Best way to see rare blue supermoon for last time until 2029

A rare blue supermoon, which won’t occur again until 2029, will light up the sky this week. Here’s what you need to know.

Aussies will get the chance to look up at the sky this week and gaze upon a rare blue supermoon for the last time in six years.

The blue supermoon, which will be visible on Wednesday and Thursday night, won’t occur again until 2029, according to Weatherzone.

Here’s everything you need to know about the phenomenon.

What is a supermoon?

A supermoon occurs three to four times a calendar year when a full moon appears at the same time the moon is closest to the Earth.

“The moon is orbiting around the Earth and that orbit isn’t a perfect circle, so there are times of the orbit where the moon is closer and it’s further away,” Kovi Rose a astrophysics PhD candidate from the University of Sydney told news.com.au.

“When it’s at its closest point … around 360,000km away, and there’s a full moon at the same time, we get a supermoon.”

A supermoon in Sydney in September 2015. Picture: AAP Image/Dan Himbrechts

What is a blue supermoon?

Despite its name, a blue supermoon isn’t actually blue in colour. Instead, the name comes from the age-old expression ‘once in a blue moon’ as it’s a rare sight, occurring only once every two or three years.

“The moon’s orbit is 29 and a half days, so every so often, you will have a full moon more than once a month. And when that happens, that second moon is called a blue moon,” said Rose.

This week, we will not only be able to witness a blue moon, but a supermoon at the same time – a phenomenon that only occurs every 10 years on average.

A supermoon rising over the Perth Hills in Western Australia in November 2016. Picture: AAP Image/Richard Wainwright

What time will the blue supermoon be visible and what is the best way to see it?

This week’s blue supermoon, which will be just 357,344km away from Earth, will be visible in Australia on August 30 and August 31.

Appearing larger in size than usual, the moon is expected to peak at 11.36am AEST on August 31, when the sun has risen.

However, Rose suggested the best time to see the moon is after sunset on Wednesday or Thursday night.

“The moon rise is starting in the late afternoon so I recommend people get out there just after sunset and look to the southeast for a good view.”

Professor Richard De Grijs from Macquarie University said Wednesday would be most “ideal”.

“Look up at dusk, as the moon is rising. The optical illusion of a supermoon is most impressive when the Moon is near the horizon, when optical distortions owing to the Earth’s atmosphere make it look even bigger. While Wednesday night might be ideal, Thursday night would still be quite impressive.”