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Cosmic creatures

Dennis Overbye, Aug 27, 2013, NYT services:

Cosmology

Researchers are suggesting that all the gold in the universe might have been produced by neutron star collisions and insects like the dung beetle use the Milky Way as their guide. It is hard to imagine a more beautiful or humbling connection between the sacred and the profane, writes Dennis Overbye

Who was it that first said that people are stardust? Some people, of a certain age, might say Joni Mitchell, who sang, “We are stardust, we are golden, and we’ve got to get ourselves back to the gar-ar-den,” in her paean to the Woodstock festival. Others will say Carl Sagan, the author and host of “Cosmos.” In fact, the answer goes back before those acolytes of beauty and consciousness were born.

In 1929, the Harvard astronomer Harlow Shapley declared, “We organic beings who call ourselves humans are made of the same stuff as the stars” — a remarkable observation, considering that at the time nobody even knew what made the stars shine.


It would be 30 years before Geoffrey and Margaret Burbidge, William Fowler and Fred Hoyle showed in a classic paper that the atoms that compose us are not only the same as the ones in stars — they were actually manufactured in them. Starting from primordial hydrogen and helium, denser elements like iron, oxygen, carbon and nitrogen were built up in a series of thermonuclear reactions and then spewed into space when these stars died and exploded as supernovas in a final thermonuclear frenzy.

Any gardener knows that ashes make good fertiliser. Our atoms were once in stars. I was reminded of all this by a pair of recent news items. One involved dung beetles, among the least lordly occupants of this cosmic garden, which apparently navigate by orienting themselves to the light of the Milky Way.

The other was the announcement last month that astronomers had tentatively traced the existence of gold in the universe to a cataclysm known as a gamma-ray burst, which can light up a galaxy.

As Joel Achenbach wrote in The Washington Post, “The bling apparently begins with a blam.” The blam in question happened — or rather was noticed here on Earth — on June 3. It was then, astronomers, alerted by a brief flash of high-energy gamma rays in the sky, think a pair of dead, ultradense neutron stars collided, leaving behind only a distant radioactive glow. Edo Berger of the Harvard-Smithsonian Center for Astrophysics said the explosion could have created an amount of gold equivalent to the mass of 20 Earth moons. Neutron stars are themselves a result of cataclysms, those supernova explosions that can squeeze the space out of atoms and compress a mass more than the sun into a ball 10 miles across — essentially a great ball of neutrons, hence the name.

On Earth, a teaspoon of the stuff would weigh about five billion tonnes. Astronomers have always wondered whether ordinary supernova explosions could produce very heavy elements like gold, whose nucleus has 79 protons and 118 neutrons — a far cry from the single proton that is a hydrogen nucleus. If a pair of neutron stars are in orbit around each other, they can collide — a second cosmic act that will add to the universe’s repertory of elements, the bling from blam.

Berger and his colleagues suggested that all the gold in the universe might have been produced by neutron star collisions, which have been termed “kilanova” explosions. Of course, we aspiring gardeners have other names for what is left behind after an object’s energy has been metabolised into light and heat to nurture the cosmos. Which brings us back to the lowly dung beetle, the scarab.

These creatures, which live on the feces of larger animals, have a problem. Once a beetle has found some dung and rolled part of it into a ball, he’s got to get it out of there, rolling it in a straight line away from the dung pile, or the other beetles will come and poach it. How they manage this, even on moonless nights when obvious cues and landmarks are absent or invisible, has been a mystery.

In January, a team of Swedish and South African researchers reported that African dung beetles, Scarabaeus satyrus, can use the Milky Way as their guide. In a series of experiments in a game preserve and a planetarium, a team led by Marie Dacke of Lund University in Sweden found that when the beetles were fitted with little caps that prevented them from seeing the sky or the stars were clouded out, the beetles wandered aimlessly, putting their little dung treasures at risk. But a starlit sky, or just a dim band representing the disk of our humble home galaxy, is enough to keep them on track.

“Although this is the first description of an insect using the Milky Way for their orientation, this ability might turn out to be widespread in the animal kingdom,” the scientists wrote in Current Biology. It’s hard to imagine a more beautiful or humbling connection between the sacred and the profane, the microscopic and the large, inner space and outer space.

The Milky Way is one of nature’s grandest creations: hundreds of billions of glittering stars, wreathed in ribbons of gas and dust, a cloudy, starry pinwheel so vast that a light beam would take 1,00,000 years to cross it and the Sun with its planetary entourage takes a quarter of a billion years to circle it once.

And it is only one of countless galaxies, scattered like sand from here to eternity, rushing outward in the great expansion, whose meaning, if we are honest, is as fathomless and careless to us as it is to a scarab pushing its carefully wrought investment portfolio through this garden of earthy delights.

Scarabs were sacred to the ancient Egyptians for their ability to create life from waste. They were a symbol of the eternal renewal of life from death, not unlike the waxing and the waning of the stars themselves. Egyptians wore representations of them as amulets. And wouldn’t you know, in one of the ultimate symbols of recycling, some of them were even gold.

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