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Listening to the universe

July 24, 2013

The CARMA dishes at Cedar Flat take on the aspect of a drill team or conga line the longer you look at them. The antennas track their subjects across the skies. Photo by Deb Murphy

The Combined Array for Research in Millimeter-Wave Astronomy offers much to boggle the mind. The drive through a landscape, beautiful in its starkness, ends with a display of sky-focused dishes at Cedar Flat, a scene so incongruous it’s reminiscent of “Lost.” The dishes themselves are giving scientists a look at the birth of new planets formed from the gas and dust whirling around young stars, the same process that produced Earth.
Perhaps the biggest mind-boggler is that laypeople can actually understand what scientists like Dr. Steve Muchovej and Rosalie McGurk are studying and how the Owens Valley Radio Observatory’s Big Ears, moved more than 3,000 feet up the side of a mountain, provide the data toward that study. That ephemeral understanding may have evaporated by the time those laypeople returned to the valley floor, but for a short time, the 320 innately curious at CARMA’s open house held June 8 felt really smart and more than a little awed.
The OVRO just north of Big Pine represents a partnership between the California Institute of Technology, the University of Maryland, the University of Chicago, the University of California, Berkeley and the University of Illinois Urbana Champaign, CARMA is the biggest but just one of a number of projects under the umbrella of OVRO. Big Ears first appeared in the Owens Valley in the 1950s; the larger 10-meter dishes were moved to higher, drier ground in the Whites in 2005 with the smaller 3.5-meter units making the trip in 2008.
As the number of arrivals at the open house reached critical mass, the CARMA tours began with an overview of the facility with a scientist as the tour guide. Muchovej explained the evolution from massive single telescopes used at Griffith Observatory and Palomar to the arrays at CARMA. The way to up the resolution of optical telescopes is to simply make them bigger, which at one point becomes an engineering nightmare. The solution is to position smaller dishes farther apart and point them all at the object to be studied.
Another difference between Griffith/Palomar telescopes and the Big Ears is even more important. “With an optical telescope, you know what the stars in a distant galaxy look like,” said Muchovej. “However, a galaxy is made up of much more than stars. It has gas clouds, charged particles, etc. All of those objects emit light, but not necessarily in optical wavelengths. Dust and gas clouds emit in radio waves. Since gas clouds are what stars form out of, you might want to answer the question of whether this one galaxy has a lot of gas still left, in which case you can infer whether more stars will form. Or, the galaxy may be running out of gas in which case no new stars will form.” Radio wave telescopes give the scientists insight into where a galaxy is in its evolution and can track that progress.
“The beauty of CARMA is in the diversity of the dishes,” he said. “The the smaller ones (dishes) provide data on the dark energy that is driving the universe” by scrutinizing dust particles and gas clouds.
The next stop on the tour is the array control room and McGurk. The UC Santa Cruz graduate student was awarded time at CARMA to observe, schedule the telescopes and deal with whatever problems arise. This is her third stint on the mountain. Her particular study is merging galaxies and black holes. She addressed the group with the enthusiasm one would hope grade school science teachers convey to their students. Galaxies, each with their own nuclei or black hole, grow, she explained. “So what happens when they merge?” she asked the curious without any hope of an answer. “What happens with the black holes? They’re hard to study, because they’re black and their gravity is so strong, so massive. So, how do you see them? We look at the effect they have on the gas around them. They keep pulling in all the gas and dust, they eat it. This gas and dust lights up so we see the effect of black holes on their surrounding materials.”
At present, McGurk is looking at the position of two merging galaxies, determining their tilt in relation to the earth so the velocity of the dust can be measured. She is lucky enough to witness the merger of two relatively close galaxies. “They seem close,” she said. “But in reality they’re 11 kilolight years apart; not close at all, actually. We don’t get to see mergers this close that often. It’s extremely exciting.” It is obvious from diagrams drawn from the data provided by the array that there is a disparity in the size of the two merging galaxies; one is apparently gobbling up dust at a much more aggressive rate.
“We’re in the Milky Way galaxy,” said Muchovej. “And we’re moving toward the Andromeda Galaxy which has a super massive black hole. At one point, they will collide. What’s going to happen? Rosalie will know what’s going to happen.”
McGurk is working with the end product of the data derived from the array. The tour, basically, backtracked the signals from the information McGurk studies in reverse to the dishes receiving the signals. “If you’re a lightwave coming from the sky,” said Muchovej, “this is the exact opposite path of how you’d see the array.” McGurk’s data on the voraciously merging galaxies comes from the correlator room where all the signals are processed by massive banks of computers, or custom electronics, that “perform the mathematical calculations to properly combine the antenna signals,” Muchovej explained.
A lay brain more accustomed to the theoretical begins to falter in this chilled room with vinyl, see-through curtains keeping dust off the parallel rows of electronics, stacked to the ceiling. The signals the custom electronics process come from the receiver lab where the receiver engineer explains how the signals are chilled so they’re “easier to move around.” The temperature is expressed in Kelvin. Most lay brains Googling Kelvin will suffer brain implosion. While the equipment in the correlator room looks like computers, the equipment in the receiver lab doesn’t quite look up to the task of “propagating” signals and moving them along a coax cable to be processed. Now the discussion seems more like magic than science.
All the lay people in Muchovej’s group were then released onto the mesa to wander among the dishes and discuss their function and idiosyncrasies with scientists stationed around the array. Those who realized their brains cannot assimilate one more scintilla of information, just wandered, photographing the dishes, watching them adjust to keep an eye on the formation of new earths, feeling both random and small but also amazed that our species’ curiosity has led us to Cedar Flat.
On the drive back down the roller coaster that is S.R. 168, there is also a commitment to keep coming back to CARMA’s annual open house in the hopes that the gizmo in the receiver lab will make more sense next year, or maybe the next.

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