The other day someone mentioned the thirteen planets, and it gave me pause, since I thought there were less than when I was little, not more.
Oops. I didn’t realize all the dwarf planets had been named. Obviously I knew Pluto, and Eris sounded familiar, Ceres I thought was a large asteroid, and I didn’t remember Haumea or Makemake. I thought it was a good time of year to take a quick look at Ceres.
Ceres was the Roman goddess of agriculture, grain, fertility and motherhood. She’s essentially the Roman version of the Greek goddess Demeter. Linguists aren’t sure where the name Ceres comes from, one theory is that it shares a lost indo-European root with create, kernel, increase, corn, etc. We get the word cereal from her name.
She was credited with discovering wheat (spelt) and with yoking oxen for plowing. Her main festival was held in spring, but now fall seems the appropriate time to visit the myths. The Romans saw her as connected to the line between life and death. She had a personal connection to the dead once the Romans nabbed Persephone from the Greeks and named her Proserpina.
In 1801 a newly discovered planet was named after her. It was first discovered on January 1, observed two dozen times, lost, then finally independently confirmed on December 31rst. (Perhaps Janus would have been a better name…) It has fluctuated between asteroid and planet and now seems to be considered both a dwarf planet and an asteroid.
Ceres is the only dwarf planet in the inner solar system. It lies in the asteroid belt between Mars and Jupiter. Even at its brightest it is too dim to see with the naked eye except in the darkest, clearest skies. When he first saw it, its discoverer wasn’t sure if it was a comet or planet, but it seemed to be too stable for a comet.
Ceres is about 600 miles in diameter, about the size of Texas.
I wasn’t sure if the dwarf planet designation was all about size.
There seems to be a little more to it than that. Planet is a cultural and not a scientific designation, so the whole thing is sort of vague. The 2006 dwarf planet description is basically a spherical object in a more or less regular orbit around the sun that isn’t large enough for its gravity to have cleared its orbit of most other celestial bodies. (So too small to enlarge itself by eating all its neighbors.)
What’s cool is in March 2015 (scary how not far away that is) NASA’s Dawn mission will be studying the structure of Ceres and a nearby asteroid, Vesta, to see how they were formed. They think these small bodies have altered less in the past 4.6 billion years than the planets have, since Jupiter’s gravity both protects them and stopped them from forming a planet.
Photograph of Cerium from Theo Gray’s wonderful book on the elements.
The element cerium (58) was discovered in 1803, and named after the recently discovered planet.
It is the most common (and least expensive) of the rare earth elements. It’s nearly as common as copper, the rare earth elements are named less for their scarcity than for the trouble it takes to isolate them. Cerium is a soft silvery metal that can catch fire when it is struck. The whole piece won’t burn, but any bits knocked off burn as they’re made. So cerium is used in lighter flints and in special effects where lots of sparks are needed.
At high temperatures (65-80 degrees Celsius) it can ignite spontaneously in air. Its fumes are toxic and you can’t douse it with water since cerium will react with water ot product hydrogen gas. So as much fun as it sounds like to play with, it sounds like an element to avoid unless you have the training.
The Greeks sometimes call cerium dimitrio, after Demeter.
Okay, so it’s a dwarf planet and a rare earth element named after her second hand, but still not bad for a goddess mostly defunct for centuries!