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planets - or not
by Kim Hyatt 02 Aug '05

02 Aug '05

I asked this group some time ago if anyone knew of a consensus definition for "planet" and one of you responded with what I believe was the IAU's working definition for a range of objects. Forgive me, but I don't now remember who that person was. As I recall, the definition went something like this: If an object is massive enough to be spherical and is in orbit about a star, it's a planet. If an object is massive enough to sustain the fusion of hydrogen to helium, it's a star, and so forth. Does anyone recall and can cite the source for these definitions? I've always thought that the simplest definition is the best, and I liked this definition for planets. Therefore, both Pluto and "Xena" are planets, as may also be the larger Kuiper Belt objects. All the rest of the arguing by the "professionals" about what constitutes a planet seems somewhat petty and fruitless. After all, we still have to fix those damn tiles... Kim

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Article from Globe
by Michael Carnes 02 Aug '05

02 Aug '05

Interesting article in the Boston Globe: http://www.boston.com/news/globe/editorial_opinion/oped/articles/ 2005/08/02/nasas_failure_of_vision/

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RE: [Utah-astronomy] planets - or not
by Dale Hooper 02 Aug '05

02 Aug '05

Of course, if they do ever demote Pluto (and don't allow "Xena") we could crank it back up to 9 with our "Moon". If I remember correctly - if you observed our Moon's orbit from above or below the plane of the solar system - it would be a highly perturbed orbit - around the Sun. I.e. you wouldn't see "loops" in its orbit. But, instead you would see it "weaving in and out". So, I say to the IAU - give us our tenth planet or we'll take the Moon hostage. <g> Clear skies, Dale. -----Original Message----- From: utah-astronomy-bounces+dale.hooper=sdl.usu.edu(a)mailman.xmission.com [mailto:utah-astronomy-bounces+dale.hooper=sdl.usu.edu@mailman.xmission. com] On Behalf Of Joe Bauman Sent: Tuesday, August 02, 2005 1:52 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] planets - or not Very good point, Kim. When I was talking with my son, Sky, the other day he suggested the same definition for a planet, large enough that its gravity forms it into a sphere and in orbit around a star. The last part rules out moons that are big enough but are not planets. I think it's a fine definition. The question is, what is the lower limit for enough mass to create a sphere? And how perfect does the sphere have to be? (In a sense, Jupiter isn't a very good sphere -- it's oblate because it is so large and spins so fast and is so gaseous that it bulges at the belt).) -- Joe _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.utahastronomy.com

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Planetary chauvenism
by Chuck Hards 02 Aug '05

02 Aug '05

It appears that to some scientists, pedigree determines whether an object is a true planet or just an "interloper". Size has absolutely nothing to do with the argument. Dr. Andrew Prentice (Centre for Stellar and Planetary Astrophysics) considers "Xena" a likely outcast from what he terms a "hostile" star system. He believes that technically, to be considered a planet an object must orbit on a relatively flat plane with respect to the ecliptic and have a somewhat circular orbit, and by that means that it must have formed about the same star it orbits. Folks, I'm not an astrophysicist or a planetary scientist, but since when did anything but sheer size enter into the equation? I've never heard that place of origin was an important criterion of planethood. We were all taught that small, rocky worlds were for the most part, inhabitants of the inner solar system, the gas giants, denizens of the outer realms. But Carl Sagan got us thinking that the solar system model is just one possibility in a universe of limitless possibilities, and recent exoplanetary discoveries seem to bear this out remarkably well. On Dr. Prentice's grounds, and he freely admits this, Pluto should be cast out of the planetary ranks too (here we go again). Dr. Charley Lineweaver (Australian National University): "Either we have a 10th planet or we have only eight planets." OK, let's take that line of reasoning and extrapolate: An object starts out life as a planet, gets tugged out of the star system it was formed in, and goes wandering about it's part of the galaxy until it falls under the influence of another star- at which point it is no longer a planet, but now just a mere "interloper" (Dr. Prentice's term). Suppose a star that had no planets formed from it's original accretion disk, but has dozens of Xena-sized objects in similar non-uniform orbits. Do future explorers report back to mission control "system has no planets, it's totally barren of planets". The term "planet", then, does not denote an intrinsic quality of an object at all. An object can be a planet, then not a planet, depending on just where it is. And, by extension, does the same logic apply to planetary satellites? Do moons in retrograde, inclined, or highly eccentric orbits need to be struck off the rolls? Obviously they didn't form with the other natural satellites around the same planet, and the size limits for natural satellites have never been rigidly defined, either, to my recollection. It will be interesting to see what definition of a "planet" is finally decided upon. I'm hoping that origin plays no part in it. Call it the "Solar System Statue of Liberty Theory" or SSSLT (copyright 2005). "Give me your tired, your poor, your huddled planetary masses yearning to breathe free, the wretched refuse of your stellar shore. Send these, the homeless, gravity-tossed to me, I lift up the Sun beside the golden door!" ____________________________________________________ Start your day with Yahoo! - make it your home page http://www.yahoo.com/r/hs

