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  2. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    This is because the distance between Earth and the Sun is not fixed (it varies between 0.983 289 8912 and 1.016 710 3335 au) and, when Earth is closer to the Sun , the Sun's gravitational field is stronger and Earth is moving faster along its orbital path. As the metre is defined in terms of the second and the speed of light is constant for all ...

  3. Orbit of Mars - Wikipedia

    en.wikipedia.org/wiki/Orbit_of_Mars

    Extra-close oppositions of Mars happen every 15 to 17 years, when we pass between Mars and the Sun around the time of its perihelion (closest point to the Sun in orbit). The minimum distance between Earth and Mars has been declining over the years, and in 2003 the minimum distance was 55.76 million km, nearer than any such encounter in almost ...

  4. Historical models of the Solar System - Wikipedia

    en.wikipedia.org/wiki/Historical_models_of_the...

    In 1672 Jean Richer and Giovanni Domenico Cassini measure the astronomical unit (AU), the mean distance Earth-Sun, to be about 138,370,000 km, [83] (later refined by others up to the current value of 149,597,870 km). This gave for first time ever a well estimated size of the then known Solar System (that is, up to Saturn), following the scale ...

  5. 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”.

  6. List of the most distant astronomical objects - Wikipedia

    en.wikipedia.org/wiki/List_of_the_most_distant...

    Kepler correctly characterized Mars and Earth's orbits in the publication Astronomia nova. It had been conjectured that the fixed stars were much farther away than the planets. Sun: Star 3rd century BC — 1609 380 Earth radii (very inaccurate, true=16000 Earth radii) Aristarchus of Samos made a measurement of the distance of the Sun from the ...

  7. Astronomical system of units - Wikipedia

    en.wikipedia.org/wiki/Astronomical_system_of_units

    The astronomical unit of length is now defined as exactly 149 597 870 700 meters. [4] It is approximately equal to the mean EarthSun distance. It was formerly defined as that length for which the Gaussian gravitational constant (k) takes the value 0.017 202 098 95 when the units of measurement are the astronomical units of length, mass and ...

  8. Titius–Bode law - Wikipedia

    en.wikipedia.org/wiki/Titius–Bode_law

    This latter point seems in particular to follow from the astonishing relation which the known six planets observe in their distances from the Sun. Let the distance from the Sun to Saturn be taken as 100, then Mercury is separated by 4 such parts from the Sun. Venus is 4+3=7. The Earth 4+6=10. Mars 4+12=16. Now comes a gap in this so orderly ...

  9. Orders of magnitude (length) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(length)

    1 astronomical unit (au); mean distance between Earth and Sun 10 12: 1 terameter (Tm) 1.3 Tm Optical diameter of Betelgeuse: 1.4 Tm Orbital distance of Saturn from Sun 2 Tm Estimated optical diameter of VY Canis Majoris, one of the largest-known stars: 5.9 Tm Orbital distance of Pluto from the Sun ~ 7.5 Tm Outer boundary of the Kuiper belt: 10 ...