NOVA scienceNOW : 18 – 10th planet


ROBERT KRULWICH: Big news in the neighborhood.
This is our solar system. And a couple of years ago, almost everybody would have told
you that orbiting our Sun you would find one, two, three, four, five, six, seven, eight,
nine planets; but, as of this past year, we’ve got a tenth. Or do we? MIKE BROWN: This will absolutely rewrite the
“History of Astronomy” textbooks. There is now a tenth planet out there. ROBERT KRULWICH: When Mike Brown and his team
at Caltech announced they’d discovered what looked like a new planet, they did not give
it a name. Names are bestowed by an international commission of scientists. So, in the meantime,
since they were looking at this little bright light for more than year, they gave it a nickname. MIKE BROWN: It had no name at all, so we had
to call it something, so when we talked to each other we’d know what we were talking
about. So we always give things code names, nicknames, and this one we codenamed Xena. ROBERT KRULWICH: From…? MIKE BROWN: From, of course, the TV show,
Xena, Warrior Princess. Of course, Xena has a satellite, which we
had no choice but to call Gabrielle, which is Xena’s sidekick in the TV show. ROBERT KRULWICH: No choice? MIKE BROWN: No choice. ROBERT KRULWICH: But in proper scientific
circles, when scientists talk about this object they use… MIKE BROWN: …the very unwieldy 2003UB313. ROBERT KRULWICH: And it will stay 2003UB313
until the International Astronomical Union officially decides that this is, indeed, a
planetówhich by the way, they have not done. They’re not even close. MIKE BROWN: We’re in committee limbo, international
committee limbo, which is about the worst possible place you could imagine being. ROBERT KRULWICH: But what exactly is the problem?
It looks like a planet. I mean, it’s round; planets are round. MIKE BROWN: Nothing’s really round. The Earth
has got a bulge in it, and Saturn is actually quite squashed. ROBERT KRULWICH: Okay, but Xena’s round enough;
and it’s got a moon, which is very planet like; and it orbits the sun. But it turns
out, this matter is still debatable because there’s no precise scientific definition for
“planet,” and there hasn’t been one for a long time. NEIL deGRASSE TYSON: Did you know that in
1801 a new planet was discovered orbiting between Mars and Jupiter? ROBERT KRULWICH: Neil deGrasse Tyson is director
of New York’s Hayden Planetarium. NEIL deGRASSE TYSON: They called it Ceres.
And they looked some more, and they found another planet, and another and another. The
count of planets in the early 1800s was greater than it is today, thirteen planets in the
solar system. And they kept looking, and the numbers kept growing. And they were running
out of names, and they realized that, rather than counting new planets, they had discovered
a new swath of real estate in the solar system called the asteroid belt. ROBERT KRULWICH: So Ceres became an unplanet,
and was re-designated to a new class. And it became the biggest asteroid. NEIL deGRASSE TYSON: So we’ve been there before.
We know how to demote something. ROBERT KRULWICH: And that’s exactly what he
did to Pluto. When the Hayden Planetarium reopened in the year 2000, Neil Tyson decided
to de-planetize Pluto. “In our opinion,” he said, “Pluto is now an icy object that’s different
from the other planets.” NEIL deGRASSE TYSON: It’s got enough ice,
so that if you were to take Pluto and transport it to where Earth is right now, the heat from
the Sun would evaporate the ice and it would grow a tail. And that’s just no kind of behavior
for a planet. We have words for things with tails, they’re called comets. ROBERT KRULWICH: Same for Xena, another icy
body that lives in the Kuiper Belt out beyond Neptune. But a lot of people simply ignored
Neil Tyson and the Hayden Planetarium and stuck with the list they’d learned in school.
Remember those planets in the right order? Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus, Neptune and Pluto. NEIL deGRASSE TYSON: My very educated mother
just served us nine pizzas. MIKE BROWN: Martha visits every, Martha visits
every Mondayómust be for Marsóand just stays until noon, period. So there are two stupid
things there. There’s an “and” which is dumb, except the “and” is right where the asteroid
belt is. I don’t know if that’s an accident or not. And then, I remember at the time,
being in third grade, thinking that there’s something funny about Pluto if it’s really
just a period at the end of a sentence. ROBERT KRULWICH: Sophisticated scientists
and ordinary folks can’t seem to get together on this one. And Mike Brown, even though he
discovered what could be the tenth planet, has this advice for the scientists: MIKE BROWN: What I favor is the “give up”
approach, which is to say, the word planet is not scientific, and it doesn’t need to
be. And as astronomers, we just need to get over it. NEIL deGRASSE TYSON: These are the Pluto files,
okay? This is hate mail that I’ve gotten from elementary school children. Handwritten letters
saying, “Please, Dr. Tyson, what are you doing with Pluto? What? That’s our favorite planet!” “You are missing Pluto. Please make a model
of it. This is what it looks like. It is a planet. Turn to the other page. A picture
of Pluto.” “Dear Dr. Tyson, I think that Pluto is a planet
for a lot of reasons, but you treat it like nothing! So if you can, please leave it a
planet. And if you don’t, then I say it is. And have a good day.”

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