Galactic Nuclei

The first thing I noticed when I walked into the lab was how loud it was. There was an intense humming coming from a large metal crate, and a ventilation that created an additional whooshing noise. I almost had to shout to be heard over the noise as I said hello to the people with whom I would be working on MUSTANG-2, a cosmological project in the department of Astrophysics at University of Pennsylvania. The people in the lab were my sponsor, Sara S., a tall, friendly, and confident graduate student, and Simon, a kind, soft-spoken researcher who visited UPenn from England and met his wife. The two were managing the huge crate of electronics, fitted with five different computers, and a gigantic, homemade cryostat (to cool materials down to within fractions of absolute zero). Sara introduced me to the general idea of the materials they were using, and then sat down to solder some pieces together on the lens of the telescope. As she worked, she told me about the goal of the project.

The types of things one would find in the UPenn Experimental Cosmology lab

“The metal crate has four different computers that output signals from our detectors to the main computer where we read the data. Our detectors are only made in a few places in the world, and we have one of the highest resolutions available, with many more pixels than most telescopes. We’re going to bring this apparatus down to a gigantic telescope in Virginia, where light will bounce off a large mirror and focus onto our lens, which will be cooled down to millionths of a Kelvin away from absolute zero. The signals will travel along the wires, which, due to their coldness, will become superconducting. The infrared rays we measure will be registered on a series of resistors, which will change in resistance rapidly with changes in temperature. Then, we can create what is essentially a heat map of galaxies in the universe in order to learn how they were formed and what they’re doing now.”


Thanks to T. Larry’s successful efforts to control and teach my Physics 4 class, I understood at least a fraction of what Sara was trying to tell me.

“So, basically, we’re making a heat map?” I asked timidly.

“Yep!” she exclaimed with a smile. “And you get to help load the lenses into the cryostat!” A big responsibility for me, when each detector is worth thousands and the whole project has taken years of hard work. I sure didn’t want to drop anything!

While Sara continued to solder, Simon pulled one computer out of the crate, telling me it wasn’t ventilating properly. The resistance of the apparatus they had was higher than expected, which meant a higher base voltage had to be run through the circuitry in order to maintain the desired resistance, right on the edge of superconductivity. As a result, the computer and the crate were overheating, and something had to be done. We opened up the computer, which was sealed with metal tape to keep the signals from interfering with any technology, and took a look at the circuitry.

“See those parts right there?” asked Simon, pointing to a few bits of the circuit smaller than the nail on my pinky finger. “For seven months those didn’t work, until we dabbed a drop of silver paint under them. Seven months of failed work just to discover a unit the size of the head of a pin was not grounded correctly.” That floored me. I couldn’t even imagine working on something for seven months, only to realize one tiny thing was the reason I couldn’t look at the stars! Keeping the issue of grounding in mind, the problem was easily solved and the ventilation issue was resolved.

“I’m done!” said Sara when she finished soldering the central lens of the project together. She carefully carried it over to the cryostat, and I watched with bated breath, knowing it was the result of tens of thousands of dollars and years of work and research. We cleaned the parts that had to fit together with alcohol in order to create a vacuum seal, flipped the heavy cryostat over. The lens then went in the top, and had to be screwed in carefully. After Sara and I completed that, we put tape around the edges to ensure there were no light leaks hat would affect the readings. Then, three more lenses, each more delicate than the last, had to be installed, screwed in, and taped. Finally, a lid was placed on the top and screwed in to ensure a vacuum seal and no light leaks. The cryostat was loaded. We flipped it back over and admired the work. It was ready to be transported to Virginia, where it would be cooled using an isotope of Helium and then hung from the ceiling to absorb the light focused on the mirror. Then, we could look at the stars! It was incredible to be able to help install something that was state-of-the-art, something technologically advanced and important for the understanding of our universe. The theory I have learned in class on a microscopic scale was playing out in front of my eyes on a large scale, and I was able to take part in it! I could feel the excitement filling me as I looked around the room, realizing I could be a part of something like this, that I could help to explore worlds we know nothing about. I am excited when I look forwards to next week and the work I will do next, analyzing data and trying to understand the mysterious bodies that make up our universe. Stay tuned for more updates on the galactic nuclei heat map!

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