The universe is bigger and older than first believed, but sci-fi writer JG Ballard sees space as a vacuum
New evidence shows that previous assumptions about space were wrong, reports Lesley Cowling
A SOUTH AFRICAN astronomer this week presented evidence to international cosmologists that the observable universe is 10% larger than previously supposed. This means that the universe is also older than astronomers have calculated.
Michael Feast, professor emeritus at the University of Cape Town and former director of the South African Astronomical Observatory, this week told a meeting of the American Association for the Advancement of Science in Seattle that direct measurements of stars by a custom- designed satellite showed that previous calculations of the distances of these stars from Earth were inaccurate. Recalculation resulted in longer distances and a larger universe.
Feast and his team’s conclusions are the result of a long and time-consuming process, starting with the 1989 launch of the Hipparcos satellite, designed by European scientists and engineers to fix the precise positions in the sky of 120 000 stars and log another million with slightly less accuracy.
Feast was asked before the launch for his input and suggested that Hipparcos measure the distance of a number of variable stars – the winking stars known as Cepheids and the pulsating type called Miras. Variable stars are used by astronomers to calculate distances across the universe, using a technique and calculations similar to those used by land surveyers.
Until Hipparcos, these measurements were made from earth, starting with the nearest stars, using those measurements as the basis for measuring other stars. “But when you’re working from the earth’s surface, it’s like being at the bottom of a swimming pool,” says Patricia Whitelock, one of the research team. The earth’s atmosphere gets in the way.
Just as the Hubble telescope takes clearer pictures from space than from earth, Hipparcos took more accurate measurements. The satellite collected data for four years, until 1993. Then the European Space Agency’s scientists took another two years to do all the basic calculations and to hand those results to the various scientists involved in the initial research.
It took Feast’s team of South African, British and Russian cosmologists some more months to work out their conclusions, and they are still waiting for results coming in from other scientists working with Hipparcos data.
As well as Cepheids being further away, these young pulsating stars are also more luminous than previously thought, the calculations show. Cepheid stars alternately squeeze themselves and relax, like a beating heart. They wax and wane rhythmically in brightness, every few days or weeks, at a rate that depends on how bright they are. Henrietta Leavitt at the Harvard College Observatory discovered in the early years of this century that bigger and more brilliant Cepheids vary with a longer period, according to a strict rule.
Some of the calculations of Feast’s team also solve a problem astronomers recently had when the oldest stars in the universe were calculated to be older than the universe itself.
“I hope we’ve cured a nonsensical contradiction that was a headache for cosmologists,” Michael Feast says. “We judge the universe to be a little bigger and therefore a little older, by about a billion years. The oldest stars seem to be much younger than supposed, by about 4 billion years. If we can settle on an age of the universe at, say, 12-billion years everything will fit nicely.”
Michael Perryman, European Space Agency project scientist for Hipparcos, anticipates a warm debate among astronomers. Should the Hipparcos Cepheid results be taken at face value, with all their implications for the size and age of the universe? He remains confident that the issue will be settled by other results quarried from the Hipparcos data.
“Until Hipparcos, the cosmic distance scale rested on well-informed guesses,” Perryman says. “The distances we now have, for stars of many kinds, provide for the very first time a firm foundation from which to gauge the distances of galaxies. The work has only just begun.
“If it should turn out that the Cepheids have given the final answer straight away, that might be surprising. But there will be no reason for astonishment when Hipparcos’s direct measurements of stellar distances lead to a revised scale for the universe.”