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Interesting Shuttle picture
by Howard Jackman 02 Aug '05

02 Aug '05

I saw this very interesting picture of the Shuttle on the Astronomy picture of the day website. Looks like you can see one of those pesky tile fillers sticking out just behind and to the left of the nose gear doors, looks like a white triangle. Howard http://antwrp.gsfc.nasa.gov/apod/image/0508/shuttle_sts114_big.jpg __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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(no subject)
by James Cobb 01 Aug '05

01 Aug '05

In today's Wall Street Journal (page A8) Charles Beichman gives a pithy diagnosis of the current state of manned space-flight in the US: > While robotic space science has produced glorious results (and a > few inglorious debacles) over the past decade, human spaceflight > has languished without clear goals. If you think of the space > shuttle as a tugboat in the harbor of low-earth orbit, then the > international space station is a man-made island built in the > middle of the harbor for want of a better destination for the > tugboat. While both the shuttle and the space station are wonderful > engineering accomplishments, no one can really explain why they > were built other than to keep the human spaceflight program alive > while waiting for something better to happen. Unfortunately, > instead, while we were waiting, something worse happened: 14 > astronauts died in two horrible shuttle accidents. While the skill > and courage of our astronauts is beyond measure, the tasks we have > given them are not worthy of the risks they bear with each launch > and each descent. His thrust is that at present we're confined to "harbor tours" of low earth orbit. Instead, he argues, "Let Virgin Galactic offer private harbor tours to rich tourists. We must leave the harbor and venture again into the 'blue water' of deep space." Jim

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Imaging the new planet
by Patrick Wiggins 01 Aug '05

01 Aug '05

Those who might have plans of getting CCD images of the 2003 UB313 might be interested this message that was just posted to the Minor Planet Mailing Group: "Over the last two nights I aimed an 11 inch SCT at 2003 UB313 and did 10 minute guided exposures. It appears as a sharp point of light on these exposures. Over 1.5 hours on the first night no movement was visible. However, it is certainly visible over a time interval of one day."

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Re: [Utah-astronomy] Heat Shield Technology
by Michael Carnes 01 Aug '05

01 Aug '05

No. You might need a slightly larger chute to slow you down a little more, but nylon's cheap. By the way, the Soviets did lose a couple of cosmonauts when a chute didn't open. >So, was their technology superior to ours in terms of being able to land on >ground?

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Re: [Utah-astronomy] Heat Shield Technology
by Michael Carnes 01 Aug '05

01 Aug '05

Hi Mike, I think it's purely that we had more unoccupied water and they had more occupied land. Our Mercury/Gemini/Apollo capsules all used ablating shields of glass--designed to burn away and carry the heat with it. I believe that's what Russian capsules still do. The shuttle tiles act more as insulators--if they burned away, you'd have to replace them after every flight. I had a chance to handle a piece of that material once--fascinating stuff. Other than the more permanent nature of the material, I don't know if it's any more effective than the ablating shields. Back before the Soviet Union broke up, in the days of Glasnost and Perestroika, we had a great exhibit of Soviet space technology in Boston. They had an actual Vostok, along with a number of pieces of gear that never flew--including the Soviet moon buggy. It was an amazing show, and I'd guess that collection has long since been broken up. There were even a few old cosmonauts wandering around the exhibit hall. Michael .................................. Mr. Bailey wrote... If I remember correctly, back in the 60's and 70's while U.S. manned spaceflights ended with a splash in the ocean, Soviet manned spaceflights landed on earth in Soviet territory. What were the technological differences between our parachute-and-heat shield-system, and the way the Soviets did it? Why did the two systems evolve differently--was it merely because the U.S. had more extensive freedom on the seas? Other than the fact that our space capsules "dropped" (?) through the atmosphere, and the space shuttle "glides"(?) down, and the shuttle's heat shield is made of tiles, how has our system evolved since the Apollo program? Mike Bailey _______________________________________________

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Re: [Utah-astronomy] Heat Shield Technology
by Olhomorto＠aol.com 01 Aug '05

01 Aug '05

So, was their technology superior to ours in terms of being able to land on ground? Mike

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