Replicas of five major scientific medals won by former UW-Madison astronomer Joel Stebbins more than 50 years ago are now on display in the astronomy department lobby, second floor, Sterling Hall on campus.
“We wanted to honor professor Stebbins (1878 – 1966), and to show how the technology he originated a century ago has continued to shape the research agenda of our department to this day,” says James Lattis, a faculty associate in the University of Wisconsin-Madison astronomy department.
Stebbins invented a technique for capturing light from space, and developed applications that changed how we view stars and our galaxy.
The essential Stebbins advance was an instrument containing the metal potassium that absorbs a photon of light and ejects an electron, creating a weak electric current.
“The electrical signal is directly proportional to the amount of light; no other technology gave such a linear response,” Lattis says. Using the detector, “he could do things that were not possible with photographic film, the only other detector available at time except for the eye.”
Stebbins’s photometer was critical for observing variable stars, which astronomers had previously seen by measuring star spots on photographs or using primitive visual photometers. Brightness changes may indicate the tandem movement of binary stars.
Photometers were also used to analyze the distribution of matter in galaxies, Lattis says. “By looking at the effect of interstellar matter on starlight, Stebbins allowed us to devise a more accurate measurement of the dimensions of our own galaxy, the Milky Way.”
Photometers were eventually replaced by the charge-coupled devices at the heart of many modern telescopes, Lattis says, but studies of variable stars and the interstellar medium remain mainstays of his department.
The technology Stebbins created reached its apogee in the “high-speed photometer” that orbited on the Hubble Space Telescope. After the photometer was removed to accommodate Hubble’s corrective spectacles, it went on display at the UW-Madison Space Place on Park St.