Question re binary star systems & possible orbits

In summary, there are three types of systems (S-type, P-type, and T-type) when it comes to planets in a binary star system. For a S-type planet, the second star orbits like a superior planet and has oppositions and superior conjunctions once a year. For a P-type planet, the second star orbits like an inferior planet and has superior and inferior conjunctions twice in its own orbital period. It is possible for a planet to be in the trojan point L5 of the dimmer star in a T-type system, resulting in a daily "pre-sunrise" and "post-sunset." However, T-type systems are problematic due to mass ratio requirements for stability. If a planet has retrograde rotation and
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Kate_C
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Would it be theoretically possible to have a planet in a binary star system where there is a daily "pre-sunrise" and a "pre (or post) sunset" due to the dimmer star?
From what I gather, there are S-type, P-type & T-type systems, but I'm having a hard time wrapping my mind around the orbital possibilities. Would it be theoretically possible to have a planet in a binary star system where there is a daily "pre-sunrise" and a "pre (or post) sunset" due to the dimmer star? And could there be daily syzygy with the stars or might it need to be less frequent? If anyone can advise, it would be so appreciated! Thank you!
 
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For a S-type planet, the second star orbits like a superior planet. It therefore has oppositions and superior conjunctions - both of them approximately once a year.
For a P-type planet, the second star orbits like an inferior planet. It therefore has superior and inferior conjunction - total of approximately twice in its own orbital period. Stars may orbit on quite close orbit, but there is no particular reason for the orbital period of stars to coincide with twice the rotational period of planet.
 
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Kate_C said:
Would it be theoretically possible to have a planet in a binary star system where there is a daily "pre-sunrise" and a "pre (or post) sunset" due to the dimmer star?

Yes, if the planet is located in the trojan point L5 of the dimmer star (T-type system).
 
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T-type is problematic, though, due to the mass ratio requirements of Lagrange point stability.
 
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snorkack said:
For a S-type planet, the second star orbits like a superior planet. It therefore has oppositions and superior conjunctions - both of them approximately once a year.
For a P-type planet, the second star orbits like an inferior planet. It therefore has superior and inferior conjunction - total of approximately twice in its own orbital period. Stars may orbit on quite close orbit, but there is no particular reason for the orbital period of stars to coincide with twice the rotational period of planet.
Thank you for clarifying! Very helpful!
 
  • #6
DrStupid said:
Yes, if the planet is located in the trojan point L5 of the dimmer star (T-type system).
Great to know! Thank you SO MUCH for your help with this and for the expertise!
 
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  • #7
DrStupid said:
Yes, if the planet is located in the trojan point L5 of the dimmer star (T-type system).
So, if I'm understanding correctly, that would make for a post-sunset in this case by the dimmer star?
 
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Kate_C said:
So, if I'm understanding correctly, that would make for a post-sunset in this case by the dimmer star?
Both L4 and L5 are equally stable, or not, depending on the mass ratio of primary and secondary.
Elongation to primary star is 60 degrees each case. Whether it is evenstar or morningstar depends on the rotation axis of tertiary.
 
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Thank you!
 
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snorkack said:
...Stars may orbit on quite close orbit, but there is no particular reason for the orbital period of stars to coincide with twice the rotational period of planet.

What if the planet has retrograde rotation? Assume it is close enough to tidal lock with one of the red dwarfs if the dwarf was non-binary. The heavy side of the planet that would otherwise face the star would see the smaller dwarf at sunrise, the stars would eclipse or pass close together (conjunction) at noon (if at zero longitude), and then at sunset the smaller dwarf would still be up later. Why would it slow rotation below 1:1 resonance?

Is there any reason it could not lock into a 2:1 resonance?
 
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Thank you for weighing, stefan r! I viewed some simulations that appeared to illustrate this and proceeded to write a sci-fi novel around the premise. I'm very glad to know it sounds within the realm of possibility.
 
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stefan r said:
What if the planet has retrograde rotation? Assume it is close enough to tidal lock with one of the red dwarfs if the dwarf was non-binary. The heavy side of the planet that would otherwise face the star would see the smaller dwarf at sunrise, the stars would eclipse or pass close together (conjunction) at noon (if at zero longitude), and then at sunset the smaller dwarf would still be up later. Why would it slow rotation below 1:1 resonance?

Is there any reason it could not lock into a 2:1 resonance?
What do you mean - lock of planet rotation to planet orbit, or to star orbit?
 

Related to Question re binary star systems & possible orbits

1. What is a binary star system?

A binary star system is a system in which two stars orbit around a common center of mass. This means that the two stars are gravitationally bound to each other and revolve around each other in an elliptical orbit.

2. How are binary star systems formed?

Binary star systems are formed through the same process as single stars - the collapse of a molecular cloud. However, in binary systems, the cloud collapses into two separate cores that eventually become the two stars in the system.

3. What is the most common type of orbit in a binary star system?

The most common type of orbit in a binary star system is a circular orbit. This is because it is the most stable type of orbit and requires the least amount of energy to maintain. However, some binary systems may have elliptical or even highly eccentric orbits.

4. Can binary star systems have more than two stars?

Yes, binary star systems can have more than two stars. These systems are called multiple star systems and can have three or more stars orbiting around each other. However, the majority of binary star systems in our galaxy are composed of only two stars.

5. How do scientists study the orbits of binary star systems?

Scientists study the orbits of binary star systems through a variety of methods, including spectroscopy, astrometry, and interferometry. These techniques allow scientists to measure the positions, velocities, and other characteristics of the stars in the system, which can then be used to determine their orbits.

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