University of Illinois at Urbana-Champaign

September 5, 1998

Robotic telescope sheds light on cosmic microwave background

CHAMPAIGN, Ill. -- For the past nine months, astronomers have been imaging the southern heavens in hydrogen-alpha light every night while keeping their day jobs, and without losing any sleep. Thanks to a new robotic telescope installed at Cerro Tololo Inter-American Observatory in Chile, the tedium of sky mapping is handled autonomously.

"We are surveying the sky in order to identify new low-surface-brightness phenomena within our own galaxy, and to provide a method of decontaminating Galactic emissions from measurements made of the cosmic microwave background," said Peter McCullough, a University of Illinois astronomer.

The team of astronomers collaborating on the two-year mapping project, in addition to McCullough, includes John Gaustad of Swarthmore College, Wayne Rosing of Las Cumbres Observatory in California, and Dave Van Buren of the California Institute of Technology. Observations began in November 1997, after more than two years of planning and instrument construction.

One goal of the project is to map the intricate structure of the interstellar medium, the gas and dust between the stars that is the site of new star formation. Illuminated by stellar ultraviolet light or heated by shock waves, the interstellar gas shows a structure of arcs and bubbles, wisps and filaments, generated by the expanding shells of supernovae, stellar winds and cloud collisions.

"But even where the robotic camera sees nothing, the data is still of great scientific value," Gaustad said, "for it allows other astronomers to be certain that their observations of the cosmic microwave background are not contaminated by radiation coming from the gas of our own galaxy."

The cosmic microwave background is the faint but pervasive glow of radiation that remains from the primordial fireball that gave birth to the universe. Measurements of the cosmic microwave background provide a picture of what the universe was like some 300,000 years after the Big Bang.

In 1992, NASA's Cosmic Background Explorer (COBE) satellite detected slight variations in the cosmic microwave background. These tiny ripples in radiation correspond to density fluctuations in the early universe, which coalesced into the galaxies and superclusters of galaxies that we see today.

By mapping the sky in hydrogen-alpha light, the survey will provide a template for subtracting Galactic emissions from the cosmic microwave background. The new sky survey could be used to decontaminate the existing COBE measurements, as well as those of future satellites, such as the Microwave Anisotropy Probe, scheduled for launch in two years.

The robotic telescope requires no human intervention to carry out its task. The instrument has been programmed to image the entire southern sky in hydrogen-alpha light. Data is retrieved weekly by a technician and sent to the astronomers for analysis. For more information and to see an image of the telescope, visit the Web site at

The researchers presented some of their early results at an International Astronomical Union symposium July 13-17 in Victoria, British Columbia.

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