Earth will see a supermoon Monday 28th September

Some of you might have heard that there is going to be a Lunar Eclipse this coming Monday, the 28th of September. Unless you’re planning to be in Africa, Europe, or the Americans on that day you’re not going to be able to see it due to the Moon and the Earth being in the wrong position for us here in Perth. But don’t cry as we get a makeup present from the Moon in the form of a Supermoon and this one is special.

Stunning picture of the Supermoon over Perth. Image Credit: Jan Polczynski

Now you’re probably wondering why it is special. Well, to understand why it’s special you have to understand what a Supermoon is. The moon isn’t in a completely circular orbit but an elliptical orbit. This means sometimes the Moon is very close to the Earth with its closest point called Perigee and sometimes it further away with the Moons furthest point called Apogee.

A Supermoon occurs when the Moon is in the new or full moon phase as the Moon reaches or nears Perigee. At perigee, The Moon lies only 356,877 kilometres away from The Earth, but when it’s at Apogee the Moon is 406,464 kilometres away, so you can see there is a difference of 49,587 kilometres between the two points. While there are 4 to 6 Supermoons a year on average, the Supermoon on the 28th occurs when the Moon is almost at Perigee which makes it the largest full moon of the year and that’s why it’s special.

Dec 2010 Comparison of the apparent size of the average moon (left) and March 2011 Supermoon (right). Image Credit: Wikipedia

As you can see in the picture, there is only a slight increase in the size of the Moon from our point of view, and it’s best to see it at when the Moon is close to the horizon. It does have a very small impact on the tides, but because we have large oceans the effects are pretty much nullified.

The term Supermoon was first used over 30 years ago but has only recently come to the forefront of our lexicon. The term isn’t actually used in Astronomy as the Supermoon can also be called the Harvest Moon, but if it gets more people looking up and talking about Astronomy I’m all for it. The singer Sophie Hunger has even written a song about it. If you miss the Supermoon on the 28th, don’t worry as the next one where the Moon will be very close to the Earth is on the 14th of November of this year.

Originally posted as a TweetPerth article: Perth Supermoon Monday 28th of September