Pluto and Charon

Pluto's features

JavaScript — Pluto-Charon

// Pluto orbital eccentricity is high
const a_PLUTO = 39.48;  // AU
const e_PLUTO = 0.249;
const peri_pluto = a_PLUTO * (1 - e_PLUTO);
const aph_pluto = a_PLUTO * (1 + e_PLUTO);
console.log(`Pluto: ${peri_pluto.toFixed(2)} AU peri, ${aph_pluto.toFixed(2)} AU aph`);
// 29.66 to 49.31 AU — overlaps Neptune's orbit at perihelion

// Solar flux at Pluto
console.log(`Flux at peri: ${(1361 / Math.pow(peri_pluto, 2)).toFixed(2)} W/m²`);
console.log(`Flux at aph: ${(1361 / Math.pow(aph_pluto, 2)).toFixed(2)} W/m²`);

// Pluto-Charon barycenter
const M_PLUTO = 1.303e22;
const M_CHARON = 1.586e21;
const distance_PC = 19.591e6;  // m
const barycenter_distance = distance_PC * M_CHARON / (M_PLUTO + M_CHARON);
const R_PLUTO = 1188e3;
console.log(`Barycenter from Pluto: ${(barycenter_distance/1000).toFixed(0)} km`);
console.log(`Pluto radius: ${R_PLUTO/1000} km`);
console.log(`Outside Pluto? ${barycenter_distance > R_PLUTO}`);  // TRUE — true binary

// Year on Pluto
const T_pluto = Math.pow(a_PLUTO, 1.5);
console.log(`Pluto year: ${T_pluto.toFixed(0)} Earth years`);

// Light travel time
const ly_per_AU = 8.317;  // light minutes
console.log(`Light to Pluto: ${(a_PLUTO * 8.317 / 60).toFixed(1)} hours`);

Why Pluto-Charon matters

• Solar system formation. Kuiper Belt — primitive material from formation era.
• Binary planet physics. Pluto-Charon: most extreme example in solar system.
• Cryovolcanism. Active geology on small frozen world.
• Atmospheric science. Thin atmosphere with seasonal changes.
• Reclassification debate. Tests definitions of "planet."
• New Horizons legacy. Detailed images we'd never have without mission.
• Future missions. Orbiter would reveal Pluto's interior, Charon's history.

Common misconceptions

• Pluto is a dead frozen rock. Active geology — flowing nitrogen ice glaciers, possible cryovolcanism.
• Pluto has no atmosphere. Thin atmosphere exists; varies seasonally.
• Pluto is just like the Moon. Different — dwarf planet, ice-rich, complex geology.
• Pluto's demotion was scientific consensus. Heated debate; "Plutoid" classification still informal among many.
• Charon is a normal moon. Half Pluto's size; they're effectively binary.
• Pluto is past Neptune always. Eccentric orbit; sometimes inside Neptune (1979-1999 was inside Neptune's orbit).