Easter Sunday for 2012 is happening at the end of this week – on April 8th. The date of Easter is determined from astronomical events — it occurs the Sunday after the full moon after the spring equinox. At least – it should! In fact the spring equinox, which can occur on either March 20th or March 21st, is taken as only occurring on March 21, and the full moon cycle is not based on the actual full moon, but on an “ecclesiastical” moon that is full on the 14th day after a new crescent moon. This will next make a difference in the year 2019 when Easter Sunday will fall on April 21st, even though there is an actual full moon on March 21st. As a result the “Computus” – the effort to work out when Easter occurs, requires knowledge of mathematics, the length of the solar year and the lunar month. An added complication is the difference between the eastern and western Christian churches – where different calendars entirely are used. The World Council of Churches, at a meeting in 1997, recommended to its members (who include many of the Orthodox denominations as well as western churches) that astronomical data be used to calculate Easter – the recommendation has not yet been adopted. Personally, I tend to look in my diary.
If you are ready to celebrate Easter, you can do so in the knowledge that the Easter Bunny is real! It is the name first given (and used for almost three years) to the dwarf planet Makemake. This remote Plutoid was discovered just after Easter in 2005. Mike Brown from the California Institute of Technology (the same Mike Brown that discovered Eris and is the author of the book “How I Killed Pluto and Why it had it Coming”) proposed the name. He originally considered a name based on the Delphic oracles, then on the goddess Oestre or another Easter or equinox related name, thirdly from one of the Rabbit gods, rejecting “Manabozho” an Algonquin rabbit trickster god, because the “Bozo” part at the end didn’t appeal to him. He finally settled on a god in the mythology of the South Pacific island of Rapa Nui. If you are not familiar with Rapa Nui, it is also known as Easter Island.
The name chosen is, according to the citation from the International Astronomical Union,
Makemake: the creator of humanity and the god of fertility in the mythology of the South Pacific island of Rapa Nui. He was the chief god of the Tangata manu bird-man cult and was worshipped in the form of sea birds, which were his incarnation. His material symbol, a man with a bird’s head, can be found carved in petroglyphs on the island.
Makemake is covered almost entirely in methane ice, making it the brightest object in the Kuiper belt apart from Pluto. It is just bright enough that it could have been discovered by Clyde Tombaugh, the man who spotted Pluto – except when Tombaugh was hunting for planets, Makemake was against a rich star field near the band of the Milky Way – so would have been almost impossible to distinguish. On Easter Day, it will be rising at sunset, in the constellation of Coma Berenices.
This episode of “What is the Stars?” was first broadcast on April 2, 2012. Listen live each week on Mondays and Fridays at 22:45 on RTÉ’s lyricfm 
