An exceptionally rare celestial phenomenon taking place this Sunday, September 27 will provide skygazers in Calgary with a double lunar treat.
Supermoons occur between three to six times a year and gives the moon an appearance that is 14 per cent larger and 30 per cent ‘brighter’ than normal full moons. A total lunar eclipse occurs up to four times a year, when the moon directly passes into Earth’s shadow and transitions into a red shade of colour.
But to have both events coincide at the exact same time? Well, that’s exactly what will happen this Sunday evening.
The last time a supermoon lunar eclipse took place was in 1982. It has happened only five times since 1910, and it is not scheduled to return for another 18 years.
Schedule for Sunday evening’s supermoon lunar eclipse over Calgary (MDT):
The next supermoon is on October 27, 2015 while the next full lunar eclipse for Calgary won’t be until January 31, 2018.
The region’s weather forecast for Sunday is currently favourable for watching the celestial double header, although it goes without saying that this could change as the weekend nears. Assuming clouds don’t block the views, the phenomenon will be viewable across Canada.
So why exactly do supermoons and lunar eclipses happen?
Full moons are ‘supermoons’ when the moon is at its Perigee stage – when it is at its closest point in its elliptical orbit around Earth. At Perigee, the moon could be as close as 356,500 kilometres away from the planet. In contrast, the moon during the Apogee stage indicates the moon is at its farthest orbital distance, as far away as 406,000 kilometres.
With lunar eclipses, the moon gains its reddish appearance when certain wavelengths on the planet’s atmosphere are refracted out. Earth’s atmosphere is approximately 80 kilometres thick, which acts similarly to a filtered lens that bends out the sun’s red light towards the other side of Earth but scatters out blue light. For the same reason, this is why sunrises and sunsets appear red.
A NASA video explains the rare phenomenon of a supermoon lunar eclipse.