascible Danish astronomer- detailed his observation in De Nova Stella ("Concerning the New Star"), scientists have been stuck with the term nova.

Too Big to Live. Supernovae are the most violent of a group of three exploding stars whose two other members --novae and dwarf novae--periodically flare up for a short time and then return to their original state. By contrast, a supernova is never the same again.

A supernova's own gigantic size is its undoing. Astrophysicist Subrahmanyan Chandrasekhar calculated that a star whose mass is greater than 1.44 times the sun's mass cannot follow normal stellar evolution. Over a few million years, burning hydrogen on the outer layers of such a star produces more and more helium at its core. The doomed star's interior shrinks rapidly; and the density of its core increases. As temperatures rise in the contracting core, the collected helium is converted into successively heavier elements, such as iron and gold, which crowd the lighter elements outward.

At this point, shrinkage accelerates, and the interior heats to about 5 billion degrees, suddenly converting the heavier elements back into the helium from which they were forged. The energy required for this reconversion comes from the only available source, gravitational shrinkage. When the energy demand becomes too great, the star collapses inward in a matter of seconds, producing such a titanic density that a matchbox full of the core material may weigh as much as 1,000 tons. Rebounding instantaneously from the collapse, the star explodes.

800 M.P.S. Astronomers now believe that as much as one-tenth of a supernova's total mass is blown out at speeds approaching that of light, and enters the earth's atmosphere as cosmic rays. A second wave of slower radiation and burning gases causes the supernova to shine with prodigal splendor for weeks or even years until the star's remains gradually fade.

Some gaseous remains survive long after. In A.D. 1054, Chinese astrologers recorded a brilliant "guest star" supernova that suddenly exploded one night in the constellation Taurus. Located near the tip of the left horn, the star remained visible even during bright daylight. This same supernova's remains can be seen today as the Crab nebula, a diffuse, glowing gas cloud 3,500 light years away, which continues to expand at 800 miles per second.

Less than 200 supernovae have ever been observed, and only three confirmed sightings have been recorded in the earth's Milky Way galaxy. The last occurred in 1604 when Mathematician Johannes Kepler was credited with a find, and the next seems long overdue.

*At 19, Tycho lost his nose in a duel over a point of mathematics, thereafter wore a false proboscis made of gold and silver.

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