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NowSky is an educational, conceptual visualization tool; it may differ from actual astronomical phenomena and observational data.
All figures, orbits, surface renderings and event reconstructions (eclipses, probe trajectories, etc.) on this site are approximate, simplified models for education. Timing, positions, scales and appearances may differ from reality. Items marked as targets (e.g. future mission schedules) are hypothetical reference dates.
All information is provided "as is" with no warranty of accuracy, completeness or currency. It must not be used as a basis for any practical decision — observation planning, navigation, research or commercial use — and the operator accepts no liability for any direct or indirect damages arising from its use. For authoritative astronomical data, consult official sources such as NASA, ESA, the IAU, NASA JPL Horizons (precision ephemerides) or the U.S. Naval Observatory.
Central radius normalized to 1; the ladder stacks objects by size.
Solar-system and atom modes normalize every distance and size to the central body (or nucleus) radius = 1. The size ladder sorts objects by size and stacks them without overlap, so each object sits at a position proportional to its size.
Atomic shell radii use the Bohr model with Slater screening (rₙ = n²a₀ / Z_eff). Orbital-view planet positions are real dated positions from J2000 elements (within a few degrees for planets); dwarf planets, comets and moons are approximate.
Eclipses — Sun and Moon positions in the sky view use the abridged Meeus ELP and solar series with a UT→TT (ΔT) correction and a full topocentric (parallax) conversion, so the moment of maximum eclipse lands within about a minute of published values. Even so, the time shifts by tens of seconds and the coverage can differ noticeably between points inside one city — a path of totality is only about 100 km wide, so a city's north and south edges may not see the same thing. For an exact view, set latitude and longitude yourself from the location chip, or use My location.
Nuclei from data + empirical formulas; electron sizes are metaphorical.
Nuclear radii use measured charge radii for A ≤ 12 and R = 1.2 fm × A^(1/3) beyond. Nuclear mass is computed as Z·mₚ + N·mₙ − BE/c² via the semi-empirical mass formula.
Electrons are point particles (experimental limit < 10⁻¹⁸ m). The three display sizes offered are metaphorical length scales, not physical sizes.
Some estimates vary widely; the catalog keeps evolving.
Hypergiant radii are contested — UY Scuti and Stephenson 2-18 shift by factors with new distance measurements. The Milky Way's diameter spans 100k–200k light-years depending on definition.
Moon counts and dwarf-planet lists keep changing. Orbital radii are semi-major axes, so eccentric objects like Sedna and Nereid range much wider in practice.
Photos are fetched live from Wikipedia; without internet or an article, only diagrams are shown. Sizes for movie/comic entries use widely known canon values.
