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Moon · evidence and sources

Moon

Earth's only natural satellite. The fifth largest moon in the solar system.

astronomy-engine Position basis, the same label the app shows on the selection card.

Open in Space Time

Every aspect, with its origin

One record per aspect. The origin says what kind of thing each value is; the source says where it came from; the limit says what it cannot tell you.

ObservedCatalogComputedReconstructedIllustrativeUndocumented
Position Computed

Position for the simulation time

Moon's position is computed for the simulation instant by astronomy-engine, an analytic ephemeris model. There is no snapshot to age: the same code gives the same answer for any date.

Sourceastronomy-engine
Methodastronomy-engine (analytic planetary and lunar model; Sun through Pluto and the Moon)
UncertaintyRoughly arcminute-level against JPL ephemerides for 1700 to 2200; fixture tests compare selected dates with Horizons.
LimitPositions in the 3D scene are heliocentric J2000 equatorial coordinates; observer-facing tables are apparent, of date, and topocentric (see the frame statements).
Physical data Undocumented

Bulk properties

Moon: mean radius 1,737.4 km. These values are bundled with the object record and drive the rendered size.

SourceBundled object record
LimitThe object catalog does not record where these values came from; treat them as unverified until the record is completed.
Appearance Reconstructed

LRO surface mosaic

Spacecraft imagery with modeled phase and earthshine. Close terrain uses available elevation data.

SourceAppearance source and method
MethodThis describes the displayed appearance only; it does not certify catalog dimensions, orbital elements or unobserved geology.
Appearance Reconstructed

Read the lunar map

This bundled Solar System Scope display map is a reference for large-scale features. The online globe may load the separate LRO mosaic; lighting and close terrain are modeled independently.

SourceSolar System Scope / INOVE · CC BY 4.0
MethodSource maps are compared with a physical globe or rings under simulated illumination. The image and camera view are not registered.
LimitThe display map is not a calibrated global height model. Bright crater rays and baked-in shadows are image features.
Description Undocumented

Description and facts

The short description and the fact list are written by the Space Time authors for orientation. They are not quoted from a catalog field and carry no citation of their own.

SourceSpace Time editorial text
LimitBackground reading is linked under Further reading; it is not the source of the displayed numbers.

Engine and frame

  • Engine: astronomy-engine (analytic planetary and lunar model; Sun through Pluto and the Moon)
  • Frame (3D scene): heliocentric J2000 equatorial positions from astronomy-engine, rotated into the scene's ecliptic basis
  • Frame (tables): RA/Dec are apparent, of date (true equator and equinox of the instant), with annual aberration applied; not J2000
  • Origin: topocentric for the chosen observer (distance is observer-to-body, not geocentric)
  • Refraction: altitude includes standard atmospheric refraction (astronomy-engine "normal" model); azimuth is unaffected
  • Magnitude: astronomy-engine Illumination(): phase-dependent planetary magnitudes (Mercury and Venus per Hilton 2005), Saturn includes ring tilt, Moon and Sun use its built-in curves; no atmospheric extinction
  • Size: angular diameter from IAU equatorial radii and the topocentric distance
  • Constellation: IAU boundaries evaluated on the position precessed back to J2000

What is not measured

  • Appearance: a reconstruction from measurements, not a direct observation. LRO surface mosaic. Spacecraft imagery with modeled phase and earthshine. Close terrain uses available elevation data.
  • Appearance: a reconstruction from measurements, not a direct observation. Read the lunar map. The display map is not a calibrated global height model. Bright crater rays and baked-in shadows are image features.

Not yet documented

  • Physical data: The object catalog does not record where these values came from; treat them as unverified until the record is completed.
  • Description: Background reading is linked under Further reading; it is not the source of the displayed numbers.

Dataset freshness

Snapshots this page depends on, read from the generated manifests at request time.
DatasetLast refreshedHorizonAutomated
Sun, Moon and planet positions
astronomy-engine (analytic ephemeris model)
 no snapshot date Valid roughly 1700 to 2200 at arcminute level; no snapshot to age Not applicable (analytic model)
npm dependency

Sources cited

Further reading

Wikipedia: Moon (background only; not the source of the displayed numbers)

More

All evidence pages Sky events and alert sources What's new All features
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