Team of Astronomers Measures Galaxy

It's a Small World After All

A recent discovery by an international team of astronomers has made the galaxy a little bit smaller.

Seven scientists from France, Sweden and the U.S. have measured the distance from the center of the Milky Way to the Earth for the first time. The group, including four Harvard researchers, determined that the Earth is about 7.1 kiloparsecs--or 23,000 light years--from the galaxy's center, which is about 30 percent closer than scientists previously assumed.

The discovery will "revise theories of everything that involves kinematic distances--measurements of brightness of stars, densities, size and mass of gas, dust, plasma, pulsars, stars, nebula, anything that's in our galaxy," said Carl Gwinn, one of the study's participants from the Harvard-Smithsonian Center for Astrophysics.


Three other Harvard-Smithsonian astronomers, James Moran, Mark Reid and Matthew Schneps also took part in the experiment. In addition, Dennis Downes of the Institut de Radio Astronomie Milimetrique in Grenoble, France, Reinhard Genzel of the University of California at Berkeley, and Bernt Ronnag of the Onsala Space Observatory in Sweden participated in the work.

Gwinn said that before the group's pioneering work scientists had not formally determined the distance which separated celestial bodies. He called the scientific community's conception of the Milky Way "maps without inch-to-mile scales."


Gwinn said the findings "will change people's understanding of the galaxy."

Confirms Growing Belief

The group's research confirms a growing belief within the scientific community that the galaxy is not as large as many at one time believed, Princeton astrophysicist James Gunn said.

"I don't think it surprised anyone," Gunn said of the group's work. He said the scientific community now generally assumes the center of the galaxy, a distance only 1000 lightyears greater than the one suggested by the international team.

Monitoring Stars

The astronomers reached their conclusions after monitoring radio emissions from stars at the center of the Milky Way, according to individuals close to the project. Five measurments were made from four radio telescopes across the country using "Very Long Baseline Interferometry"--a technique used to track objects which are far from the earth.

The five observations were made between December 1980 and June 1982. Analysis of the 500 computer tapes of data took a full year to finish.

The scientists then used a technique which Gwinn compared to the use of radar to detect speeders in order to determine the distance between celestial objects, the astronomer said.