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Saturday, July 23, 2011

The Polar Night

We are in the middle of the polar night: the single, 6-month long night that only occurs at the Earth’s poles.  Today, July 23, one month after the winter solstice, the sun is still 20 degrees below the horizon.  We all studied in school that at the Poles there is a 6-month long day and a 6-month long night.  We often associate that notion with the polar regions in general, but in reality the 6-month night only happens at the very pole.  Even at Vostok, the Russian station which is the closest inhabited location to the South Pole, at 78 degrees of latitude, twilight will show up every day of the winter, as the sun will be less than 12 degrees below the horizon at least for some time every day even in the deepest of winter.  So, it is an incredible and unique privilege to experience the polar night at the South Pole Station, where we live in complete darkness, without even the faintest of the twilight, for 80 days in a row, from May 12 to Aug 1. 

Winter at the South Pole feels like a long tunnel.  We entered the tunnel on March 21, when we switched from day to night.  But for several weeks we were able to still see the light at the entrance of the tunnel in the form of twilight getting fainter and fainter every day.  That was a time of slight apprehension for me, as I did not know what to expect as we went deeper and deeper into the night: would I still be able to navigate outside, on foot and on ski?  Would it get even colder and windier?  How big would the snowdrifts get?  Would I go insane without sunlight for so long?  Then, on May 12, we left behind the last of the twilight, and we could not see the entrance of the tunnel any more.  We have now been in the middle of this dark tunnel of the polar night for 70 days, and it has been beautiful, as I have learned how to cope with the lack of light first, and then how to truly enjoy it, to the point that I now regret that this very special time will soon come to an end.

The South Pole in winter is the most pristine environment that I have ever experienced, with no air pollution, no light pollution, and no noise pollution.  In the summer we have the noise of the airplanes and of the snowmobile, but not in the winter.  To reduce interference to the scientific instruments that look at the sky and at the auroras, we do not have lights on the buildings, and we cover all the windows, so all our buildings appear as black boxes against the glare of the snow, and we are thousands of miles away from any source of atmospheric pollution, provided we stay upwind of our power plant. 
In winter we do not have to wear goggles to protect our eyes from the solar radiation, as we do in the summer, so we enjoy much clearer views, unobstructed by the fogging that always forms on the goggles.  Unfortunately, because I do not wear my glasses outside, I do not fully enjoy the night sky, but I still can see many different stars, and even use them as navigational aid.

Soon our eyes will be pointed at the horizon, looking for the end of the tunnel in the form of a faint twilight which will get bigger and bigger as the days will progress.  We often look forward to that moment that will signal the return of the sun, without thinking that it will also mark the beginning of the end of this wonderful polar night and polar experience, so I try to go out every day and enjoy the little that is left of this mystic polar night, with its stars, its auroras, and its silence.

No photographs can make justice to the magic of the polar night, but I have selected a few, taken this winter by Dana, the scientist who operates the South Pole Telescope.  Dana is spending his sixth winter at the Pole this year.  He has done scientific work both at the North Pole and at the South Pole, a very rare distinction, and is probably the most experienced winter traveler.  During his six winters at the Pole he has walked a total of 5 ~7,000 miles on the ice, probably more than any other human being has on the Polar Plateau.  I have learnt a great deal from him on how to stay safe outside in the middle of the night.  I often meet him outside while I am skiing and he is walking back from the telescope.  If I don’t see him on the ice, there is always a chance around dinner time to exchange our impressions of the night sky that we experienced while outside, as every day the night sky is a little different.  One big difference between Dana and I is that Dana does not like it when the moon is out, because it washes away the stars, whereas I really do enjoy the moon and how it reflects on the ice.  More photos from Dana are posted on his website

We see different portions of the sky from the Northern and Southern hemispheres.  This is a photo of the Milky Way, which is our own galaxy.  We can see it both from the Northern Hemisphere and the Southern, although we see different portions of it in each.  The small blob in the upper left quadrant of the photo is the Large Magellanic Cloud: a galaxy orbiting our own Milky Way.  We cannot see it from the mid-latitudes of the Northern Hemisphere.  From the Northern Hemisphere instead we can see the Andromeda Galaxy, which is 100 times larger and 15 times farther than the Large Magellanic Cloud.  Andromeda is not visible from the South Pole.

This photo shows both the Large Magellanic Cloud (Lower left) and the Small Magellanic Cloud (Upper Right) in the same frame.  The Small Magellanic Cloud is also a Galaxy, slightly smaller and farther away than the Large Magellanic Cloud.

On June 16 our full moon was obscured for a few hours by an eclipse.  This is a photo of the moon partially eclipsed just a few minutes before it became completely dark.  I decided to enjoy the eclipse from the ice, so I went out running when the moon was still full and providing good visibility, and kept running for about 1 hour until it got so dark that I could not see well any more, at which point I came back into the station to watch the last few minutes of the moon eclipsing.  It was one of the highlights of my winter so far.
The moon at the South Pole does not have the daily cycle that it has at intermediate latitudes, where it rises and sets every day.  Here at the South Pole, instead, it stays up in the sky continuously for two weeks, then it sets and remains below the horizon for the following two weeks.  I like the moonlight because it allows me to roam around farther from the station without the risk of getting lost, and I can much easier navigate around the snow drifts when I go out running or skiing.  Therefore I have created this chart to display the brightness of the moon through the winter.  The brightness is calculated based on the elevation of the moon on the horizon, the phase of the moon, and the distance of the earth from the moon.  I look at this chart almost daily to plan my outdoor activities.

Silhouette of the South Pole Telescope against the moon ...

... and against an aurora.

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