Re: Two suns

FennelGiraffe <sraarytvenssr@xxxxxxxxxxxxxxxxx> wrote:

[discussion of solar system with second sun in place of Jupiter]

I should mention that since I took the shortcut of using Jupiter's
orbital elements, 400 days (actually 399.8) came from a table of data
about Jupiter.

Interesting.

But the time until they're aligned again is still awkward to work with
(it just gives me one point, rather than a continuing process with
different points).

To shift the position of the orbit (closer to the planet), the time the
orbit takes, and perhaps the speed if it varies, matters, too. That's
the data I need.

If you put Sun2 where Saturn is instead, it would be only 389 days.
Uranus, 370 days; Neptune, 367 days.

That's all not giving me an image, or an idea of how long they take to
travel around the sun.

The farther away you get from Sun1, the closer the time is to one
Earth year.

Is that sort of like an e-curve? (You're not going to get all the way to
zero, after all, because that would mean the sun would stand still.

On the other hand, if you put a sun-sized mass where Jupiter is, it
would orbit faster than Jupiter does (by a factor of the square root
of two, I think).

How many times bigger (massive, whatever matters) is the sun than
Jupiter?

So Sun2 will have moved farther along its orbit during the 365 days
Earth took to make one complete orbit, so it will take Earth longer
than 35 days to catch up.

It won't catch up at all if the Sun2's faster, it will be overtaken by
it.

But the point of all this is just to give you a general idea of the
size of the effects you would get. Within these general guidelines,
you could make the exact numbers anything that suits your story.

So far I don't have the numbers I need for that.

Anyway, the seasons get very complicated. For example, sticking with
the 400 day cycle,

I assume you don't mean a planet year of 400 days, comparing to an n day
Sun2 year, so this gets too awkward to follow.

Really, this is going in a completely unintuitive (for me) direction.
How about something straightforward?

Sun2 takes n planet-days a year at X orbit radius around Sun1, with n
and X shifting at <whatever ratio>. The X orbit radius in AU is fine
(multiples of planet distance to Sun1). If n (how long it takes for a
full circle) depends on its size (mass, whatever), then that's just
another variable. A Jupiter sun where it is is a small star, fine, a sun
sized sun where Jupiter is is (IIRC you said) a quarter its size, also
fine. What I don't know is the rate at which it shifts, and how the
length of its orbit shifts with that (or even just its orbit at all).

With that data I can find a suitable orbit. (Perhaps I'll have to look
up the appearance of suns different size, but that's it. Unless you tell
me.)

<snip>

That's individual points, not something where I can reason any one point
of shifting circumstances myself. And it doesn't even tell me anything
(too awkward to fix the dates to a year first, mentally settle on that
date, then imagining how the planet stands in relation to the primary
sun, then imagine how the constellation looks while keeping the planet
and primary sun in mind).

I know you want to help, but inserting your parameters, the way to go
about it, doesn't work. It's too awkward to translate that into the
image I see.

Why don't you save yourself the work and just supply the ratios? :)

That's just: Ratio of Sun2 size (or rather diameter, in fractions of
Sun1, as seen from the planet depending on the distance in AU) to its
orbit length (in planet-days as unit of time, not in relation to the
plnanet) and distance to Sun1 (in AU). Plus one example (say Jupiter sun
is <that> big with <this> year length and <that> orbit radius).

That way I get Sun1 with the planet as constants, and can shift Sun2
around in size and orbit until I get something that suits me.

Thanks. :)

--
Tina
WIP: [Untitled]: 12427 words
WISuspension: Seasons & Elements trilogy | Magic Earth series
Posted to Usenet newsgroup rec.arts.sf.composition.

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