The Tupas -Astronomical Observatories

In Polynesian cultures, the celestial dome had a very high significance.  From the interpretation of the stars, they developed cosmological songs which explained the creation of the Universe and the origins of man.  The knowledge acquired on the movement of the stars and the planets made it possible for them to become the great navigators who settled the entire Pacific Ocean”, states Edmundo Edwards, the researcher who has been living for more than 50 years on Rapa Nui, dedicating himself to the conservation of the cultural and archaeological heritage of the people of Oceanía.

Edwards explores the role of the skies in Polynesian cosmology through his work in archaeoastronomy, a new field of study which combines physical sciences with social sciences to explain how ancient cultures interpreted celestial phenomena.  As he relates, in Polynesian cosmology, some stars were placed in the sky by the gods to guide men on their way, while others represented the ancestors who were observing them from on high.  This explains that several names for stars include the word mata, which means “eye”.

In his as-yet-unpublished book in Spanish, named “When the Universe was an Island”, written with his daughter Alexandra, Edwards describes how astronomical knowledge evolved over the centuries of observation, being transmitted from generation to generation among an elite group which became specialized in observing the stars, interpreting the movements in the sky and establishing with great exactness the cycles of activities and rituals related with fishing and farming.

Astronomical observations on Rapa Nui were done by the Tumu Ivi Atua Mo Te Manu, also known as Tohunga by some Polynesians.  These were astronomer-priests who belonged to the highest levels of the socio-political hierarchy, since their knowledge was fundamental for the development of all productive activites and even survival.  These specialized wise men lived and worked in cylindrical stone towers called Tupa, which were built in specific geographic points on Rapa Nui from where they could most favorably observe astronomical events, such as the relative position of planets, the rising or setting of certain stars and/or constellations during different periods of the year and they could measure the phases of the moon.

The Tohunga, or observers of the stars, passed on this knowledge to their students who lived in caves near the Tupa.  According to Edwards, one of those caves is located behind the present-day Catholic Cemetery. “In that place you will find a small cave called Ana Ui Hetu’u or ‘Cave where Stars are Observed’.  There, according to folklore, the astronomer-priests held a school for instruction in this art.”

Rapa Nui today has 27 Tupa – as documented by Father Sebastian Englert in 1948.  Nine of them are in ruins.  Among those which are still standing, the majority are shaped like a cylindrical tower and only two have an unusual  rectangular form. In a paper published in the ‘Journal for the History of Astronomy’ with the Spanish astronomer Juan Antonio Belmonte, they established that almost all of the Tupa have a specific astronomical orientation. The tower which was rebuilt alongside the cemetery is the only one which doesn’t have one.  Most of the Tupa are located on the far eastern edge of the Island, at the foot of the Poike peninsula. It was determined that this old volcano and the surrounding plains of Ra’ai, Tongariki and Hanga Ho’onu were the most propicious places for observing the stars. These Tupa were accompanied by the placement of smaller conical stone markers, called Pipi Horeko, which complemented the observation of important astronomical events.

According to Edwards, the Tupa were used by those in charge of star watching to observe the skies from the top of the tower and announce their predictions.  These could be good or bad, depending on the position of different stars and the presence or absence of Matamea (the planet Mars) which, throughout Polynesia, was considered an evil influence.  Calling on their specialized knowledge, the Tumu Ivi Atua Mo Te Manu or Tohunga were able to create lunar calendars for planting and harvesting of many varieties of plants, for anticipating the arrival of the migratory fish, tortoises and sea birds, for determining the auspicious dates to celebrate festivals and make offerings to the gods and for placing prohibitions (Rahui) on the use of resources and the duration of these.

Edwards and Belmonte determined that the ceremonial centers, rather than being oriented to solar events, were more focused on the stars, the most important of which were Matariki (The Pleiades), Tautoru (Orion’s Belt) and Rei o Tanga o Ko Pu Tui (Antares).  This last one is the zenith star of Rapa Nui and was most probably used by navigators to find the exact position of the Island.  Edwards based their conclusion on the fact that the concept of equinox does not exist in Polynesia.  “All those structures which have a fairly precise orientation to the rising or the setting of the sun at the equinox are really oriented to Tautoru, Orion’s Belt, which has a difference of only 2 degrees with the solar phenomenon.  It is also probable that the alignments to the winter solstice on Rapa Nui are actually oriented to the rising or setting of The Pleiades (Matariki).  This coincides with the beginning of a period of abundance of natural resources and, consequently, the appearance and disappearance of this constellation in the nighttime skies determined important dates for annual rituals, such as the New Year, the commencement of the ceremonies related to the Bird-Man Cult and the opening of the fishing season on the high seas.”

The Pleiades were observed from the eastern coast of the Poike peninsula, the only place on the entire Island were both the rising and setting of this constellation can be observed in the sea.  There is a rock which has cupules carved representing the constellation, which was named “The Map of the Stars” by the ethnographer Katherine Routlege, who noted it as an instrument for astronomical use.  Such was its importance that, according to her informant Santiago Pakarati, “on the night proir to the appearance of Matariki, the priests spent the night in one of the caves on the eastern side of Maunga Vai a Heva and held commemorations for Teva, a powerful priest who once lived there with his students.”