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    MATERIAL FROM CLASS 11: Monday October 16

    Lengths:
    1AU = 1.5 x 108km or 1.5 x 1011km
    1 km (kilometer) = 1000 meters = 5/8 mile
    1 meter = 1000mm (millimeters), so 1mm = 10-3meters
    1 meter = 106microns, so 1mm = 10-6meters
    1 meter = 109nm (nanometers), so 1nm = 10-9meters

    Apparent brightness f = luminosity L/(4 &pi d2)
    L is in watts, so f is in W/square meter when distance d is in meters.

    The Sun is BIG: its radius is almost twice as large as the Moon's orbit around the Earth:
    [Sun with spots, 29 March 2001]

  • Latest images of the Sun, in various wavelengths Images of the Sun in extreme ultraviolet or X-rays (SOHO, first 4 panels on this link) or with the disk of the Sun blocked out (second from bottom) show the corona extending outward.

  • Movie of a fast eruption in the solar corona