Gerald McCormack, Natural Heritage Trust
First published CI News 14 November 2020, updated
Pleiades detail and its passage across the Southern Hemisphere sky
The Matariki or Pleiades is a cluster of several hundred stars. To the naked-eye the nine brightest stars form a distinctive, eye-catching group with a glowing background, a bit larger than a Full Moon. People with dark-adapted eyes and excellent distance vision can see eight or nine stars, while most people report five or six.
Traditionally, some Polynesians used the dawn rising of Matariki as the signal marking the next lunar years, while others used the dusk rising as the signal.
The illustration shows the Pleiades as seen through a telescope, re-orientated to the way we see it from the Southern Hemisphere with the naked-eye. Below we show the main stars enclosed in an outline of a stingray swimming from right-to-left (East-to-West) across the sky as seen by eye from the Southern Hemisphere. This movement is only an apparent movement because it is caused by the rotation of the earth, not by the movement of Matariki.
Lunar months and lunar years
In ancient times, people used a Lunar-month calendar of 30 named-nights to represent the lunar cycle of 29.5 Solar days. On every second month they had to discard the 30th named-night to start the next lunar-month a day earlier to keep the calendar synchronised with the actual lunar cycle throughout the year. In the Cook Islands the Lunar-month Calendar is called the arāpō, literally the “night path”.
People also required an annual or seasonal calendar to predict the arrival of the seasonal activities associated with fishing and planting. The seasons are determined by the Sun which has a year of 365 days. Thus, people using a repeating Lunar-month calendar would have found that 12 Lunar months (354 days) was too short, and 13 months (384 days) was too long. Every year they had to make an adjustment to keep it synchronised with the actual Solar cycle. The simplest solution was to have 13 named Lunar-months and periodically discard the 13th month.
The two Matariki events each year
Twice-a-year the apparent movement of the Sun interacts in a distinctive way with the apparent movement of Matariki. In June, Matariki is seen for a short time before sunrise and this event was used by most Māori in Aotearoa to indicate that the next New Moon would be the first night (Whiro) of the first Lunar-month (Pipiri) of the New Year.
The second distinctive event is in November when Matariki rises in the East soon after the sun sets in the West. This event was used in the Southern Cook Islands and French Polynesia to indicate that the next New Moon would be the first night (Tīroe) of the first Lunar-month (Ākau) of the New Year.
The June event is more precise because Matariki is seen for only a short time before it is burnt out by the rising sun. The November event is more complex because it requires you to decide on which night you see Matariki as near to the horizon as possible and as soon after sunset as possible.
November event in detail
In 2019 in the evening of the 14th November I saw the glow of Matariki near the horizon at 8.00pm. It was three finger-widths (6°) above the horizon, which is the lowest elevation at which one can theoretically see its six brightest stars. I took this observation to indicate that the next New Moon would be the first Lunar-month of the New Year. In that case, the New Moon of the 26th started the first arāpō month of Ākau.
The lunar calendar starting 14 Nov 2020
In 2019 determining the start of the New Year was very straightforward because even if I had not seen Matariki rise until the 15th or even 16th, the next New Moon was well in the future.
The evening rising of Matariki is a regular astronomical event and it will be visible to the naked eye at the same time (7.50 to 8.00pm) on the same date (14th November) on our Gregorian Solar-calendar.
In 2020 there was a rare coincidence with both the dusk rising of Matariki and the New Moon occurring together. Nobody had to debate whether early Cook Islanders celebrated the New Year on the rising of Matariki or on the following New Moon. They were on the same night.
Where to look
On the 14th November every yeaar you can see the first rising of the Matariki in the evening sky. If you are in a location where you can see the Sun rise, which is a little south of East, in the evening you should be able to see the Matariki rising a little north of East (at 60° true, or 75° magnetic). My favourite observation post is on the seaward end of the field opposite Takitumu School. I arrive about 7.30 to give my eyes time to dark-adapt and get orientated on the following Star Map.
Star Map showing Matariki at 7.45pm on the 14th Nov.
By 7.50pm, the start of the Astronomer’s Twilight, you can see a few stars well above the horizon, and these are shown on the Star Map.
Look for the four main Andromeda stars forming a line upward to the left, and a little distance to the south the two bright stars of Aries, the Ram. And further southward, the two bright stars of Cetus, the Sea Monster. When you have these stars located look downward to the right (south) of the Aries stars to hunt for Matariki as it rises above the horizon and becomes increasingly visible.
How high above the horizon? If you point to the horizon with your arm straight and then turn your finger tips to point across your field-of-view, each finger width is about 2° of arc. At 7.50pm on the 14th, Matariki will be up 2-fingers (4°) but extremely difficult to see. Ten minutes later at 8pm it will be up 3-fingers (6°) and visible to those with dark-adapted eyes and excellent distance vision. As it continues to rise, it becomes brighter and everyone will soon see it.
Of course, today we have star maps on our phones, binoculars and zooming cameras to make it all so easy. I recommend you leave these gadgets at home and experience the event as did people in ancient times.
On the 15th November, at the same times, Matariki will be half-a-finger (1°) higher and easier to see. On the 16th Matariki will be higher and easier to see at 8pm.
Citation
McCormack, Gerald (2021) Matariki Dusk Rising 14th November. https://cinature.org/2021/02/10/matariki-dusk-rising-14th-november/
