Something as apparently mundane as a near- invisible cloud of dust has brought international acclaim to a local astronomer, reports Bronwen Jones
ASTRONOMERS are not everyday people. While mere mortals contemplate the tarmac beneath their feet, astronomers gaze into the heart of the heavens, pondering the whys and hows of the universe.
This week a South African astronomer, Professor David Block, is celebrating his discovery of one of those previously inpenetrable answers that may, one day, foretell the beginning of the end.
He has found billions of tiny particles of dust. They are so cold that they are only 20 degrees above absolute zero — the temperature where everything stops. They each measure only a thousandth of a millimetre across. And he has never seen them.
But Krugersdorp-born-and-bred Block has proved that they are there.
To do so, the professor had to turn to military technology originally developed to locate targets at night. The highly sophisticated near-infrared sensors revealed the darkest grains in the universe, changing the shape of familiar galaxies; changing the shape of astronomy.
The information he was receiving with combined optical and infrared technology was a stream of photons — light particles. Some of them had travelled for 60 million years or more.
The data were recorded on digital tape at an observatory in the Atacama Desert in Chile. >From there, Block took it to Germany to process. Working on the computers with his long-term Danish collaborator and friend, Dr Preben Grosbol, they played maths with the stars. Subtracting the near-infrared images from the optical ones proved the answer to their question. There was cold dust between the spiral arms of galaxies.
So what is the significance for those of us more familiar with the dust rising from the mine dumps of Johannesburg or the plains of the Free State?
Block says: “Without carbon, you and I, formed from the dust of the earth, would not be here.
“Cosmic dust seems far removed from our everyday existence yet it contains the blueprints of life.”
It was the initial quest to look for something where there appears to be nothing that sets Block and other scientists apart from the rest of us. Looking through their telescopes, they knew that apparent holes and empty patches were invariably vast clouds of dust which absorb or scatter any background starlight. Block says: “It is like thick fog obscuring a traffic light.”
The dust emits very weak radiation and such cold grains had only ever been detected optically in the Milky Way by airborne observatories, satellites or special telescopes in Hawaii. Even then astronomers had not agreed on the existence of cold dust.
But now the world’s most eminent astronomers have flocked to Johannesburg to pursue the implications of Block’s find. His discovery of the interstellar dust could herald the collapse of our cosmos, but fortunately far in the future. The cosmos has been expanding since the “big bang”, when the universe began. One day all these pieces may pull together
The dust between stars doesn’t just hang around in space. It forms a host to interstellar clouds, allowing gas atoms and molecules to condense out on the dust like hoar frost on a bramble. Bombarded with light from distant stars, the dust formed complex organic materials containing what Block calls “prebiotic molecules”. These were the primeval building blocks of life on Earth.
For all his far-reaching research, Block is in some ways very down to earth. Brown-eyed and balding, he smiles easily and has an infectious enthusiasm for his field. He delves into high science but doesn’t abandon religion. He feels that science can give rational answers to many questions and that: “Rather than the world seeming a large, frightening place, it is in a friendly cosmos where self-aware human beings can enjoy the grand scale.”
While touring the darkest domains of our universe, Block doesn’t expect to bump into a divine presence, but he believes in God, “because the universe is so incredibly finely tuned. It is rational as a scientist to believe, because faith is based on evidence.”
Block is South Africa’s Patrick Moore. Not of quite the same vintage nor yet a household name, but working on it. He wants to excite the public about astronomy and thinks this is easiest in the southern hemisphere, from where one can see the centre of the galaxy. He says: “Our unique position lets us see the Large and Small Magellanic Clouds, crucial to the quest to determine the size of our cosmos.”
It is this urge to tackle questions too daunting for most of us even to ask that drives the man. Infinitely inquisitive, the astronomers abandon the urban glow of civilisation and head for the remotest mountain tops, great deserts, inhospitable islands. All in the quest for the deepest darkness to reveal the greatest light.