More on some of the planets / dwarf planets / Plutoids / whatever out there in the Solar System near the Kuiper Belt

Tuesday, July 29, 2008

Ceres videt del Hubble Spacie-Telescop. Li constraste ha esset augmentat por revelar detallies del superficie.

I wrote a bit in June about some of the large bodies out near the Kuiper Belt that reach some thousands of kilometres in diameter but many of which don't even have names and remain mostly unknown to people that don't read about space everyday and have grown up on a simple view of a Solar System with nine planet. today has a bit about what to call these bodies, which is an intensely boring debate aside from the fact that a mission is probably more likely to have its funding approved if it's visiting a planet compared to a dwarf planet, even if it's the same body (i.e. if Pluto had been demoted to dwarf planet status back in the 1980s or so it's possible that New Horizons might never have been approved. Speculation on my part of course).

What's interesting about the article though is that it has a bit of info on most of these bodies, and since they're quite newly discovered it's good to read over again just in case your memory has become a bit foggy on one or more of them:
Dwarf planets and plutoids

In addition to Pluto, the dwarf planet population of the solar system currently includes Ceres, Eris, Makemake and another world currently dubbed 2003 EL61.

* Named after a Roman goddess of grain, Ceres was discovered in 1801 and was initially considered a planet until astronomers began to spot other asteroids circling the sun in nearby orbits. While a dwarf planet, the round, potentially water-ice bearing space rock does not qualify as a plutoid because it circles the sun well inside the orbit of Neptune.

* Unlike Ceres, Eris (ee'-ris) does qualify as both dwarf planet and plutoid. It is about 70 miles (112 km) wider than Pluto, orbits the sun from about 9 billion miles (14 billion km) away and is one of the brightest objects in the Kuiper Belt.

The object's moon, Dysnomia, is named after the daughter of Eris, who served as the spirit of lawlessness.

* Makemake (pronounced MAH-keh MAH-keh) is the newest dwarf planet and plutoid to gain a name. The tiny red-hued world is though to be covered with a layer of frozen methane and is smaller and dimmer than Pluto.

Waiting in the wings

The list doesn't stop there. There are still more objects waiting for wings for either their own classification or official name:

* While it doesn't have an official name yet, 2003 EL61 is an object also discovered by Brown's team and an independent group led by Jose-Luis Ortiz of the Sierra Nevada Observatory in Spain. It has its own moon, is about 32 percent as massive as Pluto and about 70 percent that of Pluto's 1,413-mile (2,274-km) diameter. But it's also shaped like an ice-covered football, making it one weird, distant space cookie.

* Then there's Sedna (sed'nah), an object about three-fourths the size of Pluto that is so far out from the sun it takes about 10,500 years to make a single orbit. Sedna is about 1,100 miles (1,770 km) wide and circles the sun on an extremely eccentric orbit that ranges between 8 billion miles (12.9 billion km) and 84 billion miles (135 billion km). Brown's team led the discovery of that object in 2004 and named it after the Inuit goddess of the sea. Sedna does not qualify as a plutoid because of what some astronomers see as a quirky threshold for how much sunlight it reflects: Sedna is too dim.

* Quaoar (KWAH-o-ar), another find by Brown and co-discoverer Chad Trujillo, is 780 miles (1,250 km) wide, half the size of Pluto and takes 288 years to orbit the sun from about 4 billion miles (6.5 billion km) away. It was named after the creation force of the Tongva tribe of the Los Angeles basin.

* Brown's team also found Orcus (awr-kuhs), or 2004 DW, an object about 994 miles (1,600 km). It is nearly 47 AU from the Sun, was discovered in 2004, and is so Pluto-like in its attributes that astronomers named it after the Etruscan counterpart of the Roman underworld deity.

* And there's still Varuna, or KBO 20000 Varuna, an icy object 40 percent as large as Pluto and 560 miles (900 km) wide that was first spotted in 2000 by astronomers using the Spacewatch telescope in Arizona.


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