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  2. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    Average distance from the Sun — Earth: 1.00 — Average distance of Earth's orbit from the Sun (sunlight travels for 8 minutes and 19 seconds before reaching Earth) — Mars: 1.52 — Average distance from the SunJupiter: 5.2 — Average distance from the Sun — Light-hour: 7.2Distance light travels in one hour — Saturn: 9.5 ...

  3. Canonical units - Wikipedia

    en.wikipedia.org/wiki/Canonical_units

    In astrodynamics, canonical units are defined in terms of some important object’s orbit that serves as a reference. In this system, a reference mass, for example the Sun’s, is designated as 1 “canonical mass unit” and the mean distance from the orbiting object to the reference object is considered the “canonical distance unit”.

  4. Solar radius - Wikipedia

    en.wikipedia.org/wiki/Solar_radius

    Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun.The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: [1]

  5. Standard gravitational parameter - Wikipedia

    en.wikipedia.org/wiki/Standard_gravitational...

    μ = Gm 1 + Gm 2 = μ 1 + μ 2, where m 1 and m 2 are the masses of the two bodies. Then: for circular orbits, rv 2 = r 3 ω 2 = 4π 2 r 3 /T 2 = μ; for elliptic orbits, 4π 2 a 3 /T 2 = μ (with a expressed in AU; T in years and M the total mass relative to that of the Sun, we get a 3 /T 2 = M) for parabolic trajectories, rv 2 is constant and ...

  6. Grand tack hypothesis - Wikipedia

    en.wikipedia.org/wiki/Grand_Tack_Hypothesis

    Jupiter might have shaped the Solar System on its grand tack. In planetary astronomy, the grand tack hypothesis proposes that Jupiter formed at a distance of 3.5 AU from the Sun, then migrated inward to 1.5 AU, before reversing course due to capturing Saturn in an orbital resonance, eventually halting near its current orbit at 5.2 AU.

  7. Titius–Bode law - Wikipedia

    en.wikipedia.org/wiki/Titius–Bode_law

    Divide the distance from the Sun to Saturn into 100 parts; then Mercury is separated by four such parts from the Sun, Venus by 4+3=7 such parts, the Earth by 4+6=10, Mars by 4+12=16. But notice that from Mars to Jupiter there comes a deviation from this so exact progression.

  8. Rømer's determination of the speed of light - Wikipedia

    en.wikipedia.org/wiki/Rømer's_determination_of...

    By timing the eclipses of Jupiter's moon Io, Rømer estimated that light would take about 22 minutes to travel a distance equal to the diameter of Earth's orbit around the Sun. [1] Using modern orbits, this would imply a speed of light of 226,663 kilometres per second, [2] 24.4% lower than the true value of 299,792 km/s. [3]

  9. Jet Propulsion Laboratory Development Ephemeris - Wikipedia

    en.wikipedia.org/wiki/Jet_Propulsion_Laboratory...

    DE440 and DE441 were published in 2021, with improvements in the orbits of Jupiter, Saturn and Pluto from more recent spacecraft observations. [7] JPL ephemerides have been the basis of the ephemerides of sun, moon and planets in the Astronomical Almanac since the volumes for 1984 through 2002, which used JPL's ephemeris DE200.