Wednesday, December 22, 2010
Total Lunar Eclipse
New York was graced with a beautiful view of a full lunar eclipse last night. It was the first full lunar eclipse which has been visible here in almost 3 years, and there won't be another one we can see until April 2014. Consequently, Columbia Astronomy Outreach held a viewing event in the middle of Columbia's campus in front of the Alma Mater statue for anyone who wanted to come catch a glimpse.
The weather was clear but cold and windy (with windchill it reached 12F) last night. Our event was set to last from 1:30AM until 4:00AM, but there were already people present when we started setting up at 1:10AM. We set up several telescopes and binoculars for public use. We had one automated telescope and CCD combination to take images of the eclipse as it occurred. We also had a table with lots of hot cocoa and NASA swag (posters, bookmarks and the like) for anyone to take. Our volunteers answered any questions posed to them regarding eclipses, astronomy and the like.
The partial eclipse began at 1:33AM when the shadow of the Earth (the umbra) began covering the disk of the Moon. The Moon looked pretty strange as you witnessed a big bite being taken out of it, getting gradually larger with time. Throughout this period we had a huge influx of people such that the crowd grew to about 250. Most of the attendees were students walking through campus or taking a break from final exams, but probably about 25% of the crowd was made up of amateurs and members of the public.
Eventually at 2:41AM the shadow covered the Moon entirely, marking the beginning of the total phase of the eclipse. This phase was pretty spectacular--the disk of the moon was bathed in a deep reddish amber color. During totality, the Earth sits right in between the Sun and the Moon, so that most of the sunlight that normally illuminates the Moon is blocked by the Earth. However, some sunlight entering our atmosphere around the edges of the disk of the Earth can bend and refract and eventually make it to the Moon. This sunlight is effectively stripped of all blue light by our atmosphere (this is why our sky is blue) leaving only red light to shine on the Moon.
As you might guess, the hue and brightness of a total lunar eclipse is sensitively dependent on the material in the upper atmosphere of the Earth, since this is where the sunlight destined for the Moon must travel during an totality. Recent volcanic eruptions in Iceland and Indonesia have pumped lots of ash and particulate into the upper atmosphere. These small particles block all wavelengths of light (not just blue light), and it results in a darker overall eclipse. In fact, this was the darkest lunar eclipse I've seen in the last 15 years.
The crowd got pretty enthusiastic about totality with cheers at several point, a shouted countdown ("9, 8, 7,...") at another point, and just general excitement. After about 20 minutes of totality, half of the crowd dispersed and went back to studying or sleep, but there were still a hundred people or so who remained.
There were a few different media crews present including a Japanese television crew, a New York Times photographer, and a few independent media groups. Photographs taken from our event (see above) were included in a New York Times article on the eclipse. Later that morning, I was interviewed by NPR's "The Takeaway" along with Neil deGrasse Tyson regarding the eclipse and our event.
Totality lasted until 3:53AM, when the shadow of the Earth receded and the Moon began its return to full brightness. The second partial phase (where again the Moon has a "bite" taken out of it) lasted until 5:01AM. At the very end, there were still a couple dozen diehards still present trying to get the perfect picture or just enjoy the moment with a hot cup of chocolate. Overall, the event was a great success with mostly clear weather and around 300 participants. Thanks to everyone who joined us!