Haumea: Rugby Ball Planet

Dwarf planet Haumea is one of the most bizarre small bodies of the outer Solar System. It has an oddly recent surface. Even just who discovered it is controversial. It looks kind of funny too.

The 2011 Rugby World Cup is taking place in New Zealand at the moment and you are probably thinking how this could relate to Space! Well let me tell you the link…. there is a dwarf planet out there in our Solar System which could claim to have a similarity to rugby. That dwarf planet is Haumea which is in the shape of an ellipsoid (oval like a rugby ball). I know it’s a weak claim to fame, but let’s look at this strange object.

 

Image of Haumea Real

Haumea seen from the Keck Observatory (Image credit: via Wikipedia.org)

 

Haumea (pronounced how-MAY-ah) is the fifth dwarf planet coming after Pluto, Eris, Ceres and Makemake. A dwarf planet according to the International Astronomical Union (IAU) is “a celestial body orbiting the Sun that is massive enough to be spherical as a result of its own gravity but has not cleared its neighbouring region of planetesimals and is not a satellite.” Basically dwarf planets are not deemed big enough to be called planets. Haumea is also described as a Plutoid which is a term used to describe any dwarf planets which are beyond the orbit of the giant gas planet Neptune.

This icy world has a day only four hours long because it is spinning very fast, in fact no other object in the Solar System spins as fast as Haumea. It is the velocity of the spin that has resulted in this icy body being stretched into a 3D ellipse. Found in the Kuiper Belt, it takes 285 years to just orbit the Sun once! So imagine if you lived here, you would never have a birthday! But will we ever land a spacecraft there? That is the big question, as it is approximately 50 AU from the Sun. That means it is approximately 50 times further away from the Sun than what the Earth is….. I think it would be pretty chilly there, if you are planning a visit remember to wrap up warm!

Named after the Hawaiian goddess of childbirth Haumea had quite a controversial discovery. There are two teams of people who lay claim to finding this distant world. Mike Brown and his team at Caltech discovered Haumea in December 2004, and nicknaming it “Santa”, they had the intension of making an announcement of the discovery at a conference in September 2005. At around the same time, José Luis Ortiz Moreno and his team at the Instituto de Astrofísica de Andalucía at Sierra Nevada Observatory in Spain came across Haumea on images taken in March 2003 and emailed the Minor Planet Center (MPC) with their discovery in July 2005 piping the Americans to the post. Mike Brown however became suspicious of the Spanish team when he discovered that his observation logs were accessed from the Spanish observatory the day before the discovery announcement. Ortiz admitted he had accessed the Caltech observation logs but did not agree that he had done anything wrong as he was only verifying that they had discovered a new object in the Kuiper belt.

The International Astronomical Union (IAU) protocol is that discovery credit for a minor planet goes to whoever submits a report to the MPC first with enough positional data for a determination of its orbit, and that the discoverer has priority in choosing a name. However when the IAU announced on 17 September 2008 that Haumea had been accepted as a dwarf planet, they did not mention who the discoverer was. The location of discovery was instead listed as the Sierra Nevada Observatory, home to the Spanish team. But matters became interesting when the IAU announced the name of this new object, Haumea, as this was the Caltech name proposal (Ortiz’s team had proposed “Ataecina”, the ancient Iberian goddess of spring.) The Ortiz team objected to the name Haumea, suggesting that if the name Ataecina was not accepted the IAU could at least have chosen a third name which would have been neutral favouring neither party. There were rumours circulating that “Dagda”, the name of a god from Irish mythology, was indeed proposed but was not used in the end. But the saga over Haumea still rumbles on to this day!

An artist's impression of the dwarf planet, however the moons in real life are much more distant! (Image credit: via Wikipedia.org)

 

Of little doubt is who discovered the moons orbiting around Haumea. It has two satellites called Hi’iaka and Namaka (these are named after the Hawaiian goddess’s children). These moons were both discovered by Brown’s team in 2005 using the W.M. Keck Observatory. Hi’iaka (pronounced HEE-‘ee-AH-kah) is the larger of the two moons and was nicknamed Rudolph by Brown’s team. The smaller Namaka (pronounced nah-MAH-kah) had been nicknamed Blitzen. These moons are too faint to detect with telescopes smaller than about 2 metres in aperture, however Haumea itself has a visual magnitude of 17.5, the third brightest object in the Kuiper belt after Pluto and Makemake, and can be observed with a large amateur telescope.

Recently there has been some revealing news about this distant small world. It has been found that Haumea and its moons shine brightly in the darkness of space. This is because they are covered with crystallised water-icewhicappar to have been deposited recently (say in the past 100 million years). A recent international study suggests that there is a frozen outer layer with rock making up the internal structure.

Another mystery is the presence of a dark reddish spot on the dwarf planets surface which stands out and is very distinctive against the white surface. This spot was co-discovered by Pedro Lacerda, an astronomer at Queen’s University in Belfast and he believes that “this area could be a richer source of crystalline water-ice than the rest of the surface”. Lacerda also is of the opinion that there could be the presence of minerals or organic matter causing the colouration.

What this red spot would look like against the white surface. (Image credit: SINC/José Antonio Peñas)

 

So, Haumea has had quite an interesting discovery but there is so much more to learn about this icy body which will no doubt keep us entertained in the coming years!

Image of Sinead McNicholl

Sinead McNicholl, Education Support Officer (Image credit: Armagh Planetarium)

(Article by Sinead McNicholl)