Of Laser Disingenuators, Julian Dates & Color Variables

[Nathan]

USNO Julian Date Converterexactly what a 'color variable' is, it seems (from context) that it probably is (or at least is related to) the wavelength at which the local light source is most intense. If that is the case, then it should probably be 612 nm (nm = nanometers), as that is fairly close to the 'red-brown' Nita mentions and is in the correct ballpark for a G3 V star (I'm sure that Alaalu's primary is on the main sequence [i.e., luminosity class V] --mainly because it is 'about the same size as Earth's Sun,' though I do have other reasons), though the temperature obtained by using Wien's Displacement Law

[Nathan]

USNO Julian Date Converterexactly what a 'color variable' is, it seems (from context) that it probably is (or at least is related to) the wavelength at which the local light source is most intense. If that is the case, then it should probably be 612 nm (nm = nanometers), as that is fairly close to the 'red-brown' Nita mentions and is in the correct ballpark for a G3 V star (I'm sure that Alaalu's primary is on the main sequence [i.e., luminosity class V] --mainly because it is 'about the same size as Earth's Sun,' though I do have other reasons), though the temperature obtained by using Wien's Displacement Law

[meteorite]

AAkkk! You are forcing me to think; no fair! Now I will have to go back, re-read the excerpt, and try to decide if there is a reasonable explanation for those bobbles, or they need to be editorially fixed. Or if they can be filed under "willing suspension of disbelief."

[Birdhead]

What are you other reasons for believing it to be main sequence? Just out of curiosity, not because nI disagree. I don't know enough about this stuff to disagree. But why?
T

Tuibird in Aotearoa
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Chocolate lover extraordinaire...
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Spelling Freak and Typo Queen

[Diane Duane]

(chuckle) You guys give me the giggles.

(grin) The word is a placeholder. Something more effective will be replacing it. But at the time I didn't want to break the flow by getting up to construct a "real" word while I was writing,

However, as the dictionary definition of 'claudication' ('a halting or limping' --Webster's Unabridged) is so obviously divergent from its use in the YW books, this is not necessarily an error.

A hint to the suspicious or bemused: I often use technical terms in their medical modes. I should make you look it up... But in medicine a "claudication" is a squeezing, pinching or blockage of a blood vessel. The reference is to local spacetime being squeezed out of its normal shape.

The second thing I came across involves the Julian dates (2452747.125 to 2452761.125): These, according to the http://aa.usno.navy.mil/data/docs/JulianDate.html, correspond to 15:00 UTC (on April 17th and May 1st, 2003, in case you are interested), which, unless Nita & Kit use Universal Time in 'everyday' timekeeping or have changed time zones when I wasn't looking, does not correspond to 'three in the afternoon' for them ('three in the afternoon' EDT is 19:00 UTC).

Oops, forgot to change the timezone. Nice catch.

This too is a fill-in for...not the color of the star...but the skin color of the Alaalids. The only other thing I could think to put there at the time would have been a Pantone matching number, which would have been just silly...so I filled in an Angstrom number to hold the place.

BTW, I take it you noted the slightly expanded planetary data at http://outofambit.blogspot.com/2003_...html#200370299. This handles the diameter problem...

-- DD

[meteorite]

"Reasonable explanation" accepted.

[Diane Duane]

But if I had put in a Pantone number, it would have been along the lines of Solid Matte 195 M. (Though the range can be anywhere from 188 M through about 202 M.)

-- DD

[Nathan]

Thanks for the explanations, DD. I'm actually used to 'placeholder words,' as my mom and I both use them (or even placeholder phrases) quite regularly when we can't think of 'le mot juste' or the best way to phrase something.

BTW, I take it you noted the slightly expanded planetary data at http://outofambit.blogspot.com/2003_06_01_outofambit_archive.html#200370299. This handles the diameter problem...

Actually, I was referring to the arithmetical discrepancy of a radius of 34,000 km and an equatorial diameter of 64,000 km from the "slightly expanded planetary data," which is pretty minor, however (and far less severe than some of the arithmetic mistakes I've made over the years).

Birdhead: My other arguments for Alaalu's primary being a main-sequence star all involve timing and simply offer support to the size argument as none of them are insuperable (especially if wizardry is invoked). They basically boil down to either 'evolved stars aren't very good neighbors,' or 'a planet that's been around long enough for its primary to leave the main sequence (here we have to assume that the primary was not originally an early-type star, which is reasonable if one also assumes that the planet was suitable for Earth-like life to evolve soon after the star entered the main sequence) has a greater probability of a something catastrophic occurring (something that would wipe out life and preclude its re-evolution) than one whose primary is still on the main sequence' (this second line of reasoning is pretty tenuous, though).

