10-Meter South Pole Telescope

The South Pole Telescope looking at the ski directly above – the metal scaffolding is being added this year in an attempt to reduce “noise” from reflections off the snow surface.

The South Pole Telescope (often referred to as simply 10-meter or “SPT”) is an iconic feature here at Pole. Constructed during the Austral summer of 2006-2007, the impressive two dimensional rotating 10-meter dish located just across the skiway from the station is hard to miss.

In the Science Planning Summary USAP-2011-2012 the SPT project is described as:

Looking at the intensity and polarization anisotropy of the CMB. By surveying 4,000 square degrees of the sky with high sensitivity in three wavelength bands, the telescope can detect galaxy clusters through the spectral distortion they impart on the CMB. Researchers will use the resulting catalog of galaxy clusters to set constraints on the mysterious dark energy that dominates the mass-energy density of the universe and is causing the expansion of the universe to accelerate.

The telescope is looking primarily at the CMB (or cosmic microwave background) of the universe. In particular they’re interested in finding and cataloging very distant galaxy clusters and learning more about Dark Energy, the phenomena that would explain the accelerating expansion of our universe. With a 1 arc minute beam the telescope has a relatively high resolution. The WMAP satellite is also mapping the CMB in the same spectrum (95-250 Ghz) but with far less detail. Ultimately they’re looking at changes in temperature of the CMB radiation reaching us here at Earth – these variations are extremely subtle and the focal plane is cooled down to .25 degrees above zero Kelvin with liquid helium to increase sensitivity. Atmospheric water vapor acts as a barrier to this type of radiation, which makes South Pole the ideal place for millimeter and sub-millimeter astronomy.

This is all very good, but what is the CMB? This can be hard to explain, and harder to conceptualize, but here’s a try…The Big Bang theory states that in the very very early stages of the universe matter was so dense it was plasma, at some point there was an inflation event that caused the universe to expand at speeds faster than the speed of light. The CMB is essentially radiation from the boundary between space and this plasma – it’s the boundary between “empty space” with stars and suns and planets etc, and matter that’s so hot and dense light cannot pass through. This background glow is incredibly unifrom across the sky with a temperature of about 2.7 degrees Kelvin.
The CMB is not what that part of the universe looks like now, but what it looked like 300,000 years after the big bang, when the light we’re seeing today was transmitted. We’re seeing what the universe looked like everywhere before it expanded and cooled enough to have different particles separated by space. We know that light travels at a constant rate (2.9×10^8 m/s, or roughly 671 million miles per hour) – it takes ~8.3 minutes for light from the sun to reach earth, 4.24 years for light from the nearest star to reach our sun, and 100,000 years for light to travel across the Milky Way. So… Looking into space really is looking back in time.

An important fact to keep in mind is that there is no center of the universe. Though the Big Bang theory states that everything started in a condensed state and expanded rapidly from there, there’s no center and no matter where you are, everywhere in the universe will look like the center. No matter where in the sky you point the telescope it will see the CMB at the same distance – kind of like if you were in the middle of a giant bubble, no matter where you looked you would see that inside surface of the bubble the same distance away. To get much useful information from the CMB you need special telescopes, the size of which affects the resolution, but everyone has seen remnants of the CMB without even knowing it. The fuzzy static on TVs (before there was 24/7 digital broadcasting)…that is the TV picking up on this white noise penetrating the universe, this distant radiation from the birth of our universe.

Galaxy clusters are some of the largest physical pieces within the universe. They are so large they create something like a shadow against the backdrop of the CMB radiation. Because of its high resolution the SPT is able to locate, and thus catalogue, many previously undiscovered distant galaxy clusters. Part of their project is to create a database of such features to be analyzed with different types of telescopes in the future.

The second part is Dark Energy – our universe is still expanding, that’s fine, but it’s accelerating in rate of expansion! Theoretically with the amount of material and energy presently known to exist in our universe the effects of gravity should have slowed the expansion by now. It doesn’t make sense. To explain this acceleration there needs be far more matter and energy for the equations to work out. This unknown factor is termed Dark Matter and Dark Energy. NASA provides a much better explanation:

The Dark Sector Lab and the SPT in it’s docked position where they can work on the receiver.

The hinge of the telescope and the doors to the receiver area – last year I got to help clean off the grease under and around this part. In the winter the grease freezes and cracks off as it gets pushed out of the hinge, in the summer it thaws and gets very messy.

The base of the telescope – the hole is an access point to the cables and interior of the telescope, the dark piece above is the bearing on which the telescope turns.

Many meters of fiber optic cables run inside the telescope allowing it to turn more than 360. As part of the bearing change last year I got to help unwind and carefully set aside all of these.

The Inside of the telescope – where the cables are usually coiled. This picture was taken last year when the telescope was lifted up to change out the bearing.

The telescope separated to remove the old bearing and slide in a new one. The raised part of the telescope weighed over 65,000lbs!!


Filed under Antarctic, Science, South Pole

2 responses to “SCIENCE! Part II

  1. “…this background glow looks the same across the sky and is about 3000 degrees Kelvin”.
    You’ve lost me here — I thought the generally accepted value is 2.73 K.

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