Tom Cogill

Steven Majewski

Looking for dark matter, distant stars and extraterrestrial life

By Fariss Samarrai

Anyone who has looked out at the sky on a clear night has wondered: With so many stars out there, are we alone? What is out there and from where do we come?

Astronomers, perhaps more than anyone, have wondered too. They've helped engineer the observatories that make the stars appear closer. Still, with each advance of the telescope, from Galileo's simple invention in 1609, to the Hubble Space Telescope in recent years, astronomers have found more questions than answers. And they have yet to locate terrestrial planets outside of our solar system.

When he was a young boy in suburban Chicago, Steven Majewski daydreamed about galaxies, which he drew pictures of in the margins of his textbooks. His parents later took him to Cape Kennedy to see the Apollo 11 launch.

"I couldn't believe it," said Majewski, an associate professor of astronomy, who joined the faculty in 1995. "I thought, 'people get to explore space for a job?' That's when I knew I would make a career studying the stars."

Majewski and other U.Va. astronomers soon will be working on a tool that may bring the indicators of other Earth-like planets into view. NASA's Space Interferometry Mission, a space telescope to be launched by a rocket in June 2009, will provide new insights about the origin and evolution of planets, stars and galaxies like the Milky Way. With the capability to measure distances and angles more precisely than ever before, SIM will survey the stars in our galaxy to provide answers to such fundamental questions as: What is the distance of our sun from the center of the Milky Way? How much does our galaxy weigh? Ultimately, this mission should provide a key step to the discovery of other planets that may support life.

FAME Tracks the Stars

While NASA's Space Interferometry Mission (SIM) is a highly accurate targeted telescope, allowing astronomers to pick out key selected star groups to study, there also is a need for telescopes that can survey the sky, providing a broad sweep to help astronomers narrow their search for particular stars of interest, especially the ones that may have orbiting planets. Much of this survey work will be done by FAME — the Full-sky Astrometric Mapping Explorer, a satellite telescope to be launched by NASA in 2004. "FAME will provide the most accurate catalog of star positions in history," says Kenneth Seidelmann, chair of the FAME science team. eidelmann came to U.Va. last fall as a professor of astronomy after retiring from a career at the U.S. Naval Observatory in Washington, D.C. Astrometry, the science of determining the positions of stars, is the oldest branch of astronomy and has been a focus area at U.Va. for 100 years. Seidelmann, with the help of several U.Va. astronomers, will use a portion of FAME's five-year mission time to help SIM astronomers locate stars for further study when their mission goes into operation. "FAME will help us look for nonlinear movement of stars, the ones with ragged motions, possibly indicating the presence of an orbiting body," Seidelmann says. "Those are some of the stars SIM will later detail."

"SIM will be the most advanced space telescope yet, equivalent to four times the size of Hubble and a thousand times more refined in terms of showing fine detail," said Majewski, a team leader for a major SIM project to measure the Milky Way.

The optical detail of the SIM telescope, operating far outside the distorting affects of the Earth's atmosphere, should allow us to observe indicators of Earth-sized planets orbiting nearby stars." SIM's ability to resolve detail is so fine, it's equivalent to reading a newspaper headline on the moon from Earth, he said.
SIM will be directed to a position 59 million miles from Earth where it will trail our planet in its orbit around the Sun. SIM will gather light from multiple on-board telescopes working together for a combined effect, allowing the instrument to provide images with the sharp, precise clarity of a single large telescope. It is a clever, complex design, pioneered in 1907 by physicist Albert Michelson, making it possible to, in effect, deploy a huge observatory as a rocket payload.

"U.Va.'s involvement with SIM includes the important preliminary work of setting up the fundamental reference system of stars — a pre-launch grid of comparison positions in the galaxy, and then using SIM to do a key project, measuring the mass of the Milky Way galaxy," Majewski said. "We still do not know this fundamental astrophysical quantity because of the presence of an unknown amount of the mysterious dark matter. Our experiment will undertake the first study of the motions of distant stars to determine the gravitational forces that cause these motions, and this will help us better understand the amount and distribution of matter in the Milky Way."

Dark matter, its existence or nonexistence, is one of the great mysteries of astronomy, he said. Believed to be composed of exotic subatomic particles, extremely dark stars or black holes, dark matter may make up as much as 90 percent of the universe's mass.

"There may be much more matter t†hat we cannot see than matter that we do see," said Majewski, who, before coming to U.Va., was a Hubble and Carnegie Institution fellow in Pasadena, home site of the SIM project at NASA's Jet Propulsion Lab. "But although it is presently invisible to our telescopes, we can see the effects of dark matter, its gravitational pull on visible objects. SIM will help us to measure these effects, thereby allowing us to measure how this dark matter is distributed in our own galaxy. This will provide an important clue to the amount and nature of the dark matter. Knowing this, in turn, could tell us a great deal about the creation of the universe and its evolution."

SIM is a $932 million mission, part of NASA's Origins Program, a series of missions to answer the fundamental questions of how we got here and if there is other life out in space. Majewski is one of 10 principal investigators leading key science teams. Majewski's team, which includes U.Va. research scientist Richard Patterson and other U.Va. astronomers, as well as 10 researchers at seven other institutions, will be funded by NASA as a multi-million-dollar research effort over the next decade. Majewski's U.Va. group already has received $650,000 to provide NASA with the SIM reference grid. Philip Ianna, U.Va. professor of astronomy, is a member of another key SIM science team, whose goal is to obtain precise, fundamental measurements of the masses and luminosities of stars.

Through these two key projects, U.Va. astronomers will have access to 10 percent of the viewing time with the SIM telescope, a significant portion of the observational budget during the five-year mission.

Though it will be years before SIM is launched, Majewski says he is excited in his preparation for the endeavor.

"The process of discovery is what makes research interesting," he said. "The fun is not just in finding the answers, but also in seeking clear ways to discover the answers to our most timeless questions."