U.Va.-Built APOGEE to Provide New Window on Milky Way

Listen to the UVA Today Radio Show report on this story by Fariss Samarrai:

November 3, 2010 — As many astronomers have noted, we are made of stardust. Humans, all life on Earth, the Earth itself, all the known planets, and worlds not yet known – all are made of stardust.

Every heavy element, and the molecules from which they are made, originated from nuclear fusion in stars. When the universe began in a "big bang" – those words being insufficient to explain so enormous and momentous an event – it started mostly as simple, fundamental hydrogen and helium, elements still abundantly present in the universe.

These elements gathered into the making of stars and then the process of nuclear fusion, ultimately resulting in heavier elements, including the planet-forming, life-giving oxygen, carbon, nitrogen, iron and the hundred or so other naturally occurring elements that make up the universe today.

Astronomers don't attempt to explain why this has happened, but they do try to understand how.

A new project, led by astronomers in U.Va.'s College and Graduate School of Arts & Sciences, soon will take a closer look at the stars from the center to the far reaches of our galaxy, and attempt to gain new insight into how the Milky Way, as a prototype of the innumerable galaxies making up much of the universe, formed and evolved.

"We have to go back to the stars to profoundly understand the world around us," said astronomer Steven Majewski, the project's lead scientist. "We want to understand how we went from a relatively simple universe after the Big Bang to the complicated world we see around us. This will give us insight to how ultimately the planets formed, how life formed."

The project, the Apache Point Observatory Galactic Evolution Experiment – or APOGEE – will survey more than 100,000 Milky Way stars, with a high-resolution, infrared-sensitive spectrograph largely designed and built at U.Va. It is one of four major experiments of the $45 million Sloan Digital Sky Survey III, using the astronomical facilities at Apache Point Observatory in New Mexico. The survey is funded by the Alfred P. Sloan Foundation, the various participating institutions, the National Science Foundation and the U.S. Department of Energy.

The APOGEE spectrograph, to be deployed early next year, pushes the frontiers of technology and is especially unique in allowing astronomers to examine 300 stars at a time. Over the course of three years it will be used to gather data on the elemental make-up of galactic stars at a rate and in numbers far exceeding what has previously been accomplished. APOGEE will be the first comprehensive study of the chemical constitution of inner Milky Way stars, an area of the galaxy that has long been difficult for astronomers to study due to large amounts of cosmic dust obscuring the view from earth.

The Milky Way, as a "typical" spiral galaxy, serves as an excellent and accessible representative of other such galaxies, providing astronomers the insight needed to understand their development and evolution.

The stars that the APOGEE astronomers will focus on, red giants, are extremely bright, but, located at the center of the Milky Way – 25,000 or so light years away – are largely obscured by massive clouds of interstellar dust scattered across the vastness of the galaxy's plane. Because of this dust, only a relatively small fraction of stars there can be observed in visible light.

For this reason, astronomers are using infrared cameras and spectrographs, such as APOGEE, that can observe light at wavelengths longer than visible light. These instruments can peer through interstellar dust to detect the chemical makeup of stars and to calculate their motions and distances.

"We will be looking at parts of the Milky Way that traditionally have been somewhat ignored because of the difficulty of peering through the blotchy clouds of dust," Majewski said. "At present we really don't know much about the inner galaxy – where in fact most of the stars and matter of the Milky Way lie – because it is opaque when using conventional visible light telescopes."

APOGEE will provide a fuller and more high-definition picture of the stars residing beyond and amidst that otherwise obscuring dust.

The project is one of great collaboration, Majewski said, between members of the U.Va. astronomy department, other universities around the world and private companies that helped develop and produce a number of innovative, state-of-the-art components for the spectrograph being constructed at U.Va.

"We've had enormous technical challenges to overcome, and we're overcoming them," Majewski said.

Two teams at U.Va. are involved in this endeavor: a science team, led by Majewski, which designs and plans the experiments that will be conducted once the instrument is deployed; and a technical team working in the astronomy department's instrument laboratory, overseen by U.Va. astronomer Michael Skrutskie.

The instrument team includes project manager Fred Hearty, a former Navy submarine officer and astrophysics Ph.D. who "keeps the project on schedule and on budget," Majewski said, and instrument scientist John Wilson, another former Navy officer with a Ph.D. in applied physics, who leads the "hands-on" design, construction, assembly and testing of the spectrograph.

Wilson, who has worked on a variety of projects during his naval and academic career, said APOGEE is the most satisfying and enjoyable multi-institutional experience he's had.

"It's been a fun learning experience," he said. "We run into challenges every day as we build this, and each day we find a way to make it work."

The rapid pace at which the project is coming to fruition awes Majewski, who, working with Skrutskie, developed the idea for APOGEE several years ago.

"Seeing this come together before my eyes is just amazing," he said. "What we will do with this instrument will amaze even more."

— By Fariss Samarrai