Thursday, August 31, 2006

Bulldoze Pluto? I Don’t Think So

By Jeffrey Bennett
University of Colorado
posted: 31 August 2006
10:05 am ET

The International Astronomical Union (IAU) has spoken on the status of Pluto. The only thing missing when they announced the decision at their press conference was the “Mission Accomplished” banner. Yes, I’m afraid this matter is about as settled as the Iraq war in 2003.

You’ve probably heard the basics: Pluto is no longer to be considered a “real” planet, but will instead be part of a new class of objects called “dwarf planets.” These midgets may number anywhere between a handful and hundreds in our own solar system, depending on how you count them and how hard we search for them with more powerful telescopes. But no matter how you cut it, this new definition takes away any pretense of Pluto being a member of the same elite, planetary club as Earth and Jupiter.

As a scientist, I think this was a pretty good outcome, though some of the justifications used to achieve it are dubious. But as a teacher, textbook writer, and builder of scale model solar systems, I have some reservations. In particular, for the model solar systems I’ve helped develop on the University of Colorado Boulder campus and on the National Mall in Washington, DC, I have to ask: Should we now bulldoze Pluto?

A little background: Pluto was discovered in 1930, at a time when astronomers were searching for an object thought to be causing slight perturbations to the orbits of other planets around the Sun. Neptune itself had been discovered in just this way in 1846, after scientists used perturbations in Uranus’s orbit to predict the existence and location of an “eighth planet.” Neptune was found as soon as astronomers pointed telescopes to the calculated position, which is I like to say that Neptune was discovered with physics and mathematics, and only confirmed with a telescope.

Over the ensuing decades, a few scientists claimed to see ongoing orbital discrepancies and embarked on a search for a “ninth planet” that might be causing them. Pluto was found during this search, though about 12 full-moon-widths away from the predicted position. And though hailed as a planet upon discovery, its status gradually became suspect, as we learned that its orbit is much more tilted and elongated than that of any of the other planets, and that it has a mass much less than 1% that of Earth. Worse, reanalysis of past observations suggested that the claimed orbital discrepancies had simply been errors in measurement, making Pluto a solution to a nonexistent problem.

Saturday, August 26, 2006

It's official: IAU demotes Pluto

The world's astronomers have removed Pluto's planetary status.
Francis Reddy

August 24, 2006; updated August 25
Astronomers meeting in Prague have decided by a wide margin that Pluto no longer merits consideration as a full-fledged planet. The historic decision follows a week of sometimes contentious debate over how to define a planet.

Jocelyn Bell Burnell, an expert on neutron stars at the University of Oxford in England, moderated the proceedings with the help of some playful visual aids. A blue toy balloon stood in for Neptune, while a plush toy of Disney's cartoon dog Pluto played the ninth rock from the Sun. Applause followed this morning's critical vote at the International Astronomical Union's (IAU) General Assembly meeting.

"I was relieved," says Caltech's Michael Brown. Brown's January 2005 discovery of Xena (officially, 2003 UB313), which is larger than Pluto, forced the IAU to address this long-simmering issue. "Scientifically, there is no question this is the right way to go," he says. "Eight is enough."

"I am delighted that rationality has prevailed," says Richard Conn Henry of Baltimore's Johns Hopkins University.

However, not everyone is happy with the decision. The American Astronomical Society 's 1,300-member Division of Planetary Sciences — the world's largest group of planetary scientists — recommended acceptance of the original proposal announced last week. If passed, this would have retained Pluto's status and declared three other bodies — Xena, the largest asteroid, and Pluto's largest moon — planets as well.

"I just think the IAU has embarrassed itself," says Alan Stern, principal investigator for NASA's New Horizons mission to Pluto. "If you read the definition that they have adopted in that room today, it is scientifically indefensible."

"I think there's going to be a protest," says Mark Sykes at the Planetary Science Institute in Tucson. "A minority of the astronomical community passed this."

So, what is a planet?
Following fractious public and closed-door discussions, Pluto no longer makes the cut. Astronomers agreed to define a planet as "a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit."

Objects that meet all but the last requirement — like puny Pluto and asteroid Ceres — are to be classed as "dwarf planets." But a proposal that would give these objects and the "classical" planets — Mercury through Neptune — equal solar-system stature failed.

Everything else in the solar system — comets, moons, and the rest of the asteroids — will be known as "small solar system bodies."

