Star Tracker and Planet Tracker Give Us Sense of Place in the Universe
Star Tracker and Planet Tracker Give Us Sense of Place in the Universe
Faculty and students in The College of Wooster’s Department of Physics collaborate on design of celestial trackers
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This star-tracker device, developed by physicists at The College of Wooster and currently on display in Taylor Hall, is programmed to continually point at Sagittarius A*, a presumed super-massive black hole at the center of the Milky Way galaxy.
WOOSTER, Ohio — Even the most astute stargazers occasionally need help in locating their favorite celestial body, and now there is an inexpensive new device to help them in their search.
John Lindner, professor of physics at The College of Wooster, in collaboration with Todd McAlpine, now assistant professor of physics at The University of Findlay, and two recent Wooster graduates — Corey Atwood-Stone and Travis Brown — have created an instrument that can physically track and point toward celestial objects. In fact, they have created two — a star tracker and a planet tracker — both of which are featured in the cover article ("Tracking the Stars, Sun,
and Moon to Connect with the Universe") of the November issue of the American Journal of Physics.
The idea came to Lindner right in the middle of a class lecture four years ago. “I was teaching Physics 320 (Astrophysics) when I began to think about the possibility of an instrument that could physically track and point toward celestial objects like stars and planets,” he says. “I immediately described the idea to the class.”
In the summer of 2007, Lindner teamed up with McAlpine, a then visiting assistant professor of physics at Wooster, to design and build the celestial trackers. Atwood-Stone, who graduated last spring, joined the project as part of Wooster’s 10-week NSF-REU (National Science Foundation Research for Undergraduates) summer program. Together they constructed a planet tracker that
uses an Apple Mac Mini computer to run National Instruments’ LabVIEW software to control a customized LEGO Mindstorms robot, whose motors orient a celestial pointer. During the 2007-2008 academic year, McAlpine worked with Brown, a geology major, to complete the physical construction of the planet tracker. One year later, Lindner built a simpler star tracker from an inexpensive tabletop motorized equatorial telescope mount.
“The star tracker acts like a gyroscope, rigidly oriented in space, despite Earth’s motions (rotation about its axis and revolution about Sun),” explains Lindner. “Both celestial trackers indicate the passing of time like clocks and calendars. In order to track a particular object, one initializes the trackers with the proper celestial coordinates, which are available online (or through a program written by Lindner).”
What makes the two instruments particularly novel is their cost. The star tracker totaled about $100, while the planet tracker, minus the computer but including the robot, ran about $400.
The star tracker is currently on display across the hallway from Lindner's office in Taylor Hall. It is programmed to continually point at Sagittarius A*, a presumed super-massive black hole 30,000 light years away at the center of the Milky Way galaxy. Each morning before his 10 a.m. class, Lindner dutifully checks the star tracker. “What I notice is that the direction to Sagittarius A* is not quite the same as it was the previous morning,” he says. “This is because Earth rotates once with respect to the stars in just 23 hours 56 minutes. Knowing where the Milky Way’s center has been, where it is, and where it will be enlarges our world.
“For most of human history, there has been little or no nighttime illumination, so people were more attuned to the night skies,” adds Lindner. “Today it is much harder to see the stars and planets if you live in or near a metropolitan area, but the celestial trackers orient us in the real three-dimensional space of our solar system and galaxy, and thereby expand our horizons beyond the familiar terrestrial one,” he says. “These provocative lecture hall or museum displays help connect us with the stars and planets in a concrete way, and thereby invite and encourage us to contemplate our place in the universe.”