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  2. Galactic year - Wikipedia

    en.wikipedia.org/wiki/Galactic_year

    One galactic year is approximately 225 million Earth years. [2] The Solar System is traveling at an average speed of 230 km/s (828,000 km/h) or 143 mi/s (514,000 mph) within its trajectory around the Galactic Center, [3] a speed at which an object could circumnavigate the Earth's equator in 2 minutes and 54 seconds; that speed corresponds to ...

  3. List of solar cycles - Wikipedia

    en.wikipedia.org/wiki/List_of_solar_cycles

    Solar cycle 17: 1933 – Sep 5.8 1937 – Apr 199 96 3-7 10-5 Solar cycle 18: 1944 – Feb 12.9 1947 – May 219 109 3-3 10-2 Solar cycle 19: 1954 – Apr 5.1 1958 – Mar 285 129 3-11 10-6 Solar cycle 20: 1964 – Oct 14.3 1968 – Nov 157 86 4-1 11-5 Solar cycle 21: 1976 – Mar 17.8 1979 – Dec 233 111 3-9 10-6 Solar cycle 22: 1986 – Sep 13.5

  4. Sun - Wikipedia

    en.wikipedia.org/wiki/Sun

    The Sun, taking along the whole Solar System, orbits the galaxy's center of mass at an average speed of 230 km/s (828,000 km/h) or 143 mi/s (514,000 mph), [167] taking about 220–250 million Earth years to complete a revolution (a Galactic year), [168] having done so about 20 times since the Sun's formation.

  5. History of the Solar System - Wikipedia

    en.wikipedia.org/wiki/History_of_the_Sun

    [121] [122] Within 7.5 billion years, the Sun will have expanded to a radius of 1.2 AU (180 × 10 ^ 6 km; 110 × 10 ^ 6 mi)—256 times its current size. At the tip of the red-giant branch , as a result of the vastly increased surface area, the Sun's surface will be much cooler (about 2,600 K (2,330 °C; 4,220 °F)) than now, and its luminosity ...

  6. Timeline of Solar System astronomy - Wikipedia

    en.wikipedia.org/wiki/Timeline_of_Solar_System...

    The principal change was to space leap years differently so as to make the average calendar year 365.2425 days long, more closely approximating the 365.2422-day 'tropical' or 'solar' year that is determined by the Earth's revolution around the Sun. The reform advanced the date by 10 days: Thursday 4 October 1582 was followed by Friday 15 ...

  7. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    They arrived at a figure for the solar parallax of 9.5″, equivalent to an Earth–Sun distance of about 22 000 Earth radii. They were also the first astronomers to have access to an accurate and reliable value for the radius of Earth, which had been measured by their colleague Jean Picard in 1669 as 3 269 000 toises .

  8. Tropical year - Wikipedia

    en.wikipedia.org/wiki/Tropical_year

    The length of the tropical year was given as 365 solar days 5 hours 49 minutes 16 seconds (≈ 365.24255 days). This length was used in devising the Gregorian calendar of 1582. [7] In Uzbekistan, Ulugh Beg's Zij-i Sultani was published in 1437 and gave an estimate of 365 solar days 5 hours 49 minutes 15 seconds (365.242535 days). [8]

  9. History of astronomy - Wikipedia

    en.wikipedia.org/wiki/History_of_astronomy

    It is available in two recensions, one belonging to the Rig Veda, and the other to the Yajur Veda. According to the Vedanga Jyotisha, in a yuga or "era", there are 5 solar years, 67 lunar sidereal cycles, 1,830 days, 1,835 sidereal days and 62 synodic months. During the 6th century, astronomy was influenced by the Greek and Byzantine ...