MODULE:KNOWLEDGE-BASE■DATABASE:STELLAR-MECHANICS■CLASS:UNRESTRICTED
SIMULATION: ACTIVE
Circumbinary Planet
P-Type Orbit Around a Binary Pair
Circumbinary System
Star A (1.0 M☉)Star B (0.8 M☉)Planet (P-type orbit)Stability limit
System Parameters
Star A mass
1.0 M☉
Star B mass
0.8 M☉
Binary sep.
80 AU
Planet orbit
280 AU
Orbit ratio
3.5×
Stability min.
~2.8×
P-Type Orbits
A P-type (planet-type) orbit encircles both stars. The planet treats the binary as a single gravitational source from a distance. Contrast with S-type orbits, which hug one star tightly.
A forbidden zone exists between the binary separation and the stability limit. Any orbit within it is chaotically disrupted by the constantly shifting gravitational field of the two stars.
The planet experiences variable illumination— the combined brightness from both stars changes as their relative positions shift, producing complex seasons unlike anything in a single-star system.
Known Examples
Kepler-16b — First confirmed, orbits two cool stars
Kepler-34b — Two Sun-like stars, ~1 AU separation
Kepler-35b — Near-equal mass binary pair
TOI-1338b — Discovered by a teenager via TESS