Mātāmua's career in astronomy began in 1995 when as a university undergraduate he asked his grandfather Jim Moses about Matariki, the Māori New Year heralded by the rising of the Pleiades at dawn. Timi Rāwiri produced from a cupboard a 400-page manuscript written in Te Reo Māori. The manuscript had been written over many years in the 19th century by Timi Rāwiri’s grandfather Rāwiri Te Kōkau and father Te Kōkau Himiona Te Pikikōtuku, who was a tohunga of Tūhoe and Ngāti Pikiao. It was an astronomical record containing the names of 1000 stars and 103 constellations, as well as instructions for setting up a traditional house of astronomical learning or whare kōkōrangi. Timi Rāwiri told Mātāmua to share the knowledge it contained: "Knowledge hidden, he said, wasn’t knowledge at all." Mātāmua has since written widely on Matariki, identifying the nine stars that Māori perceived in the cluster, in contrast to the seven associated with the Pleiades in European tradition. His research has revealed that some of the Māori astronomical lore recorded by ethnographer Elsdon Best is slated or incorrectly translated. The translation of the word Matariki to mean "little eyes" is one such error; the name in fact is derived from Ngā mata o te ariki o Tāwhirimātea, the eyes of Tāwhirimātea, god of the winds. He has pointed out that the Matariki is often celebrated too early, when it is still below the horizon, as a result of a mismatch between the Gregoriansolar calendar and the Māori lunar/stellar calendar, where the dates for Matariki change every year. Mātāmua has been critical of the way Western scientific astronomy has ignored or belittled traditional Māori knowledge. He intends to establish a Māori observatory, based on a traditional observatory but incorporating modern knowledge and technology.
Science communication
Mātāmua regularly posts videos and podcasts on Māori astronomy in both English and Te Reo Māori, and has a large social media following: his Living by the Stars Facebook posts have over 20,000 followers, and his web series accumulated over one million views in four months. In 2019 he gave 21 presentations to a total audience of over 10,000 in New Zealand and Australia. On 30 June 2020 Mātāmua was awarded the 2019 Prime Minister's Science Communication Prize for his work writing and speaking about Māori astronomy and Matariki. He is the first Māori scientist to be awarded the prize.
