Need help of really smart astronomer

I am in the process (along with a partner) of writing a science fiction

novel. In this novel I want to create a very unique binary or twin
solar system that utilizes a very complex orbit system. I need someone
to consult about astronomical laws on gravity, gravitational forces on
the ways planets can and cannot orbit a body in space. Please help!!

On Tue, 11 Jul 2006, jmac39 wrote:

I am in the process (along with a partner) of writing a science fiction
novel. In this novel I want to create a very unique binary or twin
solar system that utilizes a very complex orbit system. I need someone
to consult about astronomical laws on gravity, gravitational forces on
the ways planets can and cannot orbit a body in space. Please help!!

IIRC, an extrasolar planet was discover in a binary star system.
I suggest you search "extrasolar planet discoveries" for ideas.

I am in the process (along with a partner) of writing a science
fiction novel. In this novel I want to create a very unique binary
or twin solar system that utilizes a very complex orbit system.

Ah, like Asimov's short story Nightfall.

As far as I could tell, Asimov didn't bother to figure out the orbital
dynamics.

Jim Kingdon wrote:

I am in the process (along with a partner) of writing a science
fiction novel. In this novel I want to create a very unique binary
or twin solar system that utilizes a very complex orbit system.

For an explanation of why I don't think anyone will be able to help you
much, look up something called the n-body problem. Gravitational
interaction among multiple objects is not (yet) solved analytically. I
think you'll find that such a system will be not only very complex, but
chaotic as well.

Ah, like Asimov's short story Nightfall.

As far as I could tell, Asimov didn't bother to figure out the orbital
dynamics.

He mentioned them, but not in detail. The scientists' preparation for
the eclipse certainly proved that *they* knew what was going on. The
story didn't require the reader to know the specifics, so the author
wasn't required to either.

In article ,
Hop David wrote:

Alan Anderson wrote:

Jim Kingdon wrote:


I am in the process (along with a partner) of writing a science
fiction novel. In this novel I want to create a very unique binary
or twin solar system that utilizes a very complex orbit system.


For an explanation of why I don't think anyone will be able to help you
much, look up something called the n-body problem. Gravitational
interaction among multiple objects is not (yet) solved analytically. I
think you'll find that such a system will be not only very complex, but
chaotic as well.

I don't think the planet's orbit would have long term stability. It
needs to orbit in a water zone for a few billion years to evolve life.

If the planet is being heavily influenced by two stars, I'd expect its
orbit to eventually be perturbed so it's periastron or apoastron would
be thrown out of the water zone.

James Nicole has come up with some interesting worlds in multiple star
systems. IIRC his planet's orbit is a plain vanilla elliptical (maybe
even circular) orbit about one of the suns. The other sun is too distant
to destroy the planet's orbit. However, it's bright enough to
substantially change insolation during different times of the year.

Hop

The nice thing about binary star systems is that the stars are really
not all that close together -- somewhere more than twice the distance to
Pluto, so each star can develop its own planetary system, with
relatively minor perturbations from the other star -- similar to the
influence of jupiter on the Earth/moon system.

Orval Fairbairn wrote:

The nice thing about binary star systems is that the stars are really
not all that close together -- somewhere more than twice the distance to
Pluto, so each star can develop its own planetary system, with
relatively minor perturbations from the other star -- similar to the
influence of jupiter on the Earth/moon system.

About _some_ binary systems. Others exist in which the stars are
so close together as to be noticeably egg-shaped due to
tides. These may be OK for planets, since their net gravitational
effect averages out very close to a single star's for
planets in the traditional habitable zone. There are even
binaries in which the envelope of one encompasses the
denser companion (but these are temporary niche things
unlikely to have much to do with surrounidng planets).

It has been demonstrated by Doppler variations that at least
some members of wide binaries (such as 16 Cygni B, IIRC)
have planets, so they are certainly fair game to consider.
There have been numerical simulations of planetary stability
over Gyr (or so) timescales for the specific case of Alpha
Centauri, whose K-type companion is at about the distance Uranus
is from us. The Earth would be long-term stable in such a system;
Jupiter at best marginally so.

Bill Keel

What about the possibility of a G class main star, an M dwarf at a near
circular orbit about 1 AU, and a habitable planet at the L4 or L5 point?

jmac39 wrote:
I am in the process (along with a partner) of writing a science fiction

novel. In this novel I want to create a very unique binary or twin
solar system that utilizes a very complex orbit system. I need someone
to consult about astronomical laws on gravity, gravitational forces on
the ways planets can and cannot orbit a body in space. Please help!!

NB I am assuming proper stars, and orbital velocities c. relativity
is ignored.

To do more than have handwving arguments you will need a decent
computer program. This in general terms is referred to as the "three
body problem". Newton of course solved the 2 body problem analytically.
After Newton attempts were made (unsuccessfilly) to solve this problem.
We now know that 3+ bodies are in general chaotic (a butterfly in Japan
cased Katrina - classic statement). Solutions are only possible in the
followeing circumstances.

1) Planet with 2 stars a long distance apart compared with planetary
distance. This is the case with the nearest fixed star Alpha Centauri.
We assume that there are centurans approximately the distance of Earth.
(Star is roughly the brightness of Sun).

2) Planet orbiting 2 stars close together compared with planetary
distance.

3) A quadrature. This is where orbital times are exact multiples. There
are quadratures (rotation of Mercury and Venus) in the solar system. To
work them out you need a proper astronomical program.

In article .com,
wrote:
...This in general terms is referred to as the "three
body problem". Newton of course solved the 2 body problem analytically.
After Newton attempts were made (unsuccessfilly) to solve this problem.

Until K.F. Sundman solved it successfully in 1912. You can prove that
it's unsolvable by normal algebraic means, but Sundman used some fairly
exotic infinite series, which are more powerful than normal algebra.

His solution is little-known because it's utterly useless for practical
purposes -- the series converge so slowly that numerical simulation uses
less computing time, and they are so complex that you can't gain useful
insight into the problem by studying them.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

In article ,
Cruithne3753 wrote:
What about the possibility of a G class main star, an M dwarf at a near
circular orbit about 1 AU, and a habitable planet at the L4 or L5 point?

Not possible. The Trojan points are not stable unless the ratio of
primary/secondary mass exceeds about 25, i.e. the dwarf could not be more
than about 0.04 solar masses. But M dwarfs only go down to about 0.08
solar masses; objects smaller than that never get hydrogen fusion started.

It would also be tricky for such a system to form. The planet would have
to be captured into the Trojan point after the stars had formed, because
the Trojan points are not stable (regardless of star masses) in the
presence of significant drag, e.g. in a presolar nebula with lots of dust
and gas around.

Finally, be careful about making assumptions about Lagrange points etc.
for a "near circular" orbit. It's tempting to assume that orbits which
depart only moderately from circular should show behavior that departs
only moderately from that found for circular orbits, but in general it's
not true.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |