Students make a find of galactic proportions
Dec. 10, 2008
It isn’t every day that a group of undergraduates is given the keys to the world’s largest and most sensitive radio telescope. Nor is it usual that the students will capitalize on the opportunity to make a discovery of galactic proportions.
But that is exactly what UW–Madison astronomer Snezana Stanimirovic’s six Astronomy 460 students accomplished this semester. Using a few hours of precious and hard-to-get observing time on the Arecibo Observatory’s massive radio telescope in Puerto Rico, the students seem to have confirmed the existence of a new galaxy in a blank spot on our map of the universe.
“It is a real scientific result,” says Stanimirovic, an assistant professor of astronomy and a veteran radio astronomer who used her cachet at the Arecibo Observatory to get her small class the chance to observe with a world-class telescope. “The undergraduate team was very lucky.”
Stanimirovic’s students used the radio telescope, which samples radio waves that emanate from celestial objects like supernovae, galaxies and pulsars, to look at a part of the sky that is obscured by the plane of the Milky Way. Known as the “zone of avoidance,” that part of the sky is impossible for conventional optical telescopes to penetrate because the vast clouds of dust that make up the plane of the Milky Way prevent light from extragalactic objects from reaching Earth.
Radio telescopes, however, can cut through the galactic clutter to “see” what’s there. “The zone of avoidance is the last frontier in mapping the large-scale structure of the universe, and holds the keys to explaining the dynamics of our local universe,” Stanimirovic explains.
Her student team keyed off of recent observations of 25 “highly obscured” galaxies in the zone of avoidance made with NASA’s Spitzer Space Telescope. An infrared telescope, Spitzer can also cut through the dust and crud of interstellar space, but not with the same clarity of a big radio telescope.
One thousand feet in diameter, the Arecibo radio telescope covers an area of about 20 acres and is the world’s largest single-dish radio telescope. A sensitive ear, the telescope has been used to discover such things as binary pulsars, twin neutron stars locked in a “dance of death”; was instrumental in helping confirm Einstein’s gravitational wave theory; and was the first telescope to detect planets beyond our solar system.
“It’s pretty cool that we could use Arecibo,” says Ryan Birdsall, a senior majoring in physics and astronomy. “This is the first time that anyone’s looked at these new galaxies in detail. It’s a galactic blind spot.”
From a small control room in Sterling Hall and in another session from her office, Stanimirovic’s students, with the help of a telescope operator at the Arecibo Observatory, first focused the telescope on known galaxies to calibrate it. “Then they really tried their luck and pointed toward the most obscured regions in the Milky Way — looking right through the Milky Way disk — in the direction that infrared observers identified as having potential new galaxies,” Stanimirovic says.
In their first foray, with just four minutes of observing, the students were able to obtain the classic spectral signature of a spiral galaxy and tease out the kind of information that is the bread and butter of astrophysics: “We could see that it is a rotating galaxy, and we can get a good estimate of the distance, which is really important because then we can line it up on the large-scale map of the universe,” says Stanimirovic.
Her students’ observations also provided enough information to estimate the mass of hydrogen gas in the galaxy. Hydrogen is the fuel for making new stars and knowing how much is there will help astronomers determine how fast the new-found galaxy is churning out new stars.
“Once you get a spectrum, you can do all kinds of things,” notes Lars Bryan, another of Stanimirovic’s students and a junior math major. “There’s all kinds of information — hydrogen mass, distance, velocity — that can be obtained if you get a good spectrum.”
Astronomy 460, Experience in Astronomical Observations, is designed to give students an encounter with the life of the observational astronomer, and teach everything from mastering data analysis software and preparing an observing plan to how to use different kinds of telescopes and how to write a research paper.
Getting time on a major telescope, according to Stanimirovic, wasn’t anticipated, nor was a moment of discovery, but that, too, is part of the overarching lesson: “Detecting new galaxies is always exciting,” says Stanimirovic, “especially when it’s done by undergraduate students.”
Radio telescope added to UW–Madison skyline
Anyone who knows the UW–Madison skyline is familiar with the small domes that denote the presence of the astronomy department in Sterling Hall. Now, thanks to a new initiative, a radio telescope has been added to the mix and to the skyline.
Just to the east of the domes on Sterling Hall, a 2.3-meter dish was recently erected and plans call for two more identical dishes to be added and configured as an interferometer, a collection of telescopes that when combined uses the interference of radio waves to obtain sharper resolution of an object being observed. Astronomers use radio waves to study such things as distant galaxies, pulsars and supernovae.
“We will use these telescopes for radio astronomy classes and can still do many interesting projects,” according to Snezana Stanimirovic, the assistant professor of astronomy coordinating the project. “For example, we will be able to obtain hydrogen spectra in many directions in the Milky Way and essentially map the distribution of atomic gas in our own galaxy.”
The new radio telescope, however, is not the first on campus. Physics professor Peter Timbie has one such telescope on the roof of Chamberlin Hall. Timbie’s telescope was built about two years ago from scratch by undergrads and high school students. “It was a project not only to measure things in the sky, but the process of building it was important” as a learning exercise, Timbie explains. His group, like Stanimirovic’s, wants to use the telescope to measure the distribution of hydrogen gas in our galaxy.
“Ideally, we could connect all these dishes together to make a mini VLA,” says Stanimirovic referencing the Very Large Array, the giant radio observatory in New Mexico that is perhaps best known outside astronomy as the fictionalized setting for the movie “Contact.”