Instrument Observed Distant Spiral Galaxy M101
By Edwin L. Aguirre
In the predawn hours of Nov. 21, a sounding rocket carrying a scientific instrument designed to observe and study the creation and destruction of interstellar dust in a faraway galaxy was successfully launched from the Army’s White Sands Missile Range near Las Cruces, N.M.
The NASA-funded experiment, called IMAGER (Interstellar Medium Absorption Gradient and Extinction Rocket), was created by a team of researchers led by physics Asst. Prof. Timothy Cook. They used a Black Brant IX, an 18-foot-long two-stage rocket, to lift the 900-pound instrument into a suborbital flight, reaching a height of 181 miles.
“It was a picture-perfect launch!” exclaimed Cook, who has been involved directly or in some capacity in 20 sounding-rocket launches so far. “It was very exciting and nerve-wracking at the same time.”
The IMAGER’s observing target was the spiral galaxy M101 — also known as NGC 5457 or the “Pinwheel Galaxy” — located about 25 million light-years away in the constellation Ursa Major, near the Big Dipper’s handle.
The rocket flight lasted for approximately 15 minutes. IMAGER was able to observe M101 for nearly seven minutes, after which the instrument and the rocket’s upper stage fell back to Earth, parachuting safely to the ground about 50 miles from the launch site.
A Dusty Galaxy
“Our primary goal is to take images of M101 at three different ultraviolet [UV] wavelengths,” explains Cook. “We’re trying to find out more about dust in M101 — that’s right, dust. It turns out that galaxies are pretty dusty and the dust is pretty important. It blocks a lot of the light from leaving, or even moving around in, the galaxy. Dust absorbs ultraviolet light particularly well, so with our UV instrument we’re particularly sensitive to its effects.”
The team is looking to find out if the differences in dust absorption are due to the formation or destruction of the dust. Determining how dust varies from M101’s core to its rim will help in understanding the evolutionary history of galaxies.
Cook’s team includes co-investigators Supriya Chakrabarti, who joined the University’s physics faculty in September, and Karl Gordon of the Space Telescope Science Institute in Baltimore.
He adds: “Our field operations were the responsibility of three people: Brian Hicks, a UMass Lowell post-doctoral researcher who just graduated from Boston University after launching Supriya’s last sounding rocket; Meredith Danowski, a BU graduate student who really was the brains of the operation, and Jason Martel, a mechanical engineer with our group who just came to UMass Lowell.”
Cook earned his bachelor’s and doctorate degrees from Johns Hopkins University and the University of Colorado, respectively. During his graduate career, he had the opportunity to construct his first sounding-rocket payload and fly it five times. He has been flying science payloads into space ever since.
After graduation, he worked as a post-doctoral researcher at the University of California, Berkeley, where he designed the instrument for STUFF, the Solar/Terrestrial Ultraviolet Flight Facility, which is a sounding rocket designed to study the interaction between the Sun and Earth’s upper atmosphere.
He then moved to Boston University where he worked on a number of sounding-rocket and satellite missions. He was program manager for the TERRIERS satellite, which was intended to investigate Earth’s ionosphere. Using spare parts from that satellite, he constructed SPINR, the Spectrograph for Photometric Imaging with Numeric Reconstruction sounding rocket, which measured dust in groups of hot, young energetic stars in the constellations Scorpius and Orion. SPINR flew three times.
At BU, he also helped develop SCARI, the Self-Compensating All-Reflective Interferometer sounding rocket, which used an interferometer to measure the properties of the interstellar medium as it flows through the solar system. In addition, he has been working to develop an Explorer mission to study ultraviolet light from the intergalactic and circum-galactic medium.
His latest projects include the PICTURE and IMAGER sounding rockets. PICTURE, the Planet Imaging Concept Testbed Using a Rocket Experiment, aims to take images of the debris disk around the star Epsilon Eridani.
“PICTURE should eventually lead to the direct imaging of the exoplanet orbiting that star,” notes Cook.
The team has just begun to analyze the data gathered by IMAGER on M101, which will become the subject of journal papers and form the basis for Danowski’s Ph.D. thesis.
“This is a cradle-to-grave experiment,” says Cook. “We’ll continue to apply for grants and, as long as we get funding, we’ll keep on launching rockets into space.”