This is what an artist thinks the dwarf planet Haumea and its two moons look like. Notice how Haumea's fast spin has stretched it into an oval (not spherical) shape. The diameter of Haumea at its equator is about twice as far as the distance between its North Pole and its South Pole.
Click on image for full size
Images courtesy of NASA, ESA, and A. Feild (STScI).
The Poles of the Dwarf Planets
As of June 2009 there are officially five dwarf planets. They are Pluto, Ceres, Eris, Haumea and Makemake.
Pluto, Eris, Haumea and Makemake orbit far from the Sun. That makes them very, very cold places. They are even colder than the North and South Poles on Earth. The interiors of planets like Earth and Mars are made of rock. The interiors of Pluto, Eris, Haumea and Makemake are made of ice instead. Their surfaces are also covered with ice.
It is so cold on these dwarf planets that even the "air" freezes. The ice on the surface isn't just normal ice made of water. Pluto's surface has ice made of nitrogen and smaller amounts of methane, carbon monoxide, and maybe ethane ices. The surface of Makemake is coated with methane, ethane, and maybe nitrogen ices. Astronomers found methane ice on the surface of Eris. On Earth at "normal" temperatures, nitrogen, methane, carbon monoxide, and ethane are all gases. On these cold dwarf planets, the gases freeze and turn into solid ice! Haumea is a bit different. It is covered with water ice. Its surface is as bright as snow.
Ceres is the other dwarf planet. It orbits much closer to the Sun in the main asteroid belt between Mars and Jupiter. Its surface is rocky. However, some scientists think that inside it might be partly ice. They think that about one quarter of Ceres might be ice (the rest is rock).
What are the poles of the dwarf planets like? We don't know much, since most of them are so far away and hard to see even with big telescopes. We can't see Makemake, Haumea and Eris well enough to tell whether they are tilted or not. Pluto is tilted a lot, about 120°. It is basically lying down, with its poles on its sides. Ceres is only tilted 3°. Its poles are almost perfectly straight up and down.
Haumea spins really fast. A "day" there only lasts about 4 hours. The fast spin makes Haumea bulge out at the equator and squash down at the poles. The diameter of Haumea at its equator is as much as 2,000 km. However, from Haumea's North Pole to its South Pole its diameter is only about 1,000 km. That is only half as far!
Shop Windows to the Universe Science Store!
The Fall 2009 issue of The Earth Scientist
, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our online store
You might also be interested in:
In 2006 the International Astronomical Union (IAU) approved a new classification scheme for planets and smaller objects in our Solar System. Their scheme includes three classes of objects: "small solar...more
Pluto is a frigid ball of ice and rock that orbits far from the Sun on the frozen fringes of our Solar System. Considered a planet, though a rather odd one, from its discovery in 1930 until 2006, it was...more
Eris is a dwarf planet in our Solar System. Eris was one of the first three objects classified as a dwarf planet, along with Pluto and Ceres. Eris was first spotted in January 2005. Eris is a large sphere...more
Makemake is a dwarf planet in our Solar System. Makemake was discovered in March 2005 by a team of astronomers led by Mike Brown. Makemake officially became a dwarf planet in July 2008. There were three...more
The outer edge of our Solar System is not empty. There are many huge spheres of rock and ice out near Pluto's orbit and beyond. Astronomers have a name for everything further out than the planet Neptune....more
Frozen water is found in many different places on Earth. Snow blankets the ground at mid and high latitudes during winter. Sea ice and icebergs float in the chilly waters of polar oceans. Ice shelves fringe...more
There is more nitrogen gas in the air than any other kind of gas. About 4/5ths of Earth's atmosphere is nitrogen gas! A molecule of nitrogen gas is made up of two nitrogen atoms. There are other molecules...more