"Tell me where else in astronomy we classify objects by what else is around them?" objects Stern. "It's ridiculous."

"I think there will be a lot of people who just choose to ignore it," Sykes adds.

Nature vs. nurture
A week ago, the International Astronomical Union (IAU) presented its first attempt to define the word planet. If an object orbited the Sun and had enough mass that its own gravity forced it into a nearly round shape, it would qualify. If passed, this meant Charon, Pluto's largest moon; Ceres, the largest asteroid; and the Kuiper Belt object nicknamed Xena would immediately join the rank of planets.

But at least a dozen additional objects orbiting in the Kuiper Belt beyond Neptune also would qualify under this definition — and possibly as many as 53. "Many more Plutos wait to be discovered," Richard Binzel of the Massachusetts Institute of Technology noted.

Many astronomers found this potential explosion of planets troubling. "Maybe planets shouldn't be so special," Sykes counters.

Others said that pushing Pluto's moon Charon to planetary status went too far. "There was a little over-reaching with this thing about 'plutons' and making Charon a planet," Stern says, "but the core ... was all pretty good." The term proposed for Pluto-like objects — "pluton" — was roundly rejected in early discussions, largely owing to its well-established use in geology.

But scientists who study how planets interact were the most perturbed. The original definition looked only at an object's physical nature without regard to its orbital environment.

During Friday's debate, Julio Fernández of the University of the Republic in Montevideo, Uruguay, suggested an alternative that defined a planet as "by far the largest body in its local population." This would keep Pluto, Charon, Ceres, and the Kuiper Belt objects from graduating to planets.

Debate continued Tuesday when the IAU's planet-definition committee put forward only a slightly modified version of the original definition — one that avoided any reference to a planet's orbital environment. "They have presented practically the same resolution as before," Fern├índez complained during the discussion. Astronomers hammered out a compromise in closed-door negotiations that afternoon.

"They've put together a hastily drafted definition that's purely dynamical," explains Sykes. "Perhaps there could have been a more dynamical definition that achieved their goal that would be better crafted, but unfortunately they just didn't have the time."

Sykes argues that, under the adopted definition, a Mars-mass planet discovered at 200 astronomical units would be classed as a dwarf. (An astronomical unit is the average distance between Earth and the Sun.) "There are some common-sense issues with this," he adds.

"I think the demotion of Pluto into the realm of other minor objects outside the orbit of Neptune is the most consistent thing to do to straighten out the nomenclature of our solar system," says William Blair at Johns Hopkins University. "However, I don't find the wording of the official planet definition to be very clear, and hence it will continue to be open to interpretation."

"Pluto should never have been called a planet," Brown says. "The only reason Pluto exists in its current orbit is that Neptune keeps it there and protects it." Neptune forces Pluto — and many other icy objects, called plutinos — to go around the Sun twice for every three Neptune orbits.

"Pluto and Xena never fit in," Brown notes, although he admits he's wistful about missing the opportunity of having discovered the tenth planet. "We have a chance now to actually educate people on how the solar system really works. I think that's exciting."

Monday, August 21, 2006

Iowa State Fair Attendance

DAY 2005 2006
Thursday 71,691 73,997
Friday 92,662 92,704
Saturday 100,041 108,331
Sunday 103,921 92,553
Monday 88,201 85,483
Tuesday 92,369 90,201
Wednesday 90,525 94,333
Thursday 82,368 81,998
Friday 82,215 77,505
Saturday 103,875 103,663
Sunday 94,775 112,295

These are the attendance figures for the eleven day run of the Iowa State Fair. Last year It had over 1 million in attendance and I expect it will be the same this year.

I attended the fair twice this year, the first time was on the first Thursday with both of my sisters, a brother-in-law, and both nieces. My younger sister and brother-in-law live in New York state and came home on vacation to go to the fair. They usually come home earlier in the year so they miss the fair. This year they decided they wanted to go.

The second time I went was on Wednesday, August 16. I went by myself, I usually go the first day alone and then another day with my older sister and my nieces. I like to go alone because I can do what I want, when I want, for as long as I want. That's what I like about being single too. I guess I'm just selfish that way! Usually during fair-time my older sister and I go to Living History Farms. That is not going to happen this year, I don't think. Sister and nieces are too busy at their jobs. Maybe next year. Click here to visit Living History Farms' Web site. I would like to volunteer or work there one year, I need a salary though.