Documentation / @interstellar-tools/types / OrbitInterface

Interface: OrbitInterface

Defined in: orbits.ts:127

Kepler orbital elements of one body around its parent.

The parent is whatever the body is gravitationally bound to: a star, a planet, a barycenter or a galaxy. It is named by the parent id on the body or system that carries this orbit, and the elements always describe the motion around that parent, never around anything further up.

INFO

• Pairs: when two bodies orbit a shared barycenter (Alpha Centauri A and B), each carries its own orbit. Both share e, period and angle, their periapses point in opposite directions, and their semi-major axes split by mass ratio: $a_1=a{m}_2/(m_1+m_2)$, where $a$ is their separation.
• Direction: period is always a positive duration. A retrograde orbit, moving against its parent's rotation, has retrograde: true; a renderer can use retrograde ? -1 : 1 as the direction of travel.
• i, w, om and q are only given where the dataset has them (comets and asteroids). Where i is given, retrograde is set exactly when i > 90°.

Example

const earthOrbit: OrbitInterface = {
  a: { value: 1.0, unit: 'au' },
  e: 0.0167,
  period: { value: 365.256, unit: 'd' },
  angle: 1.753 as Radians
};

Extended by

• FullOrbitInterface

Properties

a

a: DistanceInterface;

Defined in: orbits.ts:129

Semi-major axis of this body's orbit around the parent's centre of mass.

---

angle

angle: Radians;

Defined in: orbits.ts:137

Current orbital position at J2000 in radians (true anomaly).

---

e

e: number;

Defined in: orbits.ts:131

Orbital eccentricity (0 = circular, closer to 1 = highly elliptical).

---

i?

optional i?: DegreesType;

Defined in: orbits.ts:139

Orbital inclination in degrees, as catalogues give it.

---

om?

optional om?: DegreesType;

Defined in: orbits.ts:143

Longitude of the ascending node in degrees.

---

period

period: TemporalInterface;

Defined in: orbits.ts:133

Orbital period, always positive. See retrograde for the direction.

---

q?

optional q?: DistanceInterface;

Defined in: orbits.ts:145

Periapsis distance $q=a(1-e)$.

---

retrograde?

optional retrograde?: boolean;

Defined in: orbits.ts:135

true for a retrograde orbit. Omitted for the usual prograde orbits.

---

w?

optional w?: DegreesType;

Defined in: orbits.ts:141

Argument of periapsis in degrees.