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What Makes a Supermoon Super at Stardome?

Tuesday 15 November 2016, 5:25PM

By Beckie Wright

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Through the year we may notice the that the moon appears larger in the sky. Commonly labelled a ‘Supermoon’ this phenomenon will be visible again on 15 November as the closest full Moon since 1948. A Supermoon is the coincidence of a full moon occurring at the moon’s closest approach to earth. The moon’s orbit around earth is an ellipse, not a circle, so the moon’s distance from earth can vary from a distant apogee of 406,000km to a closer perigee of 357,000km. These distances also vary because the orbit of the moon is affected to some degree by the sun’s gravity.

 

A so-called “Supermoon” occurs when the full moon phase happens to coincide closely to the time when the moon is also at the perigee point - and therefore closest to earth. The moon passes through apogee and perigee each lunar cycle. The phases of the moon and the orbit aren’t directly linked, so occasionally a full moon will coincide with perigee, resulting in a Supermoon.

 

On 15th November, the date of the next full moon, we will have the chance to see the closest, largest and brightest full moon since 1948. From this close distance the full moon will appear about 14% bigger and 30% brighter than an apogee full moon. There won’t be a closer full moon until 2024.

 

Dr Grant Christie, Stardome’s Honorary Astronomer, says “watching a Supermoon rising in the early evening twilight is always a spectacle. If the sky is clear of clouds, it will be difficult to miss this astronomical wonder but for the best observing find a clear vantage point to view the eastern horizon. The rising moon will also look spectacular through binoculars.”

 

Being closer means the moon appears to be bigger and brighter. However, due to the way our brains process the view the apparent size of the moon is best appreciated as it is rising and close to the horizon. Our brain needs some visual clues like trees or buildings before the size difference is properly seen. On November 15th, the moon rises at 8.45pm.

 

The moon will be actually be closest to earth (356,509km) very early on November 15 at 12.23am. The exact time of the full moon phase occurs a little later at 2.52am, at which time the moon will appear high in the sky and noticeably brighter. The moon will also be close to the bright star Aldebaran in Taurus while passing through the Hyades star cluster.

 

Stardome and its team have been sharing a love of space from its premises in Auckland’s One Tree Hill Domain since 1967. A place of exploration, research and sharing of knowledge the Stardome 360-degree planetarium Night Sky shows take viewers into outer space to get a closer view of stars, planets and nebulae. Stardome night planetarium shows also include telescope viewings (weather permitting). School children across Auckland enjoy daytime visits for school trips. For more information go to http://www.stardome.org.nz .