For fun, here are a few predictions about Alaalu that I made based on the data in DD's blog (and may be rather far off, but were enjoyable to make, and afforded me good planetary astronomy practice):

1. Alaalu will have a large contingent of captured moons similar to that of Jupiter or Saturn (given its [Alaalu's] 'dynamical heft' [due to its great mass]).

2. Due to the low density (assuming a spherically symmetric density distribution, which is probably adequate for a back-of-the-envelope calculation ) required for Alaalu to have an Earth-like gravitational acceleration at its surface (and thus a small 'differential gravitational force' at its surface), Alaalu should be able to support mountains much taller than those on Earth. Whether Alaalu's geologic processes will produce such mountains, and, if so, at what rate atmospheric processes would destroy them is not something I am prepared to conjecture from the data I have (if at all, planetary geology not being a specialty of mine).

3. Alaalu will probably have a fairly sizable greenhouse effect, as it appears to be outside of the 'habitable zone' (with a semi-major axis of ~2.4 AU --it will probably also have a nearly circular orbit, for climate stability reasons).

Nathan

Ubi materia, ibi geometria. --Johannes Kepler

Non doctrinam, sed perspicuitatem quaero.

[This message was edited by Nathan on 08 June 2003 at 11:28.]

[Birdhead]

Thanks. I think I understood most of that- starting to feel like I really should brush up on my types-of-stars, though.
As to Allalu having lots of moons- do I seem shallow if I say "pretty!!"?
T

Tuibird in Aotearoa
Conservationist, Scientist, and proud of both!
Chocolate lover extraordinaire...
Ahahahaha, ahahahahaha, ahahahaha...
My mission: Bringing Maori to the world!
Spelling Freak and Typo Queen

[Nathan]

I don't think that your admission of an appreciation for the visually beautiful side of astronomy makes you seem shallow, Birdhead. In fact, I think that the beauty (visual as well as 'intellectual' [i.e., mathematical]) of the subject is as strong a draw for potential astronomers as general curiosity about the universe is.

On the subject of visual beauty and captured moons, seeing Phobos and Deimos in the Martian sky (with their rapid motion, irregular shapes and small size [compared with Earth's moon]) would be one of the main attractions of a trip to Mars for me, for unlike many other people who are interested in astronomy, I have no real interest in traveling to other planets --escape from the confines of Earth's atmosphere would be nice, as would travel outside of the solar system or (especially) the galaxy, but none of these are what I consider requisites for a full, happy life (and a good thing too! --especially considering the chances of the last two being feasible during my lifetime). In my estimation, this is most likely a manifestation of my strong theoretical (and secondarily observational) bent.

Re stellar types: If you are ever interested in stellar nomenclature, theory and observation beyond the level of the average introductory astronomy textbook, James B. Kaler's Stars and their Spectra: An Introduction to the Spectral Sequence is a very thorough and (at least for me) highly read-able account.

Nathan

Ubi materia, ibi geometria. --Johannes Kepler

Non doctrinam, sed perspicuitatem quaero.

[Wilf]

How visible are Mars' moons form its surface? The Earth's moon is very large, fairly close, and very reflective compared with the Martian moons.

[Birdhead]

nathan: Thanks!
As for Phobos and Deimos, I'm not entirely sure, but I seem to recall that, while they're visible, they move quite rapidly and so aren't visible for long. However, I could be confused; I might be able to find out, though...
T

Tuibird in Aotearoa
Conservationist, Scientist, and proud of both!
Chocolate lover extraordinaire...
Ahahahaha, ahahahahaha, ahahahaha...
My mission: Bringing Maori to the world!
Spelling Freak and Typo Queen

[FireWitch]

This is one of those occations that realy makes me want to finish A Brief History of Time so that I can understand a fraction of what everyone is saying...ug...stupid smart people...

Hillary Wan Kenobi
The first-ever Jedi Ewok
And proud of it...

[Birdhead]

Oh, you can mostly ad lib it- that's what I do, anyway, because my knowledge is pretty well basic, but I can generally pick up at least the general idea, and sometimes even specifics. And Nathan is very good for the vocabulary!!
T

Tuibird in Aotearoa
Conservationist, Scientist, and proud of both!
Chocolate lover extraordinaire...
Ahahahaha, ahahahahaha, ahahahaha...
My mission: Bringing Maori to the world!
Spelling Freak and Typo Queen

[Nathan]

Originally posted by Wilf:
How visible are Mars' moons form its surface? The Earth's moon is very large, fairly close, and very reflective compared with the Martian moons.

While Phobos & Deimos are

Originally posted by FireWitch:
This is one of those occations that realy makes me want to finish A Brief History of Time so that I can understand a fraction of what everyone is saying...

It's been quite a while since I've read A Brief History of Time