Yale Bulletin and Calendar

September 27-October 4, 1999

Volume 28, Number 6

Astronomers say universe
expanding faster than once thought

A Yale astronomer working with a team of scientists has found that the universe might be expanding somewhat faster than most current calculations indicate.

According to Stephen Zepf, assistant professor of astronomy, the team came upon this discovery by using a new determination of the intrinsic brightness of a certain class of stars, Cepheids, that are important for determining distances to other galaxies. The study was published this month in Nature magazine.

"These Cepheids are a little fainter than we thought, so this changes the distances to a whole host of other galaxies," Zepf says. "The reason this is significant is that since Cepheids are used to calibrate the expansion of the universe, if they are fainter, then the universe is expanding slightly faster. If the universe is expanding slightly faster, then it might be a little younger than we thought.

"Nearly all galaxies are moving away from us," he adds. "The question is whether this will keep going on forever or whether eventually the universe will have enough density to collapse back on itself."

One of the primary challenges in astronomy is to determine how far away things are. One of the common ways to do this is to take a "standard candle" -- an object nearby for which the intrinsic brightness can be measured. Similar objects are then found in distant galaxies.

"You can tell how far away the galaxies are by how faint the standard candle is," Zepf explains. "It is like taking a lamp with a 60-watt light bulb and figuring out how far away the lamp is by how faint the light bulb appears to be."

"What we have done is to observe Cepheid stars, which are the primary standard candles through which galaxy distances are determined and for which the distance is believed to be known very accurately by other means," he says.

"We found that the Cepheid stars may be about 15 percent fainter than previously thought," Zepf notes. "This is analogous to finding out that the light bulb you thought was 60 watts is really only 50 watts, therefore the lamp is actually closer than you originally estimated."

-- By Jacqueline Weaver

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Visit from Treasury Secretary launches new International Center for Finance

Ethics of stem cell research to be explored

Little-used Yale Library books get state-of-the-art care at off-campus shelving facility

Symposium and exhibit mark 'Celebration of Very Young Children and Books at Yale'

Gus Ranis forging unions, exploring borders at YCIAS

Forestry school dean will open lecture series on bioethics

Symposium explores themes in 'The Brothers Karamazov'

Former V.P. of European Commission named visiting scholar at Yale SOM

Philanthropist and builder Frederick P. Rose '44E dies

Astronomers say universe expanding faster than once thought

Scientists unravel 'yin' and 'yang' of how salmonella uses proteins to spark disease

Chemist to study potential benefits of sea sponge molecule with $150,000 grant

First winners of Frederick Douglass Book Prize named

Fall lecture series commemorates Brazilian writer Jorge Luis Borges

Scholars will share views on modernist art and photographyn

Paul Kennedy to open book discussion series

Professor to demonstrate his new OCTI game

Employee Day at the Yale Bowl

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