Tuesday, July 15, 2008

Plutoid on the Makemake

The International Astronomical Union (IAU) has named its first plutoid. The Kuiper belt object formerly known as 2005 FY9 has been rechristened “Makemake” and classified as both a dwarf planet and plutoid. Makemake is fifty times further away from the Sun than we are and its orbital period is 310 Earth years. It has an apparent magnitude of about 16.7, which makes it bright enough to be visible using high-end amateur telescopes. The plutoid is named for a Polynesian God and is pronounced “mahki-mahki”.

The IAU announced the new category of plutoid last month at a meeting of its executive committee in Oslo. The category covers what it calls “transneptunian dwarf planets similar to Pluto”. Plutoids orbit the Sun at a distance generally greater than that of Neptune and have a minimum defined magnitude of brightness. Makemake now joins the two other two known and named plutoids Eris and Pluto itself. The IAU fully expects that more plutoids will be named as science progresses and new discoveries are made.

The plutoid Makemake was discovered in Easter 2005 by astronomers at California’s Palomar Observatory. According to Mike Brown, who led the Caltech team that found the object, they nicknamed it “Easterbunny”. The IAU preferred to give it the interim name of 2005 FY9 but after six months of lobbying they accepted a proposal from Brown's team to rename it to Makemake. Brown says the planet is two thirds the size of Pluto and is the brightest object in the Kuiper Belt after Pluto itself. He says the surface is “covered with large amounts of almost pure methane ice, which is scientifically fascinating, but really not easily relatable to terrestrial mythology.”

Brown is also the discoverer of Eris which ultimately led to Pluto’s demotion from the major planets. The existence of Eris drastically heated up the debate over how to define a planet with over a dozen other candidates vying for acceptance. In 2006, it seemed as if the IAU was going down the path of greatly expanding the list of solar system planets but instead decided there were would only be eight. Pluto and Eris (then called 2003 UB313) joined a new category called dwarf planets which also included Ceres which lies in the asteroid belt between Mars and Jupiter. However because of its location, Ceres can not be considered a plutoid.

In keeping with the original “Easterbunny” nickname for the newest plutoid, Makemake is named for the supreme god of Rapa Nui (Chile's Easter Island). Makemake was the creator of the first humans and the patron of the Tangata bird cult. He 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. With his divine power he makes the plants and animals grow. Some believe that the huge statues on the island are connected to his cult. Easter Island was first visited by Europeans on Easter Sunday 1722, exactly 283 years before the plutoid was discovered.

1 comment:

Laurel Kornfeld said...

Only four percent of the IAU decided there would be only eight planets, and this was immediately contested by an equal number of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA's New Horizons. Only those in the room at the General Assembly could vote, and most who voted are not planetary scientists. Many planetary scientists do not belong to the IAU and therefore had no say in this whatsovever. One of the signatories of Stern's petition was Dr. David Rabinowitz, a member of Mike Brown's team that discovered Eris, MakeMake, and EL61.
This debate is far from over. The IAU determination that dwarf planets are not planets at all makes no linguistic sense and must be reversed. Dwarf planets are simply one subcategory of the broader term planet, as are terrestrial planets, gas giants, ice giants, super Earths, hot Jupiters, etc.

We have 12 planets in our solar system: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, MakeMake, and Eris. This view is shared by many astronomers, who believe that if an object is in hydrostatic equilibrium and orbits a star, it is a planet. Find out more about the latest development in this controversy, the Great Planet Debate, at http://gpd.jhuapl.edu/index.php