Aurora Australis

Aurora Borealis and Aurora Australis – the Northern and Southern lights respectively – are one of the most iconic phenomena of the polar regions.
Dancing streams of light, ephemeral and enchanting, appear in the dark sky spanning a spectrum of color from white to green to red and near purple. They have fascinated mankind and until recently were thought to be spirits or signs from god. Today we understand the physics behind aurorae, however this explanation is no less amazing. It is still one of the most awe inspiring natural phenomena I have ever witnessed.

A nice diagram showing the magnetosphere and solar wind

Charged particles emitted by the sun reach Earth and are diverted around the magnetosphere. This strong magnetic field is induced by the spinning mass of liquid iron in Earth’s core and acts like a shield protecting Earth from the solar wind. Without the magnetosphere our atmosphere would be blown away and terrestrial life would be exposed to extreme radiation emitted by the sun. The magnetic field lines originate and converge at the axis of Earth. Solar particles are charged so they follow the magnetic field lines and are essentially funneled into the atmosphere at the Poles.

The interaction between these charged particles and atoms in our atmosphere produces light. This phenomena occurs year round, but the light is only visible in the dark of night. Here at the South Pole we have one long day and one long night each year – so the auroras are only visible during the winter months.

Auroras as seen from space

An image of auroras from space

NOAA’s space weather forecast showing the aurora oval – where auroras are most likely to occur.

Walking out to the berms to check on something or find more supplies, I watch the sky above me. With no light the stars shine brilliantly, the sweeping arc of the Milky Way plainly visible. My breath hisses in the cold, my eyelashes freezing together, my steps crunch loudly on the ultra dry snow. I glance up to see a slight glow, a pale green that gradually brightens as it expands. Other bright spots appear and it unfurls in a long curtain of light – reddish at the top and green at the bottom. It seems to stream downward, undulating and pulsing, curling upon itself in sections only to unfold again. It moves across the sky sometimes breaking into parallel lines. After a while it fades away again leaving only the darkness and pure starlight behind.

During winter everyone on station carries a personal radio with them. We can call each other individually, in programmed groups, or do an All Call. With some people working nights and others “free cycling” (for example researchers who do not have to stick to a regular schedule and instead follow a 27 hour day) All Calls are reserved for emergencies only. One of the programmed groups is “Aurora Lights.” This is a channel used to announce especially good auroras. A few months ago, when it was just getting dark, everyone would go running to the upper deck at DA when there was an aurora call. Now that we’ve passed midwinter people are starting to get a little jaded. Only an especially good aurora will draw a crowd…

This past Monday however, we had a spectacular show. Here are some pictures from myself and others here on station (as referenced):

Auroras over DA from May

Auroras over DA

More auroras from this Monday

A gorgeous shot by our Research Associate Andrew

Another nice pic with a fisheye by Andrew

Auroras over the station photo by IceCuber Felipe

Another shot by Felipe

The South Pole Telescope with auroras and the Milky Way. Photo by our power plant mechanic Eddie

An awesome picture Robert Schwarz shot this week of some nice auroras and a meteor!

Home Sweet Home from the top of the ARO tower

SCIENCE! Part II

10-Meter South Pole Telescope
http://pole.uchicago.edu/

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: http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

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!!