“Aurora” over Providence

Note: this was originally published on March 6. It was updated on March 8 to include new information.

On March 6 we received local reports that the aurora was observed in New England just before sunrise. One of our visitors described seeing it from a rest area on Route 495 near Boston. There was another report from Vermont. Our automated all sky camera was running the entire night and captured the view above Providence. Also visible is the International Space Station (ISS) streaking through the sky about 500 miles from Providence as the planets Mars and Saturn shine brilliantly in the south.

ISS and aurora
A 10 second exposure taken March 6, 2016 at 4:54:18 AM EST. This image has been processed to make it easier to see the stars.

During the night the camera recorded 3,750 images of the sky. North is at right, west at bottom, and the zenith is at center. The field of view is about 140 by 90 degrees, capturing most of the sky above Providence. The images can be processed to produce a time lapse movie that shows 5 minutes of changes in the sky per second of video. Click on the image below to watch an excerpt. A number of artificial satellite can be seen streaking through the sky just before dawn.

Our sky camera has been in operation since the spring of 2008. We’ve never captured images like this before.

The sky at 4:59 AM EST.
A 10 second exposure taken March 6, 2016 at 4:58:56 AM EST. Click on the image to see a time lapse video showing the sky from 3:30 – 5:45.

While initial reports suggested this was an aurora there has been little confirmation from other locations. Another explanation was suggested by meteorologist T.J. Del Santo at Northern Lights on Sunday? The rays visible in the images could have been caused by ice crystals in the lower atmosphere reflecting city lights. This is known as a light pillar.

We would usually expect water vapor or ice crystals to move through the camera’s field of view after several minutes, in the same way that the clouds and haze move in the video. The “rays” visible in the images appear static which could be an optical illusion due to ice crystals scattering light downwards. This is much rarer than light pillars seen near the horizon.

Zenith sky brightness
Zenith sky brightness on March 5-6, 2016.

Another instrument on the roof measures overall sky brightness. The lower a measurement on the graph above, the darker the sky. During most of the night the sky was very bright indicating cloud cover. The sky clears at 3:30 AM, briefly becomes cloudy again at 4 AM, and then clears again until twilight begins and the sun rises. Although the sky was clear in the early morning it was somewhat hazy. The camera is especially sensitive to water vapor in the atmosphere which can be seen in the video. The camera is also more sensitive to light than the human eye, but a similar view would have been visible to someone looking at the sky between 4:40 and 5:10 AM.

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