Above: Lunar eclipse of September 28, 2015 as seen from New York (Edward Blake, Wikimedia Commons)
A rare spectacle was on display in the sky on the night of September 27-28, 2015: a total eclipse of a supermoon. The last time this happened was 1982 and it won't happen again until 2033.
What is a supermoon?
A supermoon is a full moon that occurs when the Moon is the closest to Earth. On average, the Moon is 384,400 km away from Earth. But the Moon's orbit is elliptical, not perfectly round. So the distance varies by about 7% over the course of each rotation. When it's closest to the Earth, the Moon appears 12-13% larger and shines 30% brighter.
What is a total eclipse of the Moon?
A total eclipse occurs when the Earth, which rotates around the Sun, gets in between the Sun and the Moon. Normally, light from the Sun shines directly on the Moon, causing it to light up the night sky on Earth. But during an eclipse, light from the Sun can only reach the Moon by refracting through the Earth's atmosphere.
As it refracts through the atmosphere, light from the Sun causes the Moon to appear blood red to those of us watching from Earth. This is the same effect that occurs during sunsets, when the light from the setting Sun is refracted by the Earth and turns the sky red. Total lunar eclipses (not necessarily during a supermoon) occur once every two and a half years.
Geometry of a lunar eclipse. Some light from the Sun still manages to reach the Moon during a eclipse. But because this light is refracted by Earth's atmosphere, it causes the Moon to appear red. Click image to enlarge (Wikimedia Commons, Sagredo)
Total eclipse of a supermoon
The total eclipse of a supermoon that occurred in September 2015 could be seen from anywhere in Canada. There are actually 12 stages of a total eclipse but stages six through eight are the most exciting ones! That is when you can see the most vibrant reds.