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About Tom Whiting
Expertise
I can answer most questions about space flight and planetary exploration from an astronomy standpoint, but not from a computer or electronics standpoint. No astrology questions please, or questions about alleged UFO identifications.

Experience
Astronomy, my main catagory, has been my hobby and pastime for over 50 years. Taught astronomy and meteorology at the University level for over 13 years.

Organizations
President- Erie County Mobile Observers Group for over 15 years. Also on allexperts.com astronomy catagory for over 8 years.

Publications
Astronomy Technology Today and also wrote the "Over Erie Skies" column in our local newspaper for 11 years.

Education/Credentials
BS Metallurgical Engineering Grove City College, PA Master's Degree, Gannon University, Erie, PA Also retired USAF pilot, 20 years.

Awards and Honors
Discoverer of the mini-coathanger asterism in Ursa Minor; also the mini-dipper asterism up in the bowl of the Little Dipper.

You are here: Experts > Science > Space/Astronomy > Space Exploration > binary stars and associated planets

Space Exploration - binary stars and associated planets

Expert: Tom Whiting - 10/25/2009

Question
Hi Tom,
         I am trying to write a book about a planet that is in a binary system.
          I would like the planet to revolve around a red star of some sort and be twinned with a brighter yellow star that is further away.
           This would give the planet four states of illumination. Night, red light, yellow light and a combination of the two.

            I feel that the planet should be in a roughly circular orbit round the red star and the diameter of its path should be perpendicular to the line between the yellow and red stars.
             Do you think there is any chance of this being viable or am I living on another planet?
              Best wishes Eddie

Answer
Hi Eddie,
Well, almost anything in the science fiction mode can be made viable one way or another. This is possible from an astronomy standpoint as long as the distances and masses are made viable too.
The yellow star (say a solar type star) would have to be far enough away as to not gravitationally influence the red star/w planet encircling it. What you've really got is a little red dwarf star orbiting (at a large- Pluto type- distance or farther) the more massive yellow star, and the red dwarf star just happens to have a close in planet orbiting it 90 degrees to the stars' orbit around each other (or more exactly their bari-center.)
The hardest thing to explain is the 90 degree orbit, but that could have happenned early on in
that Solar system's evolution, say a 3 body encounter where another planet was ejected into
space, another was swallowed by the red star, and what was left was your 90 degree orbiting planet. Of course, in this configuration, there is no night-time on the planet. In a 90 degree orbital configuration, there is few ways to avoid continuous sunlight (starlight) from one, or both stars. When said planet side is not facing the red star in it's axial rotation, it's automaticially got the yellow star in the sky. Oh wait, there is one configuration... where the planet's rotational axis is pointed toward the yellow star (which makes the yellow star said planet's "North Star"....which would not be visible in the southern hemisphere of planet. So at least the southern hemisphere would have a 1/2 day of darkness, but the northern hemispnere would
never experience a night time period. I don't know how stable this situation would be over
a very long time period though.
Clear Skies,
Tom Whiting
Erie, PA USA
PS... We have nearly the same setup in the Solar System...Jupiter just barely missed being a
little red dwarf star by just a few Jupiter masses during the accretion phase 4.5 billion
years ago. Say Jupiter would have barely attained stardom to a red dwarf; then all it's current moons would actually be planets orbiting the red dwarf Jupiter star. And it's not unreasonable to assume that a Jovian "planet" could have settled into, eventually, a 90 degree orbit around Jupiter, very close in. The biggest problem then is that most bodies that close in will
eventually achieve sychronous rotation (like our moon, and most moons of the Solar System)
keeping one side, their heavy side, always facing their primary...so they perform one rotation per one revolution. But your story is simply fiction, so have at it.
Tom

FOLLOW UP:
Oh wait, planetary axis points to same spot in space...whereas the yellow star moves around
the sky as the red dwarf orbits it...so the yellow star cannot be the planets' north star.
So for any 'darkness' on said planet, you'll have to plot it out...I think there could be
just a few hours a day of darkness, but not on a continuous orbital basis.
Clear Skies,
Tom

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