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Rodina
2002-Jul-23, 05:48 PM
National Review - whether you care for their politics or not - does express a consistent support for basic research and for the space program in general. Today was typical, with a nice article supporting Pluto Express.

There was some Bad Astronomy in it, however - saying that Pluto has the "only" elliptical orbit.

http://www.nationalreview.com/miller/miller072302.asp

My comment to NRO was as follows:

Dear NRO:

Hurray for John J. Miller's article endorsing Pluto Express!

While I appreciate the NRO's support of the space program, Mr Miller makes an understandable, but nevertheless important, error of astronomy. His statement that "Pluto is...the only [planet] with an
elliptical orbit" is manifestly untrue. All orbiting bodies are in elliptical orbits - some, however, are more eccentric than others.

Pluto's eccentricity, of .248 (the distance between the two foci of the ellipse divided by the longest diameter, or major axis, of the orbit (a perfectly circular orbit would, for example, have an eccentricity
of .000)) happens to have the most eccentric orbit of any of the planets. Mercury is close, with a .205. Venus is the least eccentric orbit, with a .0068.
Nevertheless, all of the planets' orbits are elliptical.

May I suggest that all interested parties take a look at http://www.badastronomy.com a website which debunks a lot of bad astronomy in film and television as well as the news media in general. It also has a great array of articles debunking common myths about astronomy.

Best,
/etc/

GrapesOfWrath
2002-Jul-23, 06:39 PM
Good catch.

I'd like to know what else it was that Clyde Tombaugh was looking for when he found it. From the link (http://www.nationalreview.com/miller/miller072302.asp): "It wasn't even discovered until 1930, and even then its discovery was an accident astronomer Clyde Tombaugh was looking for something else."

Rodina
2002-Jul-23, 07:01 PM
This is very stale memory for me, but I seem to recall that Tombaugh thought he was looking for a larger planet further away... rather than something so small so close.

SeanF
2002-Jul-23, 07:09 PM
On 2002-07-23 14:39, GrapesOfWrath wrote:
Good catch.

I'd like to know what else it was that Clyde Tombaugh was looking for when he found it. From the link (http://www.nationalreview.com/miller/miller072302.asp): "It wasn't even discovered until 1930, and even then its discovery was an accident astronomer Clyde Tombaugh was looking for something else."



I would assume this is a reference to the fact that Tombaugh was looking for the planet that was causing perturbations in Uranus' orbit. As it turns out, no such planet exists, but Pluto just happened to be in the spot where Tombaugh was looking . . .

GrapesOfWrath
2002-Jul-23, 07:24 PM
On 2002-07-23 15:09, SeanF wrote:
As it turns out, no such planet exists, but Pluto just happened to be in the spot where Tombaugh was looking . . .

Yeah, I suppose that makes it an accident...finding a planet in the very place where you are looking for a planet.

O well, at least they think that the voyage to Pluto is a good idea. That's enough for me.

SeanF
2002-Jul-23, 07:33 PM
On 2002-07-23 15:24, GrapesOfWrath wrote:


On 2002-07-23 15:09, SeanF wrote:
As it turns out, no such planet exists, but Pluto just happened to be in the spot where Tombaugh was looking . . .

Yeah, I suppose that makes it an accident...finding a planet in the very place where you are looking for a planet.


You know, I dang near put an asterisk after the word "spot" with a footnote saying "geocentrically speaking, that is."

Pluto is actually not in the spot in the solar system where Tombaugh expected to find something - it just happened to be generally along his line of sight at the time. /phpBB/images/smiles/icon_smile.gif



O well, at least they think that the voyage to Pluto is a good idea. That's enough for me.


Agreed.

Donnie B.
2002-Jul-23, 07:43 PM
Grapes,

Your skepticism is wasted; the discovery of Pluto was a coincidence.

Tombaugh didn't just point a telescope at a particular spot in the sky one night and say, "Hey, there it is, just where it's supposed to be". He examined a rather large area along a portion of the ecliptic where, if the perturbations had been real, the perturbing object should have been.

