Why this week's supermoon was the biggest and brightest of 2019

It was the largest of three supermoons that will dominate the sky until April this year.

Silhouette aircraft fly in front of supermoon Source: Getty Images

This week saw the biggest and brightest moon of the year lighting up the sky in Australia and around the world, with stargazers taking to social media to post snaps of the 'supermoon'.

A supermoon occurs when the moon is both full and near the closest point to earth in its elliptic (oval shaped) orbit. At the closest point, known as ‘perigee’, the moon is just 356,000km from earth.

"The great thing about something like this is everyone can see it all across the earth," Dr Brad Tucker from the ANU Research School of Astronomy and Astrophysics told SBS News of Tuesday night's event.  

A supermoon is 14 per cent bigger and 30 per cent brighter than a 'micromoon' - a full moon at its furthest point in orbit around Earth. It is around 7 per cent larger than a regular full moon.

Tuesday's moon was its fullest at 2:53am, but according to Dr Tucker, the best time to catch a supermoon is when it is rising. 

“The moon appears to be a bit bigger and brighter on the horizon. When the moon is rising you have things on the ground to compare its size to. The shape of the earth also creates a distortion so the moon naturally appears a bit bigger on the horizon,” he explains.

2019: A big year for the moon

This is not the first supermoon this year.

On 31 January, for the first time in 30 years, a supermoon coincided with two other lunar events; a total lunar eclipse and a blue moon.

Another supermoon is expected next month, just hours after the equinox on 20 March.

But Tuesday’s supermoon was the biggest of the three that will occur because February was when the moon was technically closest to earth.

"This month the moon is at its closest in perigee," Dr Tucker explained.

"Even a difference of a couple of thousand of kilometres will slightly change its size and brightness from earth."

According to Dr Tucker, it is not uncommon to have a number of supermoons in the same period. 

"The moon orbits the earth roughly every 28 and a half days. The orbit of the moon is not perfect. It varies by about 50,000 km," he said. 

“If it so happens that the moon is on that cycle of its loop where it is hitting that point of being closer to the earth, you can get a couple in a row or in a series."

In the northern hemisphere it is known as a 'super snow moon'.

'Snow moon' is a term coined by native Americans for February, a month of heavy snowfall in North America and Europe.