Physics Students At Radio Astronomy Boot Camp
SOCORRO, N.M. August 8, 2013 – Four physics graduate students spent a week catching some waves in Puerto Rico in July. But they weren’t at the beach; they were catching radio waves at the Arecibo Observatory during an intensive weeklong conference.
Lorraine Bowman, Phil Cigan, Rick Cosentino and Virginie Montes – all Ph.D. students in astrophysics – learned plenty of details about radio-astronomy and conducted team research using radio astronomy.
“They had lectures by renowned scientists during the day,” Cigan said. “The conference had nice breadth and sufficient depth. In the evenings, we actually got to collect data and do a project.”
Lectures covered areas from how the Arecibo dish works, how radio signals run through the telescope system and the wide range of research opportunities available in the radio spectrum.
“In short, radio observatory is looking at gas in galaxies,” Cosentino said. “How are stars born? How do stars die? – the life and death of stars. The story of gas in the galaxy.”
The conference participants expected to collect data using the Arecibo Observatory’s 305-meter dish. Unfortunately, the telescope became non-operational before they could collect data. So, the teams remotely used data from the Green Bank Telescope in West Virginia, which also collects radio data.
Montes and Cosentino collaborated with fellow team members on a project to compare observational techniques. They used position-switching and frequency-switching methodologies to get a grasp on how to reduce noise in the data. Montes said they came up with a new method of combining the two methods in a novel way that allows for quick access of data and reduction of noise.
Caption: Lorraine Bowman (from left), Rick Cosentino, Phil Cigan and Virginie Montes at the entrance to Arecibo Observatory in Puerto Rico.
Cigan was on a team with one of his collaborators – Dr. Megan Johnson from the Green Bank Telescope – that looked for evidence of interaction between two dwarf galaxies.
“We were trying to find the gas bridge between two galaxies – evidence that they interacted in the past,” Cigan said.
Bowman’s team looked at pulsars, also known as neutron stars. Using archival data collected at Arecibo that no one had yet examined, her team found a new pulsar that has yet to be confirmed.
Caption: the cradle that holds the secondary and tertiary dishes is 25 meters -- the same size as the VLA dishes -- is suspended over the main, 305-meter dish.
Her group found a millisecond pulsar – a neutron star which has a rotation rate measured in milliseconds. Her team measured the rotation rate at 1.93 milliseconds, which would make it among the five fastest spinning pulsars ever found.
“The signal was perfect – beautiful!”, Bowman said. “Another member of my group got excited, ‘Guys! Guys! Look at this!’ It was a good surprise! Both archival data sets we had show the same signal, which rules out earth-bound interference. But it needs to be independently confirmed.”
She said other team of researchers will observe that pulsar candidate again, which could lead to the publication of a discovery paper.
Bowman, Cigan and Cosentino all have experience with radio astronomy, predominantly from using the Very Large Array. Yet, they each said they came away from the conference with a greater appreciation and understanding for the discipline.
Lorraine Bowman, physics doctoral students, at the controls at the Arecibo Observatory.
The main dish of the Arecibo Observatory first opened in 1962.
“Single dish observing isn’t necessarily what I do,” Cigan said. “But it plays an integral role in quantitative analysis. You need to learn the basics. If you’re going to do radio astronomy, it’s another tool.”
Cosentino said the Very Large Array is a precision tool, used to look at small areas, while Arecibo’s single dish is a broader tool, used to look at wider areas.
“I’ve been doing radio astronomy for a while,” said Cigan, who earned his master’s at Tech in 2012. “Now, I see it in a different way. And the hands-on project was way cool.”
All four said the highlight of the lectures was “Pulsars Are Cool – Seriously!”, delivered by Dr. Scott Ransom of the NRAO in Virginia.
“He made me wish I was studying pulsars,” Cosentino said.
“He can get away with publishing a paper with that title,” Bowman said. “That tells you the caliber of science that he is doing.”
Arecibo, along with the Very Large Array here in Socorro County and the Green Bank Telescope, are all operated by the National Radio Astronomy Observatory, headquartered in Charlottesville, Va. The VLA is an interferometer, which combines signals from 27 dishes over an area up to 11 miles in diameter. The Green Bank facility is a steer-able 100-meter dish.
Arecibo is a static 305-meter primary dish with steer-able receivers at the dish’s focal point. The secondary reflector dish is 25-meters in diameter, which is the same size as the VLA dishes. The tertiary reflector is 10-meters in diameter.
The Tech students got to explore the dish – walking across the catwalk high above the main dish and touring the three-level dome that houses the secondary and tertiary dishes and the receivers.
“The dome is on a rail and sits in a cradle,” Bowman said. “We went into the dome, which looks like the Death Star. It’s scary.”
Technicians refill the liquid nitrogen tanks in the dome on a daily basis, to keep the electronics at about 15 Kelvins.
The Arecibo Observatory was conceived in 1958 by scientists at Cornell University.
“It was built, running and ready in 1962 for $10 million,” Cosentino said. “On time and under budget. Who does that?”
Arecibo was originally built as an active observatory to study the Earth’s ionosphere – the upper atmosphere from 30 to 600 miles above Earth – by using an antenna to probe the ionosphere. After the observatory was running, scientists started using the dish to collect radio waves from the distant reaches of the galaxy and beyond.
In the 1980s, Arecibo was used to map the surface of Venus, which has an atmosphere that is opaque to visible light. In 1995, Arecibo was used as a set for the climactic scenes of the James Bond movie, “Goldeneye”, and for “Contact” in 1997 - along with the Very Large Array. Today, Arecibo devotes half of its observing to astronomy and half of its time to atmospheric studies.
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By Thomas Guengerich/New Mexico Tech