Thursday, August 24, 2006

A Planet By Any Other Name...

Today at the International Astronomical Union (IAU) General Assembly in Prague, astronomers decided that the Solar System has eight planets. Pluto is now a "dwarf planet." To be a planet, the assembly ruled, a world must meet three criteria:

(1) It must have enough mass and gravity to gather itself into a ball.

(2) It must orbit the sun.

(3) It must reign supreme in its own orbit, having "cleared the neighborhood" of other competing bodies.

So, e.g., mighty Jupiter, which circles the sun supreme in its own orbit, is a planet--no adjective required. Pluto, on the other hand, shares the outer solar system with thousands of Pluto-like objects. Because it has not "cleared its own neighborhood," it is a dwarf planet.

This is huge! Not only do all school science textbooks need to be rewritten, but it's the first time we have a global concensus on what make a planet. Stripping Pluto of it's "planet" status might seems like a big deal. But consider that we've only known about Pluto for 76 years (discovered in 1930). On the astronmical clock, that's less than a tick of the second hand.

2 comments:

Nilda said...

DUDE! You're like 6 years late! I knew Pluto wasn't a planet back in the day (summer '00 to be exact). Then again, it was probably because the Museum of Natural History/Rose Planetarium didn't include Pluto as a planet (very controversial stuff back then). Oh yeah, and I was working as a museum/planetarium tour guide... ha ha
Yeah, I know, I'm a nerd. =)~

Anonymous said...

Glad they finlly made a decision. I was on pins and needles for awhile there. It is! It isnt! It is! It isnt! Now, the most important question: who is going to break it to Jason and Ian????