On the New Stars

On the New Stars

Unhappily, no supernova explosions have been observed in our Galaxy since the invention of the telescope, and astronomers have been chafing at the bit for some centuries.

However, supernovae are now routinely observed in other galaxies. Among candidates for the sentence that would most thoroughly astonish an astronomer of the early 1900’ is the following, from a paper by David Helfand and Knox Long in the December 6, 1979, issue of the British journal Nature: “On 5 March, 1979, an extremely intense burst of hard X-rays and gamma rays was recorded by the nine interplanetary spacecraft of the burst sensor network, and localized by time-of-flight determinations to a position coincident with the supernova remnant N49 in the Large Magellanic Cloud” (the Large Magellanic Cloud, so called because the first inhabitant of the Northern Hemisphere to notice it was Magellan, is a small satellite galaxy of the Milky Way, 180,000 light-years distant. There is also, as you might expect, a Small Magellanic Cloud).

Supernovae may be exhausts of alien star-ships on its long voyage home. Image: © Elena

However, in the same issue of Nature, E. P. Mazets and colleagues of the Ioffe Institute, Leningrad – who observed this source with the gammary burst detector aboard the Venera 11 and 12 spacecraft on their way to land on Venus – argue that what is being seen is a flaring pulsar only a few hundred light-years away. Despite the close agreement in position Helfand and Long do not insist that the gamma-ray outburst is associated with the supernova remnant. They charitably consider many alternatives, including the surprising possibility that the source lies within the solar system. Perhaps it is the exhaust of an alien star-ship on its long voyage home. But a rousing of the stellar fires in N49 is a simpler hypothesis: we are sure there are such things as supernovae.

Kepler published in 1606 a book called De stele Nova, “On the New Star”, in which he wonders if a supernova is the result of some random concatenation of atoms in the heavens. He presents what he says is “… not my own opinion, but my wife’s: Yesterday, when weary with writing, I was called to supper, and a salad I had asked for was set before me. “It seems then, “I said, “if pewter dishes, leaves of lettuce, grains of salt, drops of water, vinegar, oil and slices of eggs had been flying about in the air for all eternity, it might at last happen by chance that there would come a salad”. “Yes”, responded my lovely, “but not so nice as this one of mine”.