Sometime around the age of thirteen, I decided that I wanted to be an astronomer. (Thank you, Carl Sagan, for your inspiring character in Ellie Arroway.) If getting to explore the universe isn’t enough of a job perk, I’ve also had the opportunity to travel quite a bit to collaborate with other astronomers and to present at conferences. In June, my reach extended even further as I took a three-week trip to South Africa to help build one of the most exciting astronomical experiments to date.*
The project that I work on is called PAPER, or the Precision Array to Probe the Epoch of Reionization. The epoch of reionization, or EoR, is a period in the universe’s early history when the first stars and galaxies were forming.
Though our optical an infrared telescopes cannot yet survey a large number of these early galaxies, we will be able to see their effect on the surrounding hydrogen gas as the ultraviolet radiation from massive stars pulls apart each hydrogen atom (or, ionizes them). Difficulty: the signal given off by hydrogen has been redshifted way down in frequency to a place where radio astronomy has traditionally had difficulty, somewhere roughly between 100 and 200 MHz. Also, this signal is predicted to be really, REALLY faint.
Screenshot of an EoR simulation by Mellema et al. 2006. The tiny blue dots are baby galaxies, and the orange bubbles around them represent ionized hydrogen. What an EoR telescope is built to detect is the neutral hydrogen shown in green. See animation.
So, we are grateful that the Square Kilometer Array effort in South Africa has allowed us to park our telescope at their remote site in a desert region called the Karoo. The goal is to be as far from human-made sources of radio transmissions as possible. Such isolation makes for an interesting experience. It was a good nine hour drive from Cape Town to reach the observatory site, but the view was stunning. Desert vistas have always been a special place for me, even though I grew up in New York.
An army of dipoles are assembled by some of the PAPER team, awaiting installation.
The work itself, of course, is not all that glamorous. We had several back-breaking days of installing antennas, laying out thousands of feet of cable, and inspecting each and every part of the system. With 64 antennas out in the desert, you don’t want to have to track down a lot of problems after the fact. However, extra help came in the form of three interns from Pretoria without whom the deadline may not have been met.
We were indeed successful in having the array up and running with plenty of time to spare for troubleshooting any problems that cropped up. As we pored over the data coming in, we were grateful to have some spare parts for replacing ones that misbehaved. You can’t just pop down to the nearest electronics store, and besides, much of our hardware is custom-made!
The fruits of our labor already seem to be paying off. Though our little laptops out in the field could only process about 10-minutes of data at a time from all 64 antennas, the images we got back after a bit of calibration work were already stunning. The bright radio galaxy Centaurus A took shape with its bright center and fluffy lobes as countless other radio galaxies became visible as little points of light.
And we’re not even done yet. PAPER will expand to 128 antennas next year in order to finally reach the sensitivity needed to detect that ever-so elusive hydrogen from reionization. Now, please excuse me as I try and find where to begin in several gigabytes of data…
Radio galaxy Centaurus A, surrounded by point sources and underlined by the Milky Way. Created by Aaron Parsons and the PAPER Team.
*Yeah, so I’m biased. It IS my thesis…
Images: First (from top) – Several PAPER antennae in position in the Karoo. Credit – the author; Second – EoR simulation. Credit – Mellema, Garrelt; Iliev, Ilian T.; Pen, Ue-Li; and Shapiro, Paul R. (ADS); Third – What a beautiful sight upon arrival. Go Team 1! Credit – the author (more photos); Last – Cen A as seen by PAPER-South Africa with minimal calibration. Boo-yah. Credit – Aaron Parsons and the entire PAPER Team that made this deployment a success.