As it turned out, those measurements of perturbation were wrong... but an object did show up in one of Tombaugh's many pairs of photographic plates, in the general area where the predicted object was supposed to be.

But in other respects, it was all wrong. Pluto was much too dim (he first thought it might be an anomalous asteroid, one of dozens that he discovered during the search) to correspond to the planet he was seeking. It might have just been dark, but in due course its orbit and mass were determined; it was far too small, and in the wrong orbit, to have caused the incorrectly-expected perturbations.

Pluto was not the first planet to be sought by this technique; Neptune was discovered the same way almost two centuries earlier. It was a reasonable technique to try, but the data used to calculate the position of the supposed "Planet X" were wrong.

So Tombaugh caught a lucky break, and found the largest Kuiper Belt object (along with assorted asteroidal debris) instead of the ninth planet he was looking for.

nebularain
2002-Jul-23, 07:48 PM
Part of what makes this whole thing interesting is that the status of Pluto as a planet is in question, now that the Kuiper Belt has been discovered. It would be interesting to know for sure if Pluto really is "of the stuff that comets are made of."

I've heard, too, that Pluto was found as another planet was being looked for. The premise is that Neptune was found when astronomers were looking for a massive object whose gravity pull seemed to be affecting the orbit of Uranus. Either the figures on that pull were not completely accounted for (maybe Neptune does not have enough mass to affect the gravitational pull effect observed on Uranus) and/or it seems Neptune is under an unaccounted for gravitational influence by something else. Anyway, this massive body is what was being looked for when Pluto was discovered. I don't believe the riddle has been completely solved yet.

GrapesOfWrath
2002-Jul-23, 08:08 PM
On 2002-07-23 15:48, nebularain wrote:
I don't believe the riddle has been completely solved yet.

No, it has been solved. There is no missing perturbing mass--they went back and redid the calculations, and they'd been wrong.

I do know (did know) the history of the discovery of Pluto, and how Tombaugh found it. I even got to talk to him once (he was a neighbor of my uncle). I guess I just don't like characterizing his diligent work as an accident.

OTOH, if they hadn't been convinced by the faulty calculations that there was another planet out there to be found, then they might not have funded the search and Tombaugh wouldn't have been able to spend the time and resources searching.

So, I'll accept "Clyde Tombaugh was hired by accident, luckily." /phpBB/images/smiles/icon_smile.gif

nebularain
2002-Jul-24, 01:20 AM
On 2002-07-23 16:08, GrapesOfWrath wrote:


On 2002-07-23 15:48, nebularain wrote:
I don't believe the riddle has been completely solved yet.

No, it has been solved. There is no missing perturbing mass--they went back and redid the calculations, and they'd been wrong.

Well, that's convenient! Thanks for letting me know. I've been wondering about that for a long time.



I do know (did know) the history of the discovery of Pluto, and how Tombaugh found it. I even got to talk to him once (he was a neighbor of my uncle).

How cool is that?!

_________________
"All that is gold does not glitter / Not all those who wander are lost..."

<font size=-1>[ This Message was edited by: nebularain on 2002-07-23 21:21 ]</font>

Geo3gh
2002-Jul-24, 04:54 PM
On 2002-07-23 16:08, GrapesOfWrath wrote:


On 2002-07-23 15:48, nebularain wrote:
I don't believe the riddle has been completely solved yet.

No, it has been solved. There is no missing perturbing mass--they went back and redid the calculations, and they'd been wrong.


IIRC, they plugged in the better mass figures they got from the Voyager passes, and the observed orbits matched the calculated orbits.

informant
2002-Jul-25, 03:04 PM
GrapesOfWrath wrote:
OTOH, if they hadn't been convinced by the faulty calculations that there was another planet out there to be found, then they might not have funded the search and Tombaugh wouldn't have been able to spend the time and resources searching.

On the other hand, if they hadn't funded Tombaugh's research, there might not be this controversy today on whether Pluto is a planet or not. /phpBB/images/smiles/icon_wink.gif