Hitching a Ride on Comet 29P
Two USF researchers gather data useful for testing models of how the solar system formed and also how comets become active so far from the Sun.
Professor Maria Womack and PhD student Kacper Wierzchos's research includes telescopes such as this one shown and operated by the Arizona Radio Observatory. Photo by Aimee Blodgett. Projected image by David Harvey.
TAMPA, Fla. (March 17, 2016) – “I like comets because they are one of the few things in the night sky that change,” says Kacper Wierzchos, an applied physics PhD student. “They’re like visitors from outer space.”
Some visitor! The comet that Wierzchos will study for his applied physics dissertation is 31 kilometers across (about the size of the greater Tampa Bay area) and spews carbon monoxide (CO) as is hurtles spinning through space and, in solar system terms, not far away from us, just beyond Jupiter’s orbit. Like all comets, it is comprised of ice, dust and gas, a remnant of our solar system’s formation about 4.6 billion years ago.
“This comet is an enigma; no one knows what’s really going on with it,” says his advisor USF Research Professor and astrophysicist Maria Womack, PhD. She arrived at USF in late summer 2015 after four years as a program director at the National Science Foundation in the Division of Astronomical Sciences and serving as a professor of physics and astronomy at St. Cloud State University in Minnesota for almost two decades. She also continues to work part-time as an expert consultant for NSF.
According to Wierzchos, 29P has a nearly circular orbit and, because it is active all of the time, it is classified as a ‘distantly active’ comet. The famous and very bright Hale-Bopp comet that visited our night sky in 1997 was also classified as “distantly active” for the year or two before it became really bright.
“Right now, comet 29P is very productive, which means a lot of carbon monoxide gas is coming off of it,” he explains. “We want to find out how many CO molecules are coming off it per second and also learn about the comet’s atmosphere at extremely low pressures and temperatures.”
Comet 29P, also called 29P/Schwassmann-Wachmann 1, was discovered in 1927 by Arnold Schwassmann and Arno Arthur Wachmann at the Hamburg Observatory in Hamburg, Germany. It is unusual in that it periodically undergoes an “outburst,” with up to a ten thousand-fold increase in its brightness. No one knows exactly why things change on 29P, and that’s one reason Womack and Wierzchos want to watch it.
Wierzchos, a native of Lublin, Poland, has spent his life in Spain and started observing comets when he was 14. Since his youth has been considered an ‘expert amateur’ astronomer, one who observes comets and reports on them to international databases. For his work he was given the “Catch a Star” award by the European Southern Observatory at age 16 and invited to the Cerro Paranal Observatory in the Atacama Desert in Chile. In 2008, while in college, he was one of 26 astronomers in the world asked to observe and contribute to calculations on the trajectory of the asteroid 2008 TC3, which was in a collision course with the Earth. Just minutes before it would have crashed into the Earth it burned over the Desert of Sudan.
In 2015 Wierzchos received his master’s degree in applied physics from the University of Madrid Complutense and this fall he entered USF’s doctoral program in applied physics. Fortuitously, Womack had just arrived at USF and their similar interests have become a collaboration.
To investigate 29P’s carbon monoxide tail and other important aspects of its make-up, Womack secured a week’s time on the two radio telescopes, both located high in the mountains of Arizona. The two telescopes are owned and operated by the Arizona Radio Observatory (ARO), a sub-unit of Steward Observatory, University of Arizona, with support from the National Science Foundation. One sits atop Kitt Peak, 50 miles southwest of Tucson, and the other is located on Mt. Graham near Safford, Arizona, 126 miles from Tucson (http://aro.as.arizona.edu/telscopes.htm).
From their link to the telescopes they can gather real time data as the comet’s molecules change speed, temperature, brightness and other characteristics day-to-day as it speeds through space at about 12 miles per second.
Radio telescopes use a directional radio antenna similar to antennas that track and get data from satellites and space probes. They differ from optical telescopes in that they operate in the radio frequency portion of the electromagnetic spectrum where they can detect and collect data on radio sources. They use large "dishes" that look similar to those used for satellite TV. Observatories are located away from population centers to avoid electromagnetic interference from radio, TV, radar, and other devices.
The data gathered by the two telescopes appears on two computer screens in Womack’s office, which serves as their ‘remote observatory.’ They don’t see a visual image of the comet but, rather, streams of numbers and graphed peaks and valleys showing the CO spectrum. “Every day we have been looking at the same data points – temperature, pressure, velocity and carbon monoxide – today the amount produced has increased, for some reason,” says Wierzchos.
Important parts of the research drama are played by the telescope operators. Among other duties, the telescope operators assist researchers, including graduate students like Wierzchos, who have secured time on large telescope time to carry out their research.
“The operators are similar to lighthouse keepers; lonely jobs on mountain tops,” says Womack as she watches the computers screens in her office showing how the two telescope operators are each homing in on the comet. “Right now there is a lot of tweaking going on as the operators tune to the right frequency and then point and focus - first on Mars, because they know where it is and can calibrate the telescope - then shift to pointing on the comet.”Over the week of observation Womack and Wierzchos observed two different comets. Data from them, says Womack, will be useful for testing models of how the solar system formed and also how comets become active so far from the Sun. The next step will be to closely analyze and measure the data on the computer, which will take a few months, and then they will write up the results and submit it for publication. They are already thinking ahead to their next observing run of distantly active comets, perhaps with NASA’s Kepler spacecraft, or the ALMA radio interferometry dishes in the Atacama Desert where Wierzchos got his start so many years ago.